About 3 years ago I started building a CNC router. Used it for just a little while and quickly embarked on an upgrade. The upgraded version turned out pretty well. Very accurate. Not perfect but good enough to learn on as I have no machining experience. Its rack and pinion drive on the X and Y and a ballscrew linear actuator for the Z and NEMA 23 steppers all around . I used a lot of parts from CNC Routerparts.com, NEMA 23 motors, their PRO motor mounts, rack mounts for the rack and pinion gear and a few other things. I used off the shelf parts in critical areas where I felt that my skills were only marginal and the better solution already existed. Just had to pay the man. I built the homing and limit switches for it from the thread on here and that turned out well.
I've done a few things for people now and one of those was for the local Boy Scout troupe. They were building kayaks and each kayak had about 12 frames for the structure. I think there were about 12 kayaks in total so this involved a lot of parts but a lot of repetition. Perfect for a CNC router. The job went very well and I was glad I could contribute.
So my friend is a incredibly talented woodworker and his son was one of the Scouts and he liked my router. About a year later, his wife approached me discretely and asked if I could build one for him for his 50th birthday. I had learned a lot since building my first one and I wanted to build another one but I didnt need one or have room for it. But I would love to build one for a friend I jumped at the chance. So this will be the chronicle of my 2nd build. I'm open to suggestions so share them if you have them.
1 - Reliability. This is going to get turned over to someone else. It has to be user friendly and it has to be stone cold reliable.
2 - Speed. Time is money. The faster it works, the more time it can be used. My friend is a busy guy.
3 - Precision. I would like it to be able to hold +/- .005" when machining hardwoods. Not sure if this is unrealistic but I think I can get it rigid enough to achieve this.
General design information:
I want the cutting envelope to be 6ft in the Y and 4 ft X, with 6" of travel for the Z.
The Z will be able to travel outside of the cutting envelope in the X plane. Mostly for touch reference probing off the bed.
No sidewalls on the cutting bed. Nothing for the tool collide with and this makes the workpiece more accessible and easy to fixture.
Motivation will be NEMA 34 ClearPath Servo drives on the X and Y and a NEMA 23 on the Z. Sevo's over steppers so no lost steps.
Machine base will be welded steel.
Machine frame 8020 T-slot extrusion.
Profile linear rails and Hiwin or THK bearings on the X and Y.
Rack and pinion drive for the X and Y
UCCNC for motion control as this is what I'm using now and MACH 4 seems to be unrefined(?). UCCNC works fairly well. And I can explain how to use it to my friend when this is delivered.
For a BOB Lots of options. Was considering the Leadshine drive from CNC router parts but the Clearpath Servo's only need step and direction commands. Not sure yet. Any suggestions??
More to follow
Pic is of my first CNC router after upgrade cutting out the kayak parts.
The Z-axis linear actuator arrived today. I'm using a Kollmorgen DS4 linear actuator I sourced as new, surplus from E-bay. Its a ballscrew drive, 5mm pitch with a 150mm stroke, NEMA 23 motor mount. It also has a built in clutch that prevents damage if its driven past its travel limts. Its paperwork says it was tested to slip at 16oz/in. This seems a little light and I may have to restrict the torque or acceleration on the Z-axis drive motor to ensure it doesnt slip under normal operation. I have a similar actuator on my current router and it works well. I'll test it when the time comes. Aside from that Its a beefy actuator and sealed well to protect it from the all the debris the Z-axis has to contend with.
Looks like the forum is being a little finnicky for uploading pics. I'll have to add them later. Got to go pick up the steel for the base
Inserted 1/4 20 bolts into the pads and placed the pads under the beams at all four corners. We used a rotary laser level to project a reference plane and a straight edge ruler to measure down to the pads from the laser beam. We adjusted the leveling pads until they were all the same distance down from the laser
We got it very flat using this method. Within a 1/16th or less on each corner. Meadured diagonally across the corners and squared it up then we used some ratchet straps to hold it in position and then we tack welded all 4 corners.
Installed some flat stock across all 4 corners to hold it square and proceeded to weld it all up.
Finished the day with all the braces tack welded in place. I measured the squareness of the bottom of the legs to see if the braces had pulled the legs inward. They did a little. The long dimension at the end of the legs had pulled in about 3/4 inch. The short end pulled in about 3/16. I dont think this will affect anything as i planned from the outset to epoxy level the top to make a flat surface for the extrusion. I'll get some measurements when we flip it upright to see if its severly twisted. I dont think it is as we would have never noticed it if we hadnt measured. But just i case, im researching post weld heat treatment providers in Michigan to get it stress relieved.
I was mistaken. The braces only pulled the ends in about 3/8". Across 7ft that is just fine. We flipped it over and checked for square and flatness. Square was dead on. I used a 48" ruler for a straight edge and it appeared the corners had pulled down less than a 1/16th. That seems very good. The epoxy pour will level it out quite nicely
Starting now to work on installing some temporary casters so we can move it around easier while we build it. The casters will be removed once its in its final location and be replaced with leveling bolts.