Shop Sabre (Win CNC based) post problems

[matthewsclark]

I recently purchased a ShopSabre CNC router with a rotary axis. I'm relatively new to CNC programming and G Code but comfortable in Fusion and Inventor.  I've been doing test cuts, right now dialed back to just a circle, to try and get the machine sorted and am having problems with Fusion's tool paths (there is a post for Shop Sabre on the Autodesk post page and shop Sabre provided me with an older one that they had modified as well, they both produce the same results here).

The machine came with Vectric as well. It outputs circles as 4 90 degree arcs while Fusion uses 2 180 degree arcs. Also their lead in and out strategies are different but I've tried to match them as closely as possible.

For some reason that I can't figure out, the Fusion toolpaths are making the circle not close, even with a very gentle lead in the circle starts out too large so when it comes around the circle and closes the cut there is a scallop outside of the circle diameter at the start of the cut.  The Vectric cuts are perfect.

As I understand it with I J coded arcs, it shouldn't matter if they are 90 or 180 because the start and end point is specified and the center is calculated, so I'm suspecting the lead in but that's about as far as my thinking has come.

I've attached the code from both programs (just a single finishing pass in a pocketed circle) and a photo, any ideas?

Thanks, Matt

(p.s. - error message says .tap is not a valid file extension for attachments haha, might want to add it - I made them .txt files)

[grigorov.rv]

it's a simple postprocessor, I wrote it myself. if you have any questions, write: grigorov.rv@gmail.com

[matthewsclark]

ok, I'll take a look and see if I have any questions. Thanks

[dannyb85UYS]

Did you ever figure this out?
Staring at the posts, i see nothing that would cause this.

The posts i have seen (last updated 9/24, but mostly for docs) will linearize circles that are not in the xy plane anyway, 

They will also linearize full circles and helical motion.

I've done plenty of circles with helical lead ins, ramped lead ins, you name it, and they all come out fine for me.

Note, however, i also keep up to date on wincnc software version

I'm not sure what version you are on.

[Anonymous]

I ended up not using Fusion 360 for my toolpath. Thanks for all your help.

[matthewsclark]

I just got my Shop Sabre machine about four months ago, haven't updated since then but that doesn't seem too old, I'll check the version. 

I actually found that the X axis had play in it last week, fixed now so I'm going to start testing again. The play was manifesting intermittently so I'm sure it caused some of my weird cut results.

[matthewsclark]

It's running 3.0.12b, I just downloaded the latest Win CNC and Shop Sabre posts from the HSM post page and I'm going to try some cuts, I'll post results.

[dannyb85UYS]

Please do, i'm curious to see if it fixes it for you

For reference:

I use inventor hsm for my toolspaths (2018, but used 2016 and 2017 before that) with very slightly modified posts.

Mainly to output the feed speed more, since wincnc 2 used to end up resetting it more than it should have, i haven't checked if this was ever fixed in 3.

I have the zaxis trammed properly and have edited the unit lengths in wincnc.ini to be accurate to <0.0003 inches (IE when i command it to move 2 inches, it moves 2.0003 or better. It's actually 2.0001 or better, but the ballscrew precision is the limiting factor here).

They were pretty accurate already (I believe they set them by hand the same way i'm doing it).  Definitely within 0.001 over an inch.  I just ended up having to mess with some things that caused it to be inaccurate, so i was fixing them.

In this configuration, i've never had an issue with the toolpaths from HSM, and can even do things like thread milling (in aluminum) with good results.

I haven't used fusion 360 itself.

[matthewsclark · Accepted solution]

Just finished repeating all the test cuts from when I first got the machine. Everything is working fine, the problems were with the play in the x axis which I would have recognized if I wasn't such a newbie. Interestingly (and unfortunately) the Shop Sabre help crew just said "we don't support Fusion" and good luck.  Now that I understand a lot more about G Code and compare the G code side by side, it's pretty obvious it's not in the code, wish they would have asked me a few questions and tried to be helpful in diagnosing it.

I'm just using the Shop Sabre post processor downloaded from the HSM post site, the Win CNC post gives basically the same results but it doesn't seem to have the same provisions for tool changers, which I don't have.

Thanks for all the replies everyone.