Plastics Information

What is Compression Molding?

Compression molding is a common process used for both thermoplastic and thermoset stock shape materials. Compression molding is accomplished by placing the plastic material (can be a granular or pelletized form) in a mold cavity to be formed by heat and pressure. The process is someone similar to making waffles. The heat and pressure force the materials into all areas of the mold. The heat and pressure cycle of the process will harden the material and then it can be removed.

Typically, thermosetting compounds like polyesters, phenolics, melamines and other resin systems are compression molded using alternating layers of different reinforcement materials to create a final product. However, there are various thermoplastics that are commercially compression molded as well.

Advantages of injection molding:

– Extremely low to zero residual stress left in stock shape.

– Can economically provide large parts.

– Tooling costs are relatively low.


– Flask may require trimming, can be sharp.

– Cycle times can be slow, a factor in producing larger volume orders.

– Can be higher priced than extruded products (when comparing thermoplastics).

Compression molding is a valuable tool where it has a fit. Obviously for thermosets, it is a primary process but in thermoplastics it can often times be useful in creating a base stock shape to machine extremely complex geometries without having to take excessive time and steps to anneal parts. This can increase production cycle time and reduce overall cost while delivering exceptional finished parts. For a complete listing of available compression molded thermoplastics for machining, give Plastics International a call or email us at

Plastics Information

What is Injection Molding?

Injection molding is by far the primary process for converting plastics into useful plastic widgets. Just about all of us touch an injection molded widget every hour of every day. All thermoplastics can be injection molded with a few exceptions like polyimides and PTFE to name a few. Injection molding takes pelletized materials and heats them up to the point where they can flow properly through the injection process. The hot, molten material is then injected into a closed mold to create the desired part or shape. Then, after the part cools, the part is removed from the mold.

Advantages of injection molding:

-Extremely high output rates.

– Inserts and fillers can be used with this process.

– Process can be completely automated and run with little downtime.

– Scrap from the process can be ground and reused into the process.

– Small, complex parts can be molded economically.


-No cost effective for short runs.

-Large capital investment in equipment and overhead required.

-Molds can be very expensive requiring large runs to justify ROI of tooling.

-Requires a high degree of design and process expertise and experience to produce good parts and have low scrap rates.

-Thick cross sections can not be easily or reliable produced.

Injection molding will always be the number one way that large volume plastic parts are produced. When a part volume is too small or need to be tested before a final investment is made in tooling, machiend plastic stock shapes are the go to method for producing reliable plastic parts.

Plastics Machining

What is Casting?

Casting involves introducing a liquefied plastic into a mold and allowing it to solidify. In contrast to molding and extrusion, casting relies on atmospheric pressure to fill the mold rather than using significant force to push the plastic into the mold cavity. Some polymers have a viscosity similar to bread dough even when they are at elevated temperature so they are not candidates for the casting process. Examples of this are polymers like POM, PC, PP and many others. Casting includes a number of processes that take a monomer, powder or solvent solution and pur them into a mold. They transition from liquid to solid by either evaporation, chemical action, cooling or external heat. The final product can be removed from the mold once it solidifies.

Casting has several advantages:

-Cost of equipment, tooling and molds are low.

-The process is not complex.

-Products have little or no internal stress.

Casting can have some disadvantages:

-The output rate is slow and has long cycle times.

-Dimensional tolerances are not very good.

-Moisture and air bubbles can be difficult to manage and may cause problems.

There is a vast array of materials than can be cast. Nylon Type 6 is one of the most popular and commonly used cast products. You can see some of our product offering by clicking on this link. Polyurethanes are another example of cast materials we offer. Either way, the casting process is often times the preferred method providing large size stock shapes for machining parts. Make the most of this process by optimizing your part blank with a near net cast shape, give us a call and we can explain how.

Plastics Information

What is Extrusion?

The word extrusion is taken from the Latin word extrudere meaning (ex) out and (trudere) to push. In the extrusion process, a pellet or dry powder plastic is heated and forced through a die. The majority of extrusion is done by screws although ram extrusion is still used for UHMW powder specifically. The screws will melt and mix the material and force it out of the opening in the die. An extruder can either be single barrel or twin screw/double barrel equipment. The material being extruded determines what which extrusion technology is required. Double barrel extruders are primarily use for compounding in line of basic plastics with different plasticizers, fillers, colorants and other ingredients. Extrusion lends itself to make tube, rod, profiles, film or sheet plastic products in a variety of widths and thicknesses.

Extrusion is one of the primary ways machine stock shape plastics are made. Extrusion has several advantages:

-The high output (compared to other processes) offers lower material costs.

-Depending on the volume, there can be a greater variety in width and length options to maximize yields.

-Relatively low tooling costs.

Extrusion can have some disadvantages:

-Thickness limits for some materials.

-From a machining standpoint, the material may have a higher level of stress in the sheet making secondary or post manufacturing annealing necessary to help relieve stress so the stock shape is more machinable.

– Close tolerance shapes are difficult to achieve.

-Limited to shapes of uniform cross sections (along the length).

Extrusion is one of the most common ways to produce plastic stock shapes. When done by a reputable extruder, using the highest quality materials the machining of these stock shapes can be a successful part of any job shops business. To find the widest selection of quality stock shapes for machining, just click here.

Plastics Machining

Fear and Insanity in the World of Plastics Machining

We have all heard the old saying: “The definition of insanity is doing the same thing over and over again and expecting a different result.” Sometimes, we secretly can hope for things to be different. Fear can get in the way of making that hope a reality. We all know that fear can either motivate great change or cause great paralysis. Sometimes, fear can keep us taking a course of action we know deep down inside could make things better.

As it relates to machining plastics, many job shops keep machining the same material for the same application the same way just because that’s the way it’s always been done, even though the scrap rates are too high, the machine time is too long, and the material is always hard to find (this last one may not apply to one of our customers!). If you’ve grown to accept situations like these, please stop, and let some one know. Get help! The advances in technology and material science may offer a newer, faster, better way to do what you need to do with your process or application. Here at Plastics International our inventory and offering is constantly changing to reflect the changes in the market and the available technology of current material manufacturing. Sometimes what seemed impossible last year, last month, or last week is now the new standard.

Don’t be afraid of change. A little work and effort up front may make your business more successful in the long run. If you are not sure where to begin, feel free to give us a call and let us know what you are doing. We will be glad to listen and share ideas of what you might be able to do to improve your process. Our website has an entire section on how to work with some hard to machine materials. See our Material Resource Center. Plastics International can easily provide samples and resources to help you figure things out or test the ideas and concepts. The best part is, if something doesn’t make total sense or even seem remotely beneficial, you don’t have to do it. But don’t let the fear of change stick you with a material or process that you only wish could be or would be better and you do nothing about it. Looking at some of your existing business may not only help your business but may also offer your customer a better product or solution in the long term.

Plastics Materials

Options for Large Diameter Plastic Tubes

We sell numerous sizes of large diameter rods that are machined out into tube. This process is not just time consuming but also expensive. Some customers have to machine out more than 50% of the plastic they paid for in every operation. If you are strictly limited by your application as to the material you can use, then you may not have any other options. But if the application allows for material flexibility there are two great ways to make this process more cost effective.

The simple answer is to buy a tube in a wall thickness you can machine to size. One huge advantage of buying tube is the annealing process offers a better stock shape to machine from. Tube is essentially annealed on both the OD and ID. Another is the obvious savings in scrap and machine time. Tube can be hard to find. Let me first clarify that I am distinguishing tube from pipe. A pipe material that is meant to handle fluids is readily available in many standard products for the job. Tube is usually a stock shape to machine some hand of widget to complex geometry for a special purpose or made to print item. The reason tube stock shapes can be hard to find is because of the limits of manufacturing technology, volume and variety of sizes.

For low to medium volume machining where the afore mentioned material flexibility exists, consider using some basic materials like cast nylon or acetal tube. Both materials can work in a wide variety of applications and offer cost savings in machine and material scrap rates. Plastics International stocks a wide variety of both materials and can cut and ship a length out same day if you can use one of our many stock sizes. We can also custom order special wall thicknesses and outside diameters to fit you specific needs. Keep this in mind the next time you are machine a rod or disc, ask if tube is available in a material you can use for your application.

Plastics Information

What Makes a Plastic Food Grade?

It’s amazing today how many things are made using some sort of plastic material. Every day items from electronics to security products to health and wellness products, they all benefit in some way from plastic materials. Sometimes the benefits are cost related, other benefits might be design or physical properties related. For whatever the reason, there seems to be no end to the countless uses of plastic materials in our modern society.

When we consider the applications where plastics are used, what is the difference between the plastics in an everyday household item and the type of material we might see going into a food application? Food grade does not mean that it is edible. It also is different from environmentally friendly, sustainable, or biodegradable. Food grade means the material (like plastics) can come in direct contact with the food we consume as part of the harvesting, processing, or packaging of the food. There are several things that go into qualifying a plastics as a food grade material. An item can be certified by the FDA, NSA, or 3A Dairy as some examples (see our website for a breakdown of organizations/agencies). These compliance agencies oversee these activities in the US, while in Europe there is a slightly different process. Europe looks at things a little differently by focusing also on doing migration testing. This means that FDA and European standards for food grade plastic differ and are not direct cross reference to each other.

In the US, it all starts with a compliance agency like the FDA taking a close look at the chemical composition of the plastic material. They want to make sure there is nothing in the material that can harm the food supply. In addition, if anything affects the color, odor, or taste of the food, it will automatically fail the compliance rating. Next they take a close look at how the plastic material performs from a conditions of use standpoint. Things like how the material handles temperature ranges, alcohols, and greases are evaluated and documented. Conditions that may limit use are noted and cataloged for future reference.

Once a material has been approved for direct food contact or food grade use, now the plastic material needs to be run by a reliable manufacturer who is ISO 9000 certified and practices good manufacturing processes. This ensures that they are not only using high quality materials but are also processing them via a high quality process that will provide a safe product. Once a material is manufactured to the required specifications, certifications are generated and the final material supplier must be capable of maintaining chain of custody between the material and its applicable certifications. Having the right material on the shelf with the right certifications and compliance paperwork will ensure that your fabricated part will met the end users specifications.

If you need more help understanding what plastics materials meet different food grade standards, check out our Food Products Regulatory Guide online or visit our website at for more information.

Plastics Information

Metal Detectable or X-Ray Detectable: Which is the Better Plastic for the Job?

As the speed increases for the way food is harvested, processed and packaged in the market place, there is an ever-increasing need to make sure all of these processes are happening in a containment free environment to ensure the quality and safety of the food we consume. We often hear of countless stories of how a company had a huge recall because some contaminants went undetected and made it into the market place. Depending on the products being processed, the equipment and systems being used, companies have either preferred to use metal detectors to ensure the quality of their products. Others have chosen to use X-ray technology to accomplish the same thing. Many also add visual inspection equipment as well in different areas of their process. The challenge has grown considering the extensive use of plastics for mating wear parts in these high speed, automated processes to help equipment perform at higher speeds, and higher efficiency. Conventional plastics are impossible to detect using these standard methods due to their color or make up. Recently, plastic stock shape manufacturers have developed materials that are either metal detectable or X-ray detectable for approved use in direct food contact processing applications.

Material selection would then depend on what detection technology was being used for the process in quesiton. In addition to FDA/3A Dairy compliance, good dimensional stability, and resistance to CIP (clean-in-place) chemical washdown, we also need to narrow down which material also matches up well with the detection technology. In order to make the selection process easier and also make parts interchangeable, Plastics International is now offering an Ultra Detectable Blue material that is perfect for a large number of food industry applications. This revolutionary new Ultra Detectable Blue acetal copolymer material can be detected in food processes in one of three ways:

  1. Via metal detection equipment
  2. Via x-ray equipment
  3. Via optical scanners (because of the blue color)

This new material can machine easily into the part of your choice along with offering the ability to be detected as chunks as small as 3mm thick or shavings up to 1 mm thick (using standard metal detection equipment). So weather you are designing a scraper blade, forming plate, filler valve, cam follower or bushing or bearing, consider the value-added Ultra Detectable Blue (UD-Blue) can offer you in your food processing application.

If you would like help in determining if this material will offer value in oyur application, feel free to contact Plastics International for assistance. We would love to hear feedback from any who have used the product and if it helped solve any challenges in your business.

(Click here for a free datasheet) or visit for more information.

Plastics Suppliers

Where Do You Buy Your Plastic Stock Shapes?

The art and science of distribution is often discussed in day-to-day business in just about every market, but some may feel that they do not see it in practice often enough in the market place. Today, as markets become more competitive than ever, it has become an everyday occurrence to see the channel partners in the supply chain reposition themselves from being a channel supplier to a “value-added” partner (in other words: a competitor).

This shift is happening in many industries like our plastics stock industry, and the whole idea confuses us. Who are they really adding value to? It’s not to the job shops that buy from them who make a living machining parts to a print. It’s not to the material manufacturer whose products they do not have in stock to service the market beyond their own “value-added” demand.

We often wonder how many metal distributors would survive in today’s market place if they started to make metal parts and sell them in the local market? Who do you really want to choose to do business with, a partner or a competitor?

For years, Plastics International has been warning job shops about Coyote Plastics, a ficticious plastics company that represents all of the “distributors” in the indutry who also compete with you, their own customers in the local market place for machining business.

Coyote Plastics is run by the ruthless Bossman and his loyal employee Eddie. These two are out to sell you a sheet of plastic or two until they can figure out who your customer is and go direct. They will never tell you they are your competitors. The approach may sound something like a “full service” or “value-added” supplier with ideas around those words.

Too many job shops don’t worry about the long-term implications of whom they buy from until it’s too late and their customer is gone. Some shops have decided to take their supply chain strategy in a different direction. Consider this link to an article regarding Yeager Machine, Inc. (Yeager Machine, Inc-Partnering Not Competing With Its Plastic Supplier). Yeager Machine made a strategic decision to choose their partners carefully, with a long-term strategy in mind.

If you think you are buying from a Coyote Plastics in your area or simply would like to be able to order material cut to size, with no minimum, and have it ship the same day, feel free to call us or visit us at to see if you think we can help your business grow.