CNC Plasma Cutting Chassis

[rahilm]

Originally Posted by Wiifi

We've cut parts in steel using a plasma cutter. We haven't had any problems with the parts - they were cut very accurately. Occasionally we have to drill a small hole out though because the plasma cutter doesn't recognize it enough/give it enough power. I think that is due to our configuration of the device, some setting we need to change somewhere.

On a side note has anyone ever plasma-cut aluminum? We were planning on doing it sometime this week and could use some pointers.

Here is our frisbee-launcher being cut this year http://www.youtube.com/watch?v=RUpf_stUnaw

Yep, we do a lot of stuff out of aluminum.

Not sure what system you have, and there are a lot of variables at play here, but what we've found is that it's better to run slower feed rates than suggested by the manufacturer, as this leads to less beveled edges. This will cause more dross buildup, so you will have to do some sanding/filing afterward.

Feel free to ask if you have any questions.

[Peter Matteson]

Our 2012 robot was all plasma cut. There are a few things you need to learn out but it works well.

This is the best pic on CD of our 2012 robot:
http://www.chiefdelphi.com/media/photos/37782

[fb39ca4]

While not quite the same thing, our chassis was laser cut from plywood. The machine works in the same way with a rail for each axis and is very accurate. As long as your plasma cutter is well calibrated, you shouldn't have any problems.

[mman1506]

Is it possible to make rivet holes on the plasma cutter?

[rahilm]

Originally Posted by mman1506

Is it possible to make rivet holes on the plasma cutter?

Yes, but depending on the quality and calibration of your machine, you may have to have them be cut small and then drilled to size.

[Greg Needel]

The answer is yes, but there are some limitations which as others have pointed out have to do with the cut quality you can get from your machine. As a general example: Would I cut pockets and location holes with a plasma, yes. Would I build an integrated gearbox in a chassis, no.


The limitations I think it is important to be aware of are bending. It is extremely hard to bend accurate parts with a cheap break, and this can be as much as of a limitation as the cutting machine. The method I prefer when using a plasma is to cut location based features on the flat plates and add simple flanges for strength, which geometrically don't need to be as accurate.

A cnc Plasma cutter is an extremely valuable tool for a team to have as it can significantly reduce time and increase accuracy, you just need to learn the limitations of which ever machine you get, and make sure to experiment before the build season to learn what those limitations are.

[mman1506]

Thanks for all the help,
I'm hoping to design and build a chassis in the off season that we can modify for build season so I can learn how to use it. We do have some heavy duty brakes from the 50's but I'm not sure how accurate they are.


Are table is a plasma cam with advanced height control and are cutter is a miller 375.

[Feroz1325]

In 2012 Team1325 got our chassis conveyor and shooter cut with a plasma cutter and then gave it to a sponsor to bend. It worked out very well all in all. The cuts were not clean and took a lot of niners...i mean deburring. Also small holes (0.25 inch)did not work well so we ended up just drilling most of them in.
I forgot to mention...it was a sheetmetal chassis 0.09 5052 aluminum.

CAD of the chassis:
http://www.chiefdelphi.com/media/img...38d05805_l.jpg

[DonRotolo]

Small features like rivet holes are best drilled - although you can 'mark' their location with the plasma torch. Better are larger features, but the edge condition may not be as smooth as you prefer. It isn't like milled, laser or waterjet surface finish.

With aluminum, beware the effects of heat on the material - aluminum expands as you torch it, and so when it cools everything gets a little smaller (and closer together...).

[Peter Matteson]

Originally Posted by DonRotolo

Small features like rivet holes are best drilled - although you can 'mark' their location with the plasma torch. Better are larger features, but the edge condition may not be as smooth as you prefer. It isn't like milled, laser or waterjet surface finish.

With aluminum, beware the effects of heat on the material - aluminum expands as you torch it, and so when it cools everything gets a little smaller (and closer together...).

Don hit the nail on the head what we do to put holes in parts. We undersize and finish the holes on a drill press.

For bearing holes we precision ground a step drill to finsh the holes for a perfect press fit.

The thermal expansion is manageable by controlling feeds and knowing how much you can cut before pausing the cutter and letting things cool along with the order of the cuts. We do primary holes first (location critical items like bearings or interfaces) and then leave lightening holes and frame cutting for later with cooling down time allowed between the patterns.

Also the best way to clean the edges and remove the slag is a scotchbrite pad on a die-grinder. Deburring tools are a bad idea to try on the slag they skip off easily and don't clean it well.

[Trent B]

Originally Posted by DonRotolo

With aluminum, beware the effects of heat on the material - aluminum expands as you torch it, and so when it cools everything gets a little smaller (and closer together...).

You can also strip it of its heat treat in the area surrounding the hole.

[sdcantrell56]

Originally Posted by fb39ca4

While not quite the same thing, our chassis was laser cut from plywood. The machine works in the same way with a rail for each axis and is very accurate. As long as your plasma cutter is well calibrated, you shouldn't have any problems.

Not exactly the same thing... Glad to know someone else is doing the plywood chassis. You should put up some pictures of it

[fb39ca4]

Originally Posted by sdcantrell56

Not exactly the same thing... Glad to know someone else is doing the plywood chassis. You should put up some pictures of it

I don't know where to find any still pictures, but here is a video of it driving around: http://www.youtube.com/watch?v=GfRwK-DaZtI

Do you have pics of your robot?

[mman1506]

We started to make some real parts on are plasma cutter today. We made some c channel from 1/16. It came out great with surprisingly little slag on the aluminium. Sadly I don't have the pic of the piece but here's a gif with missing frames.

Thanks for all your help!