At 12:25 AM 12/19/00 -0800, you wrote: I've used a HP 7550 plotter attached to a PC running Windows 3.1. You can specify both the acceration and maximum pen speed in the Win 3.1 "Printer Setup". You might try telling the computer that it's a 7550 plotter since they both use HP-GL. The 7550 has automatic sheet feed but I think you can disable that in the "Printer Setup". The 7225 definitely won't be able to match the 7550 in pen speed and acceleration so you'll have to do some tweaking there. Joe

You can minimize the mass that the plotter has to transport by using one of the DREMEL tools that has a flexible cable, then support the motor independently of the plotter. I built a mechanism of that sort back in the early '80's, and it failed miserably to do what I wanted. Those plotter servos are fast at the expense of having the muscle to accomplish work. An X-Y table built from some drill rod on pillow blocks with linear bearings of which there are many relatively inexpensive types these days (check the robotics manufacturint technology mags) is not terribly difficult to build if you can get access to a machine shop with the basic equipment, i.e. lathe, vertical milling machine, surface grinder. When selecting materials, it's important to remember that steel has a typical thermals expansion coefficient of 6 ppm while aluminum has one on the order of 27 ppm/degree F. If your dimensions are referenced to a steel base, having an aluminum carriage for the "Y" feed that's pillowed on aluminum may cause some grief. The way I built mine, intended for a PCB tester of sorts, and by someone (me) who didn't know nearly enough about the job, I had to haul the motor for the "Y" feed everywhere I went.with the carriage that provided the "X" position. BTW ... a 5 TPI thread on a ball lead-screw will produce 1 mil of translation when propelled by a 1.8-degree stepper. Likewise, the pitch-diameter of a cable/pulley arrangement for hauling the carriages about needs be about 0.3183" (not easy to hold within manufacturing tolerance by an amateur, but terribly critical if you want <1.5 mil error, the industry standard having then been 3 mils) if you want 1" per revolution. However, 1.8 degrees will give you nominally 1/200". Half-stepping a 0.9-degree motor is a mite coarse. Ball lead screws are slightly heavier, but require less torque to propel the carriage. Cables worsen the potential for resonance problems, lead screws cost a lot more. It's a tough problem. The worst part is that the bearing in the handpiece on the flexible-shaft dremel can't take the side-load required for routing a hole in a PCB, though it will last a little while if all you're routing is the foil. One other thing to contemplate, by the way, is the difference between drag-cut and a climb-cut when milling/routing, since the top speed of the DREMEL tool is still on the low side for milling and drilling PCB's. There ... thats a preliminary core dump of what I encountered back twenty or so years ago. I hope I gathered what was wanted, as I couldn't find the original post. Dick ----- Original Message ----- From: "Gary M. Wheeler" &lt;g.wheeler(a)worldnet.att.net&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Tuesday, December 19, 2000 1:25 AM Subject: Re: HP plotters tool. plotter