We had a few final bits of goofing off without a Z-axis before starting to build a real one. Two beams available for construction were found to be exactly the same length as the width of our table, so they were natural candidates as the main horizontal gantry structure. Now we could use arbitrary lengths for the vertical support beams bolted to either side, because they could drape past the edge and below the table surface. Not only does it give us complete flexibility on what height to mount our main horizontal beam, we also gain the option to reinforce the beam with brackets bolted to the bottom of the table.
Once the drilling and bolting started, however we found a few unexpected problems.
A small problem was that while our horizontal beam is exactly the width of the table, we also had a black plastic moulding surrounding the edge of the table. Actually dropping the beam below the table surface meant cutting interfering pieces of plastic away. Which we could do, but we don’t need to do so just yet so that’s been deferred.
A more significant problem was that one of the two holes of a bracket overlapped with the existing metal structure of this printer table. If it lined up exactly with the horizontal parts of the metal, we could drill a hole through it just as we did the wooden parts. Unfortunately it partially overlapped with some vertical members of the support structure, which would severely weaken the table if we drilled into it. We chose not to drill, but it also meant there were only two bolts instead of four fastening our gantry to the table.
This meant we ended with a less rigid gantry than we had originally hoped. It is pretty good left-right (parallel to machine X axis) but front-back (machine Y axis) is weak. We’ll have to add more reinforcements before we get serious about cutting material, but in the meantime it is the best Z-axis yet for pen plotting.
So Emily created a program that draws a gift for our enthusiastic supportive online cheerleader. This was the machine’s first run with nontrivial G-code, and its success cleared the way to further refinement of this machine.