Plastics are essential to the current manufacturing sector because they are generally accessible, most of them are inexpensive, and they work with well-liked production techniques like injection molding, 3D printing, and CNC precision milling.
CNC machining is a subtractive manufacturing technique that involves carefully removing material from a solid block of material with spinning tools and drills to shape the component.
In terms of producing plastic components, CNC machining is more accurate than injection molding.
Additionally, compared to many other manufacturing techniques, CNC machining is more compatible with a wider variety of plastics, which makes it an attractive option for many product teams to produce parts through machining.
What is Derlin
An acetal polymer known by the trade name Delrin is widely utilized in CNC machining because of its remarkable characteristics. The substance, which is also referred to as POM (Polyoxymethylene) or Delrin plastic, may be further machined using procedures like injection molding and 3D printing. There are many grades of Delrin that each have a unique combination of characteristics.
Due to its high tensile strength, low friction and high wear resistance, creep and warp resistance, and general toughness and longevity, Delrin plastic serves as a great alternative to metal. Superior density, reduced moisture absorption, and chemical resistance to hydrocarbons, solvents, and neutral chemicals are only a few of the qualities of the Delrin substance.
What is PEEK
The PAEK family of materials includes the high-performance engineering thermoplastic known as PEEK, or polyether ether ketone. The semi-crystalline material, which has outstanding strength, wear resistance, and abrasion resistance, and maintains its qualities even at high temperatures, is utilized for a variety of industrial parts and components.
PEEK grades are comparable to PPS in terms of chemical and water resistance. PEEK, on the other hand, has a melting point of 343°C and can withstand temperatures up to 250°C without permanently losing its physical qualities. It can also be utilized in hot water or steam. PEEK is a high-performance plastic that may be found in granule, filament, and bar or rod forms for CNC machining. Typically, it is either medical-grade or industrial-grade.
What is Teflon/PTFE
Tetrafluoroethylene (TFE) is a fluoropolymer and thermoplastic. Teflon is a trademark of the American chemical corporation Chemours, a division of the industry titan DuPont (now DowDuPont).
It is resistant to almost all industrial chemicals and solvents, withstands extremely high temperatures, and is a superb insulator. It is frequently used for items that need an anti-stick surface because of its low coefficient of friction, making it an excellent choice for situations where components would move against one another.
Teflon, which is a polymer of tetrafluoroethylene (PTFE), has exceptional dielectric qualities that are stable with frequency and temperature. It doesn’t spark easily and doesn’t encourage the spread of flames. The bulk density of Teflon is exceptionally high. Some of its features include of:
Considerations for Choosing CNC Machining Plastics
The machinability of a material is influenced by its physical characteristics. As a result, the outcomes you may get from your workpiece will differ depending on the material. The size and shape of your workpiece might alter while working with plastics, either during or even after machining. Design engineers must thus consider material qualities to guarantee that their designs can be manufactured. The following should be considered while CNC machining plastics.
Thermal Expansion
At high temperatures, almost every substance expands and takes on volume. The tooling used in precision CNC milling generates heat when it comes into contact with the material. In comparison to metals, plastics have a greater coefficient of thermal expansion. As a result, they may experience a larger size shift as a result of machining. Understanding how each plastic responds to heat input from machining is therefore essential. It’s vital to consider about how much heat the plastic will be exposed to. The ability to adhere to dimensional limitations will be impacted by these variables. The heat deflection temperature of a material also shows when it will begin to distort readily when exposed to high temperatures. You might need to take this into account when choosing your final materials to make sure the part is appropriate for the application.
Strength and Hardness
You can take into account a plastic’s strength and hardness characteristics to make sure it can withstand the demands of its intended use. However, a material’s behavior during machining is also influenced by these characteristics. A material’s tensile strength can have an influence on how it creates chips, which can alter the ultimate surface polish. Hardness can also influence how chips develop, and for particularly soft materials, gouging can happen if the operator doesn’t take the necessary measures. Additionally, the wear life of the tooling used can be affected by the hardness and tensile strength of a material. When machining metals and ceramics, this is typically a more important factor to take into account.
Effects of Moisture and Chemicals
Some polymers can absorb moisture from the air or coolant or suffer negative effects from specific substances. Even air-conditioned spaces or sealed containers may be required to keep them. The material’s dimensions might fluctuate as a result of moisture and chemical reactions, which makes it more difficult to maintain exact tolerances. They may even cause the polymers to lose all of their stability and strength.
Aesthetics
Design elements like appearance and related characteristics like light transmittance may be crucial. In such case, you have fewer options for plastic materials. A rough surface finish must be avoided throughout the machining process in order to prevent any negative effects on transparency or light transmission.
The function of the plastic component
A part’s function always determines how it is built. Thus, the material you should use for the plastic CNC machining procedure will ultimately depend on the purpose of your product. The environment in which the CNC plastic component will be used will have the most influence on the material choice. Derlin, for instance, is the perfect option if your plastic item will operate in an environment with low to no friction requirements. This is due to the material’s well-known low friction, which makes it appropriate for the procedure.
Requirements for Post-Processing Treatments
In order to improve their aesthetic value, some pieces may need post-processing procedures. All plastics, however, may not be easily matched with all kinds of finishes. So, while choosing the plastic for CNC machining, take this into account as well.
Advantages and disadvantages of machining Delrin, Teflon and PEEK
Machining Delrin
Metals may be perfectly replaced by Delrin when making parts. It does, however, have benefits and downsides, just like every other material used in production. Its benefits and drawbacks are as follows:
Advantages
Delrin is lighter than metals. However, while being lightweight, it has a high tensile strength and can sustain shock loads both once and again.
Delrin has special qualities that make it simple to handle and process with both traditional and cutting-edge equipment. It also offers greater flow rates than other resins, enabling a more even filling of the mold’s thin walls.
Polymer Delrin resists wear and tear. Due to its stiffness and great mechanical strength, it may be used to create a broad variety of high-performance Delrin components with lengthy service lives.
Delrin may be used to create moving and sliding components that don’t need to be maintained. Its inherent lubricity also makes it a smart choice for components that operate with little to no friction.
Delrin has superior spring-back properties compared to metals. Additionally, it works well for snap-fit and buckle applications because to its high strain and spring-back capacity.
Delrin may be used in humid environments since it does not absorb moisture. Additionally, it is resistant to various chemical solvents as well as organic solvents like gasoline. It is corrosion-resistant because to its resistance to moisture. For many industrial operations, it is a perfect material.
Disadvantages
Delrin has a few further drawbacks that prevent its full use in product manufacture. Several of its drawbacks are listed below:
Solvent resistance is a strong suit of Delrin material. It will be harmed by some acids, though, such chlorine and mineral acids. Because of this, even extremely low chlorine levels in drinkable water can result in water pipe breaks.
Making storage containers for food is not the best use for delrin. This is because Delrin contaminates food when it mixes with acidic food ingredients.
Delrin has trouble connecting to one another because of its chemical makeup. In order to bind Delrin, adhesives like polyurethane and epoxies have been used. But doing so necessitates the assistance of adhesive specialists, which raises the price.
The substance delrin is combustible. Only a Class A fire extinguisher can put out the flames of the burning substance.
Machining PEEK
PEEK machining has several benefits, which may be divided into two groups: the intrinsic material benefits of PEEK and the particular process benefits of utilizing a CNC machine to manufacture PEEK material.
Advantages
Machining PEEK has the following material advantages:
PEEK material offers excellent resistance to corrosive substances. It offers resistance comparable to nickel steel and can maintain its non-corrosive chemical structure with the majority of metals even at high temperatures. Only strong sulfuric acid may dissolve this plastic under normal circumstances.
Components of a machine or instrument that are made of PEEK keep their chemical structure and characteristics in damp environments. It works best in moist settings, pressured hot water, or steam because of its hydrolysis resistance even at higher temperatures.
Additionally, PEEK components may function in the presence of strong ionizing radiation. It is more gamma radiation resistant than polystyrene, as was already mentioned.
Due to its excellent processing capabilities, PEEK material ensures exceptional workability during plastic CNC precision milling. Despite being a highly high-temperature thermoplastic material, it can be treated using several material processing techniques.
These techniques include melt spinning, injection molding, and extrusion molding. This compatibility is guaranteed by PEEK’s strong thermal breakdown characteristics and high-temperature workability. Additionally, this thermoplastic is a self-extinguishing substance during fire; it emits little to no hazardous gas or smoke.
PEEK and other high-temperature thermoplastics provide strong impact resistance and keep their shape at high temperatures. It has high dimensional stability and a low coefficient of linear expansion. Of all the polymers, PEEK has the strongest capacity to withstand stress and fatigue. Additionally, it has exceptional creep resistance qualities (the ability of a substance to deform slowly over a long period of exposure to stress). This quality makes it a good material that can handle high machining stress.
Additionally, PEEK offers outstanding wear resistance and a low coefficient of friction. Because of this, it can continue to retain excellent wear resistance across a variety of external physical circumstances, including pressure, surface roughness, temperature, and speed in relation to the contact surface.
Disadvantages
Machining PEEK has a number of disadvantages. A few of these include
To reduce internal tension and fractures brought on by heat, special care is needed.
required to anneal
Ineffective heat transfer.
It could crack if you drill too far.
Machining Teflon/PTFE
Teflon has the following material advantages when machined:
Process advantages
Disadvantages Of Machining Teflon
Rich
richhan@view-well.com
