Before making any more parts, the spoilboard needed to be surfaced. In order to use the 1-3/4” surfacing bit with a ½” shank, a new mount was needed to allow use of the DeWalt DW618 router. I quickly modified the CAD model of the existing mount, created the CAM setups, and cut out some new mounts from some scrap 3/4” Oak plywood. It is so nice to have a machine to make parts on now! The drill press was used to make the holes for the clamping bolts.
With the DW618 mounted, I surfaced the spoilboard by finding the lowest spot and setting the Z height right at the surface. I turned the router on and then manually jogged it around to surface the area.
I came up with an idea for a simple way to quickly hold things in place on the bed of the machine. This should work for any size object that I want to work with, in any position on the bed. I attached 2 T-tracks to the bed, outside the working area. Then I made a sled with 90 degree corners with another T-track mounted on it. This will hopefully allow easy clamping of any size stock at any location on the bed. I plan to use a few different styles of clamps and/or stop blocks to attach to the t-tracks. It will be easier to show pics than try to describe the setup and the many options it will allow:
On the other end of the bed, I attached a T-track with some low-profile cam clamps, that wedge the spoil board in place. I will eventually mount this t-track to the longer tracks, similar to the image above.
While attempting my first cuts with the machine, I learned how much pulling force an upcut end mill has. I will need some clamps to hold down my spoilboards/fixtures. In addition to the material being pulled up towards the router during cutting, the wedges I used (only hand tight) vibrated loose and the stock moved during cutting.
Switching gears from the dust shoe components that I had planned to cut out, I modeled some clamps in Fusion 360 based on a few designs I had seen. Here is video I made showing the first successful project with this machine and the finished clamps that it produced! Still not having clamps for this operation, I hammered wedges in place to get them very tight and I also used longer screws to hold the stock down more securely. Everything worked out well.
I added a spoil board and am just finishing up a design for a dust shoe. I hope to cut the dust shoe parts out on the machine shortly.
I finally got around to uploading a video of the machine performing a run through the air. This was one of the example files that came pre-loaded with LinuxCNC. It is cutting a 3D profile of a penguin (the LinuxCNC logo). I didn’t change any settings or edit anything in the G-code, just ran the file as it was.
The workbench that I have the machine sitting on is pretty wobbly when the machine starts accelerating quickly, but the the machine itself is very solid.
Now that the machine is fully assembled, I could connect all the wiring, power up the machine, and drive it around a bit!
I didn’t mention in prior posts, but in between other steps while waiting for glue and/or epoxy to dry I worked on the electronics. I soldered together the serial connectors and resistors for the steppers, wired up the power supply, then connected everything to the Gecko G540 and an old PC. I installed Linux CNC on the PC and ran through the setup wizard. I was able to run the steppers and test everything out on the bench before they were installed on the router.
I started the machine checkout by driving each axis back and forth manually, checking the travel to ensure the actual travel matched the commanded distance. It did not match at first and I believe had to go back and change the microstep settings. With the distance corrected, I slowly increased speed and nervously continued to drive each axis back and forth, faster and faster. I homed each axis and set up conservative soft limits so I wouldn’t accidentally run the machine off the end of an axis. Everything looked good, and I was able to get up to the maximum speed, as limited by Linux CNC, based on the conservative latency settings I had entered. This was about 12500 mm/min or about 500 ipm. I may try increasing the maximum step rate settings (lowering my conservative jitter setting), but for now this is plenty fast. Per my design calculations, it should be able to run significantly faster.
With everything working well in manual mode, I loaded one of the sample files that came in Linux CNC and ran some test “cuts” through the air. First 2D, then some 3D profiling. That was really exciting to see the machine running around for the first time on its own! I had to call my wife out to the workshop to watch it with me, and lucky for me, she was equally excited to see it finally running!
My first “real” test was to install a pencil in the router collet and manually draw a square on a piece of paper, using the built-in set-distance jogs. I measured the sides of the square and compared the cross corner measurements to check accuracy and squareness of the machine. The distances looked dead on, but the squareness may be out by a few thousandths. I’ll have to make some proper cuts to be able to measure it more accurately.
Before I make any cuts, I want to install drag chains, a dust boot, the e-stop switch and perhaps some limit switches.
The stepper/ball screw/support assemblies were ready to be attached to the machine. I used some K clamps across the width of the machine to use as supports to lay the assemblies on while I worked on aligning them properly.
First, I determined the front-back positioning. Moving the gantry to one end of travel, and the ball nut to the same end of its travel, I aligned the center of the ball nut coupler with the center point between the X linear bearing blocks. Then I clamped the assembly in place on that end. Moving the gantry and ball nut to the other end of their travel, I aligned the ball nut coupler with the center of the linear bearing blocks and measured the extra travel available on the ball screw. I split this measurement in half to allow equal space on both ends. I readjusted the position accordingly on both ends and clamped in place again.
To get the vertical alignment correct, I mounted the wooden piece to the ball nut coupler that would attach to the gantry. I moved one end up to the gantry, readjusting the k-clamp to set the new height, re-clamped the assembly, and then moved the ball nut and gantry back to the other end and repeated.
With everything in place and aligned, I unclamped one end at a time, applied wood glue, and re-clamped.
I then repeated the whole process for the second X axis drive assembly on the other side of the machine. After the glue was dry and I reconfirmed the alignment was still correct, I glued the pieces in place that attach the ball nut couplers to the gantry.
With the gantry mounted and the rails bonded in place, I was able to fine tune the X axis rail alignment. I loosened the linear bearings on one rail and attached a dial indicator to the gantry at that same end, reading to the reference edge of the profile rail. I ran the gantry back and forth to see how far out it was across the whole range of motion. Most of the rail was within +/- 0.001” parallel to the opposite rail. Toward the end there was a 6 inch section that was out by 8-10 thousandths. I loosened those rail mounting bolts and applied some pressure on the rail by hand to bring it back to zero before re-tightening the rail. After rechecking the whole rail it still needed some minor adjustments. After a few rounds of this I am happy with the straightness. Next up will be mounting the X axis drive assemblies.
After placing the linear guide blocks on the X rails, I placed the gantry on top of them and proceeded to align everything. I spent a lot of time aligning the X axis rails. This included making sure they were parallel with each other and also that they were perpendicular to the Y axis rails on the gantry. I clamped together a few 24” squares to get the rails parallel and then placed some 1-2-3 blocks on top of them to check that the Y axis rails were perpendicular. I clamped the rails in place as I went to keep the alignment correct. Once I was happy with everything, I marked out where the linear bearings should be mounted to the gantry. I drilled the gantry and mounted the linear bearings, then installed the gantry on the rails again. I forgot to mention that I had previously found the balance point of the gantry using a thin piece of wood running the long way under the gantry. I marked that balance point on the base of the gantry on both ends and that became the center point between the two linear bearings.
The alignment was double and triple checked prior to bonding the rails in place with the System Three adhesive epoxy. I still have some adjustment available in the rails to make fine adjustments with a dial indicator. I had previously used a chemical etch on these pieces of bar stock, but the epoxy should be applied very soon after the etching to get a good bond. I had let too much time pass and since I am experimenting and learning here, I decided to use the “wipe down with acetone” method for this to evaluate how the bond holds up compared to the other axes where I used the etching and sanding methods.
After building the first side, I just repeated the operations for the second side. I had cut all the plywood at once in the beginning to make sure the dimensions were identical, using the same saw setup. Next step was to drill and tap all the holes in the aluminum bar stock for the long X rail mounts. I followed the same process as detailed earlier to make sure the rails were straight and aligned properly.
I made plywood stepper motor mounts and bearing support mounts, all from the same birch plywood stock that I’ve been using for everything on the machine. Here you can see the left and right sides of the frame, along with the rails placed on top. The ball screw assemblies are in the center, but they will be mounted to the outer portion of the frame sides.
Here is a picture of the completely assembled Z axis attached to the Y axis. The only parts missing are the linear bearings that will be mounted to the bottom of the gantry.
With the Z and Y Axis components almost complete, I couldn’t wait to get the X frame components built up. I cut all the plywood pieces on the tablesaw, then figured out what angle to cut out the MDF webs. Once I made one that fit well, I used the waste piece with a stop on my cross cut sled to quickly cut out the rest of the webs:
I assembled these in place on the machine base and once again glued everything up and used a lot of clamps. The waste pieces from the MDF webs came in handy again to make a squared up clamping surface.
The next bit of progress on the machine was back to working on completing the Z and Y axis components. I spent some time in Fusion 360 learning to create drawings from the components in my model. This allowed me to print out a scale drawing to use as a template for quickly and accurately placing all of the holes in the following part. An 8.5″ x 11″ sheet of paper just fit all the holes for this piece.
In order to get the ball nut coupler to be flush with the Y carriage, I used a router table and a hand chisel to lower the plywood carriage slightly:
The final task on this part was to make the Z stepper mount out of plywood. I glued it together and clamped it to dry overnight.