An Informational Brief on Polymer Machining

 

Delrin®, also commonly known as an acetal (polyoxymethylene) homopolymer, is an impact and wear resistant semi-crystalline thermoplastic popular for a broad range of machining applications. To list just a few of its impressive qualities, Delrin offers great stiffness, flexural modulus, and high tensile and impact strength.

Our latest machining guide discusses what goes into machining Delrin and how its considerations differ from other manufacturing options such as metal machining, injection molding, and 3D printing.

How does AIP approach Delrin and its machining process? To start, we’ll explain the difference between machining Delrin, a thermoplastic, and machining thermosets.

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that Delrin is a thermoplastic, but what does that mean exactly?

All polymers can more or less be divided into two categories: thermoplastics and thermosets. The main difference between them is how they react to heat. Thermoplastics like Delrin, for example, melt in the heat, while thermosets remain “set” once they’re formed. Understanding the technical distinction between these types of materials is essential to CNC machining them properly.

What type of thermoplastic is Delrin in particular? Acetal homopolymer is a semicrystalline, engineering thermoplastic.

 

Properties & Grades of Machined Delrin

 

This strong, stiff and hard acetal homopolymer is easy to machine and exhibits dimensional stability and good creep resistance, among several other desirable qualities. Delrin is also known for its superior friction resistance, high tensile strength, and its fatigue, abrasion, solvent and moisture resistance.

The latter quality allows Delrin to significantly outperform other thermoplastics like Nylon in high moisture or submerged environments without losing high-performance in the process. In other words, Delrin can retain its low coefficient of friction and good wear properties in wet environments.

One of the main reasons for Delrin’s popularity is its sheer versatility. The above blend of unique qualities makes Delrin broadly applicable to various industries in the medical, aerospace and energy sectors. For example, you can machine Delrin for medical implants and instruments, or for industrial bearings, rollers, gears, and scraper blades. It is ideal for smaller applications at temperatures below 250 °F (121°C) and can have centerline porosity.

Some of the Delrin grades we regularly machine at AIP include:

 

PTFE-Filled Acetals

 

PTFE (polytetrafluoroethylene) filled grades of Delrin is ideal where impact strength and wear capability are of the highest importance.

 

Glass-Reinforced Acetals

 

Acetals that are reinforced with glass have a much higher strength and greater heat resistance than other grades of Delrin.

 

FDA-Compliant Acetals

 

There are FDA-compliant grades of Delrin available for use in medical and food-related applications.

 

Machining Delrin

 

Machining Delrin

 

It’s true that Delrin is an easy material to work with in terms of machining. It is a very stable material, which makes precise, tight tolerances easier to achieve for this thermoplastic.

While machining, keep in mind that Delrin is sensitive to heat at or above 250 °F (121°C).

Balance the material removal as best as you can to keep your dimensions stable.

We also suggest non-aromatic, air-based coolants to achieve optimum surface finishes and close tolerances. Coolants have the additional benefit of extending tool life as well.

 

Preventing Contamination

 

Contamination is a serious concern when machining polymer components for technically demanding industries such as medical and life sciences. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats, and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

 

Delrin Machining Guide: Supportive Information

 

General Engineering Materials

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An Informational Brief on Polymer Machining

 

Did you know that PPS (or Polyphenylene sulfide) products offer the broadest resistance to chemicals of any high-performance thermoplastic? It’s no surprise that this makes them a popular choice for industrial applications such as wheel bushings, chemical pumps, and compound clamp rings for semiconductor wafers.

 

What goes into machining this thermoplastic, however, and how does it differ from metal machining, injection molding, or 3D printing?

 

With Machining PPS: A Plastics Guides, AIP provides you with a guide to this material and its machining process. First, let’s start with the basics: thermoplastics vs thermosets.

 

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that PPS is a thermoplastic, but what does that mean exactly?

 

All polymers can more or less be divided into two categories: thermoplastics and thermosets. The main difference between them is how they react to heat. Thermoplastics like PPS, for example, melt in heat, while thermosets remain “set” once they’re formed. Understanding the technical distinction between these types of materials is essential to CNC machining them properly.

 

What type of thermoplastic is PPS in particular? It’s a semi-crystalline, high-performance thermoplastic that has an extremely stable molecular structure. The chemical resistance of PPS is often compared to PEEK  and fluoropolymers.

 

 

Properties & Grades of Machined PPS

 

There’s a lot to like about PPS’s material properties. As we mentioned before, PPS has exceptional chemical resistance that makes its bearing grades especially favorable for the chemical industry or caustic environments. In particular, its resistance to acids, alkalis, ketones, and hydrocarbons lend PPS stellar structural performance in harsh chemicals.

 

Additionally, PPS materials are inert to steam as well as strong bases, fuels and acids. Combine that with a low coefficient of thermal expansion and zero moisture absorption, and you get a material that is ideal for continuous use in corrosive or hostile environments. PPS has replaced stainless steel for a lot of industrial applications for this reason.

 

Most impressively, PPS will not dissolve at temperatures below approximately 200 °C, no matter what solvent is used. In fact, all grades of PPS share UL94 V-0 flammability ratings, without requiring flame retardant additives, resulting in an excellent material for aircraft where flame resistance is paramount.

 

Some grades of PPS that we regularly machine at AIP Precision Machining include Ryton®, Fortron®, TECHTRON®, TECTRON® HPV, TECATRON PVX and TECATRON CMP.

 

 

Machining PPS

 

Annealing PPS

The process of annealing and stress-relieving PPS reduces the likelihood of surface cracks and internal stresses occurring in the material. Post-machining annealing also helps to reduce stresses that could potentially contribute to premature failure. AIP’s special annealing process for PPS is designed to take the specific properties of PPS into account, and we advise anyone working with PPS to hire a manufacturer that understands its unique demands.

 

Machining PPS

PPS is a fantastic material for machining. Its low shrinkage and stable dimensional properties make it easy to machine to incredibly tight, precise tolerances. A unique characteristic of PPS is that when dropped, it sounds just like a piece of metal hitting the floor.

 

PPS, like many other thermoplastics, is notch sensitive, so take care to avoid sharp corners in design. We recommend carbide tipped cutting tools for working with PPS as they provide an ideal speed and surface finish.

 

We also suggest non-aromatic, water-soluble coolants, such as pressurized air and spray mists, to achieve optimum surface finishes and close tolerances. Coolants have the additional benefit of extending tool life as well. No known coolants attack nor degrade PPS.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats, and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

 

To learn more, read our article “Three Ways to Ensure Sterilization in Your Plastic Machined Medical Applications.”

 

 

PPS Machining Guide: Supportive Information

Chemical Resistant Materials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

 

Explore Our Inventory

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How Aluminum Got Dethroned by Thermoplastics in Aerospace

 

Cup holders. Magazines. Suit cases. Aircraft engines. Here’s a riddle, what do these items all have in common? If you’re an aircraft operator, the answer is obvious: they all add weight, making them a drain on your fuel costs.

 

If weight is one of the main operating costs of an aircraft, then it’s no surprise that airlines want to lose a few pounds. Over the last 35 years, AIP has witnessed firsthand the incredible weight savings that can be gained from using lightweight polymers and composites for aerospace applications.

 

How Airlines “Slim Down” Operating Costs


How much can an ounce cost you? Plenty. In the case of United Airlines, removing a single ounce from its in-flight magazine has translated to saving $290,000 a year. Yes, a single ounce can hit an airline with up to six digits in costs.

 

If thinner paper can have such an impact on your bottom line, then you can imagine the significant cost savings that can come from manufacturing lighter aerospace components. What’s the most lightweight solution for aircraft operators today? We have one word for you: plastics.

 

What Makes Plastics the Secret to Aircraft Fuel-Efficiency


Aluminum was popular during the “Golden Age of Aviation” because of its strength and durability as well as its lightness when compared to other metals like steel. As a result, many aircraft components have traditionally been metal, from aircraft interiors, to landing gear, aircraft engines and structural components.

 

Now consider the fact that polymer and composite materials can be up to ten times lighter than metal. It’s no wonder that as more thermoplastic materials come on the market and new manufacturing opportunities arise, metal replacement has been seen as one of the best opportunities to reduce airline weight.

 

How big is the impact of switching from aluminum to plastic parts like PEEK and ULTEM in aerospace applications? Operators can earn weight savings of up to 60%. This translates to lower lifetime fuel costs, reduced emissions and extended flight range for operators.

 

“Weighing” the Option of Plastics in Aerospace


Weight alone is a massive reason to consider thermoplastics for aerospace, but weight isn’t the only factor at play in material selection.

 

After all, wood is lighter than metal, but there’s a reason we don’t build spruce airframes like the first plane from the Wright brothers: it wouldn’t be safe today to fly a wooden plane! Aerospace components need to be able to survive in corrosive, harsh environments as well as provide resistance to high temperatures.

 

In other words, it’s crucial that your mission-critical components aren’t just lightweight, but also high-performing.

 

At AIP, we carefully apply our decades of material expertise to select the right material for your application’s needs. Remember that your aerospace plastics manufacturer should understand the unique demands of your industry and your application, and have experience machining the material you require.

 

Want to learn more about how AIP reduces costs for aircraft operators?

Read how machined polymer components can take a load off aircraft interiors in our aerospace case study.

 

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An Informational Brief on Polymer Machining

 

Machining RadelRADEL is a PPSU (or Polyphenylsulfone) widely considered to be the highest-performing of Solvay’s sulfone polymers. It’s no surprise then that we’ve regularly machined RADEL at AIP Precision Machining over the past three decades.

 

With superior impact strength and outstanding resistance to stress cracking, RADEL offers exceptional hydrolytic stability and toughness across a wide temperature range, making it a favorite of the medical, electronics manufacturing, and aerospace industries.

 

AIP has over 35 years of experience machining complex components from RADEL and various other thermoplastic materials. We are providing this Machining RADEL as yet another insightful technical brief about our polymer component manufacturing process, and how it differs from that of metal machining, injection molding, or 3D printing.

 

 

Machining Thermoplastics vs Thermosets

 

Plastic CNC machining is affected by what type of material you’re machining. Technical expertise is key to polymer machining, which is why you have to know the polymer structure and properties of RADEL before machining it.

 

There are two basic types of polymers: thermoplastics and thermosets. Thermoplastics soften in heat and become more fluid, while thermosets cross-link during curing, which eliminates the risk of a product re-melting in heat. Since these categories react differently to chemicals and temperature, it’s important to know that RADEL is a thermoplastic.

 

To be specific, RADEL PPSU is an amorphous, high-performance thermoplastic that is lightweight, available in bone-white or black colors, and can be either transparent or opaque. Like other amorphous thermoplastics, such as ULTEM, RADEL is thermoform capable, translucent and easily bonded with adhesives or solvents.

 

 

Properties & Grades of Machined RADEL

 

RADEL’s reputation as a high-performance thermoplastic is well deserved. RADEL PPSU has an impressive heat deflection temperature of 405°F (207°C) and is inherently flame retardant with low NBS smoke evolution, making it an ideal material choice for aircraft interiors. In addition, its retention of mechanical properties is superior to all other amorphous transparent polymers.

 

With improved impact and chemical resistance over PSU and PEI, RADEL PPSU has been tested for notched izod impact resistance as high as 13 ft.-lbs/in. It can endure over 100 joules of force without shattering, even with repeated exposure to moisture and extreme temperatures.

 

These inherent qualities allow RADEL PPSU to withstand unlimited steam autoclaving and provide RADEL with excellent resistance to EtO, gamma, plasma and chemical sterilizations as well. Unsurprisingly, its extreme thermal properties make RADEL ideal for reusable medical instruments and other applications where sterilization is key.

 

Not all grades of RADEL PPSU share the same exact properties, of course. Choosing the grade of your material that best meets your needs is an important part of AIP Precision Machining’s expert material knowledge.

 

One grade of RADEL PPSU we machine regularly at AIP Precision Machining is RADEL R5500.

 

RADEL R5500

RADEL R5500 is a unique polymer grade that meets the stringent aircraft flammability requirements of 14CFR Part 25, while also being a biocompatible, medical-grade resin that is FDA and NSF approved for food and beverage contact. From that, it’s clear that RADEL R5500 can be used for a wide range of applications, whether it’s for aircraft interiors, electronic burn-in sockets or surgical instruments. RADEL R5500 can be polished to a mirror finish and is available in both opaque and transparent colors.

 

 

Machining RADEL PPSU

 

Annealing RADEL PPSU
RADEL PPSU, like many polymers, can be received in the form of rods, sheets, tube or film. As we mentioned before, amorphous thermoplastics like RADEL are especially sensitive to stress-cracking, so stress-relieving through an annealing process is highly recommended before machining.

 

Annealing RADEL greatly reduces the likelihood that surface cracks and internal stresses will occur from the heat generated. Post-machining annealing also helps to reduce stresses that could potentially contribute to premature failure.

 

If the machine shop you are working with does not have a computer controlled annealing oven for plastics, then “head for dee hills” as they are obviously not RADEL machining experts.

 

Machining RADEL PPSU

Non-aromatic, water-soluble coolants are most suitable for ideal surface finishes and close tolerances. These include pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

 

Many metal shops use petroleum-based coolants, but these types of fluids attack amorphous thermoplastics like RADEL PPSU. Many past experiences have shown parts going to customer without cracks, only to develop cracks over time due to exposure to metal machine shop fluids. Be sure to use a facility like AIP who machines polymers and only polymers.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats, and machines only plastics, with any sub-manufactured metalwork processed outside our facility. This minimizes the potential for metallic cross-contamination.

 

 

RADEL Machining Guide: Supportive Information

 

Medical Sector Biomaterials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

Amorphous Materials

Explore Our Inventory

 

or request a quote here.

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An Informational Brief on Polymer Machining

 

AIP Precision Machining has worked with many thermoplastics over the past three decades, including TORLON: a PAI, or polyamide-imide, engineered by Solvay Specialty Polymers.

 

Due to its reliable performance at severe levels of temperature and stress, TORLON is ideal for critical mechanical and structural components of jet engines, automotive transmissions, oil recovery, off-road vehicles and heavy-duty equipment.

 

AIP has over 35 years of experience machining complex components from TORLON and various other thermoplastic materials. We are providing this Machining TORLON Guide as yet another insightful technical brief about our polymer component manufacturing process, and how it differs from that of metal machining, injection molding, or 3D printing.

 

Plastic CNC Machining

Before discussing the process of machining TORLON, it’s important to understand exactly what plastic machining is.

 

CNC (Computer Numerical Control) machining is a process in the manufacturing sector that involves the use of computers to control machine tools. In the case of plastic machining, this involves the precise removal of layers from a plastic sheet, rod, tube or near net molded blank.

 

The early history of CNC machining is almost as complex as a modern CNC system. The earliest version of computer numerical control (CNC) technology was developed shortly after World War II as a reliable, repeatable way to manufacture more accurate and complex parts for the aircraft industry. Numerical control—the precursor to CNC—was developed by John Parsons as a method of producing integrally stiffened aircraft skins.

 

Parsons, while working at his father’s Traverse City, Michigan-based Parsons Corp., had previously collaborated on the development of a system for producing helicopter rotor blade templates. Using an IBM 602A multiplier to calculate airfoil coordinates, and inputting this data to a Swiss jig borer, it was possible to produce templates from data on punched cards.

 

Parsons’ work lead to numerous Air Force research projects at the Massachusetts Institute of Technology (MIT) starting in 1949. Following extensive research and development, an experimental milling machine was constructed at MIT’s Servomechanisms Laboratory.

 

Due to the many different kinds of polymers and composites, it’s important to have strong technical expertise of polymer materials when machining plastic components; some plastics are brittle, for example, while others cut similarly to metal. The challenge of plastics is their wide range of mechanical and thermal properties which result in varying behavior when machined. Therefore, it’s important to understand the polymer structure and properties of TORLON if you’re machining it.

 

Thermoplastics vs Thermosets

When it comes to polymers, you have two basic types: thermoplastics and thermosets. It’s crucial to know which one you’re working with due to distinct differences between how these two main polymer categories react to chemicals and temperature.

 

Thermoplastics soften when heated and become more fluid as additional heat is applied. The curing process is completely reversible as no chemical bonding takes place. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties.

 

They possess the following properties:

• Good Resistance to Creep

• Soluble in Certain Solvents

• Swell in Presence of Certain Solvents

• Allows for Plastic Deformation when Heated

 

Thermosets plastics contain polymers that cross-link together during the curing process to form an irreversible chemical bond. The cross-linking process eliminates the risk of the product re-melting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances.

 

They possess the following properties:

• High Resistance to Creep

• Cannot Melt

• Insoluble

• Rarely Swell in Presence of Solvents

 

Phenolic, Bakelite, Vinyl Ester and Epoxy materials would be considered examples of a thermoset, while ULTEM, PEEK, DELRIN and Polycarbonate materials are examples of thermoplastics.

The thermoplastic category of polymers is further categorized into Amorphous and Crystalline polymers per the figure below:

 

Machining Ultem
 

TORLON is considered an amorphous, high-performance thermoplastic. Most amorphous polymers are thermoform capable, translucent and easily bonded with adhesives or solvents.

 

 

Various Grades of Machined TORLON

 

What makes TORLON unique is how it possesses both the incredible performance of thermoset polyimides and the melt-processing advantages of thermoplastics. The compressive strength of (unfilled) TORLON PAI is double that of PEEK and 30% higher than that of ULTEM PEI. In fact, TORLON is considered the highest performing, melt-processible plastic.

 

High-strength grades of TORLON retain their toughness, high strength and high stiffness up to 275°C. This and its impressive wear resistance allow TORLON to endure in hostile thermal, chemical and stress conditions considered too severe for other thermoplastics. TORLON is also resistant to automotive and aviation fluids, making it a favorite of aerospace and automotive engineers.

 

One concern of using TORLON is that its moisture absorption rate is not as low as other high-performance plastics, so special care should be taken when designing components for wet environments.

 

There’s more than one particular type of TORLON PAI you can machine, and each has slightly different properties for perfecting this material’s use in different applications.

 

Here are several grades of TORLON PAI we machine regularly at AIP Precision Machining.

 

TORLON 4203

TORLON 4203 is the unfilled or natural grade of TORLON PAI that outperforms other grades with the best impact resistance and the most elongation. TORLON 4203 PAI can be used for a variety of applications but due to its good electrical properties, it is commonly machined for electronic equipment manufacturing, valve seals, bearings and temperature test sockets.

 

TORLON 4301

TORLON 4301 is a wear-resistant grade of TORLON PAI containing PTFE and graphite. It has high flexural and compressive strength with a low coefficient of friction, as well as good mechanical properties. Typical applications of 4301 are anything that requires strength at high temperature with wear resistance and low friction. This material is useful for parts such as thrust washers, spline liners, valve seats, bushings, bearings and wear rings.

 

TORLON 4XG

TORLON 4XG is a 30% glass-reinforced extruded grade of PAI well suited to higher load structural or electronic applications. When you need a high degree of dimensional control, this grade offers the high-performance you need. Various uses of TORLON 4XG include burn-in sockets, gears, valve plates, impellers, rotors, terminal strips and insulators, among others.

 

TORLON 4XCF

TORLON 4XCF is a 30% carbon-reinforced extruded grade of PAI that has the lowest coefficient of thermal expansion and the most impressive fatigue resistance of all plastic materials. This uncommon grade works well as a replacement for metal applications as well as mission-critical aerospace components, in addition to impellers, shrouds and pistons.

 

 

Machining TORLON

 

Annealing TORLON
TORLON PAI can be received in the form of rods, sheets, tube or film. Stress-relieving before machining through an annealing process is crucial, as it reduces the likelihood that surface cracks and internal stresses will occur from the heat generated. This also helps prevent any warping or distortion of your plastic materials.

 

TORLON additionally benefits from post-machining annealing to reduce any stress that could contribute to premature failure. Extruded TORLON parts, such as those machined from TORLON 4XCF and TORLON 4XG, benefit from an additional cure after machining to further enhance wear resistance; this is unique to PAI. Proper annealing of Torlon can require more than seven days in special ovens at AIP.

 

If the machine shop you are working with does not have a computer controlled annealing oven for plastics, then “head for dee hills” as they are obviously not TORLON machining experts.

 

Machining TORLON

An important consideration to have when machining TORLON PAI is how abrasive it is on tooling. If you’re machining on a short run, carbide tooling can be used, but polycrystalline (PCD) tooling should be considered for lengthier runs, machining for tight tolerance and any time you are working with reinforced grades.

 

Another thing to keep in mind when machining extruded TORLON shapes is that they have a cured outer skin, which is harder than interior sections. The outer skin offers the best wear and chemical resistance. If wear resistance and chemical resistance needs to be optimized, extruded TORLON should be re-cured.

 

TORLON PAI will nearly always require the use of coolants due to its stiffness and hardness. Non-aromatic, water-soluble coolants are most suitable for ideal surface finishes and close tolerances. These include pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

 

Many metal shops use petroleum-based coolants, but these types of fluids attack TORLON. Many past experiences have shown parts going to customer without cracks, only to develop cracks over time due to exposure to metal machine shop fluids. Be sure to use a facility like AIP who machines polymers and only polymers.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

 

 

TORLON Machining Guide: Supportive Information

Medical Sector Biomaterials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

Amorphous Materials

 

 

Explore Our Inventory

 

or request a quote here.

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An Informational Brief on Polymer Machining

 

 

One of the high-performance thermoplastics that AIP works with is ULTEM: a PEI, or polyetherimide. ULTEM was developed by General Electric Plastics Division (Now SABIC) back in the early 1980s. Polyetherimide (PEI) is an amorphous, amber-to-transparent thermoplastic.

 

Among other uses, ULTEM is popularly used in medical instrument components, aircraft interiors, missile and defense-related components, electrical insulation parts, and semiconductor equipment components.

 

AIP has over 35 years of experience machining complex components from ULTEM and various other thermoplastic materials. We are providing this Machining ULTEM as yet another insightful technical brief about our polymer component manufacturing process, and how it differs from that of metal machining or injection molding.

 

Plastic CNC Machining

Before discussing the process of machining ULTEM, it’s important to understand exactly what plastic machining is.

 

CNC (Computer Numerical Control) machining is a process in the manufacturing sector that involves the use of computers to control machine tools. In the case of plastic machining, this involves the precise removal of layers from a plastic sheet, rod, tube or near net molded blank.

 

The early history of CNC machining is almost as complex as a modern CNC system. The earliest version of computer numerical control (CNC) technology was developed shortly after World War II as a reliable, repeatable way to manufacture more accurate and complex parts for the aircraft industry. Numerical control—the precursor to CNC—was developed by John Parsons as a method of producing integrally stiffened aircraft skins.

 

Parsons, while working at his father’s Traverse City, Michigan-based Parsons Corp., had previously collaborated on the development of a system for producing helicopter rotor blade templates. Using an IBM 602A multiplier to calculate airfoil coordinates, and inputting this data to a Swiss jig borer, it was possible to produce templates from data on punched cards.

 

Parsons’ work lead to numerous Air Force research projects at the Massachusetts Institute of Technology (MIT) starting in 1949. Following extensive research and development, an experimental milling machine was constructed at MIT’s Servomechanisms Laboratory.

 

Due to the many different kinds of polymers and composites, it’s important to have strong technical expertise of polymer materials when machining plastic components; some plastics are brittle, for example, while others cut similarly to metal. The challenge of plastics is their wide range of mechanical and thermal properties which result in varying behavior when machined. Therefore, it’s important to understand the polymer structure and properties of ULTEM if you’re machining it.

 

Thermoplastics vs Thermosets

 

When it comes to polymers, you have two basic types: thermoplastics and thermosets. It’s crucial to know which one you’re working with due to distinct differences between how these two main polymer categories react to chemicals and temperature.

 

Thermoplastics soften when heated and become more fluid as additional heat is applied. The curing process is completely reversible as no chemical bonding takes place. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties.

 

They possess the following properties:

  • -Good Resistance to Creep
  • -Soluble in Certain Solvents
  • -Swell in Presence of Certain Solvents
  • -Allows for Plastic Deformation when Heated

 

Thermosets plastics contain polymers that cross-link together during the curing process to form an irreversible chemical bond. The cross-linking process eliminates the risk of the product re-melting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances.

 

They possess the following properties:

  • -High Resistance to Creep
  • -Cannot Melt
  • -Insoluble
  • -Rarely Swell in Presence of Solvents

 

Phenolic, Bakelite, Vinyl Ester and Epoxy materials would be considered examples of a thermoset, while ULTEM, PEEK, DELRIN and Polycarbonate materials are examples of thermoplastics.

 

The thermoplastic category of polymers is further categorized into Amorphous and Crystalline polymers per the figure below:

 

Machining Ultem

 

ULTEM is considered an amorphous, high-performance thermoplastic. Most amorphous polymers are thermoform capable, translucent and easily bonded with adhesives or solvents.

 

Various Grades of Machined ULTEM

 

ULTEM PEI (polyetherimide) is a high-strength amorphous polymer. PEI has more than just excellent heat and flame resistance. It can perform continuously up to 340°F thanks to its high flammability rating. That’s not all, though: this polymer is also hydrolysis resistant and highly acid-resistant. ULTEM PEI also outperforms both Nylon and DELRIN with the highest dielectric properties of thermoplastic materials.

 

While ULTEM is relatively chemical resistant relative to lower end amorphous polymers, you will need to carefully assess the chemical compatibility for the application. This material is also more notch sensitive than RADEL PPSU.

 

There’s more than one particular type of ULTEM PEI you can machine, and each has slightly different properties for perfecting this material’s use in different applications.

 

Here are two grades of ULTEM PEI we machine regularly at AIP Precision Machining:

 

ULTEM 1000

ULTEM 1000 is an unfilled grade of ULTEM PEI. This is considered the “virgin” or “neat” grade of the resin… this basically means no-fillers. It’s well suited to interior aircraft components thanks to its impressive flame resistance and limited oxygen index. Its resistance to UV and gamma radiation and low NBS smoke evolution, low thermal conductivity, and ability to retain 85% of its tensile strength at 10,000 hours of immersion in boiling water make it useful for a variety of structural food processing components. ULTEM 1000 is also FDA, USDA, and NSF-compliant, as well as USP Class VI-compliant.

 

ULTEM 2300

ULTEM 2300 or Glass Filled ULTEM 4

ULTEM 2300 is a 30% glass-reinforced grade of ULTEM PEI. This gives the high-performance polymer greater tensile strength and rigidity than ULTEM 1000, plus greater dimensional stability, meaning less movement with temperature or load changes. It possesses low thermal conductivity and excellent electrical insulation properties. Additionally, it reacts well to autoclave sterilizations, making it useful for reusable medical applications where repeated cycles are required. ULTEM 2300 is commonly used for structural components where light weight is valuable such as found in many aerospace and defense-related components. ULTEM 2300 is a common direct replacement for aluminum as it has a similar coefficient of thermal expansion to 6061-T6.

 

Machining ULTEM

 

Annealing ULTEM

ULTEM can be received in the form of rods, sheets, tube or film. Stress-relieving before machining through an annealing process is crucial, as it reduces the likelihood that surface cracks and internal stresses will occur from the heat generated. This also helps prevent any warping or distortion of your plastic materials.
If the machine shop you are working with does not have a computer controlled annealing oven for plastics, then “head for dee hills” as they are obviously not ULTEM machining experts.

 

Machining ULTEM

Glass-reinforced ULTEM will require coolants during drilling operations, as they are especially notch sensitive. Non-aromatic, water soluble coolants are most suitable for ideal surface finishes and close tolerances. These include pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

 

Many metal shops use petroleum-based coolants, but these types of fluids attack ULTEM. Many past experiences have shown parts going to customer without cracks, only to develop cracks over time due to exposure to metal machine shop fluids. Be sure to use a facility like AIP who machines polymers and only polymers.

 

Another difference between glass-reinforced ULTEM and non-filled ULTEM is that non-reinforced thermoplastics can be machined with high-speed steel cutting tools. You’ll want hard metal tools for reinforced materials.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

 

ULTEM Machining Guide: Supportive Information

 

Medical Sector Biomaterials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

Amorphous Materials

 

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Thermoplastics in Medical ApplicationsWhen it comes to choosing a thermoplastic material for your medical applications, product durability, agency approval, biocompatibility and cleanliness aren’t just desirable—they’re essential. Beyond even that, though, a host of other factors must be considered when determining which high-performance plastic or composite material to use for an implant, orthopedic surgical guides, body fluid contact components, spinal devices, or surgical instruments. Medical product applications are becoming more and more advanced due to critical performance and alignment requirements as well as the need for radiolucency to support minimally invasive procedures. Therefore, the choice of plastic material specified for a given application as well as a manufacturer with battle-hardened experience is the critical first step in your decision process.

 

AIP has well over three decades of expertise with thermoplastic materials, and understands how plastics react when machined. We are one of a very select few companies able to hold incredibly tight tolerances in plastic parts. AIP has been successfully audited by some of the most stringent OEMs in the orthopedic and medical device industries, and are ISO 13485:2016, ISO 9001:2015 and FDA registered.

 

Here are just a few initial, yet critical considerations that take place when we determine the thermoplastic to best suit your particular medical or life science application.

 

Biocompatibility

 

If your components are going to come into contact with body tissue or fluids, then those components must be biocompatible per ISO 10993; if the manufacturer you are working with is not familiar with this standard and cannot provide you with this certification for the material, then move on to a manufacturer with medical industry knowledge. This is especially true if the polymers will undergo long-term contact with body tissues and fluid, such as when used as an implant. Polymers can undergo degradation due to biochemical and mechanical factors in the body, which results in ionic attack and formation of hydroxyl ions and dissolved oxygen. In turn, this can lead to tissue irritation, inflammation, and other reactions with body-like corrosion, wear and potential death. Due to this, very few polymers are available as medical grade for medical application, with an even smaller amount considered a candidate for implants.

 

AIP Precision Machining includes machined PEEK implants among its many capabilities for custom medical applications precisely due to PEEK’s biocompatibility. PEEK is also inert to body fluids, making it exceptional for bone surgery as well as areas of traumatology and orthopaedics. Another valuable trait of PEEK is that this material has a very similar modulus to that of human bone. The similar modulus to bone reduces the potential for stress shielding. Stress shielding is common with metallic implants whereby the metal implant and bone do not become one nor work in unison to form a single construct. By using Invibio’s PEEK Optima or Solvay’s Zeniva PEEK as an implant material, the bone and PEEK will grow into a single construct mimicking the bone’s natural tendency to repair the fracture or fusion.

 

Sterilization Compatibility

 

Plastics react differently to various sterilization methods, and if a product is not a single-use device and involves body tissue and fluid contact, then it may regularly undergo sterilization. The usual sterilization methods are radiation (gamma/e-beam), chemical (ETO), or autoclave (steam). ETO is rarely a concern, but radiation and autoclaving both require resistance from plastics. Several radiation resistant thermoplastics are:

 

 

When it comes to autoclaving, the best polymers for resistance are PPSU and PEEK, with both capable of handling exposure to thousands of cycles.

 

AIP takes the matter of sterilization seriously and ensures the highest level of sanitation down to the sub-molecular level for its products. By designing, stress relieving and machining only plastics, AIP significantly reduces the threat of metallic cross-contamination and therefore allows for the highest hygienic products possible.

 

Chemical Resistance

 

A polymer can be exposed to plenty of disinfection chemicals in a hospital. That exposure can deteriorate plastics, and negatively affect part performance. Polymer chains can be affected by isopropyl alcohol, bleaches, and peroxides. Semi-crystalline polymers like PP, PE, PTFE and PEEK can be expected to have better chemical resistance than amorphous polymers like ABS and PC. However, it’s important to check the performance to be certain of resistances, as exceptions can take place.

 

With decades of experience working with thermoplastics, AIP guarantees extreme chemical resistance in its material selection for your medical applications.

 

Electrical & Thermal Properties

 

Dielectric strength and thermal resistance are necessary for medical devices enclosed in areas that require high heat resistance. Thermoplastics such as PC (Polycarbonate), PC blends, PPS (polyphenylene sulfide), PEI and PS (polystyrene) blends have electrical properties that perform well, some even at elevated temperatures.

 

AIP’s material library includes thermoplastics that exhibit extreme thermal performance, and we are familiar with machining them in applications for medical life & sciences.

 

Mechanical Properties

 

Properties such as tensile and compressive strength, wear resistance, impact strength, and bending stiffness also must be considered when choosing your thermoplastic. Engineered thermoplastics such as PC, PEEK, PPSU, POM, PEI and reinforced grades of these same materials (glass, aramid and carbon fillers) perform very well in this respect, making them ideal for a variety of climate conditions, such as during transportation.

 

AIP provides thermoplastics that show extreme wear resistance, x-ray visibility or invisibility and high structural performance.

 

These are just a few of the many considerations that take place when choosing the right plastic for your medical applications. AIP offers you our full material consultancy from concept to completion, so that together, we find the right thermoplastic for your projects.

 

 

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Your Brief Guide to Polymer Materials

 

When it comes to polymers, you have two basic types: thermoplastics and thermosets. When machining plastic, it’s crucial to know which one you’re working with due to distinct differences between how these two main polymer categories react to chemicals and temperature.

 

Thermoplastics soften when heated and become more fluid as additional heat is applied. The curing process is completely reversible as no chemical bonding takes place. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties. 

 

Thermoplastics possess the following properties:

  • • Good Resistance to Creep
  • • Soluble in Certain Solvents
  • • Swell in Presence of Certain Solvents
  • • Allows for Plastic Deformation when Heated

 

Thermosets contain polymers that cross-link together during the curing process to form an irreversible chemical bond. The cross-linking process eliminates the risk of the product re-melting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances.

 

Thermosets possess the following properties:

  • • High Resistance to Creep
  • • Cannot Melt
  • • Insoluble
  • • Rarely Swell in Presence of Solvents

 

Phenolic, Bakelite, Vinyl Ester and Epoxy materials would be considered examples of a thermoset, while ULTEM, PEEK, TORLON and Polycarbonate materials are examples of thermoplastics.

 

The thermoplastic category of polymers is further categorized into Amorphous and Crystalline polymers per the figure below:

 

 

Most amorphous polymers are thermoform capable, translucent and easily bonded with adhesives or solvents. One example of this would be TORLON.

 

Semi-crystalline polymers are difficult to bond or thermoform, but possess better chemical resistances, electrical properties and a low coefficient of fiction. An example of a semi-crystalline polymer would be PEEK.

 

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Plastic CNC Machining

A Brief History of CNC Machining & Plastic Machining

 

An important part of working with any company is understanding what they do; at AIP Precision Machining, plastic CNC machining is what we’ve done best for the past 35 years.

 

CNC (Computer Numerical Control) machining is a process in the manufacturing sector that involves the use of computers to control machine tools. In the case of plastic machining, this involves the precise removal of layers from a plastic sheet, rod, tube or near net molded blank. This subtractive manufacturing differs from additive manufacturing techniques, such as 3D printing.

 

The History of CNC Machining

The early history of CNC machining is almost as complex as a modern CNC system. The earliest version of computer numerical control (CNC) technology was developed shortly after World War II as a reliable, repeatable way to manufacture more accurate and complex parts for the aircraft industry. Numerical control—the precursor to CNC—was developed by John Parsons as a method of producing integrally stiffened aircraft skins.

 

Parsons, while working at his father’s Traverse City, Michigan-based Parsons Corp., had previously collaborated on the development of a system for producing helicopter rotor blade templates. Using an IBM 602A multiplier to calculate airfoil coordinates, and inputting this data to a Swiss jig borer, it was possible to produce templates from data on punched cards.

 

Parsons’ work lead to numerous Air Force research projects at the Massachusetts Institute of Technology (MIT) starting in 1949. Following extensive research and development, an experimental milling machine was constructed at MIT’s Servomechanisms Laboratory.

 

CNC machining can be used for a wide variety of materials, but at AIP Precision Machining, we solely machine polymers and composites. This significantly reduces the threat of metallic cross contamination in our products, allowing us to provide the most hygienic devices and components for our clients.

 

The Complexity of Polymer Machining

There are benefits to machining polymer components over metallic materials, but it’s a mistake to assume both machine the same way. Due to the many different kinds of polymers and composites, it’s important to have strong technical expertise of polymer materials when machining plastic components; some plastics are brittle, for example, while others cut similarly to metal.

 

The challenge of plastics is their wide range of mechanical and thermal properties which result in varying behavior when machined. Therefore, it’s important to understand the polymer structure and properties of a material if you’re machining it. Having expert material knowledge is essential for this reason, which is why AIP has it as one of our core offerings.

 

One example of this would be knowing if you’re machining a thermoset or a thermoplastic.

 

Here are a few polymer machining guides that discuss the specifics of plastic machining various materials:

 

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With over two decades of experience machining precision plastic and composite parts for the Aerospace & Defense industry, AIP Precision Machining knows that weight and strength are critical for your flight ready hardware. That’s why we’ve carefully selected, machined, and tested all our thermoplastic materials to various aerospace industry standards. Our lightweight polymers and composites have stable chemical and corrosion resistance, as well as improved strength to weight ratios when compared to exotic alloys and non-ferrous metals. AIP’s polymer and composite materials maintain their properties even at high temperatures.

 

Here are some examples of thermoplastic materials commonly used in the Aerospace & Defense industry.

 

ULTEM-PEI

ULTEM – PEI

ULTEM has one of the highest dielectric strengths of any thermoplastic material, meaning it works very efficiently as an electrical insulator. Being resistant to both hot water and steam, ULTEM can withstand repeated cycles in a steam autoclave and can operate in high service temperature environments (340F or 170C). ULTEM also has one of the lowest rates of thermal conductivity, allowing parts machined from ULTEM to act as thermal insulators. ULTEM is FDA and NSF approved for both food and medical contact, therefore, is an excellent choice for aircraft galley equipment such as ovens, microwaves and hot or cold beverage dispensing systems. UL94 V-O flame rating with very low smoke output makes this material ideal for aircraft interior components.

 

 

CELAZOLE - PBI

CELAZOLE – PBI

CELAZOLE provides the highest mechanical properties of any thermoplastic above 400F (204C) and offers a continuous use operating temperature of 750F (399C). CELAZOLE has outstanding high-temperature mechanical properties for use in aircraft engine and other HOT section areas. This impressive lightweight material retains 100% tensile strength after being submerged in hydraulic fluid at 200°F for thirty days.

 

 

 

 

RYTON – PPS

RYTON’s inherent fire retardancy, thermal stability, and corrosion resistance makes it perfectly suited for aerospace applications, while its dimensional stability means even the most intricate parts can be molded from RYTON with very tight tolerances. RYTON is typically used for injection molded parts, however, there is limited availability of extruded rod and plate for machining.

 

 

 

 

DURATRON PI

VESPEL or DURATRON – PI

Like RYTON, VESPEL is dimensionally stable and has fantastic temperature resistance. It can operate uninterrupted from cryogenic temperatures to 550°F, with intermittent to 900°F. Thanks to its resistance to high wear and friction, VESPEL performs with excellence and longevity in severe environments—like those used in aerospace applications. VESPEL is a trademark material of DuPont and can be provided in direct formed blanks or finished parts directly from DuPont. AIP provided precision machined components from DuPont manufactured rod and plate stock. VESPEL is typically used in high temperature and high-speed bearing and wear applications such as stator bushings.

 

 

 

TORLON

TORLON or DURATRON – PAI

DURATRON PAI’s extremely low coefficient of linear thermal expansion and high creep resistance deliver excellent dimensional stability over its entire service range. DURATRON PAI is an amorphous material with a Tg (glass transition temperature) of 537°F (280°C). DURATRON PAI stock shapes are post-cured using procedures developed jointly by BP Amoco under the TORLON trade name and Quadrant under the DURATRON trade name. A post-curing cycle is sometimes recommended for components fabricated from extruded shapes where optimization of chemical resistance and/or wear performance is required. TORLON parts are used in structural, wear and electrical aerospace applications.

 

 

 

TECHTRON

TECHTRON – PPS

TECHTRON has essentially zero moisture absorption which allows products manufactured from this material to maintain extreme dimensional and density stability. TECHTRON is highly chemical resistant allowing it to operate while submerged in harsh chemicals. It is inherently flame retardant and can be easily machined to close tolerances. It has a broader resistance to chemicals than most high-performing plastics and can work well as an alternative to PEEK at lower temperatures.

 

 

 

RADEL

RADEL – PPSU

With high heat and high impact performance, RADEL delivers better impact resistance and chemical resistance than other sulfone-based polymers, such as PSU and PEI. Its toughness and long-term hydrolytic stability means it performs well even under autoclave pressure. RADEL R5500 meets the stringent aircraft flammability requirements of 14CFR Part 25, allowing the aircraft design engineer to provide lightweight, safe and aesthetically pleasing precision components for various aircraft interior layouts. RADEL can be polished to a mirror finish and is FDA and NSF approved for food and beverage contact.

 

 

 

KEL-F

KEL – F

Kel-F is a winning combination of physical and mechanical properties, non-flammability, chemical resistance, near zero moisture absorption, and of course outstanding electrical properties. This stands out from other thermoplastic fluoropolymers, as only Kel-F has these characteristics in a useful temperature range of -400°F to +400°F. In addition, it has tremendously low outgassing and offers extreme transmissivity for radar and microwave applications. KEL-F and NEOFLON are used in many aircraft and ground-based random applications.

 

 

 

PEEK

PEEK

PEEK can be used continuously to 480°F (250°C) and in hot water or steam without permanent loss in physical properties. For hostile environments, PEEK is a high strength alternative to fluoropolymers. PEEK carries a V-O flammability rating and exhibits very low smoke and toxic gas emission when exposed to flame. PEEK is an increasingly popular replacement for metal in the aerospace industry due to its lightweight nature, mechanical strength, creep and fatigue resistance, as well as its ease of processing. Its exceptional physical and thermal characteristics make it a versatile thermoplastic polymer in many aerospace applications. AIP has provided flight control, fuel system, interior, engine and aerodynamic related PEEK components for various aircraft OEM and MRO providers worldwide.

 

 

 

KYNAR - PVDF

KYNAR – PVDF

KYNAR has impressive chemical resistance at ambient and elevated temperatures, as well as good thermomechanical and tensile strength. It’s extremely durable due to its weather-ability and toughness even in the most severe environments and is easy to machine in addition to being flame-resistant. KYNAR components are typically found in pipe fitting and various fuel or other fluid related precision manifolds or connectors.

 

 

 

 

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