Working with Lexan

[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?

Phil Paspalas
Head Coach - Team 1676
The Pascack Pioneers
2005 NJ Rookie All-Stars

[663.keith]

try lubricating the drill bit with dish soap, it generally produces good results

[RoboGeek]

go pick up a set of step drills and use them they will make life alot easier! I suppose it is possile to just use 5 different bits in and step up through them but a step drill will be alot faster and a sharp one will go through lexan like a hot knife through butter! in '04 I personally drilled almost 6000 3/4" holes in sheets of lexan for our bot (we didn't use them as they were still too heavy and if we drilled anymore holes we wouldn't have a side panel lol!!)seriously though get a set and go at it its faster then you think and quite easy!

[Greg Needel]

The problem with working with lexan and any other plastics is that they tend to melt before the bit actually chips away at the material. An easy solution for cutting plastics is to turn the drill bit or hole saw slower, this makes less heat and there is less of a likely hood of melting. Alot of lubrication on the bit and material will help as well.

[TheAnsweris42]

So, in your opinion, would lexan or another polycarb be a good choice for the outer shell as well? Some of us think we might want to try and do something like that, because it would make the visibility requirements on the controller and ball bin a lot easier, and would make good protection. We're a rookie team, though, and since we don't have any experience in how rough things might actually get, or how much the polycarb would cost...

[Greg Needel]

Originally Posted by TheAnsweris42

So, in your opinion, would lexan or another polycarb be a good choice for the outer shell as well? Some of us think we might want to try and do something like that, because it would make the visibility requirements on the controller and ball bin a lot easier, and would make good protection. We're a rookie team, though, and since we don't have any experience in how rough things might actually get, or how much the polycarb would cost...

As a rule of thumb about lexan/polycarbonate:
load bearing or going to take hits 1/8" or larger

non load bearing plates for numbers and such 1/8" or smaller.

The uses of lexan in FIRST basically come down to how flexible you can accept during use because even with the forces involved in robot collisions i have seen very little polycarbonate break. So the thicker it is the less flexibility you have and vice versa....Plexiglas is another story all together.

[Kirk]

Originally Posted by TheAnsweris42

So, in your opinion, would lexan or another polycarb be a good choice for the outer shell as well? Some of us think we might want to try and do something like that, because it would make the visibility requirements on the controller and ball bin a lot easier, and would make good protection. We're a rookie team, though, and since we don't have any experience in how rough things might actually get, or how much the polycarb would cost...

Poly Carb is great for protective panels. If you have supports under it you can go as thin as 1/16" which is what we usually use. Poly Carb is very good for resisting puncture and will not crack. One warning MAKE SURE YOU GET POLY CARB most stores will sell acrylic as poly carbonate. Acrylic is not only not allowed in first but is breaks like glass when it is impacted or bent.

Good luck on your rookie year and feel free to post up if you have questions about anything.

~Kirk

[Greg Needel]

Originally Posted by Kirk

Acrylic is not only not allowed in first but is breaks like glass when it is impacted or bent.

not true anymore..the restrictions on acrylic and plexi were lifted last year.

[Mike Betts]

For safety reasons, I would never allow plexiglass on a robot. Polycarb only. IMHO, FIRST is making a mistake in allowing plexi...

The "step" drill referred to above is usually called an omni-bit. Omni-bit may be a trade name but any hardware store will know what you are looking for. It drills through polycarb like butter.

[Greg Needel]

Originally Posted by Mike Betts

For safety reasons, I would never allow plexiglass on a robot. Polycarb only. IMHO, FIRST is making a mistake in allowing plexi...

I agree whole heartly with you i think they did this because sometimes teams only have access to specific materials and plexi is still more common and cheaper then lexan/polycarbonate.

[Kirk]

Originally Posted by Greg Needel

I agree whole heartly with you i think they did this because sometimes teams only have access to specific materials and plexi is still more common and cheaper then lexan/polycarbonate.

For those teams that don't know how to tell the difference between the two, the best way to tell is take a pair of pliers and try to bend a corner. If it bends like a piece of soft aluminum its polycarbonate if it cracks or breaks its acrylic.

~Kirk

[billbo911]

Originally Posted by Kirk

For those teams that don't know how to tell the difference between the two, the best way to tell is take a pair of pliers and try to bend a corner. If it bends like a piece of soft aluminum its polycarbonate if it cracks or breaks its acrylic.

~Kirk

There is nothing like Brute Force Testing to come to a very quick answer.

[Mike Betts]

Originally Posted by Kirk

For those teams that don't know how to tell the difference between the two, the best way to tell is take a pair of pliers and try to bend a corner. If it bends like a piece of soft aluminum its polycarbonate if it cracks or breaks its acrylic.

Kirk, et al,

I would use a sheet metal brake rather than pliers and, whichever method you use, please wear safety glasses!

Mike

[Marcel]

What are you drilling with? You using an actual drill or have you tried a milling machine perhaps?

[Elgin Clock]

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?

When doing any type of drilling in Lexan, it is best to leave the protective paper coating on (both?) sides. This prevents most cracking, and allows a cleaner cut/hole to be made.