Three Preparation Steps For Part Design

So, you have a part you want made out of plastic (or rubber). You have a drawing, maybe a CAD file. You know what the part needs to do.

What now?

This is the stage where you need to make the leap from idea to practical. To get the part finalized, material specified, and actually get the part into production. What information do you need to have to finalize everything?

1.) Know Your Operational Environment

This is absolutely critical and something we often need to work through with customers before we make a recommendation. You need to know the complete operational environment for your part. This includes:

  • Min/Max operating temperature
  • Chemical exposure (and how much exposure to each chemical – it matters!)
  • UV-exposure
  • Pressure applied on the part (in PSI)

Depending on the part there may be other critical factors but you should know at least those four.

2.) Know Your Required Tolerances

This is perhaps the most important thing that keeps getting overlooked in part design. Often we’re handed a drawing with metal tolerances (+/- 0.001″) and told to make it (hint: not possible to hold those tolerances). Or, in many cases, customers simply tell us to hold “best” tolerances. Did you know there’s a premium to that? When we work out a quote internally, required tolerances are part of that because of the time and risk involved in hitting our tightest (+/- 0.005″) tolerance. Often a (+/-) 0.03″ is suitable for many applications and since it will save you money, it’s worth it to know the demands of your application.

3.) Know Your Quantities – Buy In Bulk

Quantity usually means price break when it comes to parts. Customers will often send us a drawing and ask that we quote a couple pieces, ostensibly as samples. The issue is that the cost for prototypes will be inflated compared to the prototypes…And sometimes customers just think the price would remain constant. So know an accurate number of how many parts you will need once in production and get both prototypes and production runs quoted at once for a clear picture of your costs.

For more information on how to buy your parts in the most economical way possible, please contact us today.

 

 

 

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Plastic Angle

Out of the many parts and plastic profiles requested of Redwood Plastics and Rubber, plastic angle keeps coming up. This is typically plastic bent at a 90 degree angle halfway. This is primarily used for protection of a surface or object if machined out of UHMW or nylon plastic. However, much stronger (more rigid) fiberglass reinforced plastic (FRP) angle is available and stocked by our supplier. A common example of a FRP angle application would be to bolt it in on the edge of a platform at a train station. FRP angle is available in a variety of widths and thicknesses with 1/4″ and 3/8″ thick being the most common. It is available in all three primary EXTREN resin types (general purpose polyester, fire-retardant polyester, and vinyl ester). These angle profiles are more expensive than steel or aluminum angle; however, for certain applications such as those that demand electric or radio non-conductivity, plastic angle may be your only choice.

To get a quote on an angle profile is easy. Firstly, we need to know the width of each side of the angle, they are not always the same! We then need to know both the thickness and the material required. If you need assistance selecting a material, just ask, but me sure to be ready to answer questions about your application such as what the angle is doing, if there is any chemical or high heat exposure, etc. Angle profiles of all plastic types are typically sold by the 10 foot length; however, there are cases where we can supply shorter or longer profiles.

For a quote on your plastic angle needs, please contact us today.

 

Weathering and Exposure Concerns

There is unfortunately some misinformation in the plastics world regarding weathering, exposure, and UV-resistance. In some cases where applications go wrong, customers simply did not consider how a certain plastic might handle being exposed to certain environmental factors. One of the largest pieces of misinformation is that reprocessed-black UHMW often called “UHMW black” is UV-stable. It is not; however, and has only some limited UV-resistance due to the addition of carbon black in the resin. The following are examples of weathering and exposure concerns for some popular plastics and options to mitigate these issues.

Nylon:

-Brittle in cold temperatures (below -15 degrees C)

-Absorbs water

Solution:

-Switch to acetal or Tuffkast

UHMW/Polyethylene:

-Poor UV-resistance makes it prone to cracking with UV-exposure

Solution:

-Procure a fully UV-stable grade

Polyurethane:

-Certain varieties weaken and break down in wet environments (hydrolysis)

Solution:

-Work with a plastics expert to select a polyurethane variety not weakened by hydrolysis

Polycarbonate:

-Poor weathering resistance, will yellow and crack with exposure

-Poor scratch resistance and tends to become cloudy with small marks when used in outdoor applications

Solution:

-Request sheets with UV stable and/or scratch-resistant masking. These will be typically unstocked.

 

 

 

 

 

 

 

 

 

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.

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.

 

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.