Fusion 360 guffy Post Processing Question

I have an original MPCNC, it has an an issue with the Z feedrate, which is 240 mm/min max! The X and Y axes can do 2500 mm/min easily. The problem comes from 400 step/turn motors, a 5/16" threaded rod drive, and just 12V on the steppers.

I am using Fusion with guffy’s post. It seems to work a long as I limit all feedrates to 240 or less.

My question is, shouldn’t the post specify the rate on all G1 commands? It doesn’t! In fact, it specifies a speed near the start and it doesn’t change (on simple files anyway) until the last few commands where it moves at 800, which seems to be some boilerplate piece of code.

Is this a limitation from the free version of Fusion or the way the guffy post is supposed to work?

Although this is all new to me, I’m wondering if I should try writing a “past-the-post” processor to modify rates? Has anyone done that? Seems like this would make my machine a lot more useful since most of what I want to do is cut shapes out of sheet material.

So there were some changes to the Fusion 360 presonal/free version which introduced this problem. Most people are solving this issue by limiting the Z feedrate in firmware. You can execute the following g-code once. The change is persistent:

M203 Z4   ; Limit the feedrate of Z to 4mm/s (240mm/min)
M500      ; Save the changes to the EEPROM

This places the limit on only the Z asix, so you can up the feedrate for the X and Y. This is somewhat of a brute force solution. The better fix might be changes to the guffy post processor. Take a look at post 162 by Don in this topic.

Thank you! I wondered if it was connected to the recent personal use license. I’ll give your solution a try!

I’ve addressed these issue in a new post processor I hope to release for beta testing this eeekend, read more in this post https://forum.v1e.com/t/problem-with-fusion-and-z-feedrate/21487/14?u=flyfisher604