Many members of the “DIY” community are attracted to the concept of plastic lumber. Usually made from recycled materials it carries both benefits to the environment by using less new material. In addition, plastic lumber can be manufactured in grades that are much stronger than regular wood. Most grades of plastic lumber are UV stable and involve much less maintenance than wood. They will not require repainting, will hold their color, will not rot or splinter, and will not come under insect attack.

However, with everything there is a “catch”. In the case of plastic lumber it’s the price and delivery. The problem comes down to two factors 1.) customers assume that plastic lumber is widely stocked in the available colors, sizes, and profiles they see on the internet. 2.) Customers assume that plastic lumber is, well, “it’s just plastic”. What people do not often understand is that many plastics, including plastic lumber, are not considered the “commodity” grade of plastics that the public usually encounters in everyday life. Commodity plastics make up consumer items, what’s in your car, your toys, your kitchen. Plastics are actually available in not one but three higher quality grades above “commodity” (yes, the actual grade of plastics used in consumer items is called ‘commodity’). The other three grades are, from lower to top, engineering, high-performance, and imidized.

The DIY crowd will usually only encounter high-performance plastics in PTFE, which is used in items like telescope mounts. They will never encounter the ultra-expensive and hard to obtain imidized plastics. What you need to understand is plastic lumber falls into the engineering grade of plastic and the most commonly quoted grade, fiberglass reinforced, is at the upper end of engineering grade plastic cost.

What are we getting at here?

You need to understand that the cost of plastic lumber vs. equivalent wood will be approximately 8-10x the cost of wood! We’re just stating the facts here, folks. Plastic lumber is not “just plastic” in the way a milk jug is. These plastics are considered a premium, specialty building material, which is why you see them in so many cool applications! It needs to be a great application to be worth the cost! The reason we provided a range on cost is that the color of the lumber actually plays significantly into the cost. Black is the least expensive, followed by wood tones, and finally really off-wood colors such as yellow or white. the difference is about 30% across the spread.

So when do you go for plastic lumber?

First of all, you need to be realistic about the cost. In addition to the lumber’s cost it likely will need to be shipped in from the manufacturing plant and this can easily cost several hundred dollars. You need to be realistic that the lumber will not get to you within a day or two (getting it on site in a month is typical). Finally you need to be realistic about your project. Hey, we love plastic here, but it has it’s time and place. If you want a premium, low-maintenance building material for your project, great, splurge and make your dream project come true! The issue is you need to have the facts on hand and analyze whether or not plastic lumber actually fits your needs.

 

 

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Acrylic can be more complicated than many people would think. There are some assumptions people make about acrylic which actually could be detrimental to their application or cost them more money than is necessary. First of all there is the topic of “Plexiglas”. That name has been around for so long that people think it’s a material – it isn’t. It is a trademark for a line of cast acrylic. But, the name might or might not be important to your application.

See, acrylic actually comes in two forms: extruded or cast. Cast acrylic is the version that comes in the sheets that are oversized by 1″ on their length and width: 49″ x 97″ denotes a cast acrylic sheet. Extruded acrylic comes in standard 48″ x 96″ sheets like many other plastics. There is a difference in quality between the two: cast acrylic is stronger and has better optical qualities such as clarity and finish. As always, there’s a catch: cast acrylic is more expensive (perhaps 40-50% more) than extruded and is somewhat less widely available. In many cases especially for members of the public, extruded acrylic is perfectly fine for their application. However, if you’re a professional manufacturing a product that requires a flawless look, or is for the government or military, then cast is probably the way to go.

We would urge you to remember that brand names exist for many plastics and in most cases don’t specify the plastic itself. Be reasonable when it comes to brand names, be realistic with your application, and you’re on track for the most success at the least cost.

When machining a bearing at home often “DIY” fabricators will not consider that plastics have different tolerances than metals. Even more importantly, consideration if an application requires a press fit or running clearance isn’t considered at all. But it really should be to have a properly functioning bearing! To provide complete assistance on this topic we need to first define “press fit” and “running clearance”. Press fit is most often on the outer diameter of the bearing and it is a small amount of extra material on top of the designed diameter of the bearing to allow it to be forced into its mating partner (perhaps a wheel) and “stick” there without rotating. Frankly, if that is the type of application your bearing is going into – you need to be concerned with a press fit.

Same goes for a running clearance. In most cases the shaft in the center of your bearing needs to spin freely right? Did you account of that in the design of your bearing or did you plan to push through a 2″ inner diameter bearing over a 2″ shaft? What you’re most likely going to have is a shaft with a quasi-press fit that sticks on the plastic. Instead you need to factor into your design some extra room on the inner diameter (ID) of the bushing.

At this point you’re probably wondering how much press fit or running clearance? Redwood Plastics offers a handy online machinist chart showing guidelines for just that. You can find the chart here: https://www.redwoodplastics.com/brochures/Machinist-Chart.pdf

Admittedly plastic welding is a fabrication technique that is going to be attempted by few “Do-it-yourselfers”. Plastic welding will require the purchase of special tools and filaments which are not always easy to come by.  In addition, since most plastic welding is done by specialists, it is difficult to get fabrication tips from plastics distributors or manufacturers. You’re likely going to have to search the internet for ideas and while we cannot vouch for the tips, YouTube seems to have several good videos to get you started off right.

In particular the company “Techspan” which manufacturers plastic welding equipment has, what looks to us, as a good 4-1/2 minute video on the basics of plastic welding. In particular we like that it talks about preparing the plastic for fabrication/welding (something often overlooked in these types of videos) and it goes into topics such as “tacking” which is welding two pieces on a 45 degree angle to each other. We’d prefer to let the video speak for itself and we’ve linked it below:

 

Quadrant Engineering Plastics is a major manufacturer of industrial plastics. While they do not sell directly to end-users, and instead sell through distribution, they still invest in many resources for end-users to help them reach their goal with their applications. One of the best is the “Machinists Toolkit” which is available by clicking here. This gives a variety of tips from what coolant to use, to tool tips and even troubleshooting specific issues that come up. It also gives feed rates and end milling/slotting guides for various plastics.

One handy section the toolkit has is a rating of the machinability of various plastics on a rating system. Acetal is usually the best where tight, critical tolerances are involved. But like with all plastics, there are situations where acetal is not ideal. In those cases when reviewing the various options you need to know what the “next best option” is. More useful still, is on the left side of the toolkit page is a link to the chemical resistance chart. This will allow you to look up alphabetically various plastics and their resistance to various chemicals. Please do not think that just because plastics in general are resistant to many chemicals, that a given plastic will be resistant to chemical exposure in your application! And do not assume that just because a chemical is “household” that it will not attack your plastic – it might, so do not assume!

Finally, Quadrant has also released a short video giving some machining tips. While the video says it is geared for a few high performance materials, much of the advice given is relevant to any home machinist working with plastics. That video can be seen here:

 

Something a little different today. We found a short (3-1/2 minutes) video tutorial on how to make a corn starch based bioplastic. None of the ingredients are toxic and most are what you would have around the house. It’s easy to make, simply requiring a pot and heating element. It’s a good introduction into the world of bioplastics which is a rapidly growing segment of the plastic market. Large companies such as soda pop manufacturers and other food processors that currently use a lot of plastics in their packaging are looking for biodegradable and environmentally-friendly plastic options.

This particular project would seem best for children interested in science. The goopy starch-based plastic can be used in simple molds or laid across stencils but it doesn’t seem practical for too many functional products. Its resistance to wear and properties seem to be similar to LDPE once cooled. To be honest the examples that the host of the video shows at the end are…Underwhelming. But since the basic mixture for this plastic is so easy to do it would hopefully inspire in your mind some better things to do with it.

We’ve posted the video here:

FRP wall panels are a great product for the DIY community. The panels are strong, long-lasting, grime and vandalism resistant. Excellent for applications such as bathrooms, garages, “mud rooms”, or areas animals are kept. FRP wall panels have a relatively economical cost compared to industrial FRP panels, are widely available, and easy to install. As with any project, preparation is key to saving money and prevent disappointment with the final result.

To start the first thing you want to do is draw a quick sketch of the area to be covered. Mark each wall with how many feet it is in length. FRP wall panels come in 4′ x 8′ and 4′ x 10′ panels and the next thing you need to do is figure out how you will orientate the panels. Start at the floor – will they be arranged to provide more height by being set side-to-side by their width? or by their length to provide 4′ high coverage? In many applications, the panels can be placed on their side to cover more area and reduce costs. You should now be able to figure out how many panels you need.

Next, figure out how much FRP adhesive you need. The adhesive comes in 4 gallon buckets and covers 200 square feet. simply add up the total area of the panels you need and divide by 200. For example, if your project requires 12 4′ x 10′ panels that is 480 square feet / 200 = 2.4 or 3 buckets of adhesive will be needed. It’s always good to have some extra so never round down!

Following this step you need to figure out how many inside corners/outside corners/j-trims you need. Inside corners and outside corners are PVC plastic dividers for FRP wall panel that are purchased alongside the panels. This is pretty simple as you just count how many corners you have. The trims and corners all come in 10′ lengths. The j-trims require a bit more thought. These are also PVC but are used to join two panels where there are no corners. You need to be able to sketch or visualize where your panels will buttress up against each other along the stretches of wall and be able to count up what you need.

And that’s pretty much it! At this point you should have a clear idea of the scope of your project and all the requirements for your FRP panels and how many accessories you need. The next step is to simply contact your plastics distributor and request a quotation. Please give clear and specific requests including relevant quantities for all required components. That will ensure a quick and accurate quotation.