Hi,
I am trying to find the best way to maintain stability in the plenum over time. I need to machine a plastic board using the onion-skin technique, with the onion skin layer no thicker than 0.1mm (anything more is too difficult to cut with a utility knife).
The issue I’m facing is that the Z-axis consistency deteriorates over time. After surfacing my spoilboard, the Z-axis stays consistent for a few days (sometimes just hours), but then differences of at least 0.3mm start appearing between the highest and lowest points.
I initially used an MDF spoilboard, then switched to HDF, but the problem persisted. For the last six months, I’ve been using a PVC vacuum table, which I surfaced. It was slightly better initially, but I had to resurface it multiple times (which is challenging with a vacuum table, as it requires remachining all the slots). Now, once again, I’m seeing inconsistencies, with some areas 0.4mm higher than others.
After some research, I decided to try an HPL board. I am upgrading to the EX controller with servos and will use this opportunity to create a new vacuum table with the HPL board. Given the cost of these boards, I want to ensure I’m following best practices for plenum stability over time.
Sometimes I need to hammer materials on the table, so I’m concerned this might cause some movement in the aluminum table that affects flatness. I’m considering adding a 1mm thick metal sheet on top of the aluminum table, beneath the HDF layer, to increase rigidity by securing all the aluminum extrusion profiles together. However, I haven’t seen anyone else do this—would this be a good idea?
What other solutions could I try? Is it unreasonable to expect 0.1mm accuracy on the Z-axis over time with an Avid CNC? It doesn’t seem too ambitious to me.