Need Help!- 4th axis control in EMC2 (Tangent knife cutter)

[EduardKieser]

Hey.
I've just finished building a small cnc router. I would like to use it to cut depron using a knife. Does EMC2 have a function that keeps the 4th axis tangent to the cutting direction so that one may be able to use a knife? Apparently Mach3 does, but I'm bent on using EMC2. I've scanned your forum, a few threads touch on the subject but none (that I have seen) seem to cover it.

Any help would be greatly appreciated.
Eduard

[jmelson]

Originally Posted by EduardKieser Hey. I've just finished building a small cnc router. I would like to use it to cut depron using a knife. Does EMC2 have a function that keeps the 4th axis tangent to the cutting direction so that one may be able to use a knife? Apparently Mach3 does, but I'm bent on using EMC2. I've scanned your forum, a few threads touch on the subject but none (that I have seen) seem to cover it. Any help would be greatly appreciated. Eduard

I believe this was just being discussed a few days ago in the EMC2 user's forum. It would not be that hard to do this. You use a couple standard HAL components to compute the angle, and then feed that to a non-gcode axis that follows the current move angle. The one place this might get tricky is that an axis that is not commanded directly through G-code can't be homed, either. So, you'd need to provide some scheme to home the knife to the right angle before connecting it to the slave axis.

If you don't know how to read the emc user's forum, see http://www.linuxcnc.org

Jon

[knoopjan]

Hi there,

I have designed (C)NC-systems since 1977. I believe EMC2 is an ¨almost¨ perfect CNC-controller for 2-9 axes, unfortunately without any tools and tricks needed for what you want to do.

My tangentially-controlled tools however work great with EMC2 since I programmed various post-processors for those tools needed to cut cardboard and vinyl and to (jig)saw anything in plywood and non-ferro metals, up to 12mm AlMg4.5 and brass.

I currently use EMC2-2.4.2 with the Ubuntu 10.04 RTAI kernel and run VMWARE-player with an other (non-RTAI) one. In a Windows-XP Virtual Machine I prefer using AutoCAD as well as Inventor to generate any DXF-file needed for plotting/milling/routing/cutting/sawing workpieces. The importance of AutoCAD: all programs and post-processors I ever wrote since 1985, still function today and deliver truly automatic 3, 4 and 5-axes EMC2-compatible G-code.

If there is enough interest I probably should document and upload some of my hard- and software details for use on this forum.

So, please let me know!
Jan

[chester88]

Im sure this has been done. There was a mail list discussion in feb of 2009 about it.
I thought someone made a HAL component to help but don't remember.
check the EMC mail list archives and/or post this request on the EMC maillist.
Most of the developers don't read the forums

Chris M

[Dan Falck]

I would be interested in a general view of your setup. Are you using Autocad Autolisp to generate the gcode? I assume you are generating rotary motion commands to knives based on the geometry in Autocad.
So you're also selling commercial machines with EMC2 controlling them? That's great.
Thanks,
Dan

Originally Posted by knoopjan Hi there, I have designed (C)NC-systems since 1977. I believe EMC2 is an ¨almost¨ perfect CNC-controller for 2-9 axes, unfortunately without any tools and tricks needed for what you want to do. My tangentially-controlled tools however work great with EMC2 since I programmed various post-processors for those tools needed to cut cardboard and vinyl and to (jig)saw anything in plywood and non-ferro metals, up to 12mm AlMg4.5 and brass. I currently use EMC2-2.4.2 with the Ubuntu 10.04 RTAI kernel and run VMWARE-player with an other (non-RTAI) one. In a Windows-XP Virtual Machine I prefer using AutoCAD as well as Inventor to generate any DXF-file needed for plotting/milling/routing/cutting/sawing workpieces. The importance of AutoCAD: all programs and post-processors I ever wrote since 1985, still function today and deliver truly automatic 3, 4 and 5-axes EMC2-compatible G-code. If there is enough interest I probably should document and upload some of my hard- and software details for use on this forum. So, please let me know! Jan

[knoopjan]

Originally Posted by Dan Falck I would be interested in a general view of your setup. Are you using Autocad Autolisp to generate the gcode? I assume you are generating rotary motion commands to knives based on the geometry in Autocad. So you're also selling commercial machines with EMC2 controlling them? That's great. Thanks, Dan

Autolisp automates the process of choosing what to cut (and how and where) on any flatbed machine. Next, in an AutoCAD shell, various programs are called to generate 3-5 axes DSP-CNC controller code as well as EMC2 compatible .ngc files. All feed rates, tool offsets for knives or circular saws and Z-axis lift-conditions are preset/stored by these programs. After an initial run, all needed to route, cut or mill is one mouse click on the XPLOT-icon in AutoCAD. What you see (autocad screen) is what you get on the flatbed table. Closed contours are optimized and sorted. For tangentially controlled tools feed rates are calculated depending on inertia/power of the various machine axes plus the radius of the move (or end- and start-angle difference of adjacent vectors).

I hope to ¨recordmydesktop¨ while processing a batch of roadsigns next week and post a link to the .avi when available.

About the Xplot-machines...
They can be controlled by any controller generating industry standard pulse/direction or CW/CCW signals. High feed rates however, for professional equipment 600-5000 mm/sec, are probably only possible with advanced DSP-based hardware.
But most 3D-machinery including the new 4-axes XPLOT-D.I.Y. gantry are perfectly usable with EMC2.
For a 4-axes machine @ 250-400 mm/sec, a low-cost tangential cutter, a ditto AMD64/2 computer with LPT-port/printer cable and an updated EMC2 live CD is all you really need to start cutting.

Jan

[Dan Falck]

Thanks for the summary Jan. This sounds very streamlined. If you do get a 'recordmydesktop' session going, please do post a link to the youtube video.

Dan

[chinsettawong]

Hi Jan,

I'm very interested to learn more about your build.

Wachara C.

[ktchk]

I saw INKSCAPE have a plugin with a tangent knife g-code generated for A axis.
This is the only thread talking about tangent knife so I am posting to see if some one have the hardware to test it.

The plugin is at:
cnc-club.ru •