RAMBO1.4 / output for plasma connection

Mostly Printed CNC - MPCNC Troubleshooting
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Hi,

I’m building a plasma MPCNC. I don’t have any problems with the CNC part, and after calibration the machine draws me beautiful 800x800mm squares :slight_smile:
But I’m having trouble with the plasma connection.
The manufacturer (GYS) indicates in its manual that a dry contact on 2 wires (3.5ohms/ 15VDC) is used to start/stop cutting. If I’ve understood correctly, I need to buy a relay and connect it to a DC output. If that’s the case, which one should I use, and what voltage does it operate at (5V or 12V, I couldn’t find on the rambo board documentation)? And then what Gcode will activate this output?

Incidental question: I came across a post from 2018 which stated that the rambo card was not compatible with THC functionality? Is this still the case?

Note: I’m using a Rambo1.4 board under firmware Marlain by V1E.

Thanks a lot

Nico

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It seems to be 12V. I’ll try it with a relay.

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Sorry nobody got back to you with an answer to your question! Let me ping @DougJoseph for you, and see if he might have an insight for you. Welcome to community!

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@nicorre

My successful build of a LowRider V3 plasma rig was based on a “tried and true” plan in which the standard commonly used control boards (also common in 3-D printers) were ditched in favor of using a laptop that has LinuxCNC installed — and which communicates with both the LowRider and the plasma cutter through a breakout board sold by MESA electronics, via CAT5 cable, and accomplishes automatic torch height control (THC) by use of a second PCB also sold by MESA electronics. My entire build project is documented here:

There are many advantages to this approach. For example, LinuxCNC can be installed using a real time kernel, and using a certain graphical user interface called QTPlasmaC, that is specifically made for plasma cutting, and that accommodates torch high control. I posted lots of video.

I bought a used Acer laptop that boasts a touchscreen. I was able to get it for a very cheap price, buying used through eBay.

Regarding the advantages of a real time kernel, imagine something is going wrong and you need to stop cutting quickly— preferably without losing everything by shutting down all power. With a real time kernel, an emergency stop operates exactly like you would want it to. Compare this with how commonly used Marlin-based control boards act. They have a buffer that is filled with Gcode commands. When you try to pause or stop the job, it doesn’t stop right at that moment, but rather it has to finish all the commands that are already in the buffer. Those commands can result in a massive amount of cutting continuing after you told it that you wanted to pause or stop.

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Hello Doug.
I’ve seen the work you’ve done and it’s really impressive. Way above my head!
I understand the interest of having a PC dedicated to cutting but it implies that I buy a control card, drivers etc…
For the cutting emergency stop I personally powered my CNC and my plasma on cut sockets via a switch (via a relay). Admittedly, it’s a rather brutal system and I’m not sure it’s terrible to cut off the plasma’s air supply suddenly, but it must work exceptionally well.
I finally managed to pilot my plasma:

  • relay powered by the 5V on the rambo board and connected to PIN 31 for control
  • use of GCODE M3/M5 to control the relay
    It works like a charm!
    Now I’m on to testing the power/speed/airflow cutting…
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Doug,
Just a quick question since you’re here:
It seems to me that on one of your videos (but I can no longer find it…), you had a laser pointer to visualise the cutting point on the sheet metal.
I’d also thought of setting up a system like that but given the conical shape of the torch nozzle and the “focal” distance (2 to 3mm) it’s difficult to place the lasers (ideally at least 2) without being hampered by the nozzle…
By any chance, how did you go about it?
Thanks again and have a nice day
Nico

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@Jonathjon beat me to the punch on answering with a link to the video where I showed how it was done. By the way, there are links in the video description to both the lasers I used and the battery pack and the Printables.com listing of the laser mounts!

Just to save you a click:

Direct link to the printable laser mounts: Printables

My “CNC Plasma Cutter” collection of parts over on Printables: Printables

I may yet wire the lasers to the 5v power supply in my control box, but for now I’m up and running with the battery pack that holds three AA batteries. I am using normal (not rechargeable) batteries.

Print / assembly info:
• Prints as oriented.
• Prints without supports.
• Suggested: either 2 perimeter walls (0.6 nozzle) or 3 perimeter walls (0.4 nozzle).
• 20% infill
• I printed using 0.6 nozzle with 0.3 layer height and 0.6 wall line width, but they should also print well with 0.4 nozzle using same settings (emulating 0.6) or regular settings.
• Use two M3 x 10mm screws, one in each holder, to tighten the flanges to “clamp” the laser diodes into the holders.

Product links for items mentioned or related*:

• Laser Modules (2 Pack) Red “Line” 650nm 5mw Diode Lasers —

• Battery Holder with Switch — (4 Pack) 4.5V, from 3x 1.5V AA Batteries — Amazon.com

• Heat Gun — 1800W, 122°F-1202°F（50°C-650°C — Amazon.com

• XFasten Double Sided Woodworking Tape w/Yellow Backing 2.5 Inches x 30 Yards —
https://amzn.to/3kD3VWq

My PayPal tip jar: PayPal.Me

Various LowRider 3 CNC remixes:
https://www.printables.com/social/127223-doug-joseph-design8studio/collections/175217

View all my models and remixes on Printables:
https://www.printables.com/social/127223-doug-joseph-design8studio/models

*Amazon product links are affiliate links.

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I just happened to see it shortly after he posted and had YouTube open in another tab lol. You came in with all the other important info!!

I do really like the laser idea and bought a pair of them. But idk how best to mount them on a spindle or if they would even be worth it since the bit isn’t always at the same depth. I’m still a little ways out from building LR3 #3 with a plasma…but it is in the plans LOL

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Because the laser lines are quite long, the “focal distance” (from material surface) over which they still provide useful marking is quite broad. If placed properly, ideally they should target the same point as the system moves up and down. The key to proper placement is the mounts. The design process I illustrated in the video should lead to lasers properly aligned to the axis of the spindle!

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Maybe one day when you are bored you can remix my mount with the laser mount added LOL.

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Just in case, go ahead and post a link directly to your mount!

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https://www.printables.com/model/360285-lr3-65mm-spindle-mount/files

Im not sure how to get just the one file. But its the last one. Remix spindle mount v2

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Can you get me a file that shows a mockup of your spindle in relation to that mount?

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ummmmmmm…Will a picture work? I don’t have anything file wise past the step file uploaded there. I wish I was good at the modeling stuff and had all of that ready to go lol.

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it could help. Is it a pic of the spindle inside the mount? If so what could really help then is measurements of the amount of distance from the mount down to the end of the spindle body, and from the end of the spindle body down to the collet bottom, etc, and average length of stick-out of your bits.

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Ok. Looks like the body sticks out about 19mm

IMG_3431
IMG_34314032×3024 1.29 MB

The collet about 55mm

IMG_3430
IMG_34304032×3024 1.55 MB

Average bit drop out 25mm or so. This particular bit is 20 mm.

IMG_3429
IMG_34294032×3024 1.37 MB

Hopefully these help. I also hope I didn’t come across incorrectly. I never once expected you to drop everything and design this right now. Or really at any time. And I would be more than willing to pay for you to remix it if it’s something you have time and want to do

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Of the 10 files in the Printables listing, which one are you actually using? Which one should be targeted for remixing?

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image
image1261×410 26.6 KB

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Thank you for sharing. But it confirms what I was thinking. I was thinking of using the laser to adjust the height in relation to the workpiece, i.e. 2 to 3mm (typically: when the 2 lasers meet, that means I’m at the right height). But geometrically that’s impossible because of the shape of the plasma nozzle…

That said, even with a much lower crossover point, it’s still handy for accurately positioning the torch in X and Y.