I have been using my MPCNC with fusion cam for a while now, but only for small and lught things. I really dont have any previous CNC experience, so I have just been happy when things work out.
Recwntly i have been having some issues though. When i am carving something everything is good for a while, but suddenly the router plunges way beyond what it should.
When i look at the Gcode it seems like both X, Y and Z uses the same feed speed. This means that if i put 310 as my cutting feedrate, and 90 as my ramp and plunge feedrate, the Z still plunges at 310mm/min…
I can only imagine what it was doing when speed was set at 620
My issue is that this happen event though i have tried both the V10 post process, and the guffys post process…
here is a section of the gcode i get:
;T4 D=14 CR=0 TAPER=45deg - ZMIN=-2 - chamfer mill
G90
;Units in mm
G92 X0 Y0 Z0
M84 S1800 ;Change Stepper disable timeout to 30 minutes
I have not used the fusion pp. But I can tell you that this kind of thing is tricky for CAM, because the moves are in all three directions. The feedrate is actually the rate along the line segment. So the Z component may not be 310mm/min. The PP would have to compute the feedrate based on the length of the line, the max feedrates in each direction and the lengths in each direction, and then adjust the overall feedrate so it doesn’t exceed the Z plunge or raise rate.
This should be solved in the Marlin firmware though. If you changed your max Z to be 1.5mm/s, then the most it would ever move in Z is 90mm/min. At least, it should. Older versions of Marlin broke when you exceeded the max rate, which is one reason it is so high.
You can set it with M203:
M203 Z1.5
And save it with M500:
M500
What you should see is that as the carving goes up or down a hill, the XY feedrate will slow down, so the Z won’t exceed your limit.
I should also say that 1.5mm/s is a very slow upper limit on Z. Even 5mm/s (310mm/min) should be fine in Z. Which makes me wonder if there is something else going on here. If you’d like to explore that, post some details about your build and maybe a few pictures.
I think some of the issue is that im using a 90 degree carving bit, and when it plunges fast it developes quite a lot of resistance. My Z-axis might actually be kind of stiff as it doesnt drop when the steppers are not powered. There might be an actual flaw in the G-code as well though.
What happened was that i was doing a test carve on chipboard, for a carve i am going to try to perform on aluminium. The carving was almost done when it suddenly plunged deep into the workpiece.
I am using the rambo board (not purchased from ryan). The stock firmware from the pages here, and china bought steppers. My machine has a working area of approximately 60x60cm, and a z- axis of approximately 5cm. I’ll take a trip to my workshop and take some pictures if that would be of any help
It is typical for the router to not drop on an MPCNC when the Z isn’t powered. But that is a big router, so it may be right on the hairy edge. You have lubrication on the leadscrew, right?
Since it is a big router, one guess is that the driver overheated, and the Z turned off. After that, either the bit was pulling, or the vibrations of everything caused the Z to fall. Does it fall on it’s own if the steppers are off, and the router is on? Do you have a fan cooling the air in the controller box?
I think technically, the drivers sink to the PCB, so a fan on the back may be the most efficient cooling. You also need somewhere for the air to go.
well, I guess the leadscrew isnt really lubricated that well. When i took the photos last night I lubricated the leadscrew with some superlube, and I could actually feel the resistance decreasing. There is no cooling in the electronics box… Does it develop a lot of heat? I’ll see if i can figure out a way to get some cooling in the enclosure. Is there a port for cooling on the RAMBO or should i just connect it directly to 24V?
The drivers are the 5 chips on the left of the board, near where the steppers plug in. They will get hot. When they do, they will shut down to protect themselves.
It should be ok at the default current settings in the air, but maybe not in a tight box.
Just plug it straight into the 12 or 24V. It will always be on then.
I’ll do that next then, the reason the box is tight is that I didnt want all the wood and aluminium dust inside the box with the card, but I guess air/cooling is important to
Put a small filter over the air intake, or put the air intake on the bottom blowing up into the box. Dust is less likely to be pulled up against gravity.
I ordered some filters and fans a couple of days ago, so i will put one intake and one exhaust fan with filters on both. Until then I’ll probably just leave the box open.
