CNC size vs Design

Mostly Printed CNC - MPCNC Troubleshooting
1

Hi,

Long time Lurker, first time poster.

I have built a MPCNC over last few months, and as many are, I am impressed with the design, really well done, and thank you for making it publically available!

I am still in the process of finetuning and figuring out the details, I intend to dissasemble the middle stack soon after I have done a few more runs, and rebuild it, hopefully it will then fit a little better.

One issue I am having is that the designs i have made end up being milled 30 - 40% larger than I intend. Is this a stepping setting issue? I have all three jumpers installed below the stepper drivers. I haven’t been able to find any comments about a size change issue.

I have used Aliexpress electronics, Ramp 1.4, DRV8825 and smart LCD. I am using ESTLCAM to convert Inkscape made SVG files, and printing via Pronterface.

Appreciate your feedback to see if I can get atleast similar sizes between design and end part.

thanks
Wouter

2

Are you using 20 tooth pulleys instead of 16?

Thanks for the kind words!

3

I ordered 16 tooth pulleys, and then didn’t count them but i will check that I did receive the right ones.

4

Ă“k, so thats the issue. I ordered 16 teeth pulleys and received 20 teeth pulleys!

Is it an easy change to update the software to reflect 20 teeth instead of 16? Is it something i can do myself?

5

Yes just update the x and y steps in the firmware.

6

Is it only changing:
#define DEFAULT_AXIS_STEPS_PER_UNIT { 200, 200, 4535.44, 200 } //MPCNC

to

#define DEFAULT_AXIS_STEPS_PER_UNIT { 160, 160, 4535.44, 200 } //MPCNC

in the configuration.h?

1 Like
7

Yes, perfect.

8

Fantastic, this has solved my size problem! On to the next one!

Thanks for the support!

9

What, no next one…positive attitude. Get ready to get it dirty and have fun and maybe learn some things along the way.

10

I like to fight it first, see if I can figure it out… Have some positioning issues to work on, in terms of how well layers are on top of eachother, but i think that is refitting the centre assy, and making sure belts are tight etc. I will be back!