After years of use, the Shapeoko has started to get a little sloppy. Since I started using the CNC machine, I've noticed that after cutting operations, it would often leave a slight onion skin on my part. This means the router is at a slight angle, or your stock is not flat in relation to the bed.
One of my favorite content creators in the CNC world is Winston Moy. He makes a lot of tips and tricks videos and shows his processes when trying new materials and tools. He recently came out with a video on how to properly tune the Shapeoko
3 and making a new wasteboard which is precisely the same machine I have access to at my local makerspace. The main thing that attracted me to his video was his tutorial on how to make a new wasteboard. A wasteboard sits upon the base of your CNC machine and acts as a bed for your stock. The reason it is called a wasteboard is that once you finish your cut on any project, you can then remove a thin layer of the bed to zero it out. Making sure you have a perfectly flat workplace. Part of the design includes using thread inserts coming up from the back of the bed so that you can secure your stock with screws or clamps.
For the 3D design of the wasteboard, I decided to have a 1.5" length in between each pocket that holds the thread inserts. I had to figure out a way to bolt the new bed onto the existing one and to do it without having to make any new holes in the metal base of the machine. I was able to do that by locating four screws and removing them. Then I would need to buy longer ones to pass through the new bed and into the base. The Shapeoko 3 has an advertised bed of 16"x 16" in its X and Y-axis. I did notice, however, that the machine isn't quite big enough to have a 16"x 16" bed, so I had to make it 16"x 15" instead, the router couldn't travel that extra inch in the Y-axis.
While I was setting up the new bed, I noticed the Z belt kept either falling off or just was loose. So I tightened that up and squared the belt so that shouldn't happen again. After securing the new piece of MDF to the existing bed, I used a 1/4" downcut two flute coated endmill from Toolstoday and started my toolpath. I first cut the four holes that would attach the new bed onto the existing one, then flipped it over and cut the holes for the thread inserts.
I ran into an issue as soon as it started the drill hole operation. I could have sworn I set it up right by having it retract every 2mm, which would prevent the endmill from recutting the same chips as well as chip evacuation. It didn't withdraw like I thought it would, and so the chips got stuck in the hole with the endmill, and it started smoking from the chips rubbing against each other, at which point I shut it down. MDF is made up of wood fibers held together by a resin-based binder and creates a powdery substance when cut. Since it's so fine, it can also catch on fire very quickly, which would have been a significant problem as pretty much everything would go ablaze. The reason the chips couldn't properly evacuate was due to the endmill being a down-cut vs. upcut bit. A downcut bit will move the chips as it cuts them down, and an upcut bit moves them up. I didn't have any upcut bits, so I ended up having it cut only 1/8" vs. the 13/16" I was initially trying, and manually drilled the rest out.
I then took my thread inserts and started inserting them into the wasteboard. I didn't have the proper Allen-key for this, however, and ended up having to fashion my way around it by using a flathead and drill. I ran into an issue right away; the thread inserts were slightly larger than the hole for them. I initially tried just forcing them in by applying pressure on the drill as I wanted to get them inserted. Which only caused the holes to strip and make them useless. I tried just drilling the holes slightly bigger, but even that wouldn't work, I tried using a 5/16" drill bit, but that was somewhat too large. I ended up having to drill it partway through with the 5/16" and then forcing the inserts the rest of the way. It solved the issue, but since I didn't have the right allen-key bits, I couldn't get them perpendicular to the board and so some of them were at a slight angle.
After I got all the thread inserts into the new wasteboard, it was time to shave off a layer and tune the trams holding the router. I started with using a surfacing tool
I got off of amazon. This allows me to remove a few thousandths of an inch after each operation, ensuring I have a completely flat workplace. After doing a single pass over the wasteboard, you could visibly see line marks where the tool passed; this is due to the router being at a slight angle to the rest of the machine. This can be fixed by adjusting very sightly the tram that the router sits on forward or backward, depending on what needs to be changed. At this point, it's pretty much trial and error until you're pleased with how it sits. It would require a ton of work and be nearly impossible to have it completely flat without any visual or physical deviation in the wasteboard.
I was able to attach it to an existing bed without a hitch successfully. I then tried to screw in some small clamps to hold my workpiece in place but couldn't get them to work right since the thread inserts were at slight angles, which were amplified through the clamps and couldn't sit flat on the stock. I can't use it with the clamps as I had intended and will need to be remade with the proper tooling to be able to use the clamps, which is a project for the future. As it stands, the new wasteboard will work great for non-clamp related work holding, namely double-sided tape for smaller stock.