Author: Maker Block

Making Blocks II

Lego nubs and underbits
Lego nubs and underbits

My lego prints connect slightly better to other printed legos than real legos.  I suspect this is in part to the ridged texture to both parts.  This also makes me think that printing legos is a fool’s errand.

While lego nubs are circular, the parts they fit into touch the circular nubs tangentially.  For instance a nub fitting into a corner piece would be held in place by two straight sides and held against a circular tube.  The picture to the right shows the underside and nubby bits for several lego (lego compatible?) pieces.  This system probably works because of the exacting tolerances of real lego parts.  I’m guessing they tested the nub heights and contact points to find an optimal mix of most of the same criteria I have for an interconnecting building block system.

Without tighter printing tolerances, I don’t think three tangential points are going to be enough to hold printed parts together.  Thus, it may make sense to have taller nubs on printed parts.  Then again, the ridged nature of printed parts may allow them to better fit together without having taller nubs.

One benefit to having circular nubs is that you can make interesting components where pieces pivot.  But, this is more of a lego-hack than an actual useful feature.  I’m not as concerned about this particular usage because I could always design a printable pivoting part.

So, other than that one narrow usage, why circular nubs?  Why not circular nubs with circular holes?  Why not square nubs with square holes?  Or circular nubs with notches in them?

Making Blocks

The design question I keep coming back to is “How do I create a reliable interlocking system for blocks?”  My criteria for a robust and useful system are:

  1. The interlocking system should allow interconnections in three dimensions.
  2. The pieces should snap/interlock together reasonably well/easily.
  3. The pieces should stay assembled reasonably well.
  4. The pieces should snap apart reasonably well/easily.
  5. The pieces should not require additional tools to be assembled and disassembled.

Why make blocks?

Making blocks with a MakerBot is almost counter productive.  Why would you want to make something out of plastic that can be used to make other things out of plastic?  Why not just print the final plastic object as a single piece all at once?

I like the idea of being able to physically play with the design of something.  Sketchup is easy to use, but legos are even easier.  I never worry about an operation that I can’t Ctrl-Z my way out of.  Plus, it’s even easier to go from idea to objection with physical building blocks.  I think it would also be a very interesting way to get around the overhang and size limitations of a CupCake CNC.

What would you print with colored ABS?

I was trying to think about what I would print with new ABS colors from MakerBot.  Here’s my list:

  • Green: Little green army men, dinosaurs, a green lantern ring?
  • Yellow: Yellow safety whistles, a yellow ring to defeat the green lantern ring
  • Red: Red clown noses, red dice, replacement monopoly houses
  • Blue: Naked smurfs

Yeah, I suppose that last one was unnecessary…

Adventures with PLA temperatures

Kinda rhymes, no?

Given Rick Pollack’s PLA printing success and temperatures at barrel entry rather than nozzle, I should probably start delineating between temperatures at the barrel and nozzle.  If barrel entry temperature is truly a critical factor, then he’s totally right about how going by nozzle temperature is like driving a bus with just the rear view mirrors.

However, this gives me pause.  Everything I’ve read about ABS suggests it may be best to melt it right at the nozzle as quickly as possible.  I’ve found that ABS cools very rapidly too.  PLA on the other hand takes a while to cool (but, then again, I was running my extruder too hot) – with the parts being quite flexible for some time after printing.  If barrel entry temperature is that important, then it seems that PLA must need a longer time to melt.  If this is the case, should the nichrome be wrapped higher on the barrel?  If so, then Rick’s heater cores (which already seem very convenient) are downright brilliant – since you can probably easily adjust where the heat is being applied.

From Nophead’s comment I gather that I was, indeed, running my extruder too hot.  I found that at my ABS temperatures (220+) made the PLA just drip right out of the heater – and once that had basically stop it would then intermittently release little amber droplets of plastic.  I must have been really cooking it.

With the limited printing I managed with PLA I found that it printed well with my non-temperature ABS Skeinforge settings.  So, before I go back to PLA I think I’ll finish tuning my ‘bot using Nick Ames’ Skeinforge tutorial.