I believe I have just hit the design complete milestone for Alpha-2. I’ve got one part left, the extruder mount, to re-design. I’m looking at different extruder suppliers, and evaluating what extruder to use. I don’t expect all three supplier samples to be in until October. This means that other than the extruder mount, which is a very fast/easy thing to design, Alpha-2 is design complete. I’ve even begun placing Alpha-2 parts on Alpha-1, and now have something like Alpha-1.5.
Here are the major changes:
- 4040 extrusions used as gantry legs. This makes it all a little bigger, but I like the characteristics of this better than the original 2040 extrusion.
- 12″x12″ aluminum bed, 13.5″ x1.5″ aluminum frog plate. Both are 1/8″ thick. The new bed is flatter than wood, but heavier. The weight has introduced some lash. I need to make the frog-plate and the belt clip stronger to compensate.
- Longer belt clips. This is to allow a new position for the rods.
- New position for the X rods. This changes the Y offset to something I like a little better.
- New belt guide. This makes printer mode more space efficient.
These new changes are being rolled out to fixed gantry mode first. It’s just because of how I work. I had been spending most of my time on moving gantry mode prior to Maker Faire, and only a little bit of time on Fixed gantry mode. Now, I’m focused on optimizing fixed Gantry mode. Once I feel that fixed gantry mode is totally awesome, then it’s back to moving gantry mode.
Currently, I don’t see any needed changes in moving gantry mode. I plan on Keeping 12mm rods. The 16mm and 20mm bearings are too big, and would require that I resize the robot larger. Doing so is something I don’t want to do — it begins to go away from my vision of a robot that fits inside the house/dorm room. I might do it for a Large version, but this size robot will keep the 12mm rods.
I’ve also looked at some cost containment measures. These include a new spindle mount that is pre-manufactured and available from McMaster, as well as new electronics based on a different stepper driver. The electronics are a killer — It’s looking more and more likely that I’ll have to design my own. The two needs I see in the redesign is the power control needs, and the connectors. I want a lot of control over the current, and I want to be able to use standard cables of some sort. So far, I haven’t found what I need to make that so. It seems I may be forced to use RJ-45/Cat-6 cable. However, this isn’t yet a change, but an evaluation. I need to see if the change is possible. Other changes may be designed in, but those are “DCR” level changes.