I need a source for sheets of plastic and advice

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dereckd
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I need a source for sheets of plastic and advice

Post by dereckd » Thu Sep 18, 2014 8:39 pm

I'm currently using my shapeoko to CNC cut a project enclosure .... my circuit board does not fit perfectly so I want to mount the board on piece of plastic, and the plastic inside the case ... my questions are as follows;

1. Does anyone know a source for thin sheets of plastic that would be suitable for this purpose? ABS, Poly, Whatever, I'm thinking it only needs to be 2mm - 4mm thick
2. Does anyone have experience using a tap bit on plastic? I'm thinking of somehow trying to use the shapeoko to tool the holes for the skrews ... perhaps this is a pipdream

JayTeague
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Re: I need a source for sheets of plastic and advice

Post by JayTeague » Thu Sep 18, 2014 9:15 pm

Depending on how far you want to travel or not:
- Home Depot has thin clear plastic sheets

If you want something thicker - a cheap cutting board will work.


For actually tapping - well, using the Shapeoko to drill the holes is one thing. Trying to do the tap bit would not really be a good idea...

dereckd
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Re: I need a source for sheets of plastic and advice

Post by dereckd » Thu Sep 18, 2014 9:59 pm

JayTeague wrote:Depending on how far you want to travel or not:
- Home Depot has thin clear plastic sheets

If you want something thicker - a cheap cutting board will work.


For actually tapping - well, using the Shapeoko to drill the holes is one thing. Trying to do the tap bit would not really be a good idea...
Yeah I figured as much (for tapping) I don't mind ordering from the internet, I'm really surprised that more people haven't had the need for plastic sheet .... to make cases and cutouts stc

WillAdams
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Re: I need a source for sheets of plastic and advice

Post by WillAdams » Thu Sep 18, 2014 10:04 pm

I.C. cuts out the parts for his DW660 dust shoe upgrade of acrylic using his (muchly upgraded) Shapeoko and then taps the acrylic if memory serves.

With an already drilled hole in a known location and homing switches and a properly shaped bit it should be possible to have the machine cut threads, even internal threads should be doable, but it's just easier and more straight-forward to make the hole and then use the proper tap.

Inventables sells various plastic sheets. I've tried to get lists of materials vendors, but little luck:

http://www.shapeoko.com/wiki/index.php/ ... #Materials

One other thought is ordering sheet plastic from either a sign or a glass shop.
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cvoinescu
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Re: I need a source for sheets of plastic and advice

Post by cvoinescu » Thu Sep 18, 2014 10:29 pm

It's not a good idea to try to tap holes without spindle-synchronized motion, and you need a much, much slower spindle with a lot more torque. The machine itself is probably fine, for tapping plastic. However, there's no point -- you can tap plastic with the tap in a cordless drill in seconds per hole. And it's not a good idea to tap thin sheets of plastic. If the plastic is somewhat flexible and not prone to cracking (the opposite of acrylic), you can use self-tapping screws. If the plastic is not prone to cracking (so no acrylic again), you can also use rivets. If you insist on machine screws, there are nuts that attach to the plastic much like a rivet, and you can then screw into those. For thicker plastic, there are metal inserts that go in the plastic (some need to be heated, some you just push in) and you thread the screws into them. Or, you can use square nuts and T-shaped (actually, cross-shaped) cut-outs for them.

At any rate, I suggest reading this: http://www.instructables.com/id/How-to- ... ally-Fast/
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Improbable Construct
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Re: I need a source for sheets of plastic and advice

Post by Improbable Construct » Thu Sep 18, 2014 11:21 pm

You do not want the acrylic from home depot or lowes (the stuff with clear or blue plastic covering). It is extruded acrylic and it does not machine well. You will want cast acrylic for machining (it usually has a paper backing). I buy most of my plastics from http://www.iplasticsupply.com/ When I lived in SoCal I would just drive over there but now I have it shipped to me. Their prices are reasonable and they have just about every shape and size.

I do tap the dust shoes and the delrin nuts. Most of the harder plastic tap just fine. The thicker the plastic the easier it will be to tap and the better the threads will hold.
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Marty M.
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Re: I need a source for sheets of plastic and advice

Post by Marty M. » Fri Sep 19, 2014 3:20 pm

In the past, I've purchased from US Plastics.com. with good results. The roughly 1/8" thick acrylic glazing from Lowes tends to be brittle and shatters easily from my experience.

criznach
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Re: I need a source for sheets of plastic and advice

Post by criznach » Fri Sep 19, 2014 5:30 pm

As Marty said, I've found the Home Depot/Lowes variety quite brittle. Tapping it is pretty much useless. But I've found that I can machine it with patience. I haven't tried the cast stuff to know the difference. I've had the most luck with the inventables 1/8" single flute, with a speed of 1-2 on my Makita (maybe 10k rpm?). I can't remember what my feeds were, but I think around 1000mm/min at .5mm step down. More flutes, higher RPM, or too slow of feed and you'll see melted plastic climbing up the bit and eventually it will break or leave a melted edge on your part. I'd still like to get my hands on some of the cast stuff.

ThatOtherGuy435
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Re: I need a source for sheets of plastic and advice

Post by ThatOtherGuy435 » Mon Sep 22, 2014 1:44 pm

The only stuff I have found worth buying at HD/Lowes is their polycarbonate/lexan - but size choices are pretty limited The 1/8" is actually 2.4mm, the 1/4" is actually 5mm. The 1/4" (actual: 5mm) plywood, however, is awesome for prototyping before dropping an expensive piece of plastic in, and cheap as dirt in convenient sizes (2'x4', 2'x2') if you don't have a truck for full sheets.

I get most of my plastic from Amazon (lower quantities, because Prime shipping) and onlinemetals.com (meh shipping costs but excellent material costs. OnlineMetals has a pretty mediocre website for browsing, but if you know what you're looking for it is simple and fast.

Tapping plastic with less than 1/4" of depth is probably a lost cause. I tend to mount things like you're describing by using the 5mm plywood and countersinking the bolt/screw head, then using the nut side to screw down the PCB.
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SOuser
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Re: I need a source for sheets of plastic and advice

Post by SOuser » Tue Sep 23, 2014 1:03 pm

Also there is TapPlastics.com

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