What Is CNC Machining?

CNC machining refers to the automated control of machine tools through computer-based programs. Unlike conventional, manually operated machining, CNC systems execute predefined programs that coordinate the movement of tool and workpiece with very high accuracy. The technology supports a range of processes including milling, turning, drilling, and grinding, all of which deliver precise and reproducible results. In day-to-day shop floor practice, this means producing complex geometries with consistent accuracy and economy — whether for one-off parts or large production runs.

Key Steps in the CNC Machining Process

The machining process generally follows a clearly defined sequence. First, the part is designed digitally using CAD (Computer-Aided Design) software. The model contains all relevant dimensions, tolerances, and technical requirements. Based on this, CAM (Computer-Aided Manufacturing) software generates a machining program that defines the exact movements of the machine.

Next, the machine is set up: appropriate tools are loaded and the raw material is securely clamped. The machine then carries out the programmed operations and shapes the workpiece with high precision. After machining, the part is inspected and, if needed, sent on for additional finishing or surface treatment.

1. Part Design
   The part is first modeled digitally using CAD (Computer-Aided Design) software. The model captures all relevant dimensions, tolerances, and technical requirements.
2. Programming
   Based on the design, CAM (Computer-Aided Manufacturing) software is used to generate a CNC program that defines the machine’s movements.
3. Machine Setup
   The CNC machine is prepared by loading the appropriate cutting tools and securely clamping the raw material.
4. Machining
   The machine executes the programmed operations and shapes the workpiece with high precision.
5. Inspection and Finishing
   After machining, the part is inspected. If needed, additional finishing or surface treatment steps follow.

Types of CNC Machines

Machining centers come in a variety of configurations and are specialized for different manufacturing tasks. The two fundamental principles are milling and turning, which differ in how the tool and workpiece move relative to each other.

CNC Milling Machines

In CNC milling, rotating cutting tools remove material from a stationary workpiece. Milling metal is one of the most widely used processes in industrial manufacturing — whether carbon steel, stainless steel, or aluminum, CNC milling machines can shape virtually any metallic material precisely and economically. Milling stainless steel in particular places high demands on tooling and process control, since the material tends to work-harden and requires effective cooling. Milling aluminum, on the other hand, allows significantly higher cutting speeds and is especially common in the automotive and aerospace industries.

A defining feature of modern milling machines is their capability for 3D milling. In 3D milling, workpieces are machined not in two but in three or more axes simultaneously. This makes it possible to produce free-form surfaces, undercuts, and complex surface geometries that conventional methods cannot achieve. 3D milling is used wherever geometric complexity meets tight tolerances — for example in tool and mold making, medical technology, and prototyping.

Vertical Machining Centers (VMC)

Vertical machining centers use a vertically oriented spindle and are available in 3-, 4-, and 5-axis configurations. 5-axis CNC milling in particular has become a key technology for demanding parts. With 5-axis CNC milling, the tool can approach the workpiece from almost any direction, allowing complex features to be machined in a single setup. This reduces setup times, improves dimensional accuracy, and significantly lowers manufacturing costs. Typical applications for 5-axis CNC milling include turbine components, medical implants, and tool and mold geometries with challenging features.

Horizontal Machining Centers (HMC)

Horizontal machining centers are designed for high volumes and especially efficient series production. Because of the horizontal spindle orientation, chips fall away more easily, which improves process reliability during long production runs.

Double Column Milling Machines (DCMC)

For large and heavy workpieces, double column milling machines are used. Their rigid construction provides the stability and accuracy needed to machine massive parts with precision.

Lathes

In turning, the workpiece rotates while a stationary tool removes material. This process is used primarily for rotationally symmetric parts such as shafts, bushings, and rings, and is known for its high speed and repeatability.

The Role of Metalworking Fluids in CNC Machining

Beyond machines, tools, and software, high-quality metalworking fluids play a decisive role in the efficiency, quality, and economics of machining. They have a direct impact on tool life, surface finish, process stability, and overall cost — and are therefore far more than mere consumables. They are strategic process elements.

Water-Miscible Coolants

Water-miscible coolants are used in many applications because of their excellent cooling performance. By dissipating heat effectively, they help maintain dimensional accuracy and reduce thermal stress on tools and machines. They also provide essential functions such as lubrication, chip flushing, and corrosion protection. Well-formulated products enable longer tool life, higher cutting speeds, improved surface quality, and lower scrap rates. Their stability and long service life also reduce maintenance effort and operating costs.

• longer tool life
• higher cutting speeds
• improved surface quality
• lower scrap rates

Neat Cutting Oils

Neat cutting oils are used primarily in demanding machining operations where lubrication is the critical factor. They significantly reduce friction at the cutting edge and are ideal for difficult materials or processes such as deep-hole drilling, tapping, and gear cutting. High-performance neat oils minimize tool wear, improve process reliability, ensure consistent surface quality, and reduce energy consumption through lower friction.

High-performance neat oils:

• minimize tool wear
• improve process reliability
• ensure consistent surface quality
• reduce energy consumption through lower friction

In doing so, they make a meaningful contribution to lowering total operating costs.

Impact on Efficiency and Cost

The selection and quality of metalworking fluids has a direct effect on the economics of manufacturing. Optimized products improve machine utilization, reduce tool changes, prevent rework, and support stable production planning. Metalworking fluids are therefore not simple consumables, but strategic process factors for efficiency, sustainability, and profitability.

Common Materials Used in CNC Machining

CNC machines can process a wide variety of materials. Among ferrous metals, carbon steel, stainless steel, and cast iron dominate. Carbon steel is strong and versatile; stainless steel offers excellent corrosion resistance and is widely used in medical and food-related applications; cast iron is durable and stable, for example in engine and machinery components.

Non-ferrous metals such as aluminum, copper, and titanium round out the spectrum. Aluminum is lightweight and easy to machine, ideal for automotive and aerospace. Copper offers excellent electrical conductivity, while titanium combines high strength with corrosion resistance. Composites such as carbon fiber and fiberglass can also be machined with high precision.

Ferrous Metals

• Carbon Steel – strong and versatile
• Stainless Steel – corrosion-resistant, common in medical and food applications
• Cast Iron – durable and stable, e.g. for engine and machinery components

Non-Ferrous Metals

• Aluminum – lightweight and easy to machine, ideal for automotive and aerospace
• Copper – excellent electrical conductivity
• Titanium – high strength and corrosion resistance

Plastics

• Polycarbonate – impact-resistant and stable
• Acrylic – transparent and easy to machine
• Nylon – wear-resistant, often used for gears

Composites

• Carbon Fiber – extremely lightweight and strong
• Fiberglass – durable and versatile

Advantages of CNC Machining

The process stands out for a combination of precision and efficiency that manual methods cannot match. Tight tolerances and high repeatability make it the first choice for series production. Automated processes reduce error rates and allow flexible processing of a wide range of materials and geometries. In demanding industries such as aerospace and medical technology, these characteristics are indispensable.

• High precision and tight tolerances
• Repeatability in series production
• High efficiency through automated processes
• Flexibility across materials and geometries
• Lower error rates through automation

Applications of CNC Technology

Today, CNC technology is essential in nearly every manufacturing-intensive industry. In aerospace and automotive, it makes it possible to produce highly precise components with tight tolerances. Medical technology benefits from the repeatability achieved when machining implants and instruments. In electronics, fine features are milled and drilled, while construction and heavy machinery rely on CNC for large, robust components.

Choosing the Right CNC Machine

When selecting a CNC machine, application requirements, technical capabilities, control and software technology, and service and maintenance offerings should all be carefully considered. Ultimately, what matters most is the cost-benefit ratio in the context of your specific production environment. A sound decision accounts not only for the initial investment but also for ongoing operating costs — including process media such as metalworking fluids, which significantly influence the efficiency and economics of the entire operation.

The following aspects should be considered when choosing a machine:

1. Application requirements
2. Technical capabilities
3. Control and software technology
4. Service and maintenance
5. Cost-benefit ratio

Der Beitrag CNC Machining Explained: Types, Processes, and Applications erschien zuerst auf Kluthe Magazine.

In chemistry, fractionation refers to the process of separating mixtures into their individual components. This is achieved using a variety of specialized chemical separation techniques. The term “fractionation” is typically used when mixtures consist of more than two substances that need to be isolated individually or in groups. Here you will find an overview of the most important methods and their areas of application.

Natural Phenomena Commonly Used in Fractionation

Chemistry often utilizes physical methods to separate mixtures. These methods harness natural phenomena such as:

• Changing states of matter at different temperatures (e.g., distillation)
• Differing solubilities of substances (e.g., extraction, precipitation, absorption)
• The natural tendency toward concentration equilibrium (e.g., diffusion, osmosis)
• Selective accumulation of substances on the surface of solids (adsorption)
• Varied permeability of particles or molecules through porous solids (e.g., filtration, ultrafiltration)

Typically, these phenomena lead to equilibrium states where differences are balanced. In chemical fractionation, the intentional adjustment of process parameters such as concentration, temperature, pressure, shifts the equilibrium toward the desired outcome. Mixtures then form distinct phases with substances accumulating differently between each phase or concentrating at the interfaces. Phases may differ by state of matter (solid, liquid, gas) or by immiscibility (such as oil and water). They often separate spontaneously: gases escape from liquids and can be collected, solids settle as sediment, and immiscible liquids form distinct layers. If needed, fractionation is completed using filters, separators, or centrifuges.

Conducting Fractionation

Fractionation in chemistry typically involves sequentially applying different separation methods. For example, solids may first be filtered from a liquid mixture, followed by precipitating dissolved salts, filtering them out, and finally separating the remaining liquid mixture into its components through distillation processes. Each step produces two new fractions, either final products or further processed materials. Examples include:

• Solvent extraction of plant oils from biomass
• Fractional distillation of crude oil or solvent mixtures
• Adsorption of organic pollutants onto activated carbon for wastewater treatment
• Adsorption of water vapor onto silica gel for air drying
• Reverse osmosis for seawater desalination

How Solvent Extraction Recovers Plant Oils from Biomass?

When extracting plant oils from biomass, oil-rich plant parts are mixed with petroleum ether or alcohol. The oils dissolve in the solvent. After the solids are filtered out, the solvent-oil mixture is distilled, resulting in pure oil. Small amounts of oil evaporate with the solvent; this vapor mixture condenses in a cooler and can be reused. Extraction, which involves selectively dissolving components, is frequently used in chemical fractionation. Liquid mixtures are combined with solvents that dissolve the target substances but remain immiscible with other components. This process creates two separate liquid phases, allowing the separation of the solvent and the extracted material.

Fractional Distillation of Crude Oil or Solvent Mixtures

In chemistry, solvent mixtures containing more than two substances are often produced. Such mixtures also occur in surface technology, for example in industrial parts cleaning — more specifically, in solvent-based parts cleaning. Fractional distillation commonly separates these solvents, exploiting differences in vapor pressures. Lower-boiling substances concentrate more in vapor than in liquid phases. As a liquid mixture evaporates, its boiling temperature gradually rises, introducing heavier-boiling substances into the vapor. By periodically collecting and condensing the vapors separately, different fractions containing fewer components from the original mixture are obtained.

Technical Implementation of Fractional Distillation

Fractional distillation is typically performed in distillation columns—tall, vertical steel towers with evaporators at the bottom and condensers at the top. Columns usually contain internal packing materials. As vapor rises, some condensate trickles downward. Constant mass transfer between vapor and liquid phases occurs. Vapor accumulates lighter-boiling components, while heavier substances concentrate in the liquid. Individual fractions are collected at various heights along the column from the liquid phase.

Adsorption of Organic Pollutants onto Activated Carbon for Wastewater Treatment

Activated carbon has the property of retaining organic substances on its surface. This is utilized, for example, in wastewater treatment in chemistry. Activated carbon typically exists as granules, maximizing surface area and adsorption capacity. Water percolates through or is mixed with activated carbon before filtering. Once carbon capacity is exhausted, it can be regenerated with steam, allowing the newly separated solvents to be recovered.

Adsorption of Water Vapor onto Silica Gel for Air Drying

Fractionation also includes air drying by adsorption of moisture onto silica gel or other drying agents. These materials have a high capacity for absorbing water vapor, preventing condensation and moisture-related damage during temperature fluctuations. Small packets of drying agents, such as silica gel, are commonly included with leather goods and metal products during transport to prevent corrosion.

Reverse Osmosis for Seawater Desalination

Membrane-based methods are also frequently used in fractionation. Reverse osmosis for seawater desalination is a prominent example. Osmosis naturally balances concentration differences, causing ripe cherries to burst after rain, for instance. When a concentrated solution (e.g., juice) and water are separated by a semi-permeable membrane allowing only water molecules to pass through, the water moves into the solution, diluting it and increasing internal pressure. When equilibrium is reached, the process stops. In reverse osmosis, applying pressure greater than the equilibrium pressure to the concentrated side forces water through the membrane, enabling the collection of purified water.

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Criteria for distinguishing types of metal corrosion

Corrosion damages the material. Without countermeasures, many metal products would have a very short service life. Suitable solutions for corrosion protection can only be identified if the causes and mechanisms of corrosion processes are  considered. Individual metals and alloys react differently to corrosive attack by environmental media. Both the chemical elements involved, and the material structure formed during solidification of the melt play a role in the type of corrosion. In addition, prior metal processing, and the design of the component influence corrosion behavior. Finally, differences arise in the way material degradation spreads, whether limited to the metal surface or extending into the depth of the material. Based on these criteria, distinct  types of metal corrosion are classified  to facilitate targeted prevention.

Types of corrosion based on reaction mechanisms

Formation of local galvanic cells

Understanding corrosion starts with the atomic structure of metals. Atoms are arranged in regular lattices. The outer electrons of the atomic shells are freely movable within these lattices. Their absence from individual atomic shells allows the positive charge of the atomic nuclei to dominate. Strictly speaking, these lattices consist of ions that respond to electric fields. When moisture is present, galvanic cells form. Such corrosion processes correspond in their processes to galvanic coating or the electrolysis of water. A small electric current causes metal ions to dissolve at locations where there is an electron deficiency (anode) and combine with oxygen from  moisture. At locations with an excess of electrons (cathode), gaseous hydrogen is produced, which immediately reacts with oxygen in the air to form water. The material areas in which these processes take place usually have only a very small spatial extent. This results in the term local galvanic cells.

Contact corrosion

When different metals come into contact with each other, an electrical potential difference can be observed between them. An electric field forms. When metals are arranged according to the magnitude of these potential differences, the electrochemical series results. Hydrogen is arbitrarily placed in the middle of this series. Metals that are more positive in the electric field are considered noble, while those that are more negative are considered base. The greater the distance between metals in the series, the greater the potential difference and thus the electric current that flows when a closed circuit is formed. This current consists of ions from the less noble metal, which detach from their lattice, migrate toward the more noble metal, and deposit there. These types of corrosion can be suppressed by using identical materials within a system or by careful electrical isolation.

Chemical oxidation

In addition to electrochemical processes, some types of corrosion are caused by direct chemical reactions. When certain dry gases, salts, bases, or acids make contact with metal surfaces, they form molecules whose stability is based on shared electrons. These corrosion processes are known as redox reactions. The metal receives electrons for shared use and is oxidized. The reaction partner provides these electrons and is reduced. These processes occur more intensely at high temperatures. Substances that can trigger such behavior include oxygen, hydrogen sulfide, ammonia, chlorine, and ammonium salts. These types of corrosion can be avoided through the use of resistant materials or suitable coatings.

Biocorrosion

Biocorrosion is another important type of metal corrosion. In this form of corrosion, the substances responsible for the corrosive attack originate from the metabolic processes of living organisms. Microorganisms, fungi, lichens, plants, and animals that colonize metal surfaces produce an almost inexhaustible range of organic substances that can form chemical compounds with metals. These include  various organic acids, such as formic acid, acetic acid, uric acid, and citric acid. In addition, metabolic by-products such as hydrogen sulfide and nitrogen oxides can form, which under certain conditions react with water to form sulfuric or nitric acid.

Types of metal corrosion based on propagation mechanisms

Uniform corrosion

In this type of corrosion, the electrochemical conversion of the material occurs evenly across the metal surface. Depending on the material used, thin passive layers quickly form under the influence of atmospheric oxygen and moisture, protecting the underlying material from further degradation. This is the case, for example, with chromium, tin, and stainless steel. However, the oxide layers on many iron-based materials are loose and porous. Without corrosion protection, material degradation continues until the material is completely consumed.

Pitting corrosion

Pitting corrosion is one of the electrochemical types of corrosion. It occurs primarily when passive layers on metal surfaces contain defects. Material degradation is intensified by the influence of chloride or bromide ions. These ions occupy the defects and prevent oxygen from reaching the surface, which would otherwise repair the passive layer. As a result, localized damage initially forms and continues to penetrate deeper into the base metal.

Crevice corrosion

If a metal structure contains narrow crevices, for example at overlapping edges, attached components, or interrupted weld seams, the concentration of surrounding substances inside the crevice differs from that outside. This concentration difference creates a potential difference similar to that between different metals. As a result, electrochemical reactions occur within the crevice.

Additional types of metal corrosion

Depending on material composition, microstructure, mechanical stresses during metal processing or operation, and operating temperature, numerous additional types of corrosion are distinguished. Examples include:

• Intergranular corrosion
• Stress corrosion cracking
• Corrosion fatigue
• Undercutting corrosion
• High-temperature corrosion
• Knife-line corrosion
• Erosion corrosion
• Stray current corrosion

Damage caused by these types of corrosion is primarily prevented through careful material selection and corrosion-resistant design.

Corrosion protection through substances and surface engineering processes

Corrosion inhibitors for protection during processing and transport

Corrosion inhibitors protect metal materials from corrosive attack during processing and transport. These substances are added to process fluids such as metalworking fluids or cleaning agents, or are included in packaging. Corrosion inhibitors work through two main mechanisms. Some protect metal surfaces by covering vulnerable areas of the material. Others react with corrosive media and thereby neutralize their effect.

Surface treatment to protect metal products from corrosion

The most common types of metal corrosion can be suppressed through appropriate coatings. For this purpose, a wide range of processes are used in surface treatment and surface pretreatment.

Examples include:

• Formation of conversion coatings (conversion processes)
• Painting
• Powder coating
• Electroplating
• Galvanizing

These coatings prevent environmental media from reacting with the metal surfaces.

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Flocculation is a process in which very small solid particles, finely dispersed in a liquid, clump together into loose aggregates. The fluid and flocs can then be separated with minimal effort. Read on to learn how the process works and how flocculants are used in surface technology.

Mixtures of Liquids and Solids

First, consider the physical and chemical principles of flocculation. Liquids that contain solid particles are called suspensions. In surface technology, such mixtures typically occur during cleaning and rinsing processes, spray painting, and the dewatering of phosphate or paint sludge. The behavior of particles depends on their size, density, and other physical and chemical properties. Large particles with a density that differs significantly from that of the fluid separate relatively quickly from the suspension. They either settle at the bottom (sedimentation) or float to the top (flotation).

The smaller the particles, the slower this process occurs. Particles smaller than 1 µm remain largely unchanged in their distribution in the liquid. Such mixtures are called colloids. Colloids represent an intermediate form between a suspension and a solution. In a solution, solids are distributed at the molecular or atomic level and thus become an integral part of the liquid substance. A more soluble substance can displace the dissolved substance from the solution. This process, known as precipitation, turns a solution into a suspension or a colloid.

Flocculation as a Pre-Step to Separation

Flocculants (coagulants), sometimes referred to as flocculating agents, cause solid particles in a liquid to come together (coagulate). The particles dispersed in the liquid repel each other due to their identical electrical charges. Flocculants with opposite charges neutralize these repulsive forces and enable the particles to clump into small microflocs. To form sufficiently large macroflocs, flocculation aids are added to the mixture. These are usually polymers with very large molecules that capture and hold the microflocs together.

The chemicals used in flocculation and the process parameters must be adapted to each individual mixture. This can be achieved with series of tests in which flow rates, stirrer speeds, retention times, and dosages are varied until a satisfactory result is obtained. The optimal result depends on the subsequent separation steps. The aim is to achieve cost-effective conditions for filtration, sedimentation, or flotation.

How Flocculation Is Conducted

Flocculation can be performed continuously or in batches. In a continuous operation, flocculants and flocculation aids are usually added at the same time. Mixing and floc formation take place in a stirred tank or flow tube. The constant inflow and outflow of the liquid mixture, along with the size of the equipment, determines the retention time. The mixture then flows into a settling tank or is passed through a filter. This method is suitable when only minor fluctuations in wastewater composition are expected. Batch operation allows for more efficient management of composition variations. In addition, flocculant can be added before the flocculation aid. In the first phase, microfloc formation can be intensified by strong mixing at high stirrer speeds. In the second phase, low speeds provide gentle mixing, which promotes floc formation and prevents large macroflocs from breaking apart.

Where Flocculants Are Used

Paint Coagulation

One of the main applications of flocculation in surface technology, is paint detackification. This occurs primarily in paint-laden wastewater from water curtains that capture overspray—the portion of water-based or solvent-based paint that passes by the surfaces of the workpieces. Wastewater contaminated with paints is also created during the cleaning of machines and tools. The main focus here is on recovering the liquid—namely, the water—and reusing it as process water for water curtains and cleaning operations. The paint sludge formed during flocculation can be dried and used for energy recovery. Increasingly, methods are being developed to recover valuable substances from paint sludge.

Kluthe offers coagulation agents under the ISOGOL product line for flocculating solvent-based paints, water-based paints, and mixtures of both. These products typically consist of multiple components. To achieve the best results, the concentrations of flocculants and flocculation aids are adapted to the wastewater present and optimized by adding defoamers and other additives. This results in a detackifying effect on the paint.

Wastewater Treatment

In surface technology, wastewater of varying composition arises during part cleaning, during equipment cleaning as part of maintenance, and in sludge dewatering from pretreatment (e.g., phosphating). Waste water treatment and the recovery of process water generally require several process steps, depending on the substances involved.

Before flocculation, emulsions may be broken down, fats and oils separated, coarse solids filtered out, and dissolved substances precipitated. Flocculants are then used to bind suspended and turbid matter. Sedimentation or filtration can then be used to clarify the wastewater after flocculation.

Der Beitrag What Is Flocculation? erschien zuerst auf Kluthe Magazine.

Global raw material reserves are finite. Humanity consumes more resources than nature can regenerate. At the same time, so much waste is generated that the environment is overwhelmed by the burden. This situation calls for action: recycling conserves resources and reduces environmental impact. If the foundations of life on Earth are to be preserved, recycling must be pursued much more intensively in the future. What types of recycling are there? What contribution can the chemical industry make to recovering valuable materials? Here is what you need to know.

Capabilities and Limits of Recycling

Recovering valuable materials from waste requires a certain amount of energy and, in many cases, processing chemicals. The scale of this effort depends primarily on how many different materials the waste contains and how strongly these are bonded or intermixed.

The chemical industry can provide and develop processes that enable material separation and the transformation of processed substances back into raw materials. Whether the required effort is justified and to what extent sustainable chemistry can be applied, depends on the specific properties of the waste. That is why more effective recycling will only be possible if recyclability is built into product design and manufacturing.

It is also necessary to harmonize the design of components that serve the same function so that they are interchangeable. This has long been the case with screw threads and electrical connectors. A tentative step in this direction is the unification of charging cable connections for cell phones.

Future Recycling: An Overview of Key Types

In the future, three distinct types of recycling will continue to be utilized:

• Material recycling (recovery of raw materials)
• Production waste recycling (direct recycling of industrial waste)
• Product recycling (reuse of materials and components)

Prevention of waste generation always takes precedence over recycling. Since this principle cannot be fully realized in the future, recovery and reuse in industry will become increasingly important. The recycling methods used should require as few process steps as possible, consume little energy, and make use of sustainable chemistry.

Material Recycling

The chemical industry is particularly important for material recycling in the future. If an object or its individual parts can no longer be used, at least the materials they contain should be returned to the economy. Material recycling begins with dismantling products into their components and separating the materials. Through further processing steps that ideally meet the principles of green chemistry, the materials can once again be made available to industry as raw materials.

Material Recycling of Metal, Glass, and Paper

Metals are the easiest to sort and recycle. Different physical properties such as electrical conductivity, density, solubility, or melting point make it possible to automate this process—at least in part. The recovered metals are melted down and cast into new products or semi-finished goods. Metallurgy has used this type of recycling throughout history. The recycling of wastepaper and glass has a similar history. For glass and paper recycling, the chemical industry has developed processes that consume less water, energy, and processing chemicals than producing these materials from virgin raw materials. These methods will also maintain their importance for recycling in the future.

Material Recycling of Plastics

Material recycling is more difficult with plastics. Their closely related physical properties make it harder to separate materials. That is why collecting recyclable materials separately is especially important here. For mixed plastic waste, the chemical industry has different processes (pyrolysis, liquefaction, gasification) that break the material down into its basic building blocks and make them usable again as raw materials. However, these processes require so much energy that energy recovery is still more economical at present. If the chemical industry succeeds in further improving these methods, material recycling of plastics will gain importance in the future.

Production Waste Recycling

In manufacturing, material waste and sometimes defective goods are generated on a regular basis—including in surface treatment. In these cases, composition and properties are well known, and contamination is minimal. As a result, recycling in industry is relatively straightforward. The best-known example is the return of chips and scrap from metalworking into the economy. Collected by type, this waste also generates a worthwhile return.

In the chemical industry, most waste consists of used process chemicals. These can be broken down into their components by various separation processes. Many chemical companies operate facilities in which they reprocess residual materials from their customers. For this purpose, Kluthe founded the subsidiary Rematec. Rematec has developed specialized patented processes that use green chemistry for processing waste from the chemical industry.

Product Recycling

Product recycling preserves either materials or complete components. In this area, reuse and repurposing takes place. Reuse means employing a part again after an overhaul. Repaired and cleaned, the components resume their original function. This is the case, for example, with reusable deposit bottles. Frequently, old car parts also get a second life in this way. Repurposing uses materials for a new purpose. A well-known example is single-use deposit bottles that are collected by type and processed into granulate. New plastic products can then be manufactured from this.

The prerequisite for product recycling is careful separation of waste. For future recycling, deposit systems will therefore become increasingly common. Current practices such as separating household waste and returning electronics or batteries do not attract enough participation from the public and industry. Corresponding deposit systems would provide stronger motivation in the future.

Sources:
[1] https://ethz.ch/content/dam/ethz/special-interest/mtec/sustainability-and-technology/PDFs/ETH%20Global%20Recycling%20Survey%202020.pdf

Der Beitrag Recycling in the Future erschien zuerst auf Kluthe Magazine.

Decarburization in Steel Production

In nature, iron is always found in combination with oxygen as iron oxide. To extract the iron, this bond must be broken. The required chemical reaction is called reduction. The most common reducing agent is elemental C. At elevated temperatures, this element bonds with the oxygen in the iron oxide to form CO2. From the reducing agent’s perspective, this is an oxidation reaction. The overall process is known as a redox reaction. To fully reduce the oxide, an excess of the reducing agent is required. This results in an alloy containing this element, which increases the strength of naturally soft iron.

However, as the content of this element increases, the material becomes more brittle. Decarburization allows adjustment of this content. This adjustment creates steel with the right balance of strength and toughness for its intended use. This is achieved by blowing air through the molten metal, causing the excess to burn off, this process is known as refining. Steel with a content of this element up to 2.06% can be forged and rolled, which is the defining characteristic of steel. Alloys with higher content are classified as cast iron.

Decarburization in Semi-Finished and Finished Components

The mechanical properties of steel depend not only on the amount of this element but also on how it is distributed within the microstructure. This structure forms as the molten metal cools. Once the melting point is reached, individual crystals begin to solidify, and more atoms attach to them. These crystals grow until they meet each other, forming a grain structure. The cooling rate determines whether carbon atoms are incorporated into the crystals or settle at the grain boundaries. When steel is further processed into semi-finished parts, forming processes apply mechanical force and heat. This process alters the microstructure.

To achieve the desired properties for a given application, semi-finished and finished parts are often heat-treated. During hot forming or heat treatment, unintentional decarburization of the surface layer can occur. This happens as carbon atoms migrate to the surface under elevated temperatures.

At the surface, the element reacts with oxygen from the air to form carbon dioxide. This can result in complete removal of the element from surface areas. This condition is known as complete decarburization. If only a reduction in carbon content occurs, the process is referred to as partial decarburization.

Effects of Unintended Decarburization

Decarburization reduces the strength of the material near the surface. In finished parts subjected to bending or stress, this can quickly lead to cracking or structural failure. The resulting damage may necessitate  costly repairs and create significant safety hazards. A further effect occurs with wear and corrosion protection.

Many parts are provided with coatings in subsequent surface technology processes that protect against corrosion and wear. These coatings may lose their adhesion due to reduced carbon levels, weakened surface strength, or the formation of cracks. This can cause them to peel or flake off. To avoid expensive consequences, it is important to check whether heat-treated or hot-formed parts have experienced decarburization before applying any surface coatings.

Measuring the Depth of Decarburization

The depth of the affected surface layer is referred to as the decarburization depth. Determining this value is often necessary for quality assurance or failure analysis. The measurement is done using metallographic methods.

For this, sample sections are cut and polished. Etching reveals the microstructure when examined under a microscope. Decarburized areas appear much lighter than the carbon-rich base material and can be clearly measured.

Preventive Measures

During hot forming, suitable forming lubricants can reduce exposure to air and help prevent decarburization. In surface technology, there are lubricants designed to create dense, tough, and tightly adhering films. Alternatively, designers can plan for machining allowances. These allowances help remove the decarburized surface layer during finishing processes like grinding or milling.

Decarburization During Operation of Machine Components

Decarburization can also take place during  service, especially in machine components made of steel that are exposed to high temperatures. In such cases, surface coatings can help prevent carbon loss, by shielding   the material from direct contact with air.

Der Beitrag What Is Decarburization? erschien zuerst auf Kluthe Magazine.

Foam formation is a common issue in many industrial systems. In such cases, defoamers are needed to either suppress or prevent foaming altogether. This article offers an overview of how foam forms and how foam control agents work.

Foam Formation in Liquids

Foam consists of gas bubbles surrounded by thin membranes, which may be either solid or liquid. Solid foams are used in construction and insulation materials or in sponges. Liquid foams appear in products like foods and personal care items—where they are often beneficial. In process and surface technology systems or in wastewater treatment, however, foam formation is generally undesirable. It can cause reaction mixtures to overflow, disrupt containment, or compromise product quality. Foam forms when a gas mixes with a liquid capable of creating stable membranes, also known as lamellae or films.

This phenomenon often occurs in solutions containing proteins or surfactants. The gas may be introduced externally,  such as air entering agitated or flowing liquids, as in a washing machine,  internally, through chemical or biochemical reactions (e.g. carbon dioxide during fermentation), or through the evaporation of volatile components (as with milk boiling over). To prevent foam from forming, defoamers can be added to the liquid. These agents destabilize the bubble membranes so that any gas bubbles reaching the surface burst immediately.

What Makes an Effective Defoamer?

To effectively suppress foam, a defoamer must meet three key criteria:

1. It should be insoluble in the foaming liquid.
2. It must be able to penetrate the bubble membrane.
3. It should spread efficiently along the gas-liquid interface.

Defoamers are typically dispersed into the foaming liquid as small droplets—a property known as dispersibility. For these droplets to penetrate the foam film, their surface tension must be lower than that of the liquid. Once they reach the interface, they weaken the membrane until it ruptures.

This rupture is aided by a process called spreading, where the defoamer droplet spreads out along the bubble surface. For this to happen effectively, the interfacial tension between the defoamer and the liquid must be low. If it is  too high, the droplet remains intact and cannot spread.

What Are Defoamers Made Of?

The composition of a defoamer depends on the system  in which it is used. Mineral oils are commonly used to prevent foam, thanks to their low surface tension and good distribution in aqueous media which is often aided by small amounts of emulsifiers.

To improve performance, defoamers may include hydrophobic solid particles that help droplets penetrate bubble membranes more easily. Many formulations also contain biocides to prevent microbial growth. Silicone oils are highly effective due to their very low surface tension, although they are often incompatible with water-based systems. Modified silicone oils, however, offer high efficiency in foam control.

Where Are Defoamers Used?

Defoamers have a wide range of applications—across the food industry, pulp and paper manufacturing, textiles, wastewater treatment, surface technology, and metalworking. Foam often arises from ingredients in raw materials or auxiliary substances that were used earlier in the process.

Metalworking

In metalworking, cooling lubricants are used to dissipate the heat generated by friction. These fluids are mixed intensively with air during operation, which promotes foaming.

Excessive foam would interfere with heat dissipation and disrupt circulation of the coolant.

Surface Pretreatment

Surface pretreatment involves cleaning and degreasing metal parts. The cleaning agents often contain surfactants that tend to foam. Defoamers are added to this process to reduce foam levels and prevent overflow during the process.

Surface Coating

Surface coating processes rely on wetting agents to evenly distribute chemicals across the workpiece. These agents often consist of foam-producing surfactants. Foam bubbles on the surface would interfere with wetting and reduce the adhesion of the coating. Trapped foam in paints or coatings can cause defects such as craters or pinholes.

Wastewater Treatment

Foam control is also essential in wastewater treatment. In biological treatment, bacteria break down pollutants while consuming oxygen.

Chemical Processing

There are a number of  operations in the chemical industry which involve close contact between gases and liquids—such as distillation or gas scrubbing. If the chemicals used have a tendency to foam, this can cause serious disruptions, reduce process efficiency, or even pose safety risks. In such cases, foam prevention is critical to maintaining stable and safe operation.

Der Beitrag Avoiding Foam Formation erschien zuerst auf Kluthe Magazine.

What Standards Apply To Tank Truck Cleaning?

Tank trucks (whether trucks or trailers) are designed to carry dry bulk, liquid, or gaseous products in a built-in tank. Many are equipped with hoses, pumps, or blowers to help with unloading. In the United States, tank truck cleaning is regulated by multiple federal agencies depending on the cargo type. The EPA’s Transportation Equipment Cleaning (TEC) Effluent Guidelines (40 CFR Part 442) govern wastewater discharge from tank cleaning facilities. The FDA sets food safety requirements under the Food Safety Modernization Act (FSMA) and the Pasteurized Milk Ordinance (PMO) for Grade A milk.

While the FDA does not directly certify tank wash facilities, it expects shippers and carriers to comply with sanitary transport rules, and many facilities undergo third-party inspection and certification to meet customer requirements. The Department of Transportation (DOT) sets cargo tank specifications and inspection requirements under 49 CFR Part 180. Together, these standards help ensure product quality, environmental protection, and worker safety during cleaning operations.

What Documentation Is Required?

US tank cleaning facilities must provide proper documentation to demonstrate compliance with federal regulations. For food-grade tanks, facilities issue cleaning certificates that must be presented at loading locations before new products can be loaded. The FDA recommends that tank wash facilities performing food industry services receive third-party inspection and certification. EPA-regulated facilities must maintain records under NPDES permit requirements. The benefit of standardized documentation is that cleaning requirements are clearly communicated, and proper procedures are verified regardless of the facility location.

How Are US Cleaning Standards Structured?

Unlike European systems that use letter-number codes, US tank cleaning standards are organized by regulatory category and cargo type:

EPA Categories (40 CFR Part 442):

• Subpart A – Tank trucks and intermodal containers (chemical and petroleum)
• Subpart B – Rail tank cars (chemical and petroleum)
• Subpart C – Tank barges and ocean tankers (chemical and petroleum)
• Subpart D – Food-grade cargo tanks (direct discharge facilities)

FDA Food-Grade Requirements:

• Grade A milk – Must be cleaned at permitted facilities with specific sanitization
• Juice concentrates – Special cleaning protocols to prevent contamination
• Kosher products – Additional certification and rabbinical oversight required
• General food products – Cross-contamination prevention and bacterial control

DOT Cargo Tank Specifications:

• DOT 406 – Non-pressure liquid petroleum products
• DOT 407 – Low-pressure chemical liquids
• DOT 412 – Corrosive liquids
• MC 306/307/312 – Legacy specifications still in service

How Is Compliance Verified?

EPA compliance is verified through NPDES permits for direct dischargers and pretreatment programs for indirect dischargers. FDA compliance involves inspection by federal, state, and local authorities, as well as representatives of shippers and carriers. DOT compliance requires periodic testing and inspection by qualified personnel.

Key areas assessed for tank cleaning facilities include:

• Technical equipment specifications (design, inspection, maintenance, calibration)
• Operating procedures (work instructions, OSHA safety, qualified staff, emissions monitoring)
• Documentation (proper records, incoming inspection, cleaning method selection, final inspection)
• Environmental compliance (waste management, discharge permits, air quality)
• Specialized requirements (food safety, hazmat handling, cross-contamination prevention)
• Facility conditions (buildings, equipment, cleaning systems, waste treatment)

This multi-agency approach ensures that tank truck cleaning meets safety, environmental, and food quality standards while protecting both workers and consumers.

How Does Interior Tank Cleaning Work?

Modern  Cleaning Facilities

State-of-the-art cleaning stations have sophisticated technology, including:

• Extraction systems for liquids and gases
• High-pressure pumps
• Hot water and steam generators
• Tanks for cleaning and disinfecting agents
• Tank washing heads
• Blowers for drying tank interiors
• Measuring and testing equipment
• Wastewater and exhaust air treatment systems
• Control systems

This equipment usually makes it unnecessary for workers to enter the tank. However, if entry is needed, strict safety measures protect workers from slips, falls, hazardous substance exposure, loose residues, and oxygen deficiency.

Incoming Inspection and Choosing the Right Method

When a wash order is received, the facility gets all necessary information about the truck, its last load, the required level of decontamination, and any final inspection steps. The chosen procedure, the use of special cleaners, rinsing or disinfecting agents, and safety measures all depend on this information. Therefore, the company must carefully verify that the details provided match the actual conditions.

Use of Cleaning Agents

Preferred methods for interior  treatment include utilizing cold water, hot water, or steam. If these are not sufficient, special detergents or chemical solutions are needed. The agents chosen must be both effective and compatible with the residues being removed. Using the wrong product can trigger unexpected chemical reactions with leftover cargo. Given the wide variety of loads tank trucks carry, selecting the right cleaning solution is always a challenge.

Helpful advice can come from customers familiar with their cargo. Manufacturers of tank cleaning agents should be reputable providers and offer expert advice on selecting the best cleaning solutions for each cargo type.

Kluthe, for instance, is a member of the ATCN (Association of Tank Cleaning Networks), ensuring high standards internationally and offering solutions for every cleaning challenge, including:

• Interior cleaning with food-grade approval
• Exterior cleaning
• Removal of latex residues
• Removal of resins
• Removal of labels and safety tags
• Final Inspection

The effectiveness of tank cleaning must be verified by tests. At a minimum, a visual and odor check is performed at the tank dome. For trucks that carry chemicals or food products, additional checks — such as the ATP (adenosine triphosphate) test — may be used to confirm that no microorganisms remain inside the tank. Proper truck cleaning is a critical link in the supply chain, safeguarding product quality, environmental protection, and public health.

Der Beitrag Everything You Need to Know About Proper Tank Truck Cleaning erschien zuerst auf Kluthe Magazine.

Gas-to–Liquids is the term used for the conversion of natural gas into liquid hydrocarbons. In several process steps, GtL oil and fuels are produced that differ from those derived from crude oil due to their high purity. GtL fuels burn more cleanly, are biodegradable, and reduce environmental impact. Lubricants produced in this way are skin-friendly and nearly odorless. These advantages justify the complex production process.

Various Gas-to-Liquids Processes Available

In the GtL process, purified natural gas is first converted into synthesis gas, which is then further processed into long-chain hydrocarbons. These form the basis for the production of oil and fuels.

Treating Natural Gas

Natural gas is primarily composed of methane and contains a range of gaseous impurities (water vapor, simple hydrocarbons, carbon dioxide, hydrogen sulfide, nitrogen, noble gases). Before further processing, these substances must be removed. Water and hydrocarbons like ethane, butane, or propane are removed from the natural gas through drying methods. In most cases, absorption methods are used, where a hygroscopic liquid trickles countercurrent through the natural gas and binds the water along with the other substances. The degree of drying is described by the dew point. This is the temperature at which parts of the gas mixture just begin to condense. Carbon dioxide and hydrogen sulfide can be bound by washing the gas with special solvents. When larger amounts of hydrogen sulfide are present, sulfur is produced as a byproduct.

The low boiling points of nitrogen and noble gases allow for separation at exceptionally low temperatures. Nitrogen only liquefies at -321 °F, and noble gases have similarly low boiling points. Methane liquefies at -260 °F. If the gas mixture is cooled to a temperature between -321 °F and -350 °F, the methane is mostly liquid, and the other gases escape from this liquid.

Producing Synthesis Gas

Synthesis gas is a mixture of carbon monoxide and hydrogen. Both components are highly reactive and can be combined into new chemical compounds using suitable methods. Producing these compounds and further processing them is the core of Gas-to-Liquids processes. Before these processes can begin, the relatively stable methane molecules must be split. Synthesis gas from methane is therefore also called split gas. A number of methods can be used to achieve this splitting,

In steam reforming, methane decomposes through the addition of hot steam at temperatures above 1650 °F. The process takes place in the presence of a catalyst.

Another method is partial oxidation, where pure oxygen is introduced at temperatures above 2200 °F. This leads to the partial combustion of methane, yielding carbon monoxide and hydrogen. Ultra-pure synthesis gas can also be produced using a plasma converter, which splits methane into carbon and hydrogen at extremely high temperatures. The resulting carbon reacts with carbon dioxide or steam to form carbon monoxide, thus producing pure synthesis gas.

Gas-to-Liquids: Converting Synthesis Gas into Liquids

Methanol Synthesis

Using copper, zinc oxide, and aluminum oxide compounds as catalysts, methanol can be produced from synthesis gas. This substance can be further processed into gasoline or diesel fuel. In reference to the term Gas-to-Liquids, the production of gasoline is also known as Syngas to Fuel.

Fischer-Tropsch Process

Developed in the 1920s by German chemists Franz Fischer and Hans Tropsch, this GtL process is based on the action of catalysts that temporarily form intermediate compounds during the chemical reaction and then release them again. This enables reactions that would otherwise not occur or would proceed only very slowly. Catalysts such as iron, nickel, or cobalt are used. During the reaction, temperatures range from 320 °F to 570 °F, and pressures reach up to 360 psi. The type of catalyst and the reaction conditions determine the composition of the resulting liquid mixture. A broad spectrum of hydrocarbons is created, with the main goal being the production of synthetic motor oils, lubricants, and fuels. In addition, long-chain wax-like substances can be produced. Byproducts often include oxygenated compounds, such as alcohols and acetone, which are used in the chemical industry as solvents or raw materials. In order to process and use the individual components, the liquid mixture must first be separated.

Processing the Hydrocarbon Mixture

Long-chain, wax-like hydrocarbons are converted into smaller molecules through a process known as cracking, which involves applying heat or using catalysts to break the bond. Fractional distillation uses the varying boiling points of the hydrocarbon components to separate them. This process takes place in tall columns. At the bottom (the sump), part of the liquid is vaporized. At the top (the head), part of the vapor is condensed and returned into the column. As the vapor rises through the column, it encounters the descending condensate. 

The vapor increasingly absorbs the more volatile substances. The condensate becomes enriched with the less volatile components. By drawing from the column at different heights, it is possible to specifically extract individual components (fractions), such as GtL oil or fuels.

Advantages of Gas-to-Liquids Products

Unlike petroleum-based products, products obtained through Gas-to-Liquids processes contain no aromatic hydrocarbons and hardly any sulfur or nitrogen compounds. Most aromatic hydrocarbons are toxic, evaporate easily, and raise both the vapor pressure and flash point of fuels. Sulfur and nitrogen compounds can quickly cause corrosion to metal surfaces, equipment, and pipelines.

The high purity of GtL products is evident from their clear, bright appearance and barely perceptible odor.

Fuels burn with higher efficiency and release virtually no soot particles, sulfur oxides, or nitrogen oxides. As a result, local emissions and environmental impact are reduced. Lubricants from Gas-to-Liquids production are also characterized by good skin compatibility, which is particularly beneficial when using cooling lubricants that workers in metal processing regularly encounter.

Der Beitrag Gas-to-Liquids erschien zuerst auf Kluthe Magazine.

Have you ever accidentally snagged yourself on an overhanging piece of metal? Sharp edges, splinters, or burrs on parts made from wood, plastic, or metal not only compromise aesthetics but can also lead to injuries or hinder further processing. In technical terms, these unwanted formations are referred to as burrs , and in many processes, the formation of burrs is unavoidable. How can metal be deburred to prevent further negative effects?

Burred or Burr-Free?

In metalworking, various methods are used, some of which inevitably create burrs. A burr is technically defined as an unwanted projection of the material, that forms on the surface of a workpiece when the material is displaced, or edges are created. These protrusions extend beyond the workpiece and are therefore undesirable. Burrs commonly occur in primary shaping processes such as metal casting, sintering, or electroforming. They are also unavoidable in pressure-forming methods such as rolling or die forging. Cutting and separation processes like shearing, grinding, or planing, as well as joining processes like welding or casting, also produce burrs.

Various Deburring Methods

Deburring methods ensure the safety, functionality, and aesthetic quality of the workpiece. Numerous approaches exist for deburring metal parts. These include mechanical, chemical, and thermal deburring methods.

Mechanical methods include brushing, where technical brushes, often round brushes, rotate along the edges to remove burrs. There are various types of brushes, including disc brushes, cup brushes, conical brushes, and internal brushes, each suited to specific applications. A process  similar to brushing is grinding which can also be used for deburring, employing methods such as vibratory grinding or flow grinding. These processes can be manual or fully automated. For smaller parts, vibratory grinding is particularly effective,  using abrasive media made of ceramic, plastic, metal (such as steel or bronze), or natural materials like walnut shell granules to remove unwanted burrs.

Within vibratory grinding, techniques such as barrel finishing, vibratory finishing, or drag grinding are differentiated . In barrel finishing, workpieces, abrasive media, and additives are placed in a barrel that rotates or oscillates,  a process which removes burrs through relative motion. A simple manual method for deburring is filing, which uses different file types for various applications. Other mechanical options include milling, countersinking, or other machining processes.

Burrs can also be removed chemically or electrochemically. Chemical deburring immerses workpieces in corrosive or etching solutions to remove edges. Electrochemical deburring uses electrolysis and is particularly suitable for extremely hard metals. In this process, the workpiece acts as an anode, and the tool as a cathode, with material removed through an electrolyte solution, typically an aqueous solution of sodium chloride or sodium nitrate.

Thermal deburring is another option available,  which uses a gas mixture of oxygen, hydrogen, natural gas, or methane ignited in a deburring chamber. This produces remarkably high temperatures, whereby excess oxygen burns off the protruding edges. This method is ideal for thin burrs and can access hard-to-reach areas.

Multiple Deburring Methods Available

Just as there are diverse metalworking methods, there are equally varied deburring techniques. Often, multiple processes are combined to achieve the desired result. Automation has also significantly advanced in this field, making procedures more economical and efficient. Deburring is crucial for subsequent processes, not only to prevent tool wear and  ensure worker safety but also to create a solid foundation for other treatments. For example, a rounded edge allows for uniform coating, which results in long-term corrosion prevention.

What’s Next for the Future?

As in many industrial fields, automation continues to revolutionize the deburring processes, with robotic systems increasingly used as standalone or in subsequent process steps. This makes the entire metalworking process chain even more efficient.

Additionally, existing technologies are being refined, and new methods are continually introduced. One such evolving method is laser-based deburring, which is applicable to both glass and metal. This technique melts the metal’s surface layer using absorbed laser radiation. Laser deburring smooths roughness, precisely rounds edges, and even heals micro-defects.

Finally, high-pressure water jet deburring is worth mentioning. Under high pressure, water is directed at the workpiece through rotating multi-nozzle heads or single jets. The output of intense kinetic energy deforms and subsequently breaks off the burr, as it cannot withstand the impact force.

Der Beitrag Overview: Deburring Metal erschien zuerst auf Kluthe Magazine.