One thing that I haven’t quite figured out is wood for the desktop cnc machine. Ideally for my purpose of quickly getting ready for building patterns, I’d like to source some wood to build patterns and teach everyone in the lab how to make larger pieces of wood from smaller ones. By the way, I’d like it to be quick and cheap too, see rapid prototyping post about difficulties with this. So, there are some nice discussion about the types of wood for pattern making in the patternmaker’s manual published by AFS. However, for my purpose I just want to go with the easiest available white pine that we get in various quantities from shipping containers or cheaply from local suppliers in 2×4 dimensions. For better machining, I’d probably get 2×10 or 2×12 but I just want to illustrate what I’m trying. Also, for this post I’m going to discuss the dimensions in inches unless otherwise specified.
Given my mold lock (which I’m going to change the outer dimensions to 10×16 for the knives, thanks for pointing this out @workshopshed), I’m ready to start machining if only I had some wood. Now, probably the best thing to do is get some 2x10s but I’m going to talk about making essentially a 2×10 using 3 sections of 2×4. For that purpose, I gathered all the miscellaneous 2×4 sections around the lab and began to cut them to 16″ lengths. Of course the horizontal band saw is probably not the preferred method, but it was effective for me. I made about 6 pieces that I can take to the planer.
The objective if I want to join them together is to prepare an edge to join them together that reduces the gap as much as possible. Don’t assume the wood is square and use a planer to create the square surface to mate. I went ahead and planed the 4″ wide section of each 2×4 top and bottom to make consistent surfaces removing any roughness on the as received pieces. Then I needed a way to secure these sections together so that I could plane them all at the same time on edge. So I built a small frame using some strut channel that we had lying around from some earlier projects and a short 12″ length of 3/8″ threaded rod. Basically, I was going for a way to hold this section of 6 sections of 2×4 together so that the planing would remove the same thickness from all to then be able to join.
Next I used a joiner to cut a slot into the side of the 2×4 for a #20 biscuit. This method is quick and easy for joining these 2×4 together on edge. Couple pointers here, make sure the depth is set correctly and that your angle is set for 90 degrees on the joiner. My joiner kept slipping below 90 degrees and the biscuits wanted to be inserted on an angle.
You can see the final product (prior to glue drying) of the wood base for my CNC milling. I used 2 biscuits between each 2×4 and the final dimensions are about 9 5/8″ by 16″. After the glue dries, this should be ready for milling. The circumference around this piece will be cut one last time at an angle to build the box for the molding once the CNC milling of the part is complete. So the fact that this is not quite flush on end and not quite flat between the 2×4 sections don’t bother me too much.
Dr Monroe Thoughts 