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?

 

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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 HomopolymerPP 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

 

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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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When design engineers need a custom-machined component for a project, many consider metals first for their strength and durability.  However, this is not the case anymore; metals are moving over as polymers and composites become a more sensible alternative for precision-machined, high-strength durable parts.  This is true across many industries, but especially in the aerospace and defense sectors.  In this article, we will explore the benefits of opting for a plastic material for mission-critical aerospace and defense parts.

 

Overall Benefits

 

Machined polymer and composite components are the most cost-effective solution compared to metal.

 

First, machined plastic parts are lighter and, therefore, provide immense advantages over metals by offering lower lifetime freight costs for equipment that is regularly transported or handled over the product’s lifetime. Furthermore, polymers allow lower power motors for moving parts due to lower frictional properties of polymer wear components compared to metals. The low frictional properties preserve the integrity of the part as well, which translates to less maintenance-related downtime. What does this mean for operators?  Equipment remains online longer doing what it’s supposed to do – produce profit and functionality.  Not only are plastics lighter, but they’re also less expensive than many raw metal materials used for parts. Plastics can be produced in faster cycles than metals, which helps keep manufacturing costs down as well.

 

At AIP, we can machine and deliver parts in as little as 10 business days.

 

Explore AIP’s Machining Capabilities

 

Plastics are more resistant to chemicals than their metal counterparts.

 

Without extensive and costly secondary finishes and coatings, metals are easily attacked by many common chemicals. Corrosion due to moisture or even dissimilar metals in close contact is also a major concern with metal components. Polymer and composite materials such as PEEK, Kynar, Teflon, and Polyethylene are impervious to some of the harshest chemicals. This allows for the manufacture and use of precision fluid handling components in the chemical and processing industries.  These parts would otherwise dissolve if they were manufactured from metal materials. Some polymer materials available for machining can withstand temperatures over 700°F (370°C).

 

Plastic parts do not require post-treatment finishing efforts, unlike metal.

 

Polymer and composites are both thermally and electrically insulating. Metallic components require special secondary processing and coating in order to achieve any sort of insulating properties. These secondary processes add cost to metallic components without offering the level of insulation offered by polymer materials. Plastic and composite components are also naturally corrosion resistant and experience no galvanic effects in a dissimilar metal scenario that require sheathing. Additionally, plastic materials are compounded with color before machining, eliminating the need for post-treatment finishing efforts such as painting.

 

Aerospace and Defense benefits graphic
 

 

Benefits to the Aerospace & Defense Sector

 

Polymers bring many advantages to the aerospace and defense industry, particularly in the form of weight-saving capabilities.  Let’s take a closer look at the benefits of precision machined mission-critical components.

 

  • Lightweight: Polymer and composite materials are up to ten times lighter than typical metals. A reduction in the weight of parts can have a huge impact on an aerospace company’s bottom line. For every pound of weight reduced on a plane, the airline can realize up to $15k per year in fuel cost reduction.

 

  • Corrosion-Resistant: Plastic materials handle far better than metals in chemically harsh environments. This increases the lifespan of the aircraft and avoids costly repairs brought about by corroding metal components an in-turn reducing MRO downtime provides for more operational time per aircraft per year.

 

  • Insulating and Radar Absorbent: Polymers are naturally radar-absorbent as well as thermally and electrically insulating.

 

  • Flame & Smoke Resistances: High-performance thermoplastics meet the stringent flame and smoke resistances required for aerospace applications.

 

Aerospace and Defense benefits graphic
 

Other Benefits for Aerospace and Defense

 

  • High Tensile Strength: Several lightweight thermoplastics can match the strength of metals, making them perfect for airplane equipment metal part replacement.

 

  • Flexibility & Impact Resistance: Polymers are resistant to impact damage, making them less prone to denting or cracking the way that metals do.

 

Plastics have a variety of unique attributes which place them above metals in terms of utility, cost-effectiveness and flexibility for precision-machined mission-critical components.  To learn more, search specific plastic materials and their applications per industry with our useful material search function.

 

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An Informational Brief on Polymer Machining

 

Among 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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Learn about the re-useable capabilities of precision plastics

 

In the world of recycling, plastic tends to have a bad reputation or it gets whispered like a dirty word.  Indeed, according to the UN Environment Programm, one million plastic drinking bottles are purchased every minute.  This is certainly a disturbing statistic, and we are tasked with addressing the consequences of this waste.  However, it is important to distinguish the type of plastics causing severe pollution.  Plastic bottles and plastic bags are single-use, disposable plastics.  These are the ones that are clogging up the environment.

 

What people don’t discuss often is plastics that are re-usable and recyclable.  At AIP, the plastics that we precision machine are high grade, quality polymers made for durability and continuous use in the following industries: Aerospace and Defense; Medical and Life Sciences; Power and Energy; Specialized Industrial.  That means they are evergreen materials that will not only last, but could be repurposed for a different application altogether.  Read on to find out about some of the high-performance polymers we work with, what they are used for and how they can be recycled.

 

Everyday Sustainable Precision Plastics
PolymerPropertiesAIP’s Machined Applications
PPSBroadest chemical resistance; zero moisture absorption; dimensional stability; ultra-low wear factors and structural strength

*available in several grades

Case Study: High-quality PPS wheel bushings for a theme park water ride.

  • Reduced ride downtime
  • Saved on maintenance and inventory costs
  • Lower energy cost
  • Efficient design
  • Low-wear
TORLONHighest performing, melt-processible plastic; maintains strength and stiffness up to 500 F; chemical, thermal and stress resistance

*available in several grades

Ideal for critical mechanical and structural components for severe levels of temperature and stress

  • Jet Engine Components
  • High Temperature Electrical Connectors
  • Automotive Transmission components
  • Wear Rings in Oil Recovery
  • Valve Seats
PEEKBiocompatible; abrasion and chemical resistant; low moisture absorption; very low smoke and toxic gas emission

*available in several grades

Case Study: PEEK Dynamic Telescopic Craniotomy (skull plate for brain traumas

  • Reduced ride downtime
  • Saved on maintenance and inventory costs
  • Lower energy cost
  • Efficient design
  • Low-wear
RADELImpact resistance; hydrolytic stability; excellent toughness; chemical resistance; heat deflection temperature of 405 F (207 C)
ULTEMExcellent heat and flame resistance; high rigidity and strength; low thermal conductivity; highest dielectric strength

*available in several grades

Used as structural components in several industries

  • High-voltage circuit-breaker housings
  • High-temperature bobbins, coils, fuse blocks and wire coatings
  • Jet-engine components
  • Aircraft interior and electrical hardware parts
  • Microwave applications
  • Replaces glass in medical lamps

 

Thermoplastics – The Green Plastic

 

There are two types of polymers – thermoplastics and thermosets.  The plastics that we work with primarily at AIP are thermoplastics.  So, what’s a thermoplastic and how is it re-usable or recyclable?

 

It’s all about how the polymer reacts to chemicals and temperature.  Thermoplastics soften when heated and become more fluid, which makes them a very flexible polymer.  For this reason, these plastics can be remolded and recycled without losing their mechanical properties or dimensional stability.  Let’s go in depth on some of the common thermoplastics we use for evergreen applications.

 

The AIP case study focusing on the use of PPS for the log flume ride bushing component is an excellent example of a thermoplastic built and machined for continuous use.  The bushing made from PPS could be used over and over again without wear.  Furthermore, it could be immersed in water and other chemicals without losing dimensionality or durability.

 

PEEK and ULTEM are both common polymers we machine at AIP.  With PEEK’s high chemical resistance and biocompatibility, it is ideal for surgical applications such as the Dynamic Telescopic Craniotomy Case Study.  This polymer can withstand the internal temperatures and fluids of the body for extended use.

 

ULTEM is known for its strength and rigidity in extreme environments and temperatures.  This polymer is often used for re-useable medical instruments, since it reacts well to autoclave sterilizations.  Additionally, it’s flammability rating and dimensional stability make it ideal as a weight-saving aerospace component.

 

As the plastics industry continues to innovate, the next generation of research will turn towards more sustainable and environmentally conscious materials.  Thermoplastics are one of the pioneers of this industry – leading plastics into the future as a material that can be reused and recycled.

 

Unrivaled Expertise. Unparalleled Results

 

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.  Unrivaled Expertise.  Unparalleled Results.

 

 

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Key Moments in Aircraft & Aerospace Innovation

 

Aviation technology has come a long way to get to where it is today. Over the course of the last century countless test flights, thousands of blueprints, and endless research from passionate minds have propelled the evolution of aircraft and aerospace technologies. Read on to discover how aviation materials have shifted to create a better, safer, and more efficient flight experience.

 

The Pioneers of Aviation

 

For much of human history, we have been fascinated with taking flight. The ancient Greeks contemplated sprouting wings in myths like Icarus and Daedalus – the boy who flew too close to the sun with wax and feather wings. Leonardo Da Vinci sketched flying machines that were way ahead of Renaissance times. It all came to fruition in 1857 when Félix du Temple de la Croix, a French Naval officer, received a patent for a flying machine. By 1874, he had developed a lightweight steam-powered monoplane which flew short distances under its own power after takeoff from a ski-jump.  Finally, in 1903, the Wright Brothers made the first controlled, powered, and sustained flight near Kitty Hawk, North Carolina. The Wright Flyer featured a lightweight aluminum engine, wood and steel construction, and a fabric wing warping. According to the U.S. Smithsonian Institution, the Wright brothers accomplished the “world’s first successful flights of a powered heavier-than-air flying machine.”

 

 

Just 12 years later, the first all-metal airplane (Junkers J1), built by Hugo Junkers (1859-1935), took flight in 1915. Previously, aircraft experts believed that airplanes can only fly with light materials such as wood, struts, tension wires, and canvas. Junkers thought differently and believed that heavier materials like metal were necessary to transport passengers and goods.

 

The Golden Age

 

The Roaring 20’s ushered in airplane racing competitions, which led aircraft designers to focus on performance. Innovators, such as Howard Hughes, found that monoplanes (aircraft with one pair of wings) were more aerodynamic in comparison to biplanes, and that frames made with aluminum alloys were capable of withstanding extraordinary pressures and stresses. Due to its lightweight properties, aluminum also made its way into the internal fittings of the aircraft decreasing the weight and allowing for a more fuel-efficient design.

 

In 1925, Henry Ford acquired the Stout Metal Airplane Company, utilizing the all-metal design principles proposed by Hugo Junkers, Ford developed the Ford Trimotor, nicknamed the “Tin Goose.” The “Tin Goose” propelled the race to design safe and reliable engines for airline travel. A few years later, Henry Ford’s Trimotor NC8407 became the first airplane flown by Eastern Air Transport, a leading domestic airline in the 1930s flying routes from New York to Florida. This positioned metal as the primary material for domestic aircraft, and eventually military applications with the onset of WWII.

 

 

Plastic’s Mettle: Wartime Materials Take Flight

 

By the 1930’s, the use of wood became obsolete and all-metal aircrafts were produced for their durability. Imperial Airways, known today as British Airways, made headway in the air travel industry with advertisements of luxury and adventure to cross borders. However, those borders were sealed off with the breakout of WWII. In 1939, Imperial Airways, a private commercial airline, was ordered to operate from a military standpoint at Bristol Airport.  Across the Atlantic, engineers focused their efforts on building aircraft meant specifically for military strategy – strength, durability, agility, and weaponry.  The Boeing P-26 “Peashooter” entered service with the United States Army Air Corps as the first all-metal and low-wing monoplane fighter aircraft. Known for its speed and maneuverability, the small but feisty P-26 formed the core of pursuit squadrons throughout the United States.

 

 

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.

 

The Race for Space

 

Lighter and more fuel efficient were the key words following World War II as nations turned their attention to the skies and beyond. The space program in the 1960’s brought together illustrious minds to solve the seemingly impossible feat of being the first country to put mankind on the moon, thus, the great race for space began. Aircraft were now going beyond the sky and NASA scientists knew they were dealing with new territory in aero innovation. They needed a material that could break the Earth’s atmosphere and carry a hefty amount of fuel, while protecting the spacecraft’s crew from extreme temperatures. NASA scientists turned to plastics, specifically Kevlar and nylon. Layers of nylon and other insulators were wrapped under the body of the spacecraft to protect the crew from the extreme temperatures of space. Both of these plastics are still staples in the aerospace industry – keeping the Hubble telescope and many other satellites scanning humanity’s charted and uncharted expanse.

 

 

Plastics of the Future

 

Plastics continue to lead the future of materials in aerospace and aviation industries for their durability, precision, and ingenuity. For example, in 2009, the 787-8 Dreamliner made its first maiden flight, becoming the first aircraft to have wings and fuselage made from carbon-fiber plastics. Besides being lightweight, plastics offered increased safety with their resistance to high impact, and their proven ability to withstand chemically harsh environments. This proved plastics an invaluable material when compared to alternative material choices like glass or metal.

 

 

Starting in the 1970s, plastics began to play a more crucial part in the defense and military industry, especially in stealth aircraft. The U.S. Air Force saw the potential of plastics when they learned that plastics could absorb radar waves. The added benefit of reduced radar signature makes plastics ideal for creating stealthy aircraft. Plastics continue to contribute to innovation in the defense industry, especially with stealth fabrics and other composite materials which can virtually create invisibility to radars in the near future.

 

Aside from plastics becoming increasingly popular for use in the defense and military sector, high grade plastics like PEEK are highly favorable for space travel due to its ability to function in hostile environments, critical in space exploration. Plastics are even being researched for lightweight radiation shielding for the International Space Station and flights to Mars.

 

At AIP, we’re proud to be a continued part of aviation and aerospace advancements and we look forward to engineering solutions for the next frontier. In fact, at the time this article was written, we are AS9100D:2016 certified, which means we meet the high-quality standards of applications in the aerospace industry. In addition, we are also ISO 13485:2016, ISO 9000:2015, FDA audited, and ITAR certified. Above call, we strive to create genuine relationships with our customers to deliver mission critical components with promise. To learn how we can help you, contact us today.

 

Interested to learn more? Read “Plastics in Aerospace: The Secret to Fuel-Efficient Aircraft

 

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Ask the Plastics Professionals at AIP Precision Machining!

 

Do you know why AIP Precision Machining includes stress-relieving and annealing plastics as part of our machining process? We’ve talked about this a bit in our plastic machining guides (like our polymer machining brief on RADEL, but this post serves as a more thorough explanation of annealing does to improve your machined parts.

 

What’s the purpose of stress relieving and annealing plastics, then? Read on to learn the answer from the plastics professionals at AIP Precision Machining.

 

What is annealing, and how does AIP anneal its plastic parts?

 

Let’s start with the basic definition of annealing: it’s a heat treatment that changes the properties of a material to make it easier to machine. Annealing does this by increasing ductility and reducing hardness for the material.

 

AIP Precision Machining has programmed annealing ovens for plastics that heat the material above its recrystallization temperature. By maintaining the heat at that specific point, the structure of the material changes to become finer and more uniform. This process relieves internal stresses in the material.

 

The final part of annealing is allowing the material to cool back down once after it’s been heated for a suitable amount of time. Proper annealing requires precise temperatures and timing control to accomplish the right result, which is why AIP uses computer controlled annealing ovens for plastics.

 

Why is annealing & stress-relieving crucial for plastics?

 

While not every machined component has to rely on annealing, we at AIP believe it is an important part of the plastic machining process for several reasons. For one thing, it reduces stress in the material.

 

Plastics that experience internal stress can turn out warped or cracked, have inferior physical properties, or finish with unexpected changes in their part dimensions. Obviously, we want to avoid this as much as possible.

 

Reducing stress enhances the mechanical and thermal properties of a material by limiting the opportunity for cracking and other issues like the ones above. Since stress build-up can lead to part failure or reduced performance, stress-relieving improves the overall quality of your product.

 

By doing this, annealing extends the life of your machined plastic parts and components.

 

Is the process of annealing plastics the same for different materials?

 

Not at all. Some engineering plastics like ULTEM and TORLON benefit enormously from post-machining annealing. At AIP, proper annealing of TORLON can require more than seven days in special ovens!

 

Other materials that will undergo a lot of machining time, like some applications of PEEK, can require more intermediate annealing steps to make sure they maintain critically tight tolerances and flatness.

 

That means it’s essential for your machinist to know what plastic material you’re working with and what particular needs it has. Be sure you’re working with an experienced plastics manufacturer like AIP or else you risk having a lower quality product.

 

With over 35+ years of experience working with hundreds of polymers and composites, we’re more than just familiar with the machining process. We’re ready to handle any geometry and any challenge.

 

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Strict Hygienic Procedures for Precision Machining

 

It’s no secret that cleanliness and sterilization are crucial for applications in the medical industry. Any manufacturer you hire for machining your plastic component should be aware of this, and taking actions to prevent any contamination from taking place.

 

Here are three ways you can ensure that your medical application is being precision machined by a manufacturer committed to following strict hygienic procedures.

 

1) Check Industry Standards

 

Ensuring sterilization starts with picking the right manufacturing company, and you’ll want to be sure they take the matter of contamination seriously. To start, check their commitment to quality management and industry standards.

 

All product manufacturing companies must follow industry standards like International Organization for Standardization (ISO) and Food and Drug Administration (FDA). Before you work with a manufacturing company for your medical application, look at their certifications.

 

For example, ISO 13485 specifies requirements for a quality management system where a company demonstrates it can provide medical devices and related services to consistently meet customer and regulatory requirements. ISO 9001 focuses on meeting customer expectations and continually delivering satisfaction, plus reflects constant improvement from the company.

 

If the manufacturer you are interested in using does not have any of the above standards, then you may want to ask them why.

 

Here at AIP Precision Machining, we have 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.

 

2) Plastic Machining isn’t Metal MachiningMetal vs Plastic Machining

 

Be wary of any manufacturer who machines both plastics and metals in the same facility. The tiniest sliver of metal embedded in a plastic part can have widespread ramifications, such as an unexpected electrical problem in the medical device.

Additionally, it’s common for metal machining companies to use oil-based cutting fluids. Any equipment that machines metal, then, can contaminate your plastic parts with those fluids. Many plastic materials are especially sensitive to those petroleum-based liquids, and they can degrade when in contact with them; others are hydroscopic and will absorb the oils.

 

It should be noted that plastic parts manufactured using equipment that machines metal parts will not meet FDA-approval, or the other industry standards mentioned above. The safest way to avoid this is to hire a plastics expert, not a metal machining company.

 

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.

 

3) Look for Experience

 

The most important factor to take into account overall is experience. Your supplier should be familiar with the types of polymers and composites you need machined, and should additionally know the best machining process for your application.

 

For the medical industry, you want to know that your manufacturer is experienced with the complex needs of your applications. For example, if your components are going to come into contact with body tissue or fluids, then they must be biocompatible per ISO 10993.

 

Which is to say: If you’re machining implants, your plastics will require different needs than if you’re machining reusable surgical instruments. Both require, however, careful attention to detail. A surgical instrument must be designed with sterilization compatibility for regular cycles in mind, while an implant requires biocompatibility to be safe for use.

 

Be sure that your manufacturer is familiar with the processes that come with your application, and check that they’ve done it before.

With 35+ years of experience, AIP is well acquainted with precision machining for the medical industry and guarantees careful material selection and processing for your medical applications.

 

The #1 Best Way to Avoid Contamination?

Overall, the best thing you can do to avoid contamination is to hire a plastic manufacturer with the experience and the credentials to complete your project to the highest standards of quality possible. Keeping the above three factors in mind will help you do just that.

 

To ask about AIP Precision Machining’s capabilities for precision machining medical applications, please contact us.

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An Informational Brief on Polymer Machining

MACHINING PEEK

 

The recent popularity of PEEK (polyetheretherketone) in complex industries such as Aerospace & Defense and Medical & Life Sciences is well documented, and for good reason: this lightweight thermoplastic bears properties that make it ideal for a variety of specialized applications. This versatility makes PEEK equally capable of being used for implants and custom medical devices or machined lightweight aircraft components.

 

What is less known, however, is the process that goes into machining this plastic material. With over 35 years of experience machining this thermoplastic material, we at AIP have written a brief introduction to machining PEEK. We hope this gives you some insight into our polymer machining process, and how it differs from that of metal machining or injection molding.

 

Plastic CNC Machining

 

Before discussing the process of machining PEEK, 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 material. The technique of utilizing drilling tools to carve plastics was introduced by MIT during the 1950s, and because this process is computer-controlled, products with extremely precise tolerances can be achieved.

 

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 properties and varying behavior when machined. Therefore, it’s important to understand the polymer structure of PEEK 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 those polymers react to heat and temperature.

 

Thermoplastics are capable of being repeatedly softened and pliable when temperature increases, meaning that when heat is applied, that results in a physical change for the polymer. They possess the following properties:

 

  • – Good Resistance to Creep
  • – May Melt Before Turning to Gaseous State
  • – Soluble in Certain Solvents
  • – Swell in Presence of Certain Solvents
  • – Allows for Plastic Deformation when Heated

 

Thermosets, in contrast, turn into an infusible and insoluble material when cured by application of heat or chemical means, making for poor elasticity. They possess the following properties:

 

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

 

Phenolic materials would be considered examples of a thermoset, while PEEK is an example of a thermoplastic.

 

In particular, PEEK is considered a semi-crystalline, high-performance thermoplastic. This gives it enough elasticity to be machined to various custom designs, with strong mechanical properties that provide resistance to fatigue and stress-cracking, as well as a good structure for bearing, wear, and structural applications.

 

Industrial Grade vs Medical Grade PEEK Machining

 

Depending on your application, you’ll want to machine either industrial-grade PEEK or medical-grade PEEK.

 

Industrial-grade PEEK is a strong, flame-retardant and abrasion resistant thermoplastic with high impact strength and a low coefficient of friction. It’s known for retaining its mechanical properties, even at elevated temperatures. As suggested by its name, this grade is most commonly used in aerospace, automotive, chemical, electronics, petroleum, as well as food and beverage industries.

 

Medical-grade PEEK adds biocompatibility per ISO 10993, high chemical resistance, and sterilization compatibilities to the above list of qualities. In addition, this thermoplastic is radiolucent, meaning it is not visible under X-ray, MRI or CT. Medical-grade PEEK includes polymers suitable for implants, such as PEEK Optima and Zeniva PEEK, which can stay in contact with blood or tissue indefinitely while mimicking the stiffness of bone. Other variations of medical-grade PEEK can be used for custom medical components and applications, such as articulating joints and spinal devices.

 

Machining PEEK

 

Annealing PEEK

 

Most shops receive PEEK in the form of rods of various lengths, ranging from 6mm to 150mm in diameter. 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. Additional benefits of annealing include increased levels of crystallinity and the opportunity to limit dimensional changes.

 

If your PEEK components will undergo long stretches of machining time, it is likely you will require additional intermediate annealing steps to assure the ability to maintain critically tight tolerances and flatness.

 

Machining Industrial-Grade & Medical-Grade PEEK

 

Both industrial-grade and most medical-grade PEEK machine similarly, save for PEEK reinforced with carbon fiber. Silicon carbide cutting tools work well for natural PEEK, while diamond tools work well for PEEK reinforced with carbon-fiber.

 

For medical-grade PEEK applications, the best way to avoid jeopardizing the biocompatibility of the material is to machine dry. However, PEEK doesn’t dissipate heat the way that metals do, so often a coolant is necessary. In that case, air is the coolant option least likely to affect medical-grade PEEK’s biocompatibility. Any chips that are a result of machining medical-grade PEEK can be reused for industrial applications.

 

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.

 

PEEK Machining Guide: Guidelines

(Courtesy of Invibio)

 

Natural PEEK

Carbon-Fiber-Reinforced PEEK

blank
SawingblankPreheat material to 120 C degrees
Clearance angle—degrees15 to 3015 to 30
Rake angle—degrees0 to 510 to 15
Cutting speed—m/min500 to 800200 to 300
Pitch—mm3 to 53 to 5
DrillingblankPreheat material to 120 C degrees
Clearance angle—degrees5 to 106
Rake angle—degrees10 to 305 to 10
Cutting speed—m/min50 to 20080 to 100
Feed rate—mm/rev0.1 to 0.30.1 to 0.3
MillingblankNo material preheat is necessary
Clearance angle—degrees5 to 1015 to 30
Rake angle—degrees10 to 3010 to 15
Cutting Speed—m/min50 to 200200 to 300
TurningblankNo material preheat is necessary
Clearance angle—degrees6 to 86 to 8
Rake angle—degrees0 to 52 to 8
Cutting speed—m/min250 to 500150 to 200
Feed rate—mm/rev0.1 to 0.50.1 to 0.5

 

PEEK Machining Guide: PEEK Variants

 

Peek-Variants-Guide

Click to Enlarge

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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:

 

Want to learn more about AIP Precision Machining’s capabilities?

Explore our extensive plastic machining capabilities here, or if you like, you can contact us to get a quote here.

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