Second go round

[NB Forrest]

I've been using a Hypertherm powermate 30 to hand cut firepits out of 55gallon barrels. I want to develop a CNC plasma to cut them but there is not anything I have found that will accommodate a 55gal drum so I want to make one. I started this project a year ago and got distracted but I'm back on it now.

[Joe Jones]

Hi,

Where are you located?

Your project is doable. It all depends on how handy you are, how well you are able to design and assemble a cnc machine and handle the software.

If I were cutting oil drums, I believe I would use a PlasmaCam DHC2 4x4 table and DesignEdge software. I would remove the grates from the table, and rotate the oil drum on rollers beneath the table frame, using the gantry motor and associated belts, etc. to rotate the drum at the proper speed.

With this setup, oil drums would be a breeze to cut, using either the hand torch or a machine torch.

That is my advice. Do as you wish. There are many other options out there.

Joe

[NB Forrest]

I believe I can put together the stepper and driver for the x axis and was going to make a y axis a rotary. Barrels weigh about 37 pounds and I might need some advise on the size of the stepper and ratio of a gear box. I was thinking a 10:1 gear with a 34 stepper but not sure.

[Joe Jones]

This brings up a valid question...

Can a PlasmaCam table be constructed with rollers beneath the frame, and become a dedicated pipe and tube cutter? With the torch centered on the 60" frame, and the carriage allowed to move along the gantry at that point, why couldn't I just have two rollers beneath the frame that are linked together via a chain or belt, and driven by the standard PlasmaCam gantry motor?

This would seem to be an ideal situation for cutting pipe. An external roller support could be used for longer lengths of pipe that extend beyond the frame to one side.

Joe

[NB Forrest]

I have thought about using rollers to drive the round barrel but I thought they may slip. Plus, I haven't really figured how much torque I will need when the barrel is stopped and then fully reverses. My plan is to make a gantry that is stationary for the x-axis mounted along the length of the barrel and I am making a chuck that will hold the barrel for turning on the y-axis. If I am not mistaken I believe the cutting speed for that gage metal is about 200 in/minute. That would make the barrel turn at 2.8 rev/min. If the barrel is turning at full speed and reverses I don't know how much torque that would require for a 37 lb barrel.

[Joe Jones]

I have thought about using rollers to drive the round barrel but I thought they may slip. Plus, I haven't really figured how much torque I will need when the barrel is stopped and then fully reverses. My plan is to make a gantry that is stationary for the x-axis mounted along the length of the barrel and I am making a chuck that will hold the barrel for turning on the y-axis. If I am not mistaken I believe the cutting speed for that gage metal is about 200 in/minute. That would make the barrel turn at 2.8 rev/min. If the barrel is turning at full speed and reverses I don't know how much torque that would require for a 37 lb barrel.

I see your point. Cutting a star shape where a point runs one way and then suddenly reverses direction would be problematic, as you would need to overcome the inertial force of the rotating barrel. Creating breaks at the ends of paths that closely follow the circumference of the drum would help. The machine would stop at the end of one path, and then begin the torch cutting again in the opposite direction to cut the next path.

Joe


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