rotary post processer

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oldmanofgf
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rotary post processer

Postby oldmanofgf » Mon Jun 27, 2016 3:50 pm

dose any one have a rotary post processer that will work with Vectric Aspire 8.5 that you would share. I have a request to Probotix for one but have not heard back from them
Machine 2015 Probotix meteor running Linux cnc
thanks
Glenn

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HANNAH024
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Joined: Fri Aug 21, 2015 9:57 am

Re: rotary post processer

Postby HANNAH024 » Mon Jun 27, 2016 9:58 pm

Glenn
Here is the one I use
You will have to unzip the attachment
LinuxCNC_Wrap XtoA_inch.zip
(998 Bytes) Downloaded 294 times
It is what it is!
Have a great day.
HANNAH

probotix
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Re: rotary post processer

Postby probotix » Tue Jun 28, 2016 7:33 am

Hey Lyman! I sent you an email asking about this, but never heard back. Everything okay with you?

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HANNAH024
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Re: rotary post processer

Postby HANNAH024 » Tue Jun 28, 2016 10:54 am

I sent it to you attached to a return email and never heard anymore.
So assumed that you received it and all was well at Probotix.
Then I got distracted and was working on other projects until a couple of weeks ago.
Now I am back working on the rotary....
There has to be a better way to speed up the rotation than the way I am doing it.
If you set the feed rate to 100 inches per minute then the rotary also runs at 100 but is switched to degrees per minute.
That means that on a 3" Dia. piece that converts to a circumference of 9.425" or .02618 inches per degree.
At 100 degrees per minute, you are only cutting at 2.618 inches per minute.
I have been rounding 2" square stock and reducing it to 1.625" by rastering along the Y axis. That way there is a minimum amount of rotation.
But, I have 18 grooves to cut around the cylinder after it has been rounded and reduced....That will require way too much time for any kind of
reasonable production. After considerable tweeking, I am running the rotary at 300 and the Y raster cutting at 200 taking a 0.15 " depth of cut and
getting by. At 0.25 inch depth of cut and 200 IPM, the wood was flying off in splinters. Climb cutting worked much better with the RPM in the 20,000 range, but there is some blackening of the wood at the end of the travel and when changing directions.
Any ideas on how to speed up the rotary without speeding up the Y feed rate. LinuxCNC seems to have them tied together. A little later in this project, I need to do some checkering on the parts after rounding them. so there has to be some kind of coordination between "y" axis movement and "A" axis rotation.
What's new with you and Probotix?
It is what it is!
Have a great day.
HANNAH

oldmanofgf
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Joined: Wed Oct 28, 2015 12:09 pm

Re: rotary post processer

Postby oldmanofgf » Tue Jun 28, 2016 11:28 am

Hannaho24
Thanks for the post processer now I will try and turn something
Glenn

probotix
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Re: rotary post processer

Postby probotix » Tue Jun 28, 2016 1:54 pm

I have talked to the LinuxCNC guys at length about the issue, and I have to agree with their assessment. When A is included in a line of g-code, then Feed has to be in degrees. Its not the job of the controller to do anything other than execute g-code, and the only way it could do Feed in IPM for a rotary would be if it knew the diameter of the stock at any given depth of cut into it. It has to be the job of the CAM software to do this, and unfortunately the Vectric software does a bad job of this.

sgano
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Re: rotary post processer

Postby sgano » Tue Aug 02, 2016 9:58 pm

I found some additional information about the rotary axis being so slow while using LinuxCNC. It appears that the issue is that LinuxCNC strictly adheres to NIST standard (NIST RS274NGC) that requires rotational axis to have a feed rate in degrees per minute units while linear moves in inches per minute. But most of the rest of the world seem to treat rotational axis with the units of length/time units and the controller then corrects for the radius (given that the Z-0 has been set at the center of rotation -- then the controller knows exactly what radius it is at all the time and can compensate -- Mach3 has this exact option - using the z-position/radius for the rotational speed)

This NIST spec becomes a problem for any CAM software if there are simultaneous rotations and linear movements since only one federate can be specified for a given line. (e.g., if you want to move down in z 0.1" and cut the full 360deg rotation at the same time, if you set the feed rate to 80 inches per minute, this will result in a normal z-plunge speed but it will then rotate at 80 degrees per minute which will take 4.5 minutes to rotate the full 360 degrees!).

If the rotations are specified on separate lines then the feed rate units can jump back and forth.

It also appears the best way to handle this is by using G93 - is Inverse Time Mode - which essentially specified how long a particular move should take -- this would then allow rotations and linear moves to happen at the proper speeds. But not many CAM software packages seem to support this since most controllers (one notable exception for us Probotix / LinuxCNC users) don't have this problem - or have options like I mentioned before (e.g., Mach3).

Here are some interesting places to read about this:
https://en.industryarena.com/forum/a-ax ... 83448.html
http://www.deskproto.be/forum/forum.php ... 300&page=1

No solution yet to speeding up the rotation axis -- but hopefully this might help us get there. Or maybe for rotary axis jobs - it might be possible to dual boot the computer into windows and run Mach3?

UPDATE: here is a solution to speed up the A-axis/4th axis: https://www.ganotechnologies.com/cnc/rapidrotary/
Last edited by sgano on Sat Sep 03, 2016 1:03 am, edited 1 time in total.

4DThinker
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Re: rotary post processer

Postby 4DThinker » Wed Aug 03, 2016 8:15 am

When I use my rotary axis, I just set the feed speed for any toolpaths/tools using the X axis to 5000ips. All X moves are converted to A (rotary) moves. Any Z moves are limited by the machine so you don't have to worry the Z axis will move too fast.

4D


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