Buy Better!

Posted: January 2, 2020 in Basic Plastic Tips

Every once in awhile on this blog we like to educate our readers on how you as a hobbyist can be more efficient in your plastics purchasing. The idea is to get you the plastic you need at the lowest cost and like anything there are strategies to do that. Here are some tips to get the best deal on the plastic you need.

1.) Ask For Offcuts

“Offcuts” are pieces of plastic left over from fabrication jobs. Distributors who do fabrication work tend to have little pieces left over which just take up inventory space waiting for a future job to come in where they may be used. If you get in touch with a distributor, let them know the piece size you need but ask if there’s an offcut you can buy close in size. Any reputable distributor will be glad to check and they’ll price it for less than it would retail in standard sheet form. In addition, you might be able to get a higher grade of plastic for cheaper asking for offcuts! Just be aware that offcuts will not always be available though it never hurts to ask.

2.) Ask about a “generic” grade

Just like with other products, many plastics have brand names, which are more expensive than equivalent plastics from “generic” manufacturers. We can tell you the quality is almost always identical and you often cannot tell the difference even in how it looks. Often hobbyists hear brands such as “Delrin” on the internet or the DIY community and assume that’s what they need; however, that’s usually not the take! For example, “Delrin” is the brand name of a homopolymer acetal plastic. The plastic is called “acetal” not “Delrin”. If you get a quote on name brand “Delrin” it will likely be more expensive than generic alternatives. The best way to pose the question to your distributor would be “Can I get a quote on [brand name] or generic equivalent?”

3.) Do the fabrication work yourself

This might appear to be a no-brainer but it really isn’t! Even though we’re members of the DIY community and enjoy our home projects, lots of hobbyists ask for the distributor to cut their plastic to size or even engage in light fabrication. While the distributor will price you out on that – make no mistake, you’re paying for it. You may not realize that fabrication isn’t free yet also most plastics can be easily cut or fabricated at home with no special tools! Why waste money when you’re a hobbyist in the first place?

 

There are many assumptions people make with plastic and one of those is that the DIY community finds beautiful acrylic applications on the internet and thinks that acrylic “just comes like that”. Unfortunately, there is no “easy button” when it comes to acrylic – to make it look beautiful requires specialized techniques. In fact, most plastic companies will not provide these finishing services unless they’re an acrylic specialist. The disappointment often occurs when someone cuts into acrylic and finds the finish of the edges isn’t what appears on the internet. So how do you get that amazing edge?

Well, there’s two techniques only one of which we’ll cover today. To get the “smoked glass” effect you need to sand the edges; however, for the beautiful glass-like edge you need to do what’s called “flame polishing” which is exactly what it sounds like: you take a flame to the edge of the acrylic melting it and letting it reform in a glass-like appearance. Fortunately for most of us in the DIY crowd, home flame polishing where perfection isn’t required is easy to do and a quick run to a hardware store will give you all the “equipment” you need. We found a short video that gives some quick instructions on home flame polishing and you can view that here:

Do you like to look clueless and unaware?

Didn’t think so.

This is why so many customers trying to ask a distributor about a certain plastic or rubber get themselves into trouble. Being in the industry, it’s frustrating to see as we want what you want – success in your plastic or rubber applications. Errors in plastic selection or identification are more critical then many would think. After all, most plastics feel the same in their hardness and strength, right? Well…Getting it into an application might result in a nasty surprise. Despite how plastics or rubber may look or feel the same, the fact is their greatly differing properties could result in an under-performing application or even a failure.

So, in the case you’ve used a plastic or rubber in the past and need more of it, you need to make sure you request the right thing. There are several ways of doing this. Firstly, we’d recommend you keep the invoices for all plastics and rubber orders you make. The invoice will typically be detailed enough to identify the material. If you don’t have that, the next best thing would be to bring the distributor even a sample of your old material. They can either analyze it on site (sometimes) or send it away to get tested. That extra time and effort is worth it to avoid a failure!

You need to be aware that color does not equal type! It’s common when a customer doesn’t know the plastic they’re trying to purchase to tell us it’s red, or black, or brown, etc. This unfortunately does not identify the material – not only are many materials typically in those colors but many plastics can be supplied as custom colors which throws this option out the window as far as identification.

Rubber is an issue all its own. Most rubber is not colored and is black; however, this again does not denote the type of rubber or the grade. Many rubbers are available in inexpensive consumer grades as well as high-performing premium grades. As we joke internally, when you ask many customers what type of rubber they use the answer is “It’s flat, black, and stored out back.” More commonly, a customer will identify all rubber as “neoprene”. While neoprene is a good all-purpose rubber it has limitations and shouldn’t be assumed to work well in all applications.

The moral of the story is when it comes to plastic and rubber there is no shame in admitting you need help in identifying what you’re looking for. Ask an expert, don’t feel ashamed, and get the application right the first time.

SAMSUNG

 

Plastic lumber is one of the most intriguing materials for the DIY community because it’s so easy to wrap your head around how one might use it. Since it comes in profiles that are the same dimensions as wood and bears the same load as wood (if not better) substituting it for wood makes a lot of sense. Plastic lumber has very low maintenance requirements: most of it is UV stable and rot proof as well as resistant to splitting and insect attack. A concern you need to have is that a fiberglass reinforced HDPE product should be used when bearing weight, such as a deck without a reinforced backing. Also, despite UV resistance, the color will fade somewhat over time so you need to have fair expectations.

Another expectation is price. People are usually exposed to cheap single plastics or otherwise “commodity” plastic found in consumer products. Unfortunately for members of the public, the inexpensive cost of these materials does not reflect the cost of higher grade engineered plastics. When members of the DIY community pursue plastics the first time around their “sticker shock” often leads to the exclamation “but it’s just plastic!” We need to change our way of thinking: besides the cheap commodity plastics, plastics are a premium material that offers significant advantages over metal and wood at a premium price. However, you really do get what you pay for!

Plastic lumber will look great for years and function well in many applications but just know that you’re getting into an investment.

The application we found today highlights the means, not the end. We found a short Youtube video that shows how one “DIYer” manufactured UHMW hex nuts in his own shop. There isn’t necessarily a prevailing application for these nuts though. They will not have the sheer strength or rigidity of metal; however, as one commentator noted on Youtube – the ideas shown in this video could be applied to functional applications such as spacers or high-quality washers.

Perhaps more than anything, this application highlights how UHMW polyethylene is a “Jack of All Trades” material. UHMW performs good service in a variety of applications due to balanced properties. It does have deficiencies and should not be used as an automatic substitution everywhere but particularly for a spacer/washer application, it’s ideal where tolerances are not critical.

Hopefully the video inspires you to a successful application!

 

HDPE vs. UHMWPE

Posted: September 30, 2019 in Education, HDPE, UHMW
Tags: , , , , , ,

Hobbyists are often unsure of the differences between closely related plastics. When it comes to two commonly available plastics in the polyethylene family: “High Density Polyethylene” (HDPE) or “Ultra-High Molecular Weight Polyethylene” (UHMWPE or simply UHMW) – what is the difference? Are there any times it’s critical to use one verses the other?

The answer is in many cases the differences are not pronounced but there are a couple things to watch out for.

Where the products are more or less equivalent is any application where they’re being used as, for example, a spacer, a lining, a surface, or other “static” applications. Both products will appear to be the same color and will be the same weight. It’s when mechanical properties start getting involved that you should be concerned. Firstly, UHMW takes significantly more impact than HDPE does, so if you have an application where a part is being banged around – UHMW should be your choice. UHMW is also significantly slicker and an application involving “sliding” UHMW is the ideal choice. An example would be as sled rails on a snowmobile or toboggan: UHMW will traverse the snow much better! You can in fact find some good Youtube videos that make a comparison between the two materials on this application.

One note about the static applications listed above is that HDPE is superior as a cutting board. While both products are food grade and work great in the application, UHMW will dull blades over time whereas HDPE will not. With both products being highly available, HDPE would be the better choice. This is why HDPE is preferred for synthetic ice as well.

Speaking of other properties the plastics are pretty comparable with their UV resistance (poor), chemical resistance, availability, machinability, and heat tolerance. As always, if you’re unclear what to use for your application just contact Redwood Plastics and Rubber for assistance.

A lot of what we offer here on the “DIY” blog is material information; however, as the hobbyist, you actually have to cut, drill, and machine the plastic yourself. It’s beneficial to educate yourself on practical fabrication matters. Most hobbyists grow up working with metal and wood; however, industrial plastic is only usually encountered when one knows to look for them – usually when one is a teenage “DIYer”.

The prevalence of CNC machines in recent years makes machining knowledge even more critical. In the video linked below, Instagrammer Tom Zelickman educates on issues he’s had with machining plastics and how to overcome various challenges including his stressing about one “aggressively” machining plastics and cleaning them.

You can view the whole video on YouTube here: