Hi, I suppose the answer is maybe. Use a wimpy spindle motor and detect the loading when in quits cutting air and starts cutting pumpkin. This assumes a rotary tool. For a chisel, knife use the increased force necessary to drive the Z when the cutter hits the pumpkin. Maybe (cheap and easy).
Dave On Jan 29, 2007, at 3:23 PM, Michael Dubno wrote: > Try this link for the image - > http://www.dubno.com/pictures/misc/pumpkin1.jpg.html > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Michael > Dubno > Sent: Monday, January 29, 2007 6:01 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Is there an easy way to work > withanirregularsurface? > > The problem gets even more elaborate and potentially more constrained. > > First, when most people carve a pumpkin they don't worry about the > depth. Unfortunately, I don't usually carve like most people > *grin*. I > actually vary the depth of the cut. Sometimes I use a Dremel, > sometimes > chisels, the result is fairly cool - the light shows through and the > results are quite pretty. I've enclosed a picture or a hand carved > pumpkin done without varying the depth. > > Second, the correct solution may be to create a subtractive depth > map of > the pumpkin but there is a cost constraint imposed by the target > audience. I would like to submit the mechanism to my friends at MAKE > magazine. Their projects are generally very low cost. While my > personal > preference would be to use high-tolerance motion stages, simple > surplus > helical screws will be used with drawer-slides instead! > > Except for the motor drivers and PC, I'm pretty sure an entire (albeit > low-tolerance) machine could be created for less than $200. I view > this > as one more "fun" dimension to the project. > > Third, someone pointed out that the more information you give the > better > the answers you get. There is much truth to the comment. But there is > also something to boiling down the problem. Sorry for not > explaining all > of the constraints up front. > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Kenneth > Lerman > Sent: Monday, January 29, 2007 5:17 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Is there an easy way to work > withanirregularsurface? > > When I carve a pumpkin by hand, I don't worry about the depth. I > jab my > knife all the way to the center. Then I remove the piece I've outlined > the > perimeter of. > > Ken > > [EMAIL PROTECTED] > Mark Kenny Products Company, LLC > 55 Main Street Voice: (203)426-7166 > Newtown, CT 06470 Fax: (203)426-9138 > http://www.MarkKenny.com > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Chris > Radek > Sent: Monday, January 29, 2007 12:31 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Is there an easy way to work with > anirregularsurface? > > > 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. 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