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.
It’s looking like a CNC machine!
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.
While the glue-ups were drying on the gantry, I went back and did some more work on the Z-axis. I finished the router mount for my smaller DeWalt DWP611 router. I glued a few pieces of wood to the carriage with threaded T-nuts driven into the wood. The two router mount pieces get bolted into those T-nuts so that I can install other mounts for my larger DW618 router or anything else I may want to mount in the future.
Next I started drilling and tapping the aluminum bar stock to accept the Z rail mounting screws. I decided to initially install the rails without any machining and see how it works out for this proof-of-concept machine. If necessary, I can always go back and have these machined flat, or have shoulders machined to mount the rails against. The bar stock is still not attached to the carriage in this picture. It is just a test fit prior to epoxying the bars in place.
Here is the Z axis carriage after unclamping from the glue-up and giving it a light sanding. I am using aluminum bar stock to mount the profile rails. I chose this method in case I wanted to mill a perfectly flat surface on these or to mill shoulders (the preferred mounting method for HIWIN rails). At this point the bar stock is just positioned for a test fit. They will be epoxied in place after drilling and tapping the rail mounting holes.
After making this first piece for the Z axis, I noticed it had a very slight warp to it. I don’t think it will be a problem, since I can lay the bar stock on a flat surface, coat the carriage with a thick epoxy, and lay it on top of the bar stock, so that the rail mounts will remain perfectly flat and in the same plane. The epoxy should take up any space due to the slight twist.
I now realize that I will need a perfectly flat work surface to make the remaining parts on. I also will need a perfectly flat base for the machine, so I decided to go ahead and build up the torsion box base at this point. The machine base will serve as my assembly table for the rest of the build.
To build a perfectly flat torsion box, you need to start with a perfectly flat surface. Inspired by this article on popularwoodworking.com, I made two small torsion box beams. This allowed me to practice the techniques for making a torsion box, and then I could use these to create a flat work surface for building the torsion box machine base. You will see later what I mean. Here is a picture of the two torsion box beams being constructed.
I started with the Z axis since the parts are small and if I make any mistakes, it will be easier to redo with less wasted material. Working with the dimensions and images from my solid model, I started by cutting all the pieces out of a sheet of birch plywood to make up the Z axis carriage, laid them out for a test fit, then glued and clamped them together.
This is the Z Axis design:
Gluing up the first pieces:
It is starting to look just like the model :-). It is fun to see something come to life that you have been working on designing for so long!
Lots of clamps:
My table saw left some burn marks on the wood. They will get sanded down later to make it look nicer. After these cuts I spent some time tuning up the table saw to align everything properly. Perhaps a new blade would help as well.