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Offline piv

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5 axis kinematics and coordinate transformation
« on: January 23, 2010, 09:56:40 AM »
I am trying to find out if mach3 can be setup somehow to do do 5 axis kinematics, also known as RTCP (Rotation about Tool Centre Point) so you can program a five axis toolpath at the tip of the tool and do the tool length compensation in Mach3. Is this what Formulas is used for?  Ive only got a demo setup at the moment, with a DSPMC clearing customs so I can try it out on a 5 axis CNC router next week. Its a bit hard to tell from the demo exactly how it will work with DSPMC as I have to have the DSPMC to run the plugin.

Also is it possible to somehow program on an inclined plane (or coordinate transformation), this is often used in 3+2 machining so you can program as if its a three axis job but then say machine on a face inclined at 39 degrees with the spindle at right angles to the inclined plane.

My guess is I might need to write a plug in to do this, unless someone else has done it, is working on it, or volunteers to do it.  Im a newbie to Mach3 so writing a plugin will be a big learning curve. The docs ive found on plugins are for mach2 or am I looking in the wrong place or is it still the same?

Offline Dan13

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Re: 5 axis kinematics and coordinate transformation
« Reply #1 on: January 23, 2010, 12:03:50 PM »
I don't know the details of how Mach3 handles the moves, so don't know if a plugin can be made. I DO know that 5 axis kinematics are not supported with Mach3, and I just guess that since all the moves are handled in the trajectory planer, it is unlikely that a plugin would work for this.

Daniel

Offline piv

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Re: 5 axis kinematics and coordinate transformation
« Reply #2 on: January 23, 2010, 08:51:29 PM »
I've read somewhere that the moves were going to be handled outside of the trajectory planner but I dont know if thats happened yet. A kind of work around is possible if the CAM package writes the G code moves close together, then the transformation/kinematics can be done on the G code file before it goes to the trajectory planner, not perfect, but it gives the same good result that you get if the CAM package puts out joint positions rather than TCP (Tool Centre Point).  A similar thing could be done for machining on an inclined plane, except a reason for doing that is so you can program circles and arcs with G02 G03, which really needs the transform to happen in the trajectory planner.

Offline bowber

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Re: 5 axis kinematics and coordinate transformation
« Reply #3 on: January 24, 2010, 06:02:48 AM »
I've seen a site were they are using gmax? and a plug in to write gcode for 5 axis milling, I'll try to find it again and post the address for you.

Steve

Offline bowber

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Re: 5 axis kinematics and coordinate transformation
« Reply #4 on: January 24, 2010, 06:09:50 AM »
Just found it

http://cnc4free.org/

look under essentials then cnc toolkit
More for hobby/ small business use but may be of some help.

Steve
Re: 5 axis kinematics and coordinate transformation
« Reply #5 on: May 07, 2011, 02:36:47 PM »
hiya guys,
ive had good results with cnc toolkit
ive also had good results with 'cheating 5axis' by rotating head and then re zeroing and cutting 3 axis with a tilted head.
Im thinking about doing the math and code for one of 2 things:
a gcode modifier that you feed in 4'5 axis offsets then it will filter 1,2,3 axis locations. effectively doing what cnctoolit does very well already.
I was also thinking about using the math formula feature in mach3 to do the same thing but suspect it would slow down with all but the coarsest 5 axis movements, again this would work if you only moved 4,5 axis ocassionally while off the work surface. I could live with this as i think good work is possible if you keep life simple.
Can you let me know what you made of the vitalsystems DSPMC, im thinking of ordering one shortly and would love to hear your expereince.
regards
Benergy
Re: 5 axis kinematics and coordinate transformation
« Reply #6 on: May 07, 2011, 06:46:13 PM »
I have Madcam. A 5axis cam software. It's 3+2, maybe 4+1. Supposedly true simultaneous soon. It has a Mach post processor. I haven't used it yet but in searching for a cheap 5 axis cam.. it seems very capable.

Offline piv

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Re: 5 axis kinematics and coordinate transformation
« Reply #7 on: May 08, 2011, 08:01:57 PM »
Ive got DSPMC on two 5 axis routers and it is very good.  Rufi is developing a "point streaming" plugin so that we can send 1ms points to the DSPMC. This will allow an external software (user to write it) to do kinematics and trajectory planning outside of the cnc. The idea is that I will write a program that takes the g code and interprets it and does trajectory planning and kinematics, then the plugin streams that file to the dspmc. It will have lots of limitations but will enable user control over accelerations and limits and kinematics that is not possible within Mach3 alone. ITs all vapour ware at the moment.
Re: 5 axis kinematics and coordinate transformation
« Reply #8 on: May 09, 2011, 01:29:26 PM »
Hiya Piv
so thats a thunbs up for dspmc then. you run steppers or servos? How are you toolpathing your 5axis?
b

Offline piv

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Re: 5 axis kinematics and coordinate transformation
« Reply #9 on: May 09, 2011, 08:20:51 PM »
Machines are running servos in torque control mode.

Toolpathing is by Topsolid and Mastercam.  Have other machines on Unigraphics NX and ProEnigneer.