OoeyGUI

Through the kindness of their heart, PSM North America has provided me with a small quantity of Polystarch plastic. Polystarch plastic is made with a biodegradable resin made from corn starch. It has most of the same qualities of petrochemical based plastics, but will compost completely very quickly.

Currently, I have it in granule form. One of the options I’ve been looking into is an extruder which can source granules instead of filament.

My first approach at decomposing an object to voxels, then to generate primitives from this “voxel space” may not be the best algorithm. I’m finding that I use edges to discover if a voxel is set, then during reconstitution need to find edges. I’m worried about curve detection – Sketchup has context if an edge is part of a curve. Not to mention that it takes an hour to “voxelize” a small simple object…I still believe that locating sub-volumes is the correct approach for the path generator, but moving forward I’m going to look into using the edges themselves not voxels.  Stay Tuned.

I was discussing the prospect of “home fabricators” with a reluctant friend of mine recently. The idea that a “3D printer” would be as ubiquitous as Microwave ovens in 10 years may seem far fetched. I likened the hobbyist nature of home fabs today to the garage computers of the ’70s. The device I’m building is like “Lego meets the Easy Bake Oven”.One of the oft mentioned complaints of using Fused Deposition Modeling (FDM) for toys is that you end up with a highly aliased volume – it has ridges. And while ridges are fine for potato chips, they aren’t very good for toys; or so they say.  The smallest of  Lego have a dimension of about an eighth inch – an order of magnitude larger than an FDM modeler.

 

The voxel generator is complete. I spent quite a bit of time attempting to use Sketchup’s intersection APIs in order to build voxels; only to discover that Sketchup doesn’t maintain volume information – just edge information.The current implementation of the voxel generator uses a guillotine to slice the model into layers. For each apparent voxel, it uses a line crossing point-in-polygon algorithm to determine if the voxel is set. This code doesn’t handle curves yet – sketchup represents curves differently than simple edges.My next step is build composers – which walk the voxels to generate specific objects. These will be used to generate layer commands which will be sent to the motor controller.

I posted the Sketchups for the 3D printer, the motor controller board and what I have of the decomposer plugin. You can fetch the sources here:

svn co https://ooeygui.com/Arduino .

The Decomposer doesn’t work yet. I had been working under the assumption that Sketchup performed true volume intersections. Well, it doesn’t – it only performs edge intersections. If you attempt to intersect a voxel in the middle of the model, there’s nothing generated. This requires a minor change in plans. My original discussion mentioned a slice, then a strip then a voxel, but I tried to short circuit it in code; my mistake.Something for another night.

I received my order from Batch PCB today. After the boys went to bed, I started populating the board. This is my first board using surface mounted components. The variable resistors turned out to be the hardest – they have 3 points of contact. I didn’t label the capacitors or resistors, so I’ll need to print out a guide when I put those in.

   

Things are finally starting to get real. Time for some progress photos!

Structure

I ordered a bunch of components from the 8020 garage sale on eBay. I had opted for plastic end joins, and 3 linear motion bearings. The bearings were very expensive, so I may look for something different in the future.

Extruder Barrel

I spent a few hours on the extruder this past weekend. Was able to construct the head, heater barrel, and motor mount. I picked up the parts from from the plumbing isle – 4″ brass barrel, coupler, and an square end stop.  I filed the end stop down to a pyramid, and drilled out the inside to reduce the amount of material I needed to punch through with the small bit. In hind sight, I should have hand drilled the extruder hole as 500 rpm was too much for the tiny drill bits – I broke 3 on the attempt. I coated the barrel and coupler with a high temp enamel finish in order to prevent the nichrome wire from shorting out to the barrel.

Here’s the result:

I also received some HDPE cord from Village Plastics.Here’s 5 lbs:

Thought it would be fun to show off the “shop.”  It’s part woodworking, part auto, part metalworking, part robotics shop:

And my workbench, with the ill fated toaster parts:

In other words:Louie: 1Toaster: 0In the beginning of Jimmy Neutron, little Jim launches a satellite made from his mother’s toaster. I couldn’t help but think of the boy genius as I disassembled a toaster, in order to obtain the vital element to my printer’s extruder head.  Buried in the heart of the beast – a twisted network of sheet metal delicately twisted together by an underpaid worker in a foreign land, lay the prize – several feet of Nichrome wire. While therapeutic, the disassembly of the toaster had a lasting impression upon me. The toaster isn’t directly recyclable, yet when I was finished my disassembly I had reduced it to electronics components and wires I could use and sheet metal – which can be directly recycled. While I did end up with some plastic components which could not be identified for recycling, these were put into my chipper box for later reduction to granules – and hopeful later identification.(I love Jack Johnson’s music.)

Motor Control Board

The motor control board is currently “panelized”, and being fabricated. I had expected it to be done last week, and started populating it this weekend. After I submitted it, I realized I could make a simple modification to the design which would enable the board to be switched into “high res” (microstep) or “high speed” (full step) mode. This is done by routing two control lines on each of the drivers to an output pin on the controller; a high signal on both lines is microstep, low is full step.I’m starting to look into building a 2.5 amp version of the board using the 44pin PLCC 3977 from Allegro Micro. They have been fantastic about supplying samples for development.

Extruder

Where, oh where, do I find plastic? Finding small quantities of HDPE or ABS in 1/8″ cord or granules is difficult. I can get granules in 55 pound bags, for $2 per pound or ABS cord in 25 pound rolls at $7 per pound. The cheapest I’ve found is Village Plastic will offer 5 pounds of HDPE cord for $6 per pound.I’ve been looking into ways of simplifying the heating barrel and extruder screw. Instead of using a metal pitch screw, I think a concrete screw will be able to grip either the granules or the cord with equal efficiency.

Software

I’ve been playing with the Sketchup API. Still not sure how I’m going to slice the printing object. I’ve been looking at some code which generates STL files, so I should garner what I need.

Structure

I’ll be ordering structure parts this weekend, and start assembling it next week.