A new design and an old problem

I don’t have killer 3D modeling skills – but am able to build a reasonable model using Sketchup.  It may be closed-source, but it’s got a fantastic UI.  (Heck, Apple has made an entire business model out of this proposition).

I’m trying to design a printable nut and bolt – and have a pretty good design.  The diameter of the threads on the bolt is almost 1cm, so it’s pretty large.  Constructing spirals manually is a real pain, so I used a plugin/script for generating the internal and external helixes.  (Helixi?)

The difficulty with Sketchup is that it’s not really a 3D modeling program – it’s a sketching program that makes really good looking images and reasonably good 3D models.  The problem is that it doesn’t really check to make sure triangles are properly oriented, sides are facing the way they should be, or that it is manifold.  Oh, and when the model is small it will start making little holes in your object.

There are plugins for exporting Sketchup files to STL files, but either due to a flaw in Sketchup or the plugins, they results are not as good as what you would find in other programs.  The end result is that to get a really good STL out of Sketchup I have to design in Sketchup, export as a 3DS model, import into Blender or NetFabb, fix it up, and then export back to a fixed STL.

If you’ve got a better way for transmuting a Sketchup file into a reliable STL, please let me know!

Open Source Monopolies, Unicorns, and Perpetual Motion Machines

Want a hint?  They’re all imaginary.

There’s no such thing as a monopoly on a truly open source hardware project.  So what if someone cornered the market on some critical widget?  The plans are open source and your options are infinite:

  • Build your own widget.
  • Hire someone to make it for you.
  • Design an alternate part.
  • Design a new assembly using more available part.
  • Hack a work around until you can get the part.

Or, my personal favorite:

  • Start your own business producing and selling that very same critical widget.

These are not problems.  These are opportunities for creativity and innovation.

A totally imaginary interview

It’s been an interesting year for RepRap/MakerBot.  We’ve seen demand for parts and electronics increase.  The MakerBot crew reported that for certain components they’ve actually cleaned out every source in the world.  I’m not sure which component they’re referring to, but I suspect it’s the toothed extruder pulley.  I love the idea that MakerBot has created a product garnering such high demand the entire freaking planet ran out of parts.

Can you imagine giving an interview after such an announcement?

  • Reporter: Guys, this has been a great year for MakerBot.  What are your plans for next quarter?
  • MBI: Gosh, we’ve got so many ideas!  The community has been hugely supportive and their rate of contribution and development has helped us so much.  Right now we’re splitting our time between production and development.  Batch 12, consisting of  about 147 robots, is out the door.  Batch 13 has already started to ship as the parts come in.  We’ve come a long way since the 22 robots of Batch 1.
  • Reporter: Fantastic!  What are your plans for Batch 14?
  • MBI: Dang, we were hoping you wouldn’t ask that.  Zero.
  • Reporter: I’m sorry – zero robots?  Why did demand drop off so suddenly?
  • MBI: Quite the opposite – we’ve completely exhausted the entire world’s supply of aluminum toothed pulleys.  We’re hoping to have some custom made, but at this point we’re competing with the Japanese for aluminum.  Some people suggested we start melting down soda cans for the metal.
  • Reporter: <incredulous> You’re competing with the Japanese?
  • MBI: Not every Japanese person, but the automotive industry, sure.  For a while India looked to be a competitor, but with the strength of the rupee I’m just not expecting that much competition.  We’re far more concerned about the ability of Chinese to scale their production to meet demand.  Fortunately, we think we’ve found a toner cartridge factory willing to switch over to aluminum toothed pulleys.
  • Reporter: <even more incredulous> Wait, wait, wait…  You’re concerned about the ability of an economy of one billion people to scale production to meet the needs of a DIY robot kit start up???
  • MBI: Concerned is a strong word.  The Chinese ambassador has been leaving us messages about this issue.  When we finally got around to returning his calls he assured us they’re up to the task.  I’d say we’re cautiously optimistic.

A bargain

The cheapest commercially available 3d printer on the market is the Dimension uPrint Personal 3D Printer, clocking in at $14,900.  The media cartridges run $250 – and consist of coiled ABS in a plastic box.  I can’t tell from their website how much plastic is in each cartridge, so I don’t know how cost effective it is.  I’m not positive exactly how their cartridges operate – but I would not be surprised if they were tamper resistant, not able to be refilled, and contained special chips which authenticated them as being untampered and coming direct from the manufacturer.

Am I jaded by inkjets?  Probably.  I’m tired of buying printers with 1/3 full cartridges and expensive refills.  The warranties are so much worse:

“Expensive manufacturer refills only!  Only use paper made from unicorn tears and the hopes and dreams of orphans!  Only power your machine with live baby seals.  Using reasonably priced alternative supplies, making disparaging remarks, failure to properly maintain your machine, or printing will destroy your machine and void your warranty.”

My MakerBot came with more plastic than I can print in two years runs just barely over $1,000 with shipping.  If something were to happen to MakerBot Industries, I can always find new filament elsewhere, adapt my ‘bot to a new source, or even a new material entirely.  Or, I could just toss in a Dremel and have a mini-CNC/drill press.

Backing out the filament

I’ve found that backing out the filament after each print, while a pain, has been helpful in avoiding extruder jams.  Or, rather, I have found fewer extruder jams while doing this. 1

I suspect the reason this has helped is that it removes from the PTFE insulator any of the remaining plastic that might have been about to ooze near the barrel top.  Have you found that this helps you?

  1. Not to confuse coincidence, correlation and causation, but I have also found fewer extruder jams when wearing my underwear inside out… [↩]

Ideas for Cupcake CNC upgrades

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.