Thermoplastics in FIRST

[lynca]

Kydex is a type of thermoplastic useful for creating 3D plastic shapes by heating. (plastic vendor - http://www.regal-plastics.com/sheets.html )

I've used thermoplastic a few years ago, but I'm curious if CD has any useful FIRST applications for Kydex ?

I found a good tutorial about making a knife sheath with kydex,
http://www.youtube.com/watch?v=mKWe1vliHeY

Are there any other types of common thermoplastics people have use in FIRST ?

[NorviewsVeteran]

We used reformed PVC pipe for brackets to hold our compressor above the drive motors last year, as well as reformed Lexan "fender wells" to prevent wires and pneumatic tubing from getting tangled in the mecanum wheels. Both worked fantastic.

[kramarczyk]

We used sheet ABS for our control board last year and were pretty happy with it. We basically heat bent it as if it were sheet metal and secured it with rivits as required.

We started by modeling the board and bump in Inventor and imported in the AM step files of the chassis to come up with the dimensions. Then we used the sheet metal functions in inventor to figure out the flat dimensions. We mocked it up in cardboard to make sure it fit as expected and to help figure out the order to do the bends. Yes, we prototyped our control board.

Finally we clamped the sheet to the workbench with a piece of aluminum angle and heated the bend line with a heat gun till we could bend it easily by hand. Repeat until all the bends are complete.

We are pretty happy with the perfomance and will definately consider a similar process in the future.

This is a process that I picked up during my time at 1189.

http://lh5.ggpht.com/_vgCKSOVW8Ek/S151JYeRmVI/AAAAAAAABBk/NBqsFtmqctI/s800/2010-01-25%2018.07.45.jpg

http://lh5.ggpht.com/_vgCKSOVW8Ek/S2ZMU3RX6oI/AAAAAAAABBk/5t3P7GG4yWc/s800/2010-01-30%2013.10.50.jpg

http://lh3.ggpht.com/_vgCKSOVW8Ek/S2gDuXXp2II/AAAAAAAABBk/BjGyfXxuVjk/s800/2010-02-01%2019.15.54.jpg

http://lh5.ggpht.com/_vgCKSOVW8Ek/S2ZMVk_Q66I/AAAAAAAABBk/B8PQBpuBN3s/s800/2010-01-30%2016.15.24.jpg

[Gdeaver]

Last year we vacuum formed some chain guards from polycarbonate. Heat soaking polycarbonate so you don't get bubbles is a pain. We may try PETG this year.

[lynca]

We used sheet ABS for our control board last year and were pretty happy with it.


Where did you buy your sheet ABS (model# and thickness) ?



Finally we clamped the sheet to the workbench with a piece of aluminum angle and heated the bend line with a heat gun till we could bend it easily by hand. Repeat until all the bends are complete.


Were you happy with this process, was it difficult to uniformly apply the heat ? We are considering other ways of heating the material like using a heat strip from Tap Plastics :
http://www.tapplastics.com/shop/product.php?pid=169&

They have some neat videos about bending and molding plastics.
http://www.tapplastics.com/info/video.php?

[lynca]

Last year we vacuum formed some chain guards from polycarbonate. Heat soaking polycarbonate so you don't get bubbles is a pain. We may try PETG this year.

Can you describe the vacuum forming and heat soaking process in more detail ?

Why would PETG be better than polycarbonate ?

[Madison]

While expensive, something like this (http://www.tapplastics.com/shop/product.php?pid=291&PHPSESSID=201101071042471805689629) is a great tool for making bends in plastic.

I've never used that myself, but they had one in the shop at a company I worked for previously that dealt with plastics frequently and the quality of the work from it was always top notch.

[Chris is me]

While expensive, something like this (http://www.tapplastics.com/shop/product.php?pid=291&PHPSESSID=201101071042471805689629) is a great tool for making bends in plastic.

I've never used that myself, but they had one in the shop at a company I worked for previously that dealt with plastics frequently and the quality of the work from it was always top notch.

This tool is great. I used one the other day to put some heat bends in polycarbonate (note: don't heat bend polycarbonate unless you have to, use a break instead) and it heated the material in a nice uniform fashion without bubbling. Always remember to bend with the heated side out!

[kramarczyk]

Where did you buy your sheet ABS (model# and thickness) ?

We buy from Laird Plastics - http://www.lairdplastics.com/ It looks like you have a local distributor in Houston. It was 1/8" thick and textured on one side (not that that is important). My invoice calls out p/n: 176372, but I am not finding it on thier site at the moment. Your best bet is to callor stop in and ask for 1/8" ABS sheet; it is not a complicated purchase. I picked up a 48" x 96" sheet for ~$40.


Were you happy with this process, was it difficult to uniformly apply the heat ? We are considering other ways of heating the material like using a heat strip from Tap Plastics :
http://www.tapplastics.com/shop/product.php?pid=169&


Happy enough to do it again. I don't recall it being difficult to get uniform heat; we just kept the gun moving. The free portion of the sheet was left hanging off the desk, so it was very clear when it was ready to bend and overheating was not an issue. If we do it again I will get a second gun to speed up the process.

I have used those strip heaters before and they work great when your part can accomodate the size of the heater. I can see cases in our design for last year where it would have been tough to get a strip heater into where we needed to bend. That may just be me not thinking about it hard enough though.

[Gdeaver]

This video was the inspiration for our vacuum forming projects last year.
http://www.youtube.com/watch?v=hGBRiYhxRTM&feature=related

Polycarbonate absorbs moisture. To thermoform it you must heat it to drive out the moisture or the water will turn to steam and give you bubbles. Thermoforming plastic is very do-able for teams however you can get better strength and results with composite methods if you have the resources.

[Coach Norm]

Andrew,
We used ABS from Regal Plastics here in Austin. I am sure you used them when you were here in Austin. They actual had some 13" wide x 8' lengths that they gave me at a very good discount price. We used it for the skirt of our robot last year. It was haircell (textured on one side).

We heated it using a heat gun. It was very easy to accomplish using a workbench and scrap 2" x 4" boards. If you have ever heated and shaped PVC, it is very similar in process.

The only problem we had was we design it to attach to the chassis with one inch tabs by riveting. We did experience some problems with the tabs breaking.

[Hawiian Cadder]

my team has a sort of jury rigged method for molding plastics as well as mold abilities for smaller parts. we made several attachments for a soldering iron to melt plastics together, basicaly the two strips op plastic are put on either side of a high heat brass plate on a soldering iron, held there until tacky, then the soldering iron is pulled out and a heat gun is used to keep the plastic as sticky as possible while it is pressed together very tightly, we also use a heat gun to heat lexan up to near melting point and then put it on a sheet metal break, this makes bending thicker plastic with a break easier, as well as makes the whole thing cleaner.