Category: Machining Guide

Machining Ultra-High Molecular Weight Polyethylene (UHMWPE): A Plastics Guide

July 30, 2020
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Source: Plastics Today

Ultra-high molecular weight polyethylene (UHMWPE) is part of the umbrella of polyethylene thermoplastics. Other peers include low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Although UHMWPE embodies many similar qualities as HDPE, it is much stronger and carries a significantly higher resistance to chemicals, wet environments and withstands abrasion 15 times greater than carbon steel. This is why, among its many applications, it is the most common material for total joint replacements.

 

AIP has over 37 years of experience machining complex components from thermoplastics like ultra-high molecular weight polyethylene. In this insightful technical brief, we will discuss what goes into machining UHMWPE and how it differs from other manufacturing options such as metal machining, injection molding, and 3D printing.

 

Properties of UHMWPE

 

Keeping information about the properties of a thermoplastic beforehand is always beneficial. This helps in selecting the right thermoplastic for a project. Furthermore, it assists in evaluating if the end use requirement would be fulfilled or not. Here are some of the key properties of ultra-high molecular polyethylene:

 

UHMWPE is a part of the family of polyethylene thermoplastics. One of its defining characteristics is its toughness and high impact strength; this is due to long polymer chains with a molecular mass between 3.5 and 7.5 million amu. With a long chain, it has great bearing load which strengthens the intermolecular interactions. The result is a tough material that withstands incredible impacts and extreme temperature fluctuations.

 

Properties Value Units Method
Resistance to Weathering Excellent – –
Tensile Strength at Break 24 MPA ASTM D638
Elongation at Break 300 % Elongation at Break
Thermal Expansion 20 10-4K ASTM D696
Coefficient of Friction P = 0.05 N/m2, v = 0.6m/s 0.29 – –
Impact Strength No break kJ/m2 ASTM D256
Compressive Stress at 10% Deformation 3,000 psi PSI ASTM 695
Dielectric Strength 44 kV.mm ISO 60243-1
Melting Point 130 – 136
266 – 277		 C
F		 –
Service Temperature Short term.120
Long term. 90		 C –
Flammability HB – UL94

 

*This information represents typical figures intended for reference and comparison purposes only.
Key features of ultra-high molecular weight polyethylene:

 

  • Low moisture absorption
  • Chemical resistant
  • High thermal conductivity
  • Low dielectric constant
  • FDA compliant
  • Low coefficient of friction
  • Self-lubricating
  • Resistant to UV radiation

 

Applications of UHMWPE

 

Common applications for UHMWPE include: food processing equipment, water treatment, conveyor lines, wear strips, bearings, gears, pistons, valves, marine equipment and wet environments that require harsh cleaning. Let us take a closer look at some of the major applications of this mighty material.

 

Fiber
UHMWPE as a fiber is branded under the name Dyneema and Spectra. They have yield strengths as high as 2.4 GPa (2.4 kN/mm2 or 350,000 psi) and density as low as 0.97 g/cm3. High-strength steels have comparable yield strengths, and low-carbon steels have yield strengths much lower (around 0.5 GPa). Dyneema and Spectra have a strength-to-weight ratio eight times that of high-strength steels.

 

This fact makes UHMWPE a top-pick for industries requiring heavy-duty protection and strength from a fiber. Applications include personal armor and vehicle armor for military and defense industries.

 

Civil applications containing UHMWPE fibers are cut-resistant gloves, bow strings, climbing equipment, automotive winching, fishing line, spear lines for spearguns, high-performance sails, suspension lines on sport parachutes and paragliders and yacht rigging.

 

Medical
Since the 1960s, UHMWPE has also been the biomaterial of choice for total joint arthroplasty in orthopedic and spine implants. Clinical studies continue to work to improve its effectiveness for hip, knee and spine implants.

 

In 1998 one advancement introduced highly cross-linked UHMWPE. These new materials are cross-linked with gamma or electron beam radiation (50-105 kGy) and then thermally processed to improve their oxidation resistance. They have since become the standard of care for total hip replacements.

 

As of 2007, clinicians started incorporating anti-oxidants into UHMWPE for hip and knee arthroplasty bearing surfaces. The anti-oxidant improves oxidation resistance to the UHMWPE without the need for thermal treatment.

 

Marine
UHMWPE is a polymer that retains its properties in extreme environments, such as the marine industry. It is often used in marine structures and vessels for the mooring. UHMWPE forms the contact surface between the floating vessel and the fixed one. UHMWPE is chosen as the facing of fender systems for berthing structures because of the following properties: wear resistance, impact resistance and low friction (wet and dry conditions).

 

Grades of UHMWPE

 

At AIP, we machine various grades and brand name ultra-high molecular weight polyethylene. Branded names include the following: TIVAR®, POLYSTONE® M, LENNITE®, HOSTALEN GUR®, UHMW-PE, CERAM P, ULTRAPOLY CL6, ULTRAPOLY W1.

 

Our close ties with the industry’s leading plastics manufacturers give us even further insight and access to technical help in material selection, sizing and manufacturing procedures. Whatever your application, our machinists can help you in material selection, sizing and manufacturing techniques from concept to completion.

 

Machining UHMWPE

 

Annealing UHMWPE

Thermoplastics are prone to stress cracking and premature part failure when placed under high heat and tensile load. Therefore, annealing is crucial if you want a quality, precision machined part out of the stock shape. The annealing process at AIP greatly reduces the chances of these stresses occurring from the heat generated during machining UHMWPE and other polymers. Our machinists use computer controlled annealing ovens for the highest quality precision machining.

Generally, UHMWPE should be heated between 135 C to 138 C in an oven or liquid bath of silicone oil or glycerine. It is then cooled down at a rate of 5 C/hour to at least 65 C. Afterwards, it should be wrapped in an insulating blanket for 24 hours to bring to room temperature.

Machining UHMWPE
We recommend non-aromatic, water-soluble coolants because they 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.

 

Some companies machine both metals and plastics, which has detrimental outcomes for machined polymer products. Many past experiences have shown parts going to customer without cracks, only to develop surface cracks and warping over time due to exposure to metal machine shop fluids. Be sure to use a facility like AIP that only machines polymers.

 

Preventing Contamination
Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical 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. This allows us to de-risk the process from metallic cross contamination.

 

Ultra-high Molecular Weight Polyethylene Machining Guide: Supportive Information

 

Medical Sector Biomaterials

 

Miscellaneous Materials

 

Quality Assurance Certifications

 

UHMWPE is one of several thermoplastics we machine for the medical and life sciences sector.

 

Learn about 8 other common thermoplastics and their medical applications.

 

Read Our Blog
 

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Machining Polypropylene (PP): A Plastics Guide

May 18, 2020

An Informational Brief on Polymer Machining

 

Since it was first polymerized in 1954 by Karl Rehn and Giulio Natta, polypropylene (PP) has become one of the leading polymer choices for a wide array of applications from automotive to commercial to medical.

 

Polypropylene plays a significant role in medical applications due to its high chemical resistance, lightweight, radiolucency and repeated autoclavability. Furthermore, medical grade PP exhibits good resistance to steam sterilization and moisture resistance. Disposable syringes, instrument or implant caddies and fluid delivery systems are the most common medical application of polypropylene. Other applications include medical vials, diagnostic devices, petri dishes, intravenous bottles, specimen bottles and surgical trays.

 

Want to learn more about the polymers we precision machine for medical applications?

 

Read Our blog

 

AIP has over 35 years of experience machining complex components from thermoplastics like polypropylene. In this insightful technical brief, we will discuss what goes into machining polypropylene and how it differs from other manufacturing options such as metal machining, injection molding, and 3D printing.

 

Homopolymer vs Copolymer – What’s the Difference?

 

The two main types of polypropylene available on the market are homopolymers and copolymers. Although they share many properties, there are some differences that help guide machinists and engineers in choosing the right material for their PP application. For the purposes of this blog, we will briefly review the differences between PP homopolymer and PP copolymer.

 

PP Homopolymer PP Copolymer
  • High strength to weight ratio and stiffer & stronger than copolymer
  • Good chemical resistance and weldability
  • Good processability
  • Good impact resistance
  • Good stiffness
  • Food contact acceptable
  • Suitable for corrosion resistant structures
  • Bit softer but has better impact strength; tougher and more durable than homopolymer
  • Better stress crack resistance and low temperature toughness
  • High processability
  • High impact resistance
  • High toughness
  • Not preferable for food contact applications

 

Properties of Polypropylene

 

Keeping information about the properties of a thermoplastic beforehand is always beneficial. This helps in selecting the right thermoplastic for an application. It also assists in evaluating if the end use requirement would be fulfilled or not. Here are some of the key properties of polypropylene:

 

Polypropylene is characterized by excellent chemical resistance in corrosive environments, resistance to cleaning agents and solvents and by a high heat deflection temperature.

 

It also has great dimensional stability and is fairly easy to machine. As noted above, it is available in heat-stabilized homopolymer and copolymer grades. At AIP, we machine POLYSTONE P, PROPYLUX HS and HS2, PROTEUS LSG HS PP from MCAM, TECAPRO MT and TECAFINE PP from Ensinger. Interesting to note is that both the PROPYLUX and TECAPRO heat stabilized PP grades are available in both standard and custom colors for medical sorting and sizing organization. Whatever your application, our machinists can help you in material selection, sizing and manufacturing techniques from concept to completion.

 

Melting Point of Polypropylene – The melting point of polypropylene occurs at a range.

 

Homopolymer: 160 – 165°C
Copolymer: 135 – 159°C

 

Density of Polypropylene – PP is one of the lightest polymers among all commodity plastics. This feature makes it a suitable option for lightweight\weight saving applications.

 

Homopolymer: 0.904 – 0.908 g/cm3
Random Copolymer: 0.904 – 0.908 g/cm3
Impact Copolymer: 0.898 – 0.900 g/cm3

 

Machining Polyproylene

 

Annealing Polypropylene

Due to its low annealing temperature, PP, like any polymer under heat and pressure, has a tendency to deform during machining. The annealing process at AIP greatly reduces the chances of these stresses occurring from the heat generated during machining PP and other polymers. Our machinists use computer controlled annealing ovens for the highest quality precision machining.

 

Machining Polypropylene

As a part of the polyolefin family, PP is semi-crystalline, which means that it can be machined at tight tolerances. We recommend non-aromatic, water-soluble coolants because they are most suitable for ideal surface finishes and close tolerances.

 

Bear in mind that polypropylene has variable levels of thermal expansion and will move a great deal with slight temperature changes. Some examples are pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

 

Some companies machine both metals and plastics, which has detrimental outcomes for clients. 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 that only machines polymers.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical 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. This allows us to de-risk the process from metallic cross contamination.

 

Polypropylene Machining Guide: Supportive Information

 

ISO 13485:2016 Certification
ISO 9001:2015 Certification

 

Need a machined part from medical grade polypropylene?

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What’s the deal with the .002 mm precision tolerance?

January 7, 2020

Learn about AIP’s precision machining capabilities for mission-critical components.

 

High-performance precision plastics require high-performance precision CNC machining.  CNC machines, or computer numerically controlled machines, are electro-mechanical devices that use tools at varying axes (usually 3-5) to produce a physical part from a computer design file.

 

Our modern society runs on CNC machined plastic components – from everyday household piping to critical spinal implants.  The breadth of materials, shapes and industries served is endless.

At AIP, we precision machine parts for industries such as the aerospace & defense, medical & life sciences and power & energy.  Each part that is CNC machined comes with design specifications and dimensional tolerances.  Our machinists are capable of crafting parts at .002 mm tolerance, which can make a whole lot of a difference in the performance of a mission-critical part.

 

Let’s back up a moment though.  What are dimensional tolerances? And how do you know if your project should demand a tighter tolerance?  Read on in this month’s blog to find out.

 

Let’s Talk About Tolerance

 

What are machining tolerances?

In CNC machining terms, tolerance, or dimensional accuracy, is the amount of deviation in a specific dimension of a part caused by the manufacturing process.  No machine can perfectly match specified dimensions.  The designer provides these specifications to the machinists based on the form, fit and function of a part.

 

How are tolerances measured?   

CNC machines are precise and measured in thousandths of an inch, referred to as “thou” among machinists.  Any system is usually expressed as “+/-”; this means that a CNC machine with a tolerance of +/- .02 mm can either deviate an extra .02 mm from the standard value or less .02 mm by the standard value.

 

A precision machining tolerance scale
 

Why are tolerances critical?

Tolerances keep the integrity and functionality of the machined part.  If the component is manufactured outside of the defined dimensions, it is unusable, since the crucial features are not fulfilling the intent of the design.

 

How close can a tolerance get?

Tolerance depends on the material that you use and the desired purpose of the design.  In plastics machining, the tolerances can be from +/- 0.10 mm to +/- 0.002 mm.  Tighter tolerances should only be used when it is necessary to meet the design criteria for the part.

 

When .002 mm Matters

 

What is the .002 mm difference?  In many industries, such as the medical industry, it is crucial to machine parts with extreme precision so that they can interact with human tissue or other medical devices.  In fact, when it comes to manufacturing medical applications, subtractive manufacturing (CNC machining) provides tighter tolerances than additive manufacturing (3-D printing).

 

 

Color Pencil compared to precision machining
(AIP PEEK Eye Implant)
 

Tight tolerances like the .002 mm are important because plastics are machined to interact with other parts.  In particular, CNC milled or turned plastics are unique designs for limited quantities, such as custom-made brackets and fasteners, or components for prototyping purposes.

 

One of the most critical considerations when applying tolerances is to take into account fits. This refers to how shafts will fit into bushings or bearings, motors into pilot holes, and so on. Depending on the application, the part may require a clearance fit to allow for thermal expansion, a sliding fit for better positioning, or an interference fit for holding capability.

 

As with anything that is precision machined, tighter tolerances demand time and skill.  Make sure to work with a certified company like AIP that has the infrastructure and expertise to complete your project with unmatched precision and unrivaled experience.

 

Let our team go to work for you

 

With 36+ years of experience in the industry, our dedicated craftsmen and ties to leading plastic manufacturers allow us to provide you with unrivaled knowledge and consulting in material selection, sizing, manufacturing techniques and beyond to best meet your project needs.

 

AIP offers a unique combination of CNC machining, raw material distribution, and consultancy as a reliable source for engineering information for materials such as PEEK, TORLON, ULTEM and more.

 

We are AS 9100D compliant; certified and registered with ISO 13485 and ISO 9001 and standards in our commitment to machining quality custom plastic components for specialized industrial sectors. Quality assurance is included as an integral part of our process and is addressed at every step of your project, from concept to completion.

 

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Machining High Density Polyethylene (HDPE): A Plastics Guide

November 26, 2019

An Informational Brief on Polymer Machining

 

HDPE Product ImageAmong the many polymer materials we machine at AIP, High Density Polyethylene (HDPE) is a common material choice for commercial polymer applications.  HDPE is part of the Polyethylene (PE) family of thermoplastic polymers with variable crystalline structure.

 

First developed in the 1950s by German and Italian scientists Karl Ziegler and Giulio Natta, PE has become one of the most widely produced plastics in the world.  Polyethylene comes in several compounds each with various applications: Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE) and Ultrahigh Molecular Weight Polyethylene (UHMW) are some of the most well-known.

 

For example, you will find LDPE most likely in the grocery store as plastic wrap or grocery bags.  In contrast, HDPE, due to its high density, is much better suited for construction components like a drain pipe.  And UHMW can be machined into high performance applications for medical devices, bulletproof vests and industrial wear components.

 

In this machining guide, we will discuss what goes into machining HDPE and how its considerations differ from other manufacturing options such as metal machining, injection molding, and 3D printing.

 

A Brief History of Plastic CNC Machining

 

How does AIP approach HDPE and its machining process? To start, let’s explore what plastic machining is, specifically CNC machining.

 

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.

 

Shortly after World War II, the earliest version of CNC technology was developed as a dependable, repeatable way to manufacture more accurate and complex parts for the aircraft industry.  John Parsons is credited with developing numerical control – a method of producing integrally stiffened aircraft skins.

 

While working at the family-owned, Michigan-based business – Parsons Corp., John 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.

 

In 1949 Parson’s templates were applied to Air Force research projects at MIT.  Following extensive research and development, an experimental milling machine was constructed at MIT’s Servomechanisms Laboratory.

 

Machining polymers and composites is a precise science that requires strong technical expertise.  For instance, some plastics are brittle, while others melt at a specific temperature.  These diverse mechanical and thermal properties result in varying behaviors when CNC machined.  Thus, it is imperative to understand the polymer structure and qualities of HDPE if you’re machining it.

 

Ever wonder about the differences in cost and process among 3D Printing, Injection Molding or Plastic Machining?

 

Check out our blog:
“Settling the Debate”

 

 

Properties of HDPE

 

HDPE is a high impact, high density crystalline thermoplastic.  It also has a low moisture absorption rate and good chemical and corrosion resistance.  Compared to its sister polymer LDPE, HDPE offers much greater impact resistance and tensile strength.  This polymer has a melt temperature of 266 F (130 C).  Its tensile strength is 20 MPa (2,900 PSI); to put this number into perspective, a slab of concrete may be able to withstand 3,000 PSI.

 

Oftentimes, people use HDPE in everyday home appliances and commercial containers.  Due to its strength and corrosion resistance, it’s a common candidate for garbage bins, laundry detergent cartons and cutting boards.  It is also safe to use for food contact such as milk cartons.

 

PE is available in sheet stock, rods, and even specialty shapes in a multitude of variants (LDPE, HDPE etc.), making it a good candidate for subtractive machining processes on a mill or lathe. However, colors are usually limited to white and black.

 

Machining HDPE

 

Annealing HDPE

Annealing greatly reduces the chance that surface cracks and deformation due to internal stresses will occur from the heat generated during machining HDPE. AIP uses computer controlled annealing ovens for the highest quality precision machining of all thermoplastics.  Talk to our engineers about any questions you have about the annealing of a specific polymer.

 

Machining HDPE

As a crystalline thermoplastic, HDPE can be machined at tight tolerances; remember dimensional stability and strength!  AIP recommends non-aromatic, water-soluble coolants because they are most suitable for ideal surface finishes and close tolerances. Keep in mind however that HDPE has a very low CTLE and therefore will move quite a bit with slight temperature changes.  Some examples are pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

 

Some companies machine both metals and plastics, which has detrimental outcomes for clients. 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 that only machines polymers.

 

Preventing Contamination

 

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace 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.  This allows us to de-risk the process from metallic cross contamination.

 

HDPE (High Density Polyethylene) Machining Guide: Supportive Information

 

Miscellaneous Materials Guide

ISO 13485:2016 Certification

ISO 9001:2015 Certification

Learn more about HDPE and its applications in other industries

 

Discover what HDPE can do

 

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Machining Polysulfone (PSU): A Plastics Guide

October 16, 2019

An Informational Brief on Polymer Machining

 

Among the many plastics AIP precision machines, PSU (Polysulfone) is a high-performance thermoplastic made from UDEL Resin.  This particular thermoplastic is able to retain its properties in temperatures ranging from -150°F (-100°C) to 300°F (150°C).  This precision machined plastic also has excellent radiation stability, chemical resistance as well as hydrolysis resistance for continuous use in hot water and steam.

 

In many applications, PSU is used over stainless steel parts or aluminum as the material is seven times lighter than stainless steel and can also be steam-cleaned in areas like chemical labs.  For this reason, it has a wide range of uses in the following industries:  aerospace and defense, medical and life sciences as well as specialized industrial applications.

 

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

 

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that PSU 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 PSU, 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.

 

The table below outlines the main properties of thermoplastics versus thermosets:

 

Thermoplastics

Thermosets
  • Good Resistance to Creep
  • Soluble in Certain Solvents
  • Swell in Presence of Certain Solvents
  • Allows for Plastic Deformation when Heated
  • High Resistance to Creep
  • Insoluble
  • Rarely Swell in Presence of Solvents
  • Cannot Melt

 

From there, thermoplastics are categorized into amorphous or crystalline polymers per the figure below:

 

Source: https://www.ejbplastics.com
 

Based off of the chart, PSU is an amorphous, high performance engineering thermoplastic, meaning its molecular structure is randomly formed.  The result is that amorphous materials soften gradually with temperature increase, making them easy to thermoform.

 

Properties of PSU (Polysulfone)

 

Amorphous thermoplastics are usually translucent in color, but the gradients vary.  PSU, for instance, is amber semi-transparent.

 

Since they are isotropic in flow, they have better dimensional stability than semi-crystalline plastics and are less likely to warp.  Thermoplastics like PSU offer superior impact strength and are best used for structural applications.

 

The materials bond well using adhesives. They also tend to offer excellent resistance to hot water and steam, good chemical resistance, stiffness and strength. PSU and PEI are especially good examples of amorphous thermoplastics offering these qualities.

 

Machining PSU (Polysulfone)

 

Annealing PSU

 

Like many amorphous thermoplastics, PSU is especially sensitive to stress-cracking, so stress-relieving through an annealing process is highly recommended before machining.  Annealing PSU 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.  AIP uses computer controlled annealing ovens for the highest quality precision machining of PSU and other thermoplastics.

 

Machining PSU

 

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 PSU. 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 only machines polymers.

 

Preventing Contamination

 

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace 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.  This allows us to de-risk the process from metallic cross contamination.

 

PSU (Polysulfone) Machining Guide Supportive Information

Amorphous Materials Guide

 

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Machining Nylon (Polyamide): A Plastics Guide

September 6, 2019

An Informational Brief on Polymer Machining

 

One of the high-performance thermoplastics that AIP works with is NYLON:  a PA, or polyamide.  It is known for high strength, maintaining mechanical properties at elevated temperatures and chemical resistance.  This polymer was first introduced by DuPont in the 1930s following extensive research on polyesters and polyamides.  For this reason, polyamides comprise the largest family of engineering plastics with a wide range of applications.  Typical applications of nylon include, but are not limited to:  gears, industrial bearings, nozzles, sheaves and wear pads.  Oftentimes, it replaces metal because it is very lightweight, weighing 1/7th as much as bronze.

 

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

 

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that nylon (PA) 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 nylon, 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.

 

The table below outlines the main properties of thermoplastics versus thermosets:

 

Thermoplastics

Thermosets
  • Good Resistance to Creep
  • Soluble in Certain Solvents
  • Swell in Presence of Certain Solvents
  • Allows for Plastic Deformation when Heated
  • High Resistance to Creep
  • Cannot Melt
  • Insoluble
  • Rarely Swell in Presence of Solvents

 

From there, thermoplastics are categorized into amorphous or crystalline polymers per the figure below:

 

 

Based off of the chart, nylon is a semi-crystalline, high purity engineering thermoplastic, meaning its molecular structure is highly ordered.  The highly ordered structure of a crystalline structure is what lends the polymer to strength and rigidity.  Generally speaking, crystalline structures are opaque since the structure tends to reflect light.  Here at AIP, we machine several different grades of nylon for multiple industrial applications.

 

Properties & Grades of Machined Nylon (PA)

 

As a thermoplastic, nylon offers industrial-grade resistance to pH changes due to varying thermal conditions, as well as solvent-resisting capabilities. This can be an advantage in petrochemical industries where fluoropolymer parts are in contact with or exposed to bursts of gases, oil or detergents.

 

It should also be noted that nylon (PA) is known for its high degree of crystallinity, which results in a stronger and strain-resisting component. Furthermore, applying nylon reduces the need for heavy lubrication, and dampens sound and eliminates galling, corrosion and pilferage problems.

 

There are two common grades of nylon that should be mentioned for their properties and applications, Nylon 6 and Nylon 6/6.  They can be used interchangeably for various applications, but there are some property differences to note:

 

Nylon 6:

 

Nylon 6 is usually produced in two forms:  for textile use and high-strength types for industrial uses.  It is usually formed into filament yarns and staple fiber.  Most of the time this nylon can be found in tire cords, parachutes, ropes or industrial cords.  In comparison to Nylon 66, Nylon 6 has these benefits:

 

  • A lower density
  • Better toughness
  • Better surface appearance
  • Lower processing temperature

 

In times of war, there are often significant advancements in material usage, weaponry, and machinery. World War II was no different. Plastics entered the scene during World War II, starting with the replacement of metal parts for rubber parts in U.S. aircraft after Japan limited metal trade with the United States. Following that, plastics of higher grades began to replace electrical insulators and mechanical components such as gears, pulleys, and fasteners. Aircraft manufacturers began to replace aluminum parts with plastics as they were lighter and thus more fuel efficient than aluminum.

 

Nylon 6/6:

 

Much like Nylon 6, Nylon 6/6 has many industrial applications, from thin walled components to large thick-walled bearings.  It is also an outstanding candidate for metal replacements. Compared to Nylon 6, Nylon 6/6 has the following advantages:

 

  • Higher temperature resistance
  • Higher strength
  • Higher stiffness
  • Lower moisture absorption
  • Better abrasion resistance

 

Besides Nylon 6 and Nylon 6/6, AIP offers wide-ranging machining expertise of Nylon® and Polyamide grades that provide different strength, thermal stability, and corrosion resistance. Our decades of experience with high-performance specialty plastics and thermoplastics can help you select the best grade of nylon for your application.

 

Machining Nylon (PA)

 

Annealing is a heat treatment that changes the properties of a material to make it easier to machine by increasing ductility and reducing hardness in the material.  The process of annealing and stress-relieving nylon reduces the likelihood of surface cracks and internal stresses occurring in the material.  For more information on AIP’s annealing processes for nylon and other materials, reference our annealing guide.

 

Annealing Nylon

Annealing is a heat treatment that changes the properties of a material to make it easier to machine by increasing ductility and reducing hardness in the material.  The process of annealing and stress-relieving nylon reduces the likelihood of surface cracks and internal stresses occurring in the material.  For more information on AIP’s annealing processes for nylon and other materials, reference our annealing guide.

 

Machining Nylon

Nylon offers ease of machining and tight tolerances due to its inherent strength, toughness and dimensional stability. Machining Nylon isn’t too different from machining metals as a result of this; pretend you’re machining brass. Unlike metal, though, nylon (like all thermoplastics) will deform if you hold it too tightly as it yields easily. We generally recommend Tungsten Carbide Alloy Tooling. Also, keep the part very cool and support it well. 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.

 

Case in point, Nylon (PA) can be manufactured into industrial equipment components that may include piping and tubing, valves, gears, nozzles, and wear pads—among many other formats. It can also be combined with other materials, helping customers innovate and create new product classes with utility that exceeds its original applications.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace 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.  This allows us to de-risk the process from metallic cross contamination.


Nylon (PA) Polyamide Machining Guide: Supportive Information

AIP Nylon Variants Guide

 

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Machining Kynar Resin (PVDF): A Plastics Guide

July 1, 2019

An Informational Brief on Polymer Machining

 

Kynar®, Polyvinylidene Difluoride (PVDF) is a specialty fluoropolymer thermoplastic known for its ease of processing and its versatility in a variety of applications.  PVDF’s manufacturing not only ensures durability in its utility, but also delivers an innate resistance to acids, bases, high temperatures, and solvents.  Harsh industrial environments are no match for PVDF parts, which is why it is commonly used in environments requiring extreme resistance to a broad range of chemicals.

 

Additional demand for fluoropolymers like Kynar® PVDF is driven by the increasing trend of specialized, small-batch production for customized parts and components. Companies developing prototypes find it extremely convenient to have access to a fluoropolymer part manufacturer such as AIP.  Furthermore, AIP’s experience with custom-engineering plastics ensures our customers’ evolving needs are always met with the same level of innovation and excitement for creating new ways to deliver value in fluoropolymer applications.

 

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

 

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that PVDF 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 PVDF, 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 PVDF in particular? PVDF is a semi-crystalline, high purity engineering thermoplastic, meaning its molecular structure is highly ordered.

 

Properties & Grades of Machined Kynar® (PVDF)

 

As a thermoplastic, Kynar® PVDF offers industrial-grade resistance to pH changes due to varying thermal conditions, as well as solvent-resisting capabilities. This can be an advantage in petrochemical industries where fluoropolymer parts are in contact with or exposed to bursts of gases, oil or detergents.

 

It should also be noted that Kynar® PVDF is known for its high degree of crystallinity, which results in a stronger and strain-resisting component. Add to that a natural resistance to fungus, ozone and weather, which makes Kynar® PVDF a great fluoropolymer for coatings and manufactured parts exposed to the elements.

 

Finally, adding to its versatile performance in industrial environments, Kynar® PVDF provides excellent resistance to nuclear radiation, allowing it to be used in both Power Generation and military applications.

 

AIP offers a range of Kynar® and PVDF grades that provide different strength, thermal stability, and corrosion resistance and can help you select the best grade of PVDF for your application..

 

Machining Kynar® (PVDF)

 

Annealing PVDF

 

The process of annealing and stress-relieving PVDF 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.

 

Machining Kynar

 

PVDF offers ease of machining and tight tolerances due to its inherent strength, toughness and dimensional stability. Machining PVDF isn’t too different from machining metals as a result of this; pretend you’re machining brass. Unlike metal, though, PVDF (like all thermoplastics) will deform if you hold it too tightly as it yields easily.

 

We generally recommend Tungsten Carbide Alloy Tooling. Also, keep the part very cool and support it well.

 

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.

 

Case in point, Kynar® PVDF can be manufactured into industrial equipment components that may include piping and tubing, valves, tanks, nozzles, and fittings—among many other formats. It can also be combined with other materials, helping customers innovate and create new product classes with utility that exceeds its original applications.

 

Preventing Contamination

 

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace 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.  This allows us to de-risk the process from metallic cross contamination.

 

Kynar® (PVDF) Machining Guide: Supportive Information

 

Chemical Resistant Materials

 

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