CNC Plasma Cutting Chassis
 

Our team has a CNC plasma cutter (PlasmaCam) laying around that I want to put to good use. I'm hoping to plasma cut our robot's chassis next year but I'm not sure it has the accuracy to do it. We also have a CNC Mill but it has a smaller working area.

Has any team successfully plasma cut there robot's chassis and/or parts? Any tips?

Thanks,

Re: CNC Plasma Cutting Chassis
 

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

Re: CNC Plasma Cutting Chassis
 

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.

Re: CNC Plasma Cutting Chassis
 

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

Re: CNC Plasma Cutting Chassis
 

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.

Re: CNC Plasma Cutting Chassis
 

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

Re: CNC Plasma Cutting Chassis
 

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

Re: CNC Plasma Cutting Chassis
 

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.

Re: CNC Plasma Cutting Chassis
 

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.

Re: CNC Plasma Cutting Chassis
 

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.

Re: CNC Plasma Cutting Chassis
 

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

Re: CNC Plasma Cutting Chassis
 

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...).

Re: CNC Plasma Cutting Chassis
 

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.

Re: CNC Plasma Cutting Chassis
 

Our "Trap Door" on our shooter was plasma cut aluminum.

http://youtu.be/dcJLn9UXuoI?t=1m24s

We have a mentor that has a plasma cutter and he made several of our parts on it. Ifyou hae any specific questions I could forward it on to him.

Re: CNC Plasma Cutting Chassis
 

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