MPCNC Printer Setup Problem

Mostly Printed CNC - MPCNC Troubleshooting
#1

Hello everybody

I’m building a MPCNC Printer. All parts are assembled now and I’ve made my first test prints. Now I need some help troubleshooting my problems.
I printed a hollow 25mm calibration cube. The first 10 to 20 layers are absolutely perfect. Everything is rectangular and the X & Y size is perfect.
But afterwards the print starts to get worse and worse.

I attached some pictures to illustrate the problem.
I’m very new to 3D printing and started with a M3D printer this spring, and shortly afterwards I started building my MPCNC. So I never calibrated a printer, every help is welcome.

Thanks in advance.

cube25.jpg
cube25.jpg1600×1200 87.3 KB

cube25_upsidedown.jpg
cube25_upsidedown.jpg1600×1200 83.4 KB

Printer.jpg
Printer.jpg1035×1380 138 KB

#2

Is everything square? I’d probably verify again that all of the parts are perfectly squared up. All the bearings just touching. Everything moves very smoothly as you move it around by hand. Distance from printhead to surface of the bed is the same in all places or as close as you can make it. It may just be perspective in the picture, but I think my extruder is a bit different on the Cnc… if nothing else, slide the stepper in the extruder as close to the gantry as you can. Looks like there is a space there.

#3

You do not have a print fan, and you are printing tiny parts.

I bet if you scaled those up to 2.5-5 times there size they would work because it has time to cool between layers.

#4

Thanks for your help! Now it is working.

First I added a print fan, and started to print a bigger cube (5x5x5cm). But still, my Z dimension was off by around 0.8cm.
I found out, that my printer settings were wrong, I used the settings for an imperial threaded rod (I have a IE).

Now I did some prints for my cable chain holder. The pieces work but the printer isn’t perfect.
First, I had to up the current for my Z motor, but still I have the problem that the threaded rod sometimes blocks.
Then my bearings at the rollers for X and Y movement don’t always touch. Is there a modification, so I can adjust the pressure on the conduit?
The current setup works, so I maybe going to reprint the roller F. The printer I previously used wasn’t very precise and I used very little infill, so maybe the roller F aren’t rigid enough…

#5

Try using the new beta firmware, with your correct z axis steps, It has slower z axis accelerations. That should help. It could also be binding of you axis so check to make sure it moves smoothly and very easily by hand for the whole travel.
There are a lot of reasons your bearings might not touch. Sometimes it just doesn’t matter, but if it is causing issues I would double check your center assembly for square.

#6

Okay, I’m going to update my firmware.

My center assembly is the very first version you published, so I don’t have the better middle Z. My old printer was too small to print it.
The printer runs fine without all the bearings touching. Only if you are printing very small details there are some errors.
I’m going to print the better middle Z this week, I suspect after that the problem will solved itself, hopefully ^^