Raspberry Pi Addition

A project log for CNC Plasma Table

Plasma Cutter + CNC Table + Auto Load/Unload = Tool to build other projects faster

willbadenwillbaden 08/05/2016 at 22:130 Comments

Seeing that there was some info on using a Raspberry Pi and Universal GCode Sender, AND it was small enough to fit inside the controller AND I could purchase a touchscreen monitor that could interface with it at a decent price. . .the combo was installed.

The pi was easy to find a location for.

The monitor and driver board, not so much. But now that I have a plasma table that can cut, as long as the hard limits are shut off, why not make a monitor housing? The unbent flat cutout was drawn up in CamBam. The plasma table did a good job of cutting it out. But the first design wasn't going to be easy to bend since the lip was integral to the housing. The image below shows the flaps having little ears coming off the corners. These were intended to act as the lip. In thinking about bending this, it was scrapped.

So one without the lip was cutout and bent to form the majority of the housing.

This didn't come out without its own flaws. Notice the holes around the cutout? These are to mount a backplate and the monitor. They are oblong due to a failure in the cutout process, and having to restart. Looks to be like there is a missed steps situation becoming apparent. The bending of the flaps did not come out as well as planned, but a little bit of welding can fill that gap.

One of the flaps has holes cut in it to allow access to the monitor driver boards setup keys.

The flange was then cut out and welded to the base.

The corners were also welded at this time. The monitor housing was mocked up and appears to look decent in design. Would have desired more room between the buttons up top, but it'll do.

The housing was removed to finish designing/fabricating the monitor housing. To mount the monitor in place, some delrin round stock had a hole drilled in it and a step milled on one side to capture the thickness of the monitor.

The above picture shows the aluminum backplate that holds the touch screen interface board and monitor driver board. With the monitor board driver attached, it was mocked up on the controller box cover. The HDMI and power cables were ran also.

The assembly was installed and looks like clearances worked out.

It was then attached to the controller and the unit powered up successfully.

Now to tear it apart and paint the cover and housing.

And the back side of the monitor housing showing the backplate.

Looking closer at the blue touch screen driver board, the ribbon cable is broke. This was broken in the mockup of the backplate. It is up in the air if I will be purchasing another touch screen (not that expensive at $15).

The backplate of the main controller box also had some wiring added to it. A LinkSYS 5V wall wart power supply was added to feed power to the pi, monitor driver and UNO. This will probably be updated in the future, but for now appears to be doing a good job.

And the assembled view.

Currently I am using a Dell wireless keyboard and mouse hoping to limit the amount of exposure the USB gets from the plasma torch. After all the work of getting this enclosed, the hard limit symptom has considerably diminished. I have had it happen recently that warranted to shut off hard limits in the settings though. Along with this, it appears that missed steps are still showing up. The separated O in the image below shows that there is a shift in the Y Axis. In prior cutout attempts, the X also showed shifting

Breaking it down, two problems persist:

  1. Hard Limit triggering (albeit not as bad as what it started out as)
    1. Appears to be solved by pulling anything USB inside of the controller box. At this point, all wiring is either shielded cable or inside of a grounded enclosure.
  2. Stepper loss of steps
    1. Appears to be solved by adding ferrite beads around all four axis drive cables that lead from the controller box to the driver box. So much for the theory of grounding the shielding immediately inside of the box to prevent this. Next time I might try to ground the shielding of the cable right at the strain relief.