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CNC Plasma Table

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

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Overall Goal: CNC plasma table that is auto loaded/unloaded through network interface.

Having a plasma table to cut metal parts would be nice. Loading the plasma table with 4'x8' or 4'x10' sheets can get awkward. Having this auto-loaded with a click of a button would be ideal. Industry has loader/unloaders either in sheet form or in roll form so the concept is there. This project is to focus on developing the software side of the loading and unloading. To get to that development stage, the mechanics will have to be hammered out:

Plasma Table
Sheet rack
Loader/Unloader

The process of the mechanical build will keep the software side in mind, ie the I/O's, motor controls, etc. Then the development stage of the software for the loader/unloader can be addressed:

Expandable to multiple material/sizes
Interface with Plasma Table
Interface with Computer that will "print" the cut

Links to Logs-

Phase I - Build a Plasma Table

Progress - Table is built and functioning. Hard limit randomly faults when enabled. Axis loses steps. GRBL/Universal GCode Sender appears to start/stop movement in a cut with multiple short line segments.

Controller - GRBL running on UNO

Interface - Universal GCode Sender running on Raspberry Pi

Mechanical - Many designs out there. Pick one and wing it.

Plasma Cutter - Use one on hand. PakMaster

Phase II - Build Material Rack

Progress - Not Started. Main rack being built with loader/unloader in mind. Not developed, trying to keep open build concept.

Mechanical - Stackable rack that is expandable to hold more sizes of to hold multiple sheets of material. Design for 4'x8' 4'x10' sheets. Allow to be expand to multiple sheet size as needed.

Phase III - Build Material loader/unloader

Progress - Not Started. Building main table that will have expansion/modification ability as the project evolves.

Controller - Use the Raspberry Pi IO or capable of interfacing with the Raspberry Pi.

Mechanical - Be able to slide material out from rack, lower raise material to plasma table height, slide under plasma table. Reverse order for uncut material unload. Finished parts will fall down when trap door under plasma table hinges downward. The finished cut *should* drop down if fully cut. Then the uncut material, if completely exhausted, will be cut from the main sheet. Trap door to drop exhausted material down same path as finished part.

Phase IV - Develop/Find network capable "cutting" queue to send file from office computer to plasma table.

Progress - Not Started

  • 3 × 452 oz in steppers Bipolar bought off of ebay
  • 1 × ?? oz in stepper Z axis motor pulled from some copy machine or printer at some point
  • 99 × Miscellaneous bearings These were pulled from copy machines and printers through the years.
  • 3 × A 6A55M072NF1512 72 teeth pulley x and y axis drive
  • 6 × A 6A55M024DF1510 24 teeth pulley x and y axis drive

View all 20 components

  • Clean Cuts Come Hard

    willbaden02/25/2017 at 02:30 0 comments

    As there have been a few cuts under the plasma tables belts, it is time to get the cutting experiences documented.

    Speed changes (I think, it was a while ago that these pictures were taken)

    Go too slow and overcut happens:

    Go a faster speed and things look better:

    Dragging a torch along flat steel causes the arc to go out. The loss of arc path is highlighted in yellow:

    Having a non perpendicular head can cause splatter/incomplete cut in certain directions:

    To be continued. . .

  • Crashing Comes Easy

    willbaden02/25/2017 at 02:14 0 comments

    Using a floating head on corrugated tin seemed it was the ticket. Especially when torch height control is still not implemented. Touch off of the material, back off the material to allow an arc to fire, plunge the head down on top of the material so the plasma cutter drags along the height changes of the tin. Then the head drops into a hole and gets ripped off the first time. No big deal, the v'd plastic guides that support the floating head deform enough to allow the head to pop off. The second time wasn't as fortunate:

    So new pulleys were made out of more rigid bearings and the v'd guide itself made out of aluminum. In the picture below, the old plastic piece is off to the left with the bearings that popped out laying beside it. The left side of the plastic pulley has a black line where it was sheared:

    In the process of machining the aluminum pieces, the bearing bore was too large on one. The installed bearing would slide in and out smoothly. Instead of making another one, the pulley was dinged with a punch to help trap the bearing:

    With two new v'd guides created it was assembled and installed. Back in business:

    To help with this kind of problem in the distant future, a magnetic break away floating head should probably be built.

  • Exhausted Material Cut

    willbaden08/30/2016 at 02:18 0 comments

    With the table capable to cut across the width of the material (48 inches), a program was created to act as the final cut to remove the completely cut material from the main sheet.

    G21 G54
    G90X-665Y10
    G0Z1.0
    G38.2Z-300F1000
    G92Z-18
    G90G0Z1
    M3S10000
    G4P1.2
    G1Z1.0F1000.0
    G1Y-1210.0F2500.0
    M05
    G0Z10.0
    M30
    This code was ran after homing the machine ($H) and resetting G54 location5 mm from the edge of the homing resting location. It made a clean cut, except the beginning.

    I had forgotten about the delay to fire and will have to implement a primary cut that is near the cut line, but not on it.

  • Material Cut Table

    willbaden08/14/2016 at 01:12 0 comments

    The table that holds the material being cut is going through updating. The test table was four tubes clamped to a welded assembly that was re-purposed for a material table.

    It has served its purpose and is time for an upgrade. 2x2x1/8" material was ordered for the material table and for the first revision of the material rack. Using a chop saw (would have been nice to use a cold saw) the material cut table was cut up.

    There will be four lengths on the top and bottom with 4 short risers to separate the top and bottom. Below is an in process view of the material cut table acting as jigs for the first revision of the material rack.

    The plasma cut table is coming together, here is a mockup of the new table. At this point it is only tacked together for a trial fit under the plasma axis. The four holes in the bottom will be used for qty. 4 - 1/2" bolts that will be used as leveling feet. The bed has a slight skew to it after being welded together, but should be able to level with the cutting frame.

    On the top horizontal bars are three holes on both sides. These will be used to bolt the plasma cut table to the stock loader/unloader. It will also be used to bolt the plasma cut table frame work that holds the material and eventually will hinge on the closest side to allow the cut or spent material to drop out the back side.

    The table needed adjustable feet to allow for leveling. The 1/2" holes weren't enough. So 3/8" steel cut 2x2 were drilled and tapped for 1/2-13.

    These were then mocked up and welded to the table.

    The hinged table will be considered consumable. Current design is made by 1x1x1/8 steel tubing. This is intended to be a quick setup to cut some parts that I would like to see finished in the near future.

    This was set in inside the larger frame for test fitting.

    Outside of leveling the CNC table and cut table, there did not appear to be much for concern. The CNC was taken to the limits in the X axis to see where the consumable table would sit. Then the hinges were made up.

    These were then mocked up and welded to the main frame. There are two pieces of steel angle that bolt to the consumable table.

    Below is the left hinge tacked in and ready for hinge testing.

    The table hinges down and is meant to allow the material to slide down. The 1x1 hinged table is not the final design but will have the same hinging effect.

    We will see if this will be enough angle. May have to raise the table with some risers. Cross that road later. The above picture also shows the mounting plate on the right side of the table. This will bolt to the CNC tables legs.

    10/2/16

    The spacing of the bars going across has caused some issues with parts warping and being unable to maintain a decent height while cutting. IE the torch would initially touch off of a fairly level piece, but as the cut progressed the cut material drooping/warping would allow for the torch height to change too much. This would cause an intermittent/failed cut. To help out with this until torch height control can be implemented, more cross bars were added.

    The gap between the end piece and last support bar was intentional as the plasma cutter can't reach this far.

  • Axis Movement

    willbaden08/11/2016 at 02:05 0 comments

  • Delay to Start of Plasma Torch Fire

    willbaden08/11/2016 at 00:51 0 comments

    The plasma torch needs to fire and start an arc before moving or a detail can be missed or a drop out doesn't drop out. That was the case that I ran into. Thinking that it was a GRBL issue, I posted an issue on the github grbl page here. The thought was the G4P1.2 was not dwelling the proper about of time the first time it was called, but would work fine in successive calls. The program below was made to help with diagnosing the problem.

    G21 G90 G64
    G54
    G0X0Y0
    G0 Z1.0
    G38.2Z-300F1000
    G92Z-17
    G90G0Z1
    M3S10000
    G4P1.2
    G1 Z1.0 F1000.0
    G1 F1200.0 X10 Y0
    M5
    G0 Z10.0
    G0 X0 Y10
    G1F1000.0 Z1.0
    G38.2Z-300F1000
    G92Z-17
    G90G0Z1
    M3S10000
    G4P1.2
    G1 Z1.0 F1000.0
    G1 F1200.0 X10 Y10
    M5
    G0 Z10.0
    G0 X0 Y20
    G1F1000.0 Z1.0
    G38.2Z-300F1000
    G92Z-17
    G90G0Z1
    M3S10000
    G4P1.2
    G1 Z1.0 F1000.0
    G1 F1200.0 X10 Y20
    M5
    G0 Z10.0
    M30
    

    This code produced the following cuts:

    The two left columns were ran once, while the right column was ran twice in a row. It showed the same cuts the first time through, but worked the second. So it might not be a grbl issue. So a phone was setup to capture the sequence of events as the program ran. The lights on the Plasma cutter are shown below:

    Its upside down as the video shows it. Pretty straight forward what they stand for. The unit was on so the AC light was on. The gas represents when the air kicks in, the DC light, when there is juice to the plasma torch and the over temp is just that. This is located on the top of the plasma unit in the video. The relay that kicks on the plasma cutter is inside the plasma unit (lower left) and has a red light turns on.

    For the first cut, the relay kicks in to turn on the plasma torch, but there is hesitation before the DC light turns on along with the plasma torch fire. After the relay shuts off, the DC light stays on for a short time.

    The way that would be nice is if M66 was implemented in grbl (may have to dive into this, if its priority goes up). For now a cut elsewhere on the material will charge the DC side and allow the next cut to come out ok.

  • Chassis Grounding

    willbaden08/05/2016 at 22:19 0 comments

    Trying to adhere to Hypotherms grounding suggestions the following grounding methods were loosely followed. Ground bar on the machine chassis that individually connects to the Y, X and Z axis.

    The Chassis ground bar also grounds out the work ground lead from the plasma cutter.

    Which is also attached to a 4' ground rod right beside the machine.

  • Raspberry Pi Addition

    willbaden08/05/2016 at 22:13 0 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...
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  • Controller Box

    willbaden08/05/2016 at 01:42 0 comments

    The controller box started out as a headless control with the USB to the UNO being fed out of the bottom.

    It did not have an estop, start, hold or reset button. The guts were a lot simple too. The back plane just had a 24V power supply, UNO, and a input/output opto coupled boards.

    The UNO is running GRBL with few modifications to the settings. The input/output boards were designed with Eagle. Then milled out on the CNC:

    Flipping between the sides, I ran into an offset issue though and had to adjust.

    Both boards were milled on a single double sided pcb:

    These were cut apart and ready for components to be populated.

    Soldering the surface mount resistors was a task. Seeing reflow ovens soldering, makes me want to build one myself.

    The backplane fit nicely in the enclosure:

    To the left is a ground bar that distributes the ground connections and also an attempt to ground out the shielded cables. Below is a complete view of the ground.

    The stepper driver cables were then wired on the bottom of the pcbs.

    There was a temporary estop attached while some testing was done to verify cable routing. Along the way, there was issues with poor solder joints and miswiring between the UNO and output board. When that was sorted out, testing could begin. The lower right of the controller box had a bulkhead USB passthrough that allowed a laptop be connected and power up the UNO. The laptop ran Universal GCode Sender and was painless in operation. A little effort was required in installing, but came down to reading docs to figure it out. The first few cuts by the plasma table were nerve racking, but worked fine for the most part.

    And more testing was done:

    Cambam was used to make the letter B, but the majority of testing was hand written code that cut out a square. The circles along the bottom was not cut by the plasma table. They were already present.

    Then the realization that noise in an HF start is a challenge.

    The first symptom that appeared was GRBL restarting. Randomly when the plasma torch would fire, GRBL would restart. This stopped the program being fed via File Mode of Universal GCode Sender. From what I remember (I know it has only been a few months) at that time, the table and controller/driver boxes were not connected electrically. Tieing them together helped with the GRBL restart.

    Then when the hard limits were wired in, they started to trip randomly during torch fire. Thinking it was some noise feeding in from the input and output cards, capacitors were added liberally across 24V inputs (.1 uF)

    5V signal to UNO (.33 uF):

    I don't have pictures for the next individual steps of capacitors, but this photo shows multiple capacitors added: 1 uF to the 5V side in parallel, the 5V power input, 100uF and .1 uF caps were installed.

    Still had the issue with the hard limit. Along with the hard limit issue creeping in, the relay that turned the plasma torch on and off was not firing all the time or was firing and then immediately shutting off. So a 100 uF cap was added to the 24V power in on the output card and a .1 uF cap across the plasma gun on output.

    Didn't seem to help out the problem. Looking into cabling to the relay, there was a loose wire. . .

    All of this may have helped in minute ways, but the problem still persisted. Hard limits were randomly being triggered. In testing it was noticed that position of the laptop and cable "appeared" to help the problem. So the USB cable was stripped back to show the bare shielded cable. This was pushed against the controller box ground and it seemed to have cleared up the problem quite a bit.

    This left me to believe the computer should also be contained inside of the controller box.

  • Plasma Cutter Modifications

    willbaden08/04/2016 at 03:09 0 comments

    The plasma cutter that is being used for this table is Thermal Dynamics Pak Master 38XL. From what is found online it is a high frequency start (read electrically noisy) cutter.

    The handheld torch has a NO trigger that simply closes a circuit back at the main unit. In the picture below the black and white wire coming out from under the sheath is the fire command. The black wire connects to an orange wire that feeds out to the torch head's PIP (part in place) connection. A second orange wire feeds back to the NO trigger.

    Below is the PIP contacts that detects that the tip cover is attached.

    The CNC will bypass the PIP circuit and act only as a basic fire. A relay was placed back in the main unit that connects the black and white wire together.

    In the picture below, the upper white and black wires are the torch fire circuit and the red wire is the main cutting circuit to the plasma torch.

    The firing circuit was spliced and the wires fed to the NO contacts of the relay.

    A 24V relay was chosen since the opto coupler output card in the controller box uses 24V. The card was modified as a direct short to 24V with the relays coil as the load. The second from the right opto has the output resistor removed and the pads were solder bridged together.

    A strain relief was added to the top of the plasma unit for cable routing.

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Discussions

Bharbour wrote 07/28/2016 at 14:41 point

Nice Build! Seeing this project reminds me of the CNC plasma cutter that I started on. I got the carriages designed and built before realizing that I had no space in my shop to put the finished unit. 

  Are you sure? yes | no

willbaden wrote 07/28/2016 at 15:53 point

Thanks!  I did think about a smaller portable unit that would magnetically attach to a larger piece of material, but opted for this style to be able to automate sourcing from a rack.

  Are you sure? yes | no

fredkono wrote 07/28/2016 at 01:12 point

I could add some g-code if I knew what to add LOL I guess I need to read up on gcode.

  Are you sure? yes | no

willbaden wrote 07/28/2016 at 10:23 point

No worries.  Searching for grbl and probe should show some useful information.  This setup uses the following:

G38.2Z-300F1000

G92Z-17

Searching the above gcode at https://github.com/grbl/grbl should get you pointed in the right direction.

  Are you sure? yes | no

fredkono wrote 07/27/2016 at 19:13 point

What are you using to make your Gcode? I use vcarve and pcb-gcode with eagle for my small cnc, but I don't think that would work good for a plasma?

  Are you sure? yes | no

willbaden wrote 07/28/2016 at 01:08 point

Currently using evaluation period of cambam.  If you can post g1 segments and either manually add or have the post processor automate a tool height touch off, then you should be good.

  Are you sure? yes | no

fredkono wrote 07/27/2016 at 04:17 point

Nice build.,  May I ask what software you are using?

  Are you sure? yes | no

willbaden wrote 07/27/2016 at 10:39 point

Thanks!  GRBL on UNO.  Universal GCode sender as software interface.  More logs to come.  Starting with mechanical and plan on moving into electronics.

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