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Unread 27-01-2006, 13:00
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Re: Working with Lexan

Quote:
Originally Posted by Phil Paspalas
Last season, our team used Lexan (polycarbonate) to shield the electronics from damage. We found it easy to cut, bend, de-bur, and generally pretty good stuff! But it's a pain to drill!!!!!!!!!!!!! Especially when trying to drill large holes in it to remove weight. We tryed a hole saw with poor results and regular twist drills were problematic as they get past 3/4". Any suggestions?

We have used polycarbonate in our electronics enclosure for the last 3 years and have never had a problem with it. We used 1/4" thick for a base to hold our electronics down and 1/8" thick for doors.

To stop melting polycarbonate, slow down your hole saw.

When drilling "lightning" holes in polycarbonate use more smaller diameter holes as it will keep other robots from finding the hole and hitting your electronics.
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Unread 27-01-2006, 14:53
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Re: Working with Lexan

We've used Lexan for just about everything at one time or another. The best way for cutting/drilling holes that we've found is to use WD-40 as a lubricant.

Have someone spray it onto the bit while you are cutting/drilling.

You have to keep the bit cool. Once the Lexan starts to melt, it grabs the drill right out of your hands. Been there, done that. Ouch.

Also, If you have any plans on screwing into the stuff, we've found that drywall screws work very well. You have to drill a pilot hole and use lithium grease (or some other lubricant) on the screws. If you are using a drill to drive the screws, be sure to set the torque limit down to about 6. You will shear the screws and they are not fun to get out after that.
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Unread 28-01-2006, 05:48
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Re: Working with Lexan

Another thing about poly carb is that if you are planning on using any kind of loctite DON'T. We made the mistake and the poly carb actually developed hairline cracks leading out from the center of the hole.
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Unread 07-02-2006, 15:28
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Re: Working with Lexan

I didn't see it specifically addressed anywhere in this thread (except in the Andy Baker "blue" index), but all polycarbonate is not the same. We have found a huge difference in Lexan brand versus other generic polycarbonates and the name brand is worth the price difference in terms of machinability and strength.

We love the stuff - it absorbs energy like crazy during the "rigors of competition". The self-tapping drywall screws work very well if you follow the instructions Warren gave for pilot hole and Lithium grease; using .375 thick Lexan you can mount into the edge and it makes a nice butt joint.

And the loctite issue Kirk mentioned - been there and done that too. It causes some sort of thermal reaction while curing that shatters the lexan from the inside.
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Unread 07-02-2006, 16:19
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Re: Working with Lexan

Quote:
Originally Posted by Gary Dillard
I didn't see it specifically addressed anywhere in this thread (except in the Andy Baker "blue" index), but all polycarbonate is not the same. We have found a huge difference in Lexan brand versus other generic polycarbonates and the name brand is worth the price difference in terms of machinability and strength.
So true. Here is how I *believe* things work in the thermoplastic world:

a. There are only a handful of places where polycarbonate resin is made. This is done in chemical plants, with huge capital costs and very big environmental considerations. Polycarbonate resin looks somewhat like white grape nuts, but a bit smaller.

b. Resin is sold to extruders or compounders. Some extruders make sheet, some make plastic pellets. Sheet is cut and sold to end users. Plastic pellets are sold to molders. Compounders mix other things with resin to make co-polymers or other special applications. They may mix in other materials (fiberglass, micah, other plastics, etc.) or they may filter it to make specialty grade products.

Like anything else, resins are tested and graded. The best resin sells for a higher price. Lower grade resin sells to lower prices, of course. Some companies focus on the high grade stuff while others sell cheaper grade material. These companies usually list the mechanical properties of their materials, like this for LEXAN 101R. You can compare other polycarbonates by looking at elongation, hardness, fatigue, and other ratings.

Andy B.
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Unread 07-02-2006, 20:18
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Re: Working with Lexan

What are you drilling with? You using an actual drill or have you tried a milling machine perhaps?
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Unread 07-02-2006, 21:48
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Re: Working with Lexan

is acrylic easy to mill? anything i should be careful of?
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Unread 08-02-2006, 17:29
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Re: Working with Lexan

Quote:
Originally Posted by greencactus3
is acrylic easy to mill? anything i should be careful of?
We had some acrylic that we had mistaken for lexan, and it shattered as soon as we put a drill to it. We tried to use it up one year as a mount for our sponsor decals, and it broke and shattered just about every time we touched it. I'd stay away from it personally.
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Unread 09-02-2006, 09:09
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Re: Working with Lexan

You just have to have skill to work with acrylic. HAHA
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Unread 09-02-2006, 11:54
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Re: Working with Lexan

A good suggestion for electronics and lexan is to mount the actual electronics (Victors, Controller, etc.) on a plank of wood (lighter), and just cover it with a sheet of Lexan. The electronics are still protected and you don't have to worry about drilling lots of holes in the Lexan.
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Unread 09-02-2006, 15:25
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Re: Working with Lexan

Quote:
Originally Posted by sdcantrell56
You just have to have skill to work with acrylic. HAHA
very helpful. do you want to share those skills?
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Unread 09-02-2006, 16:14
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Re: Working with Lexan

Quote:
Originally Posted by greencactus3
very helpful. do you want to share those skills?
Are you talking about acrylic or polycarbonate? They are two different creatures. Its like talking about tube vs pipe both are steel but they have different properties. Polycarb (or lexan) is fairly easy to work with. Just make sure you use some kind of lubricant (WD-40 was suggested) and watch that you don't start melting the plastic instead of drilling it.

If you are working with acrylic every time you try to drill it, bend it, or screw into it you are risking it cracking if not shattering. Acrylic was not allowed for use on FIRST robots for a while because of this. Personally I don't know why they changed the rule. Acrylic can be dangerous if you do not know what you are doing. Because of this we do not allow it on any of out robots or even in the shop.

If you can help it just stay away from the stuff. You guys will be much happier with the results you get from working with polycarb.

Kirk
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