Page 2 of 3

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Sat Apr 06, 2019 4:06 pm
by cbb1962
Swissi, Thanks!

Can you give a little more explanation of what the differences are between "Along +X" and "Along -X."
Fusion V9 post.png
Fusion V9 post.png (41.78 KiB) Viewed 10903 times
Clint

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Sat Apr 06, 2019 4:32 pm
by swissi
Clint,

if you install a rotary axis along the X-Axis, you can install it in two ways. Either the rotary axis is facing in the +X direction or in the -X direction. Fusion 360 needs to know in which direction your A-Axis is pointing to generate the correct code.

Hope this explains it. For more details on the 4th Axis setup, see Autodesk's Instructions how to Setup a 4th Axis

-swissi

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Sat Apr 06, 2019 4:50 pm
by cbb1962
The machine I am rebuilding has the 4th axis headstock at the far end of the machine Y=96. Would that mean I would need to use "Along -Y"?
image1R.jpeg
Clint

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Sat Apr 06, 2019 5:28 pm
by cncsnw
My guess is that this choice is tied in with rotational direction. It is not so much a question of "at which end is the rotary table headstock"; it is more a question of "which way does positive rotation of the rotary axis go?". That is determined by how your servo or stepper motor is wired, as well as by how the rotary headstock is oriented.

Perhaps swissi can confirm, but I would expect that "+X" for an A axis means that the positive direction on A is a right-hand rotation around the X+ direction.

What does "right-hand rotation around the X+ direction" mean?

Hold out your right hand. Point your thumb in the X+ direction. Curl your fingers. The curl of your fingers indicate the positive direction of rotation.

Looking at the picture cbb1962 posted: Y+ is to the far end of the machine. If positive B rotation means that the part turns clockwise from the photograph's viewpoint, then the B axis rotation would be around Y+. If positive B rotation means that the part turns counter-clockwise from the photograph's viewpoint, then the B axis rotation would be around Y-.

It is possible I have this definition backward, since I have been talking about how the rotary table turns the workpiece. In CNC programming, we are generally not looking at how the workpiece moves; we are looking at how the tool moves. It is possible that what Fusion360 considers positive rotation is right-hand rotation of the cutter around the workpiece. That would be left-hand rotation of the workpiece under the cutter.

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Sun Apr 07, 2019 12:36 pm
by swissi
While there's a good definition and not much disagreement about the positive direction of linear axis, the same can't be said for rotational axis. What most people agree about is this:

axisdefinitions.JPG
axisdefinitions.JPG (27.04 KiB) Viewed 10883 times

So most people agree that the right hand rule applies to determine the positive rotational direction (cncsnw explained the right hand rule very well in the post before). Now the discussion if the workpiece is rotating in that direction or if the tool in relation to the workpiece is rotating in that direction is almost as divided as the discussion if that dress was blue or gold :D

So without taking a side on that discussion, I've done a sample workpiece and checked what Fusion 360 is actually doing and these are my findings:
  • If you select "Along +? Axis" and your workpiece is pointing in the positive direction of your ?Axis, the right hand rule applies in regards of the tool moving in a positive direction in relation to the workpiece . That means the left hand rule applies for the turning direction of the workpiece (chuck is turning clock wise if you look from the workpiece side onto the chuck
To make it more clear, the difference of the selection of +X or -X is just the inversion of the rotation of the axis. If you pick one and find out your axis is turning the wrong way, use the inverted one and run it again trough the post processor.

Hope this helps.

-swissi

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Mon Apr 08, 2019 11:52 am
by wallyblackburn
This is great stuff, folks! I already managed to hack my post-processor into doing what I need, but this helps me understand it a lot better.

Thanks,
Wally

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Mon May 27, 2019 4:47 pm
by swissi
I have posted a new version of the Post Processor on GitHub

Check out the User Manual to see all the features and how to use them.

Here's an overview of what has changed in the latest version:
  • 5/27/2019 MinRev-40783-swissi-001: Version number has changed and includes now the MinimumRevision number the Post Processor is based on with the extension of swissi-001 counting up. This version is now based on the latest Centroid General Mill Post Processor MinimumRevision = 40783.

    * Add a Command to the Beginning and/or End of job
    * Check Approach has been changed to Check Tool Offset and supports now the option of M0 or a M200 message
    * Comment Formatting can be chosen between (Comment) or :Comment
    * Write #300 Tool Info Line has been changed to Write CNC12 Info Variables and supports now a variety of Fusion360 parameters
    * Rotary Axis support has been improved
    * Support for Manual NC commands Comment, Display, Pass Through and Call Program has been added to the Post Processor
    * Logic has been added that checks for conflicting Tool Information e.g. using the same Tool Number but with different geometry.
Let me know if you run into any issues with the Post Processor or if you have any questions.

-swissi

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Mon May 27, 2019 6:57 pm
by cbb1962
Swissi,
Holy Cats!!! That looks amazing!
Thank you for your diligence in figuring all this out!

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Mon May 27, 2019 10:46 pm
by Gary Campbell
One thing to remember with rotary axes. I agree complexly with the right hand rule. That said, a rotary axis must rotate negative for a positive X or Y (depending on which axis is wrapped) command. Same principle as a moving table. Bit moving positive requires material moving negative.

Re: Fusion 360 Mill Post Processor for Acorn with additional Features

Posted: Mon Jul 20, 2020 4:40 pm
by swissi
This seems to be a stale (outdated) copy of the original post.

Check the original post Fusion 360 Mill Post Processor for Acorn with additional Features for the latest updates.

-swissi