Alpha-2 Design complete

Hi All,

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:

  1. 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.
  2. 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.
  3. Longer belt clips.  This is to allow a new position for the rods.
  4. New position for the X rods.  This changes the Y offset to something I like a little better.
  5. 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.

Thanks,

–Imran

4 thoughts on “Alpha-2 Design complete

  1. Makerbot-compatible extruders seem to be popular, so you could make your mount compatible. I’m thinking of buying the qu-bd extruder in kickstarter because it seems good and cheap, and maybe in the future other companies will also manufacture that design for a good price.

    Do you think your bot could benefit from a good linear bearing system, or are they all too weak? Maybe that way the frame could be the guide and you could decrease the cost by eliminating the rods.

    They say in the updates it is compatible with the larger configurations of misumi5, that’s available in 2040 and 4040.
    They also say they hope to make them even larger if successful.

    • I backed a complete dual extruder on KS. I want to evaluate it as a possible standard for my robot. The three designs I’m testing are:
      1. Wades + J-Head. I use this now, and it’s pretty awesome. But getting a wade’s made is a pain. And it takes too long to print one.
      2. Maki. This is in design right now. I think I’ll get an Eval unit in the fall, when he’s shipping them.
      3. QU-BD. This is pre-made. That’s a huge win. I worry about such large spur gears — but I’m willing to try it out and see if my worry is justified.

      I didn’t know about openrail. Funny thing is — I designed and sent in for quote a similar design a few months ago. My design used a single sheet, and was die cast steel. It would work with 40 mm or 1.5″ sized frame. I never had it made, though. It was a “Plan B” if things didn’t work out with the MakerSlide. It’s amazing how much synchronicity there is in the world. We’re all coming up with similar ideas, and similar times! I’ll definitely back their project — MakerSlide wheels are a problem, and since they’re heavy anodizing, I can use steel wheels. That would be a win in terms of the machine’s Z stiffness. Extruded Aluminum is amazingly strong — a 4040 extrusion is probably 2x as strong as a 3/4″ to 1″ thick steel rod — at a tiny fraction of the weight. Thanks for pointing out the project!

    • That’s a pretty cool motor. I really like it. I don’t know how much inventory they have, though. These seem to be reclaimed. I’ll check with them.

      If they have a good supply, I may use this and design a milled or cast extruder mount around it. The existing Wade’s mount is too time consuming to make. I’ve seen it cast, and the once cast, it doesn’t work very well. Too much friction from the cast resin.

      I’m still seeking a friction feed. Have you seen the Maki Extruder driver?

      This is more along the lines of what I hope for an extruder. It doesn’t modify the filament, keeping pressure in the hot end constant. It’s also designed to be CNC milled, which means it should cast well. I believe that Jon can supply me with these in qty at a decent price, so I won’t have to make them myself…

      Right now, Jon’s off working on a new pellet extruder. If he gets it done in the timeframe he’s targetting, I may use it. This system uses pellets instead of filament.

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