>From my experience in dealing with irregular surfaces and such I think your best bet is to get a long distance (50-100mm/2-4") capacitive PNP/NPN sensor and use it to guide the cutter via some adapted THC logic. You should be able to pick up a decent Omrom/Turch sensor for < $50 on Ebay. A good sensor will have <1% error which I believe is quite sufficient for your work.
Usually these sensors accept a wide range of voltages but the minimum tends to be around 12v so you need a little circuitry to get that signal into your machine. Jarl (Dallur) On Mon, 2007-01-29 at 11:30 -0600, Chris Radek wrote: > On Mon, Jan 29, 2007 at 11:38:13AM -0500, Michael Dubno wrote: > > To be honest, I am trying to make an automated pumpkin carving machine. > > The mechanism would be a custom built rotary stage and a horizontal arm > > mounted on a vertical post. (Custom built because I don't want pumpkin > > goo all over my metal mills). Obviously all pumpkins come in different > > shapes and sizes and they also have ridges. I would like to use existing > > software to convert images and patterns into g-code. A small program to > > post process the g-code before it is run would be easy for me to write. > > The idea of a cutting tool who's depth is controllable being held in > > place by a spring loaded "follower" or "leader" might work out as well. > > I suppose the resolution of the pattern might make a difference. > > I think the way to look at the problem is 2 1/2 axis or 3 axis. Treat > > rotation as x, the vertical axis as y and the cutter as z. > > Thanks for all of the suggestions, they are quite helpful. > > - Mike > > Thanks for being brave and telling us what you are doing, it sounds > really fun. > > This reminds me of the torch height controller Dallur made. The > basic problem is to have a height sensor, and make your requested Z > relative to that height. > > I'm picturing that you could sense height with a spring loaded arm > with a roller on the end. You'd have the roller "close" to the tool, > and the arm pivots on an encoder. If the arm is relatively long, the > movement of the end will be fairly linear. You would derive height > from the encoder counts. > > At the HAL layer, you would add this to EMC's requested Z. (You may > have to subtract it back out for feedback to the motion controller.) > That way Z becomes relative to the pumpkin surface. Now your gcode > is very simple... > > Chris > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
