CNC Unimat SL A stepper motor driven conversion of a Unimat purchased in 1974. The stepper driver is a bipolar bi-level L/R design from Daniel Hudgins DANCAD3D shareware cad/cam programs. A sophisticated implementation of an older style of stepper driver, also doubles as a small space heater. CNC functional on both mill and lathe configurations though I tend to use the lathe as a manual machine with power feeds and DRO. Due to ongoing improvements it's not exactly the same as shown. This photo from late 2000. The unimat uses lead screws with a 1mm pitch, and the torque produced by steppers fall off as the speed increases. The quest for faster feed speeds and reduced milling times prompted the fabrication of a new mill with faster screws. Its also much more convenient to have both a lathe and mill set up simultaneously.
ViceMill In the begining there was an inexpensive chinese import X-Y vice ... Stepper motors, thrust bearings, and anti backlash lead screw nuts are amongst the modifications for CNC The Z axis spindle driven by very low power (and very quiet) shaded pole motor with cooling fan. A temporary setup which will be upgraded someday. The support structure isn't overly ridgid but I'm milling wax with very delicate tools mounted on the mill is a rotary A axis with tailstock XYZ Stepper driver is based on three Allegro 3977 bipolar microstepping translators. All of the logic and power handling for an axis in a single chip requiring only a few support components. Very smooth motor motion with very little extra heat. The rotary axis driver sitting on top is based on a 297/298 chipset, an older design providing only half stepping and a slightly higher parts count Air nozzle for chip removal is mounted on the left side of spindle (swiveled out of the way in this photo), rides up and down with spindle. This mill is a work in progress, with many of its design details dictated by having it's parts fabricated with a Unimat.
Rotary A axis Worm drive A axis. The tail stock is very useful for supporting delicate waxes The spindle is the same as the unimat facilitating moving work between the two machines. After milling a ring the wax can easily be transfered to the lathe for boring the finger hole.
Rotary C axis Partialy complete rotary C axis Small nema 17 stepper located underneath with spur gear drive; not a lot of torque, and borderline resolution. I'm testing 1/8th microstepping a 400 step motor in order to compensate for the aprox. 3:1 gear ratio. It is shown mounted on the rotary A axis spindle giving a total of 5 axis of motion.
Wax bits Doing detailed wax contouring requires very small tool bits, after all you can't drill a hole smaller than the tool. Really small carbide tools are avalable in a good selection of shapes but are rather expensive, VERY fragile and over kill for wax. The best solution which I have found is to grind my own tools from cobalt alloy High Speed Steel. Not quite as stiff as carbide but more forgiving of abuse and 5% of the price of carbide bits The photo shows a square pyramid 1.6mm diameter bit in a custom tool holder on my TAIG mill (mid 2005 aquisition, and like a junk yard dog not too pretty but worthy of much respect.) Variations from a square section to a diamond can give better cutting angles but at decrease in minimum detail resolution. For the very curious, I've installed both an air and drip coolant system. Air for blowing roughing chips and the drip for finish cuts.
Bit Grinding Jig My semi manual setup for grinding tool bits. A Unimat indexing attachment with a copy of my spindle tool holder bolted to an adjustable aluminium angle block. Diamond disc in drill press To use set height with dial gauge, manually rotate entire index attachment to grind bit, index and repeat til done. After grinding all sides (and hoping for concentricity) the very tip is hand stoned to provide a tip width of around .1mm in either a ball or flat diamond shape. At least that is the desired theory.
Since you have read this far it might be a safe assumption that you might just be another tool junkie, more pictures at random tooling pictures ,no text but I will answer questions

Copyright © Jeff Demand 2007