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justCNCit
01-07-2008, 12:43 AM
do you people know of any kind of cheaper plastic, that is machinable? I've got wood in plentiful supply but plastic is ideal for stuff that people are going to want, Delring is an arm and a leg. So is polyurethane. Where can I find a comparable product for a reasonable price?

gleas
01-07-2008, 05:38 AM
You might try ABS or PVC. They are a couple of the least expensive plastics. Plastics are a petroleium product so it goes up in price accordingly.

truckwiz
01-07-2008, 06:37 AM
I've used composite 2x4's and plywood with mixed results , it's made of recyceled plastics.

Brian

NickAshton
01-07-2008, 06:53 AM
I have been using various plastics from www.directplasticsonline.co.uk, they are very helpful if you ring them and they will supply any size you want, delivery is fast too.

I have tried Acetal, PVC, Tufnol and a few others, just avoid the Nylon ones (they just melt!!), the Acetal one cuts beautifully.

NickAshton
01-07-2008, 06:57 AM
I have been using various plastics from www.directplasticsonline.co.uk, they are very helpful if you ring them and they will supply any size you want, delivery is fast too.

I have tried Acetal, PVC, Tufnol and a few others, just avoid the Nylon ones (they just melt!!), the Acetal one cuts beautifully.

Paulo E.
01-07-2008, 07:23 AM
As someone mention before Plastic prices are directly linked to the Oil industry. Having said that yes ABS would be a good choice and while it might be easy to machine and all that, usually the finishes are not the best. As for PVC avoided if you can.... trully not only is it a crappy material but it will also eat ur tools up unless you have worked with pvc before and know all the feeds and speeds. I guess in the end what it comes to is that the plastic that you are using has the mechanical properties needed for the type of parts you make.

Good luck Bud.

bowersjack
01-07-2008, 07:52 AM
Look at UHMW and PBS. Both are a lot cheaper than delrin. UHMW is very softthough and hard to deburr

G Daggett
01-07-2008, 08:42 AM
We use a lot of different plastics and composite materials that we machine. Here is some info on what we use and have found as pros and cons.

HDPE (high density polyethylene)

Pros - Very easy to machine, cuts like butter even with dull tooling, can cut at higher feed rates, multiple color options, readily available.

Cons - Very poor abrasion resistance easily marked and scratched, very soft and flexible, not ideal for adding threaded holes for machine screws.

ABS (acrylonitrile butadiene styrene)

Pros - Higher abrasion resistance, available in a pebbled surface, more ridged than HDPE, can be threaded for machine screws, available in multiple colors, readily available, can be thermo-formed.

Cons - You need very sharp tools and good chip clearance to avoid chips melting back to the edges of cut material, feed rate to spindle speed ratio changes a bit depending on heat and humidity, not shatter resistant

PVC (polyvinyl chloride)

Pros - Easily cut, clean edges, versatile material, can be threaded for machine screws, available in multiple colors, can be reshaped with heat and cooling process, can be thermo-formed.

Cons - can be tough on tools, tooling and cut processes are very specific to this material, can be a bit brittle.

Hope this helps you. We use other stuff like phenolic that is virtually indestructible and is as versatile as wood, aluminum and plastic all rolled into one but it is found to be carcinogenic and is very expensive which cancels it out in many applications. But the stuff is wicked.

G Daggett

grahamweekes
01-07-2008, 10:05 AM
May I suggest an off the wall idea, recycled HDPE. It will not suit all uses or users but produces a solid white plastic which superficialy feels not unlike nylon rod. I wanted a large disc of thick plastic to make a vacuum chuck body for my wood turning lathe.

The following is an account of what I did but I make no recommendations and anyone trying it does so entirely at their own risk.

Here in UK we have many HDPE bottles which in most areas are not recycled and go to landfill. I don't know whether the marking system used in Europe is global but over here the bottles are often translucent rather than clear and have HDPE and a numeral 2 within a triangle on the base. I found on the web that the melting point is about 140 degrees C, easily achieved in a domestic oven.

I trialled this by shredding the bottles and placing them in a metal bowl of suitable shape in the oven. Ensure the space is well ventilated. You will need to adjust the thermostat to suit but do not turn it up too high as you may produce potentially noxious gases and toast the exposed surface of the plastic. I tried higher temperatures hoping the plastic would soften more quickly but only managed to make a stink and burn the surface. Radiant heating from a grill is not helpful in my experience as that too toasted the surface.

The plastic will not become liquid but will soften and coalesce. Translucent plastic became clear when it was soft enough to coalesce I speeded this consolidation up by periodically removing the bowl and pressing the plastic mass down to close it up and remove air pockets before topping the bowl up to get the desired thickness of plastic. Use a strong metal "tamper" dipped frequently in cold water to avoid it being glued to the surface of the plastic.

Once you have the volume you need remove from the oven and leave to cool. It takes a long time so be patient! There is a lot of thermal energy in the blob of hot plastic and you could give yourself a serious burn by being hasty.

The biggest problem I found was removing the plastic from the bowl as it sticks to metal, including polished stainless steel, like glue. Not surprising as the process is not a million miles away from using hot melt glue. It even stuck to a "non-stick" cake tin although that surface was well used and already damaged in places. If the material is succesful for my purpose and I need some more I will either try to find a way of removing the plastic as soon as it comes out of the oven and is still soft or look for a release agent. Those 2 part cake tins where the bottom can be pushed out might be suitable.

Having finally succeeded in releasing the HDPE I found I had a mass of quite hard opaque white plastic. Where it came out of the mould cleanly it has a glossy surface. It can be cut with effort using a sharp knife and looks like it will turn quite well enough for my purpose on the lathe using sharp wood turning tools.

Due to other priorities it will be a while before I get around to turning the plastic chuck body. I anticipate that my first attempt could have some voids hidden inside but hope that my second sample, where I compacted each layer carefully will be void free. Obviously I cannot comment on the engineering properties of the material. I will let you know how it turns out.

If you decide to try something like this yourself do take all sensible precautions to avoid burns or poisoning!

Happy New Year

Rebecca
01-07-2008, 10:45 AM
I use polypropylene cut to spec's for my plate holder on a HAAS VF2 that is customized. The EndMill best suited for my program is Carbide ball 1/2 2FL. I get my material from Interstate Plastics, they will deliver and if I order at least 1 sheet(cut) my delivery fee is waived.

mxtras
01-07-2008, 12:23 PM
I use HDPE for proofing programs and such.

It is, in my opinion, the most volume per $ and after all, for proofing that is what you are after.

It also works pretty well for certain parts. It will swell with moisture so you have to use with caution.

Scott

garfieldsimons
01-07-2008, 12:28 PM
Hate to state the obvious- ebay. Plenty of cutoffs from various materials.

gleas
01-07-2008, 02:28 PM
Bottom line, each type of plastic has it's own characteristics when machining and it can be tricky finding the proper feeds, speeds and cutters. It's best to stick with one type of plastic at first, and with some trial and error, you will find what we call the "happy place".

If you are just playing around you might look for a local plastic supply house. Most of them will sell retail and usually always have a REMNANT rack or bin where you can dig through and find good deals by the pound or by the piece.

If you have any questions about a particular type of plastic (thats what we sell) let me know and I could probably save you some time on the learning curve.

-Greg

jdell42
01-07-2008, 07:07 PM
Find a place like this near where you live.

http://www.piedmontplastics.com/locations.asp

I went in and asked if I could rummage through their scrap bin / non inventory items.. they were glad to make a few bucks on scrap.

Typically speaking if you are buying stock commodity plastics such has PE (HDPE, UHMWPE) will be cheaper than engineering plastics (Delrin, ABS ect).. but I'm sure that varries by region, supplier and their specialty.

Gary55Ford
01-07-2008, 08:02 PM
HI all I work for an electronics co. & build lots of PC board testers. I use Delrin exclusivly I know its expensive but its superior to anything else for machining i drill holes as small as .013 in it with no problems

fishface
09-24-2012, 06:15 PM
I found the cheapest source for HDPE in the UK is the Ikea "Legitim" white chopping board for £1. It is 240x340x8mm, although there is a handle hole to remove from that area. It machines really well and can be painted with acrylic spray paint too.

Walky
09-25-2012, 10:58 AM
I use polypropylene cut to spec's for my plate holder on a HAAS VF2 that is customized. The EndMill best suited for my program is Carbide ball 1/2 2FL. I get my material from Interstate Plastics, they will deliver and if I order at least 1 sheet(cut) my delivery fee is waived.

+1 for polypropylene, it's cheap, strong, looks good and is not a nightmare to machine.