Got my MPCNC built and I hit a snag. I’ll blog more on the details of the build later but since I haven’t posted in a while I wanted to offer a quick update on the blog.
The build went smoothly and everything was going great. I felt confident that I had a functional unit after a couple of ‘dry’ runs.
My movements were calibrated and I had hacked together a mill job that looked like it was running as expected through the dry runs.
In my ‘dry runs’ I noticed a couple of things. There was a jerkiness to the motion in some places and I had read that you should use white Lithium grease on the conduit where the rollers run.
Grease on, moving the X-Y I had the Rumba board plugged into the computer and powered from testing. As I moved the head around manually to see if I could spot binding and work it in a little I heard the computer bell from dropping the USB port and re-establishing it. I realized this was from the motor back EMF so I unplugged the USB port.
To work the grease in I moved the head through throughout it’s range including some rapid movements to see if they produced any binding. Everything looked smooth so I decided to setup for ‘real’ for one last dry run.
I had a clear warning that I was creating an issue with the manual movement because as I stated, the computer was dinging with the USB port connecting and disconnecting. I must have popped my power regulator IC because when I went to run another test run and found it was plugged in but not working.
Nothing looked fried and the power supply tested out but there were no lights on. The 12V rail on the board was even hot but not the 5V.
So I moved the Stand-Alone / USB Power jumper to USB Power and plugged in the USB and the board and display lit up and booted. So it looks like I fried he voltage regulator. I ordered a new Rumba+ board and got back up and running.
The first foam cut was behind me and I had even tried cutting plywood. Plywood is too hard and the cuts were ragged but it the MPCNC performed well. Confident the configuration was adequate I went to move the MPCNC to the garage. I tipped the unit to get through a door and gravity did the rest. The head moved very quickly to the downside and guess what? There went the replacement Rumba board.
Warning: Rapid movement on a MPCNC produces enough back EMF to blow circuits.
Lesson learned… before moving my MPCNC in the future I will figure out a way to lock the X and Y axes so the head cannot move.
Luckily I had ordered two Rumba+ boards so there was no down time. Still, two Rumba+ boards is a significant hit. Hopefully it is just the voltage regulators. I’ll blog about the experience if I am able to repair either board.
It has been a significant task to build my own MPCNC. V1 Engineering has done a phenomenal job on their web site and I will be sharing my experience to augment their effort and help others get up and running with their own MPCNC.
The table and milling bed are not part of the kit. There are suggestions on the website but actually building a functional MPCNC requires some word working skills as well. I’ve developed some word working experience and equipment over the years but I am far from skilled. I will discuss my choice and look for comments and links from other MPCNC builders in another posting.
I have found my 3D Printing experience has value, especially in understanding and setting up the hardware. Then I found that design and workflow are very different. Different software, different workflow, and different setup. I will describe the workflow I have developed in another posting.
Tags: blown board, blown circuit, build, cnc, emf, motor emf, MPCNC, printed parts, rapid movement, rumba