FILENAMES: Milldrill_fullmill.jpg Milldrill_xout.jpg Milldrill_xinside.jpg Milldrill_yout.jpg Milldrill_yinside.jpg Milldrill_zdrive.jpg DESCRIPTION: These are pictures of the CNC conversion that Dan Mauch (dmauch@seanet.com) did on an imported mill-drill machine. Dan provided the following description: ------------------------------------------------------------------------ CONVERTING A MILL-DRILL to CNC ( Computer Numerical Control) Now that I have converted my Enco mill to a servo system, and now that I have redesigned my CNC 3 axis chopper drivers, I can move on to convert my Mill Drill to CNC. The unit I have seems to be like most of the imports. The quality is fair but it does do a good job of milling. I really like how itcan drillor bore very large holes and perform various CNC duties. I set out to have a full three axis system. I have seen various methods to convert a mill drill to stepper motors but decided to do it my way. Most of the conversions use a flat plate that is mounted on spacers with the stepper motor on one side and bolted to the axis by drilling and tapping the axis. This leaves the timing belt exposed or a special guard needed to be made. Not liking this method , I choose to use 3X4 rectangular steel tubing because: 1. I had some around the shop. 2. I wanted something that would completely enclose the timing belt and 3. I wanted to use dual shafted stepper motor in the manual mode. I made the X and Y axis stepper motor mounts similarly. The 3X4 rectangular steel tubing was sawed to 9" long. I milled the bore for the NEMA34 stepper motor using a 1/2" end mill on my Enco milling machine which at that time was equipped with a stepper motors cnc system of my design.. Since thew Enco milling machine was retro fitted with ballscrews it was simple to write the G code to bore the steel tubing to fit the male fit of the stepper motor. I left a 1/4" beteen the edge of the stepper and the end of the 3X4 tubing. See the pictures for details. Drill and tap the 3X4 tubing for the stepper motor mounting holes. I used 10-24 round head machine screws. Remove the X axis left hand end plate from the mill drill. The right hand one has thrust bearings. The left one is a plain steel end plate with no bearings which I intend to modify later on for a radial ball bearing. Make a template of the X axis end plate and transfer the template to the 3X4 steel tubing . I milled the slots using a 3/8 end mill for the 5/16 bolts. I used a 1/2 inch end mill to bore the eccentric opening to fit over the hub of the end plate. Mill the slots and the eccentric for about 1/2" belt adjustment. Remove the Y axis left plate from the mill drill. Be careful not to lose the thrust bearing or the roll pin.. Make a template of the Y axis end plate and transfer the template to the 3X4 steel tubing . I milled the slots using a 3/8 end mill for the 5/16 bolts. I used a 1/2 inch end mill to bore the eccentric opening to fit over the hub of the end plate. Mill the slots and the eccentric for about 1/2" belt adjustment. You will also have to make spacers or a spacer plate to extend the square tubing out so that you have maximum travel of the Y axis. Use 3/4 inch thick plate. I used 4 " square tubing for the Z axis 9" long. I machined a piece of 1/2" thick aluminium plate to fit internally with the 4X4 tubing. I only machined it half the thickness so that It has a flange for securing it to the square tubing. The inside was bored to fit the male end of the stepper motor. Use at least 2:1 ratio timing pulleys. You can get away with 1/1 but you will need larger motors. I used dual shafted 300 oz inch NEMA 34 stepper motors for the X and Y axis but used a single shaft 300 oz in motor for the Z axis. Note that I am simply using the fine feed hand shaft for driving the quill up and down. It is not the best solution because some imported mill drills have all kind of backlash in the quill drive gears and the rack. Mine was pretty good at .010 backlash. For close work I intend to manually position the cutter with a tool change command. If you have smaller stepper motors you will want to use 3 to 1 ratio timing pulleys. I used the XL037 flanged, bore to fit, type timing pulleys. Use a 14XL037 driver and a 28XL037 for the driven. The maximum size that will fit inside the square tuning is a 42XL037 which with a 14XL037 would give a three to one ratio. That in combination with the 10 TPI leadscrews will give substantial thrust before losing steps. Using a lathe I bored all three 14XL037 timing belt pulley out to the maximum recommend bore size which matches up with my stepper motors. That is .3755. I bored the The X and Y axis leadscrew drive pulley to .6665 to fit my leadscrew shafts. Yours may vary so use a micrometer to check it first. Bore the Z axis timing belt pulley to match the fine feed hand shaft. The one I had was .4900 Modify the X-Y hand crank to fit the back of the stepper motors. I bored a piece of aluminium stock to .3755. Turn the diameter to match the bore of the hand crank. Press the bushing into the hand crank bore. Drill through the set screw hole using a .201 diameter drill bit. Retap the set screw hole for 1/4-20 NC. Assembly Install the 14XL037 timing pulleys on the three stepper motors. Install the X axis 3X4 rectangular tubing with 5/16 cap screws and flat washers leaving the bolts loose for now. Install the X axis 28XL037 timing pulley onto the X axis leadscrew shaft. Tighten the set screws. Install a timing belt over the 28XL037 timing pulley. Install the X axis stepper motor using 10-24X 3/8L RHMS. Slip the timing belt over the stepper timing pulley. Adjust the position of the 14XL037 to line up with the 28XL037 pulley. Tighten the set screws. Adjust the tension of the timing belt and tighten the motor mount bolts. Install the X axis hand crank onto the exposed end of the stepper motor. Y axis is assembled similarly except that you need to install a spacer plate between the motor mount and the base. Install a 28XL037 timing pulley on the Z axis fine feed shaft. Install the stepper motor into the 4X4 square tubing. Slip a timing belt over the Z axis driver and driven timing pulleys. Mark the location of the square tubing on the outside of the Power head frame. Remove the Z axis stepper motor mount. Remove the quill position indicator and plastic housing. Locate where you can drill two holes for 5/16-18 bolts. Drill and tap the frame at these locations making sure that they line up with slots in the Z axis motor mount. Remove the stepper motor and install the 4X4 square tubing attached to the frame loosely. Install the stepper motor and timing belt. Adjust the tension on the timing belt. Tighten the motor mounting bolts. Testing. Connect the stepper motors to your controller. Set the number of step per inch. and other parameters into the CNC program. I'm using DESKNC. Run each motor making sure that each axis operates smoothly and without binding over its entire travel. Adjust the software for backlash compensation and maximum rapid traverse speeds for the G00 commands and the feed rates for G01 or G02. I will post pictures of the cnc conversion on the drop box at http://www.metalworking.com Dan