So this week has another progress report for Eta(Part 1).
I’ve been working on making the electronics & structure for Eta, so nothing particularly flashy to show off today, but here’s to those in for the technical details.
I’ve bought an acrylic outdoor electrical box which I’m using to house the electronics, you get these in housing electrical supply stores.
These things are cheap and super handy as project enclosures, and you get them in multiple sizes too. I turned this one into my electrical control box by cutting cable & ventilation holes, and drilling holes for mounting the Arduino Mega, and then affixing the arduino in place with bolts & hot glue.
Here you can see I’ve cut a hole in the lid for cables & ventilation, and I used the leftover plastic to hot glue an 80mm computer fan into place. The fan is angled to produce a horizontal flow through the box.
For my electronics themselves, I’ve unsoldered the heat bed mosfet from my RAMPS 1.4 board, and attached a wire to the gate hole, which I’ve connected to the gate of another mosfet I have. I’m still tinkering with the finer details, but likely I’m going to use a pair of mosfets mounted on heat sinks to control the heat bed’s switching, as the connectors & traces on the RAMPs board aren’t rated for 30 amps.
Onto the structural aspect, I’ve been working on making the 8mm smooth rod support blocks. I cut a sheet of 5mm plywood into 5cm x 8cm “biscuits” and glued two of them together to make a 8cm x 5cm x 1cm biscuit of wood. Its stiff and small enough that there are few forces which can bend them.
The materials I’m using are inherently imprecise, as cold rolled steel L profiles aren’t made to tolerances worth mentioning, and my while supports were initially designed like standard aluminum support mounts, their design quickly ended up becoming more akin to biscuits of wood. Hence, the accuracy had to come in terms of construction.
I started by numbering each attachment point and smooth rod support biscuit, Z1-Z8 and Y1-4, by their axis and location. I then marked each attachment point on the L profiles with a marker so that the supports could be customized to each location.
I then marked the exact center point on each profile, and then marked the distance to the smooth rod on either side (the distance between smooth rod centers on the heat bed support is 225mm).
I then clamped each support into place, traced out the holes, and marked a parallel line on each support which were used to determine the ‘y’ coordinate of each rod on each support. I then measured across and crossed the lines, to mark the center of each rod. Finally, I used my awl to mark the centers for the smooth rod holes & mounting holes.Next up will involve drilling them with an 8mm bit.
Each support has two 8mm holes for mounting, which will allow me some wiggle room due shape of the slots in the L profiles. This will really aid in fine tuning. I also fashioned a plumb bob using an old dart, which will aid in making sure the Z rods are perfectly vertical. Each biscuit will also have a slot cut into the far end, which will allow the biscuit to be tightened down onto the rods to firmly clamp them in place. I was originally planning to use flattened hose clamps for tightening the ends, but the metal of hose clamps proved to be too thick to bend in to such a shape, so I opted for using zip ties instead.
That’s it for this week’s progress, hopefully I should have my workshop computer functional by next week, so I can get started on programming the electronics.
Thank you for following the development of my projects,