Tag Archives: nub

Ideas for Cupcake CNC upgrades

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Sometimes when using the ReplicatorG control panel I accidentally hit Z- instead of Z+ to adjust the stage height.  As you might imagine, this causes problems.  At best, I end up with the Z stage out of whack.  At worst, the hot and extruding print head slams into the build platform or model and knocks the Z stage out of whack.

Two possible upgrades would be:

  1. A simple bubble level for the build platform and/or Z stage to make it easy to verify the surface is level.  I would imagine bubble levels are relatively cheap.
  2. A bracket that fits around the lower section of the Z axis rods, which would prevent the Z stage from descending below a particular level.  It could be as simple as a little plastic nub that is bolted to the inside of the ‘bot that prevents the stage from being lowered.  Four of them would probably work fine.  OR, you could put an extra nut on each Z axis below the nut that supports the Z stage.  Someone could then design a little plastic widget that would fit on top of that extra nut and have a prong that sticks up – preventing the Z axis from lowering further.

Making Blocks II

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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?