How do I setup a 5 axis mill?

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08 Apr 2016 16:46 #72971 by Louis
Hello. I've been using LinuxCNC for a while to control a 3 axis mill. The spindle moves along Z, and the table moves along X and Y. I just ordered a 4th and 5th axis setup that will bolt to the table, and discovered that I can't use the stepconf wizard to set it up. From what I've read here, it seems that I need to select the XYZA configuration, then edit the config files to duplicate the A axis and rename it to C, specify the right pins, etc... I could use some help with this.

I'm also concerned about where I will specify things like the distance between the A axis and my table surface, the fact that my C axis is attached to the A axis. Will I have to edit a kinematics file? Is the 5axiskins file intended for this style of machine? Where are these files located?

I am using Fusion 360 for CAM, and I'm hoping to do some indexed 5 axis machining. I hope someone who has done this before can point me in the right direction.

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08 Apr 2016 20:48 #72976 by BigJohnT
The setup wizards are for simple configurations only. Yes, you could make a XYZA and copy the A.

JT

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09 Apr 2016 01:06 #72981 by andypugh
5-axis machines are complicated. You need to work out what you want the A and B G-code words to mean.

They _can_ just refer to the angles of the rotary axes, or they can alternatively refer to the angle that the tool-tip is aligned to the work at the current XYZ point.

I have attached a rather detailed document on the subject (I hope the author does not mind). Depending on your mathematical background you will find this somewhere between fascinating and baffling. If you fall in the latter camp then be reassured that you don't need to understand all this, but you do need to know what you want your 5-axis machine to be.
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09 Apr 2016 14:03 #72998 by Louis
Replied by Louis on topic How do I setup a 5 axis mill?
Thank you for the replies. I have made some progress, but I still have a lot of learning to do. My first idea to duplicate the A axis seemed to have worked, but I did encounter some problems. After selecting an XYZA mill and editing the .ini file, I was able to move the A and C axes position in the DRO, but I would often get a joint following error. Then after I attempted to edit the .hal file in the same way, duplicating the A axis and renaming to C/5, LinuxCNC failed to start with the error "pin does not exist." I am curious about why this didn't work, or how to add a pin. My next thought was that I was having this problem because I am testing this in simulation mode on my regular PC that doesn't have a parallel port. My 4th/5th axis won't arrive for another week. I edited sim_hardware.hal and was able to get different errors. That's where I stopped trying this method. Maybe instructions/explanations for modifying these files exist somewhere?

I wish I had come across that .pdf at the beginning of my search. It was very helpful. Thank you. I did take all that math in school, but it's been many years since I've used it.

From what I've read, I think that I need to use RTCP positioning to be compatible with Fusion 360, and most 5 axis CAM software. Is that the case? Since Fusion isn't able to generate tool paths from .stl files, I'm thinking about Deskproto. Any other 5 axis CAM recommendations in that (<1000$) price range?

I was using trivkins for those first attempts. I found that 5axiskins is intended for a machine with a tilt/rotate spindle, so then I found XYZACkins. I was able to compile and run it, and it is working pretty well. It has the table moving along Z instead of the spindle. I'm not sure if that is set in the kinematics or is just the way it is displayed in the vismach file. I don't think it will cause any problems for me to use it as is after I replace the offsets for the rotary axes, but I would like to change it to reflect the way my mill is configured. Any advice or links to helpful info would be appreciated.
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09 Apr 2016 14:14 - 09 Apr 2016 14:15 #72999 by BigJohnT
Yep, the instructions are here linuxcnc.org/docs/2.7/html/
And specific instructions for the ini file are here linuxcnc.org/docs/2.7/html/config/ini-config.html

I can't look at your file from this Windoze computer it doesn't know what a tar file is. A more universal compression is zip.

Did you increase the number of axes?

JT
Last edit: 09 Apr 2016 14:15 by BigJohnT.

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09 Apr 2016 15:22 #73003 by Louis
Replied by Louis on topic How do I setup a 5 axis mill?
The file I attached is the XYZAC configuration I found at:

http://wiki.linuxcnc.org/cgi-bin/wiki.pl?ContributedComponents#XYZACkins_5_axis_kinematics_for_a_milling_machine

This setup is a lot closer to what I would like to use than the XYZA mill. I think it will be easier to start with this and modify it to suit my machine. Here it is as a .zip
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10 Apr 2016 21:33 - 10 Apr 2016 21:33 #73080 by andypugh

Louis wrote: LinuxCNC failed to start with the error "pin does not exist.".


The error report will also tell you _which_ pin does not exist, and also which line of the HAL file to look at.
With that information it is generally possible to see what is wrong.
Last edit: 10 Apr 2016 21:33 by andypugh.

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06 May 2016 06:43 #74288 by Louis
Replied by Louis on topic How do I setup a 5 axis mill?
So my new machine has arrived now, and I've got it moving around. I think the "pin does not exist" errors I was getting before were because I was running in simulation mode on my regular computer in preparation of the arrival of the new machine. I've now built a dedicated computer to run the new mill. I took the same steps as before. I used stepconf to create an XYZA configuration, then edited the .hal and .ini files, duplicating the A axis sections and changing them to C, and it's working. I can now control all 5 axes, and I'm pretty happy about that. I have attached my config files in case some of you who are familiar with this stuff will spot an error I've made, room for improvement, etc...

So now I've got to generate some gcode to run on this thing. I only have 3 axis CAM software now, so my initial plan is to generate multiple 3 axis tool paths and manually rotate the workpiece between them. I think 5 sided machining will be fine for now, but I'm still wondering if if would be helpful for me to get the XYZACkins setup modified to suit my mill so I can have RTCP motion. Is that required for continuous 5 axis toolpaths?
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06 May 2016 08:30 #74289 by andypugh

Louis wrote: I'm still wondering if if would be helpful for me to get the XYZACkins setup modified to suit my mill so I can have RTCP motion. Is that required for continuous 5 axis toolpaths?


No, some CAM systems do the RTPC in the CAM software, and RTCP kinematics is counterproductive. However if you do it in the kinematics then you can run the same path with a different-length tool (for example) and the G-code paths will still work.

The configs in the PDF file I posted earlier have now been included in the JA13 branch of LinuxCNC:
github.com/LinuxCNC/linuxcnc/tree/joints...table-rotary-tilting

So if you switch to that branch you can try them out. I actually would very much recommend running joints_axes13 if you set up for RTPC, as it allows you to jog in the XYZABC space.

This is a video of one of those simulations:

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31 Oct 2019 09:13 #149264 by jackotool
Hello, the link above is dead - is there a Linux CNC version for 5 axis or not?? If not can we have clear step by step instructions to make Linux CNC control 5 axis (XYZAC) for rotary table that has two stepper motors in it.

Many thanks!

I will donate if someone can really provide very clear and simple step by step instructions ...

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