Dark Green and Black MPCNC

After about two weeks of waiting for parts to arrive and then getting everything together, my machine is finally done and moving. Hit a few snags along the way, mostly due to the printed parts having slightly smaller openings for the bolts and screws than necessary, but it did make the connections tighter.

I’m using my MacBook Air, Fusion 360 for my modeling/CAM and Repetier Host for sending the GCode to the full size RAMBo board. The post processor linked elsewhere on the website seems to work fine, see attached pictures of the crown drawing. I don’t think I got a good picture of it, but my first gcode was in inches instead of millimeters and it ended up drawing a small crown less than an inch square with much greater precision than I thought it would.

I am now trying to solve one last problem - when I try to set the home position and return to it (or when the gcode finishes and returns the pen to home position), my z-axis is trying to go beyond its zero position. Sometimes this happens with the x and y axes as well, so I have to hit the emergency stop in Repetier before the homing continues.

That aside, everything seems to be going well! Thank you for the initial help and for all the plans you’ve developed here.


1 Like

Looks great!

If you don’t have endstops, then you don’t home the machine.

When you power on the rambo, the origin is the location that the tool is at that moment. When setting up for a job, you’ll first move the tool to the origin you set in cam by: a) manually moving it if the steppers are disabled, b) jogging it with repetier or the LCD controller. The origin in your workpiece is determined by your CAM software, but it’s usually the lower left corner, on the surface of the work, or the dead center of your design, so you can center a design on an existing thing.

When you’ve moved to your new origin, you can set it by either: a) resetting the rambo, which is simple or b) sending a G92 X0 Y0 Z0. Some users have found that some history of the old origin are still present, but I haven’t tracked that down myself.

After all the moving around, if you want to go back to the origin, you can send G01 X0 Y0 Z0 F600. That won’t go back to the place where you started the machine, it will go back to the origin of the work (which probably isn’t a great idea, since the bit will be touching the work at that point.

If you want it to get out of the way and go back to the beginning location, then… Hmmm. IDK how to do that without endstops.

Thank you Jeff. The kit did come with the set of three mechanical end stops which may not be that hard to stick wherever I need to. I guess I will just delete the gcode that would try to home the machine and replace it with returning to the zero point (which I thought the homing already did, but now know that it goes to the origin and continues until it hits the end stops.

Without mounting the end stops, is replacing the gcode the only method to get the tool to return to a certain point after completing the job instead of homing?

I’m not sure why it’s homing. I use EstlCAM and it doesn’t home. There is a setting for where to end, and I choose to make it hover over the last coordinate, at the clearance plane so there’s no chance of it still cutting.

You could probably disable homing in the firmware.

If you replace the G28 and you want to go to the origin, don’t do Z0, choose something like Z3 and you’ll also want to go straight up first, then go home like:

G01 Z3 F300
G01 X0 Y0 F900

You can put appropriate speeds for z on there then.

1 Like

Got it figured out. Switched post processors and made sure to send it to the origin when finished. I can edit from there but it will get interesting when I start using a router and the z distance has more variation than just 0 where the paper is and some arbitrary height for traveling above the paper.

I have been using the one by Martin DB from github, and it has worked fine so far for laser and router. I did get a weird gcode output using laser cut “through” (I’m not sure if it is because of a change in Fusion that has multiple types of through now or not) but vaporize worked fine which is pretty much what I will have to use for cut with a 3.5W laser. Also laser etch worked great too.


That is the link if somebody should need it.

That’s the one I switched to. Thanks for the tip on vaporize - don’t know what else that would be used for (my Martian death ray or disintegrator, maybe? Mmm, yes, fascinating, yes, hm).

Where did you get your laser from? Bang good? And how’s the performance on materials (does etching/engraving work well, if you have used it)?

Yes it is the 3.5W banggood unit. Etching is working very well so far, I have done etching on MDF and cedar.

This is it doing the crown on MDF: https://www.youtube.com/watch?v=Bs0sP-7_4OQ&t=22s

I am picking up some 3mm ply today to see how well it cuts.

Did some messing around this past weekend with cutting using the laser. I could do a full cut-through of 3mm ply with 3 passes at 150mm/m, dropping 1mm for each pass. A single pass at 50mm/m worked as well, but was not as nice a cut, the edges were considerably more charred. I used, “air assist” in that I held the end of an air nozzle toward the laser to reduce flaring and discoloration. I have plans to mount an air nozzle on the end of the laser though.

Air help with cuts a lot, helps a bit with etching as well to keep discoloration down a bit.

I like the color scheme. For mine, I used the “I’m not out of this color yet.” mode of choosing colors.

Thank you all. Certainly know what laser I will get when I’m ready. Currently working on learning the program for engraving/milling as that will be the last part I think I need to learn to perform any processes. Laser should be just like plotting, where the difference is if cutting or engraving.