CNC Torch Table 2/Research Development

Status

This is my (Dan Benamy's) understanding as of Oct 2013:

There were various Stepper Motor Drivers being considered. We have an (inactive) project to develop an OSE driver called CoolRAMPS. The fallback was to use the Steppernug open source stepper motor driver. The folks behind it are amazing and we love open source. It's not clear to me (Dan), if the Steppernug is quite ready. For the short term I'd like to try to get the version 2 table up and running with the RAMPS system so we can get something working and build momentum. Then we can quickly iterate to version 3 where we switch to the Steppernug which will allow us to cut faster.

Generally, my strategy is to make lots of quick iterations with self-contained improvements so we almost always have a working table and project handoff is simpler. I'm also focusing on getting something working at FeF that we can use to cut parts we need for other machines, rather than something that's easily reproducible or perfectly documented. Being able to cut Warehouse parts will save lots of time and money on all other development. It will also be a waste of effort to carefully document stuff that turns out not to work well. Once we get to the point where we can cut useful stuff, I (or you!) will need to make any changes needed for ease of reproduction, and create awesome manufacturing guides so others can copy it.

There's a torch table base in the shop at FeF which needs just a little more work to be usable. I mounted the motors, although we didn't have quite enough of some of the proper screws with springs, but what I've got on there may be good enough for now. TODO link to issue to fix this

I ran wires from the long and short axis motors up to a mount in the ceiling and over to the table with the RAMPS electronics and laptop. TODO pic

Lots of info on the control systems at CNC Torch Table 2/Control Overview. That page predates me (Dan) so may have outdated info.

Next Steps

• Finish fixing/replacing the RAMPS hardware that I burned. Make sure each motor moved properly when using the RAMPS test code.
• Order a new "RAM" board in case this one is damaged or becomes damaged.
• Find a power supply for the arduino so it can be run without being connected to a computer to prevent a short from frying the computer.
• Attach a sharpie to the tool head and put poster board or similar on the bed for initial testing.
• Load the Marlin firmware onto the arduino and do any needed configuration. Grbl looks sweet but doesn't support RAMPS out of the box and we're going for simple here for the moment.
• The standard RAMPS setup for 2 motors on one axis is to run them in parallel off one driver. Since our motors draw a fair amount of current, try to use a separate driver for each motor and modify marlin to drive those two drivers identically.
• Run a simple test gcode program- https://github.com/grbl/grbl/wiki/G-Code-Examples.
• Draw a rectangle in librecad, run it through dxf2gcode and use [Printrun] to stream it to the arduino. Get the table to draw the rectangle.

Then I'd do incremental improvements, keeping the table working after each step so if I had to leave or something didn't work, it'd be easy to revert to the most recent working stuff:

• Add a circle to the dxf that's not touching the rectangle. Re-run and make sure the head lifts up between the shapes.
• Add gcode postprocessing if still needed for piercing and torch width. The "torch" should move back and forth while making an initial "pierce". For the circle, I think it should make the pieces inside the circle. I'm not sure if it should pierce the rectangle inside or on one edge. We want it to make the pierce in a part of the metal we won't use. I wonder how the piercing code knows what that is... There's a conversation here about integrating this functionality into dxf2gcode which would be great for ease of use and gives us a gui where maybe we could click where we want the pierce to be.
• Try it with the real torch!!! For future steps, I'd switch back to the sharpie for testing and only use the torch once things look good.
• Computer control of the torch since the ratio of fuel to oxygen should change for piercing vs cutting.
• Endstops.
• More powerful stepper drivers to allow faster movement (and use more open hardware).
• Height sensing to automatically deal with different thickness material and maybe uneven material.
• Rebuild the table using as many Warehouse parts as possible.
• There was a comment that said "Height Controller for oxyacetylene and plasma torches". I don't know what that means.
• Order proper screws to replace to replace what I used for the 2 long axis motor mount.

Developement Board

edit

Design

Lots of information about the control system in CNC Torch Table 2/Control Overview.

Additional discussion at TorchTableModularTooling

Files

• Github (solidworks 3d models and issues) - https://github.com/OSE/CNC-Torch-Table-OSE. Use this for new development
• This was originally developed at an [https://github.com/Fractal618/CNC-Torch-Table-OSE old repo) and we forked it into the OSE org. Do not use the old repo.
• [1] - Sketchup files - I don't know if there are conversions of the solidworks files in github or something else.
• [2] - DXFs of motor mounts.

Additional Notes

• As a large x-y-z coordinate table, the Torch Table has potential applications with other tooling besides a cutting torch. One limitation is that the drive system is not powerful enough or stiff enough to support heavy cutting-tool forces.
• A modular tool mounting (possibly dual mounting, so two tools could be available simultanously) would facilitate tool changeover.