Sometimes, to succeed at a project, you have to own the entire process.
I have a ShopBot Desktop CNC machine in my shop. I was experimenting with it this weekend cutting a handwheel to be used on a light-duty benchtop woodworking vise. The toolpath files were developed by a friend of mine. It’s a two-sided part so there is a roughing and finishing pass on each side, for a total of four files (each pass a separate file).
The toolpath files were set up to reference the center of the wheel as the origin of the X and Y axes. Since I was using a 1/4″-dia. ballnose bit, I drilled a 1/4″ hole through the center of the wheel blank (a 2″-thick piece of ash). This way, setting the origin point of the X and Y axes can be done by locating the cutting tool in the center hole. The Z axis was zeroed at the top of the blank.
Routing one side of the handwheel using the supplied files presented no problems. Though both the roughing and finishing pass took a couple of hours to complete, it looked great. Both toolpaths included “tabs” at each of the four quadrants to hold the handwheel in place in the blank as material was removed.
After routing one side, I flipped the blank over, again referencing the center hole as the origin of the X and Y axes. I started the roughing pass and all was looking great. Until the cutter cut through two of the tabs, which forced the handwheel to move inside the blank. I stopped the cutting and tried to figure out a way to complete the handwheel without scrapping it altogether. So I cut the rough handwheel from the blank, used double-sided tape to hold it to the CNC bed, and reset the origins of the Z, Y, and Z axes. After completing the final roughing and finishing pass, I had a complete handwheel. The only problem was, the X and Y origin was off just enough that the two sides didn’t quite match up.
So I scrapped it. And started over. Another piece of firewood.
I’ve got one blank left before I need to obtain some more lumber.
What’s the main lesson here? For me, I was at the mercy of using files that my friend had supplied to me. They worked for him on another project, but for some reason, they weren’t working out so well for me. So I’m asking him for the original design files to see what I can do to regenerate the toolpath files. Or at least find out if I need to do something different on my end. I need to see if I can find another way to make the process more accurate and foolproof. And while I’m at it, I’m going to try to optimize the cutting speed so this one project doesn’t take half a day to cut. I’m also going to have him explain to me his thought process on developing the files so I’ll have a better understanding of the whole picture.
If you’re in the business of woodworking, outsourcing some of your design work or parts can be a huge time-saver and eliminate a lot of headaches. But you need to own the entire process. What I mean is, you need to be intimately familiar with each phase of the project from the initial design sketches to delivery and installation. A sure way to wreck the budget and schedule is to be caught off-guard with an incorrect assumption from someone on your team or from an outside supplier. Stay on top of the project’s progress at every phase.
If you’re a hobbyist woodworker, owning the entire process means you’ve read and understand the plans you’re using to build the project before buying the lumber. Then you spend time selecting the best lumber for the project, taking care when milling it and fitting the joinery. Then you test out your finish on scrap material before applying it to your final project. No surprises.
Own the entire process.