Simplicity = Savings

Customers with a budget in mind often ask us how they can reduce the price of their part. They think that the price is always tied up in expensive material costs but in reality it’s usually the labor costs or a complex mold that results in a high price. What you should understand is that the more complicated a part is, the more expensive it will be. In the case of a molded or extruded part, the tooling needs to be more complex and this takes more time and effort, therefore the mold will cost substantially more. In the case of machined parts this is even more acute as every hole, angle, and cut adds cost.

Labor for machining is quoted based off “passes” that is how many times a tool needs to touch the plastic material in order to make the cuts needed to manufacture the parts. These passes are the labor cost – the more passes, the more cost. A good example to discuss are “webbed” sheaves. These are sheaves or pulleys that have the sides machined out around the outside of the hub on either side. This has the sometimes beneficial property of reducing sheave weight because it’s now made of substantially less material. However, these weight savings mean lots of extra machining has to be done and this increases the cost of the sheave. Where lowest price is desired and weight savings are not critical, webbing is not advantageous to your application.

One service we offer to customers is that we provide “blanks” these are partially machined plastic parts that are not completed, just the general profile is done. Once the parts arrive on site the end-user themself then finishes the machining. An example of this is our Redco chain channel for sawmill applications. We can offer the channel pre-drilled with weld washers but this adds about $0.85/hole. Many customers elect to simply buy the channel and drill their own holes on site. Perhaps the best method to figure out if a part can be simplified is to just talk to one of our plastic experts. We’ll take a close look at the application and ask you if the part can be redesigned to a simpler format to save money.

For assistance with your plastic application please contact Redwood Plastics and Rubber.

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To Grease Or Not To Grease?

Whether or not to grease a plastic bushing is a frequently asked question, or even just an assumption customers make (that they need to). While there are times where greasing is important, and times where it is absolutely critical, in most cases with many materials you will not need to.  Avoiding the need to grease a bushing is a strong advantage plastics have over metal in application. Many plastics are self-lubricating and can come impregnated with solid or liquid lubricants. Certain bushings, such as the Rulons, will never require grease. In general, if you want to switch from a greases metal bushing and are flexible on material, an oil-filled option would be quoted. The cost difference between oil-filled and unfilled materials is about 30% so you need to judge how important it is not to grease.

In the case where an unfilled bearing grade material is required, grease grooves can be machined into the part. These would come with a “grease nipple” or small hole in the bushing to permit application of the grease. This is common for applications such as kiln wheel bushings or sprockets. That said, there is one case where you *must* grease and that is if the demands of your application exceed the P/V/PV ratio of the plastic. P/V/PV needs to be under all three maximum limits for the bearing material; however, that’s a discussion that requires it’s own article.

If you are looking for grease-less bearings or have questions on our Redco bearing materials please contact us.

Industrial Plastics and Custom Colors

A common question we receive is “can I get this in a different color?”. That is tough to answer in the world of industrial plastics! The short answer is many plastics are available in a variety of colors but price, availability, and minimum order quantity (MOQ) are often strongly affected by this choice. In general, industrial plastics are fairly bland, coming in white, black, or a shade of brown. Certain plastics can be colorful, such as nylons and polyurethane, but for the most part they come in black and white.

When Are Colors Feasible?

First of all it never hurts to ask, and we’ll always be straightforward. For the most part; however, we do not stock any plastics in custom colors. This can strongly affect the price if orders need to be brought in on special and in small quantities. Remember that we have to ship product all over North America to “land” it at one of our Regional Sales Offices (RSO). Often, this means you are paying much more for the same plastic just to have a non-standard color. How long you have to wait for delivery is context dependent on your order, but 4-6 weeks would be typical.

Polyurethane, nylon, and some profiles of UHMW are the easiest to get in non-standard colors.

When Are Colors Not Feasible?

The primary barrier to getting a product in non-standard color is when you have to stick to a certain grade of plastic or have a certain additive. For example, we get asked if the anti-static UHMW is available in colors: it is not, because the additive itself makes the plastic black. Also regarding UHMW, “clean” reprocessed UHMW in non-standard colors are much easier to get ahold of in rod or extrusion rather than virgin grade material and a colorant.

Specs given for a product might also confuse requirements. We recently saw a spec for a project that called for black virgin UHMW that was certified to ASTM D4020 but this is impossible as ASTM D4020 specifically excludes UHMW with any and all additives, including color. Natural UHMW is white so a black colored resin, or any additive, automatically cannot meet D4020.

In summary, if you want a non-standard color for your project you need to realize that while it is technically possible you will pay significantly for it in increased cost, delivery, and minimum order quantity.

If you have questions or a request for a non-standard colored plastic – please contact us today.

 

Industrial Plastic: Strengths And Limitations

One of the key questions we ask customers is “what is the application?” This question isn’t asked in order to steal your idea but to ensure that the plastic you’re looking for is optimal, or even workable in that application! Industrial plastics are excellent mechanical materials overall; however, like anything they do have both strengths and limitations. This article will review the core line of industrial plastics we carry, give the strengths, the limitations, and common applications/places where the plastic is wrongfully specified.

UHMW Polyethylene

Strengths: Well balanced properties, economical, and readily available.

Weaknesses: Poor dimensional stability

Specification errors: high load bushings, unrealistic tolerances, not compensating for thermal expansion.

 

Nylon

Strengths: High load bearing strength, diverse formulations, suits a wide variety of applications.

Weaknesses: Absorbs water, poor impact and cold-temperature properties.

Specification errors: Impact parts, marine applications (without accounting for swell), using nylon bushings in high RPM applications.

 

Acetal

Strengths: High load bearing strength, replaces nylon in “wet” applications, machines to excellent tolerances.

Weaknesses: Impact, temperature (especially steam) resistance.

Specification errors: Using black (copolymer) acetal in food processing applications. It is not food-safe, unlike the blue and white.

 

Tuffkast

Strengths: Excellent impact, cold weather, bearing, and moisture-resistance properties.

Weaknesses: High cost, elevated temperatures.

Specification errors: Typically in applications that generate high internal heat, such as a hammer cushion for pile drivers. Tuffkast is also softer than nylon, which can lead to increased wear in certain applications.

 

Polycarbonate

Strengths: Extremely high impact strength.

Weaknesses: Very prone to scratching.

Specification errors: As glass/sight part without upgrading to a anti-scratch version of the plastic.

 

Acrylic

Strengths: Scratch resistant, economical, stronger than glass, fairly resistant to weathering.

Weaknesses: Difficult to fabricate, prone to cracking.

Specification errors: Using in “Do-it-yourself” projects without proper knowledge of fabrication procedures.

 

Polyurethane

Strengths: Impact resistance, rebound, good bearing strength (bearing grades only).

Weaknesses: Water saturation degrades the plastic (especially softer grades), vibration degrades the plastic’s composition.

Specification errors: Vibration or moisture applications.

 

Rubber

Strengths: Lots of choice between properties, cost, wide application variety.

Weaknesses: Polyurethane is superior in many applications, grades must be selected carefully.

Specification errors: Choosing an ineffective grade of rubber for an application to save on cost, assuming the lower grade will still function.

For more information about which plastic is best for your application, please contact us.

4 Tips For Your Fabricated Plastic Application

Have an idea for an application requiring machined, molded, or fabricated plastic and now you’re ready for some pricing? Having your requirements organized and prepared will not only lead to a quicker quotation but could also lead to a more successful application and quite possibly – save some money. If you’re ready for that quote these tips will help make it the smoothest possible process:

1.) Have some sort of drawing or sketch to send

We don’t expect everyone to have a technical drawing but we at least need a sketch to get started. Sometimes applications that seem simple (a bearing or a pulley) are more involved than you would think. Take a bearing for example, if you just give us the outer diameter/inner diameter/length that doesn’t answer all we need to know. We’d want to know what the tolerances are, specifically in relation to a press fit or running clearance. Does it have a grease groove? Any flanges? A simple sketch can answer many of those questions.

2.) Have quantity and budget in mind

Truth is there isn’t always just one plastic that works in an application. Often there are multiple options that are “good, better, best” and your budget determines where the ideal material lies. Quantity is important too, as quantity can (but not always) lead to price breaks. However, narrow it down to 2-3 quantities at most for quotation. There are not price breaks at all quantities and putting too many tiers will delay your quote.

3.) Know the operational environment and inform us proactively

Often our reps will ask you questions about your application. Basic, yet important parts of the operational environment often get overlooked when choosing a plastic, so think of this in advance and, better yet, inform us at the outset. For example: is the application outside and therefore needs UV-protection? Is it exposed to any chemicals, acids, or bases? Does it take impact or is immersed in water? All of those are critical to the success of an application.

4.) Ask questions

We can’t answer absolutely everything, but we do know our plastics. So if you’re unsure if a plastic is best for your application then ask. Even if we’re not familiar with the application itself, we can at least discuss how other plastics compare to the one you’re considering and that may lead to more success and satisfaction with the end result.

For help with your plastic applications please contact us.

3 Critical Issues You Need To Know About These Popular Plastics

Many industrial plastics can “overlap” in applications where sometimes the optimal choice is only marginally better than several others. Many plastics may work in an application, such as nylon and acetal for sheaves, but certain issues in the operational environment may mean you need to stay away from a certain plastic! Three of the most popular plastics we carry are UHMW polyethylene, cast nylon, and PTFE. But each of the following has a critical issue you need to know about that often discredits the material in certain applications.

UHMW – Impingement

UHMW is a great wear material at an affordable cost…Usually. The one place where it isn’t good at all is with impinging wear, that is wear from a mating partner (could be anything from grains, to rocks, to another sliding component). Impingement is when something hits that UHMW on an angle. With UHMW anything that is remotely abrasive needs to hit it on a 90 degree angle. If the angle is any sharper you risk very quick deterioration of the UHMW plastic. It simply does not hold up to impingement. Often polyurethane, which has excellent impingement resistance, is a substitute and one can be creative, for example only using polyurethane in the impact zone and use UHMW for the rest of the application.

Nylon – Cold Temperatures

Many people know that nylon is affected by moisture swell, what fewer people know is that it gets brittle in cold temperatures, about 10 Fahrenheit or -12 Celsius. This can come as a shock, as nylon is known as a high-load plastic able to handle 4,000 PSI in bearing applications. It is not intuitive to think that cold temperatures would greatly affect the nylon but it is true. Fortunately, replacements are available, specifically Redco Tuffkast is often best to replace nylon. Tuffkast solves not only cold weather issues with nylon but also absorbs much less moisture, so Tuffkast’s properties help in that case as well.

PTFE – Wear

It is often that customers request PTFE for a wear or lining application, even including heavy applications such as dump truck liners! We do try to warn them that PTFE has very poor wearing ability. It is a soft, almost waxy material, that while it is available in sheet form (and seems solid enough) it really cannot hold up to aggressive wear. Bronze filled PTFE is available which increases the wear capabilities; however, by that point there is often a less expensive, more available plastic, that can be suggested as a replacement. PTFE should be avoided in high wear applications wherever possible.

Hopefully you are surprised by at least one of those points, in the hopes that it will assist your material choice in your next application.

To discuss the optimal plastic for your application, get in touch with us today.

Amorphous vs. Semi-Crystalline Thermoplastics

If your interest in plastic extends beyond your application at hand and you start to dig the chemical makeup and processes to make plastic you may come across the terms “amorphous” and “semi-crystalline” thermoplastics. Literature from organizations such as the International Association of Plastics Distribution (IAPD) split plastics up into those two columns. This is useful as the plastics are almost mirror images of each other in regards to properties. Understanding the two types of thermoplastics may help you when starting to think of a plastic for your application.

Amorphous Thermoplastics:

These are most of your clear plastics. They include polycarbonate, acrylic, PETG, ABS and polysulfone. Advantages of these plastics are that they are easy to thermoform, they soften over a range of temperatures, and they bond well using adhesives. When compared to semi-crystalline thermoplastics of a similar grade, amorphous plastics tend to have better dimensional stability and impact resistance. Drawbacks include amorphous plastics having poor fatigue resistance and are prone to stress cracking.

Semi-Crystalline Thermoplastics:

These are most of your traditional plastics when you think of plastic “parts”. They include the polyethylene family (LDPE, HDPE, UHMW-PE), Polypropylene, nylon, acetal and fluoropolymers. Advantages of these plastics are that they are excellent for bearing, wear and structural applications. When compared to amorphous thermoplastics, these semi-crystallines tend to have better chemical resistance, electrical properties and a lower coefficient of friction. Drawbacks include semi-crystalline plastics being difficult to thermoform, difficult to bond, have a sharp melting point and only average impact resistance.

Feel free to save a copy of the thermoplastics rectangle below. Click on it for the large, high-resolution version:

IAPD_Thermoplastics_Rectangle