Posts Tagged ‘tips’

Nylon is a fairly popular plastic used by the DIY community: and it should be! Versatile, strong, and available in small quantities it offers many properties valuable to the public’s plastic applications. In most cases, nylon will be an ideal material for mechanical parts such as sheaves or bushings. But it isn’t perfect and it like anything it has its drawbacks in certain applications. Here are some tips on using nylon that will serve you well.

1.) Don’t use it in the cold

Ok, well you can but you just need to be aware of impact. Nylon gets brittle in the cold, at about 5 degrees Fahrenheit and if it’s taking any sort of impact it could break. In fact inĀ  any application where you expect impact, use Redco Tuffkast instead (it has been developed to replace nylon in applications with impact.)

2.) Don’t use it in water

Unlike most plastics, nylon absorbs a significant amount of water – up to 4% of its volume in 24 hour saturation. For marine applications or those involving tight tolerances you probably want to go with an alternative material. Acetal is commonly specified in this case but Tuffkast may be an option as well, it depends on the application, so ask your distributor.

3.) Do use it under load

Nylon can handle 4000 PSI in application and this is one of the highest loads of readily available thermoplastics. This makes nylon excellent as a bearing, sheave, or other load bearing part.

4.) Pick the optimal grade

Nylon isn’t just “nylon”. It’s available with a variety of fillers: glass for dimensional stability, moly for high load low RPM applications, oil filled for reduced friction, UV stabilizers for outdoor use, and PVM (pressure velocity maximum) for the highest load applications. These fillers add only a minor cost, or in some cases cost the same as the natural grade, and are well worth it for certain applications. Unsure if you need a filler? Discuss your application with your distributor.

Even though three of these four tips are “don’ts” knowing when to avoid a material is just as important as knowing when to use it! Don’t get us wrong – nylon is a versatile, excellent, affordable plastic for a wide range of applications. Just keep in mind that it has advantages and drawbacks: just like every other material out there.

3 “Insider” Plastic Tips for the DIY Community

Posted: September 30, 2016 in Uncategorized
Tags: , , , ,

When you’re a member of the public who just needs some plastic for a home project, dealing with a plastics distributor can be a little awkward. They’re not like a “store” in the traditional sense, with product neatly displayed with nice little price tags. Product is quoted based on specific needs – and often, you don’t even know what those needs are! Sure, you may have an application in mind, and you might have heard of a plastic that works well in that application. But how do you know for sure? In addition, industrial plastics are a premium material and the cost can be a surprise to some people. Here are three “insider” tips from those of us in the plastic industry which will help you have a more satisfying experience with your DIY application:

1.) Be open-minded – and don’t care about looks

Many people have an idea that, like with products made of consumer or “commodity” plastic, that a wide array of colors, textures, and sizes are available. This is not the case at the level of industrial plastic. Most plastics only come in one color per grade and the color is often just white or black. Colorful plastics like frosted acrylic are hard to come by in small quantities. You need to place the needs of your application beyond color matching or other aesthetics.

Also, be open-minded about material. It’s quite possible a knowledgeable salesperson will recommend a different material. If you’re worried about the increased costs, ask for some clarification on why the suggested plastic might be better and what other options you have available.

2.) Ask about offcuts

For many smaller projects you don’t need a lot of material but plastics will commonly be offered in 4′ x 10′ or 4′ x 8′ sheets. One potential option is to ask your distributor if they have some offcuts they would be willing to sell. Many plastic distributors will have companies under contract to buy their offcuts, but some are usually kept on the shelf and either way the distributor usually makes a bit more by selling offcuts for cash. You may have to take a slightly larger piece, but it could save you money, and it’s worth an ask.

3.) Arrange your own pickup/freight

“Quote and include the freight” is a common request a plastic distributor gets but do you know what you’re actually asking for? True, to get a contract done industrial supply companies will mostly quote the freight. But what they’re doing for the most part is contacting a freight broker and getting them to spit out a quote, which is then marked up to you by 10-15%. The time a salesperson takes away from their primary job needs to be compensated for. Your best option is to just ask for the product weight and dimensions and contact a logistics provider yourself. Or make a UPS, Purolator, or Loomis account for the smaller orders.

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UHMW polyethylene is probably the most popular engineering plastic for use in DIY projects. But how do you work with it? People often get overly concerned with fabrication, especially in regards to the “tolerances” needed for most home projects, but regardless here are some tips to get the most out of your UHMW application.

Sawing:

UHMW can be cut with either a circular or band saw. A band saw is best as it will vent heat away from the plastic and allow for faster cutting speeds. The band saw blades may be 10-30mm wide and about 1-2mm thick with the circular pitch between 3 and 10mm. To prevent the saw blades from becoming jammed, the teeth must be set at approximately 0.5mm. When using circular saws, saw blades with a minimum setting 0.5mm are also preferred. Normal cutting speed for band saws is 1,000-2,000m/min and for circular saws, 3,000-4,000 m/min.

Drilling:

Lower RPM drilling is recommended unless compressed air, water, or cooling oils are used – UHMW melts easily. Twist drills are most commonly used but pointed drills and circular cutters can be used for higher diameter holes.

Welding

Because of its high melt viscosity, friction and butt welding are the only practical methods for joining Redco UHMW by welding.

Machining

Machining is the principal method used to fabricate finished parts from UHMW. UHMW can be sawed, turned, planed, milled drilled, stamped and welded easily on woodworking or metalworking machines. The following general directions should be observed in these operations: To obtain surfaces of high quality, tools should always be sharp. For the most purposes, normal tool steel is satisfactory through many fabricators use special steels.

The optimum cutting speed is between 250 and 1,000 m/min. At lower cutting speeds cooling is not required, but at higher cutting speed range, water cooling or the use of soluble cutting oil is essential. In all cases, care must be taken to avoid heat build-up in the machining operation, so that the work piece does not smear the cutting edges. In milling and turning, the feed should not be too fast and the depth of the cut should be greater than 0.3mm.

Bonding

Questions about solvent bonding are common but unfortunately this is not recommended with UHMW. It resists most solvents and, at best, will create a below-average to poor bond. Mechanical fixation is recommended wherever possible.

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There are a lot of flashy “do it yourself” projects that hobbyists get in to with plastic but one application that keeps coming up that you might not think of is the simple gear. The general reasoning to use a plastic gear as a replacement for a metal gear make intuitive sense: the plastic gear will often be mated to a metal component and the fact that you have a plastic on metal connection now should greatly increase the life of the mating components. The problem is hobbyists do not really know what to use: we’ve heard of HDPE, UHMW, nylon and even polyurethane be requested by the DIY community for a home made gear application. But how suitable are these plastics for the application?

Actually – not very. Most plastics cannot be machined to tolerances as tight as metal be but many plastics, especially the polyolefins such as HDPE and UHMW, are very soft and could have the gear teeth quickly lose their shape once that gear starts working. Nylon is better, but it cannot take much impact at all – especially in the cold – meaning it is considered to be fragile. The best material for the application is actually acetal. Acetal is a very hard plastic that machines very well and holds excellent tolerances. It is widely available in rod stock from plastics distributors across North America. The gear in the picture below is made of white, homopolymer acetal. Black copolymer acetal is also widely available and would work well too – its properties are slightly worse than homopolymer in some respects but it is also less expensive.

Acetal