Todays result: Filtering cellular patterns

I have implemented some rough and ready ways to cull the thousands of cellular pattern permutations down to a few for further use.The cellular patterns are the structures I am using to fill the slices of my pink panther woman print. 

 

The algorithm that generates the patterns uses a seed value that is arbitrary and will therefore generate limitless numbers of  patterns. In reality there are actually few interesting patterns. The algorithm is actually generating the same patterns with different transformations.

 

A pattern can be transformed back to every other member of its family set by translations, rotations, and scaling. I have defined a length function that 'measures' a pattern. Each pattern can be reduced to a minimum length and patterns are members of the same family if they can be reduced to the same minimum pattern. More than one pattern in a family is redundant. This is analogous to the set of multiples for prime number. Typically its the actual prime number that is important.

After minimising, several instances of the same pattern may continue to appear different because varying floating point numbers. In this case the exact position of vertices of a pattern are not important, instead the relative order of vertices along each axis is meaningful. To homogenise patterns the integer order of each vertex along the X,Y and Z axises is substituted for its coordinates. Patterns can then be compared and duplicates identified. Eg the set of points [0.1, 0.7, 0.5] [0.4, 0.8, 0.2] and [0.6, 0.3, 0.9] would become [1, 2, 2] [2, 3, 1] and [3, 1, 3] respectively.

Today's result: A new power source

By using the outlet for the air-conditioning I can print more freely. My printer stops when other appliances are used in the house. I was limited to printing after dinner ->  before breakfast over night, and during work hours during the day, that is if no one else was using any of the disruptive appliances.

The print would usually stop when devices with electric motors where switched off. Disruptive appliances are fans, range hood, dishwasher, microwave, and I suspect the washing machine and kettle. Surprisingly the fridge doesn't cause problems.

Initial tests showed by using the AC outlet the range hood could be switched on and off safely, and a fan could be used from multiple places around the house without problems. When the fan was also plugged into the AC outlet the print stopped as expected. Since then I have successfully printed while dinner was prepared, and washing done.

Failed attempts to fix the problem

• Using a dedicated power board for the printer and laptop controlling it had no effect
• Using a desktop PC as a controller and powering the printer from the PC's power supply, this didn't seam to have enough capacity for both, in the end I accidentally shorted the 12v to GND and the power supply blew up
• Multiple surge suppressors had no effect
• Shielded USB cables had no effect

 

Individual circuit breaker for the air conditioner

Air conditioner outlet with a surge suppressor

Todays result: Part 2 of 6 the breasts

This is the second price of my pink panther model, filled with a new pattern.

The base of the print stuck well to the print bed. The part shrunk slightly as it printed and resulted in the lower 3-4 mm appearing to taper out slightly. I forgot to clean the nozzle before printing and there is some burnt plastic spots embedded in the lower levels.

I was afraid the the print would not finish. I ran it over night but it was still going the next morning.The printer stops when other appliances are used in the house. Normally I try to fit prints in the period after dinner before breakfast. Last night I started later than desirable because the printer needed fixing. Fortunately my partner had breakfast out this morning and it the print finished.

This section of the model is:
Natural ABS
50 mm high
Weighs ~80gm
Uses a hexagon style pattern
Took 10h44m to print

The second section of Pink panther woman model

Update:

It turns out that this is a good example of a slightly loose Y belt. The fine wave pattern that can be seen particularly in the the flat regions of the print was caused by the bed rocking back and forth.

Todays result: Acetone finishing chamber

A soup pot, fan, heater, grill, and acetone.

Initial experiments have been cold, some using the fan. Have not achieved even results yet. The coffee heater was insufficient to vaporise the acetone. The heater is I have is a an old USB coffee heater. The wire grill holds the part above the pool of acetone. 

I have tried parts for 10, 20, 40, and 80 minutes. 10 minutes was hardly noticeable, while the 80 minutes test came out varied. Some areas where very nice, some where very under done, and others areas melted and deformed.

Using electrical tape to seal the lid is sufficient to contain the acetone. I have use a single dribble for all the experiments, and there is still a puddle sloshing around in the base of the pot.

Before preforming longer tests I designed and printed a fine grill out of PLA. It was intended to support the ABS part while finishing deforming be base of the part less than the wire along. While the PLA didn't melt, it did soften and warp into a U shape. Heating it in the oven trying to flatten it out again only resulted in the melting the mesh into a solid disc.

Surprisingly the fan seams unaffected even after several hours operating in the pot. The wires on the heater suffered and went the consistency of jelly.

• The pot was purchased from KMart for $9. It has a 7.6 LT  capacity and large enough for most parts coming off my printer.
• The base grill was made out of 1/5" wire mesh cut slightly smaller than the diameter of the pot with each corner folded back.
•  The design for the fine grill can be found here.

Sealed pot

Old USB coffee heater, wire grill, 80mm PC fan

 Fine grill model

Todays result: Part 1 of 6, the neck

I printed out the neck piece of my modified version of the Pink panther model. The original can be found at http://www.thingiverse.com/thing:1216. The final print will be 30 cm high, it was going to be bigger but I was unsure if I would have enough plastic and printing time. This is one layer of six that will make up the full print. Each layer will have different internal structures. The final pieces are intended to be stacked vertically but remain separable so you can inspect each piece individually. The print is an ice breaker to approach the head of department I would like to network with. I used a new roll of natural ABS that I have never tried before but worked first time.

To produce the model I have used the free version of Netfabb studio, OpenScad, MeshLab, and a bunch of my own code.

• Netfabb was used to slice the model into 50mm blocks, repair models, and edit triangles manually.
• Open SCAD was used to render generated structure into meshes and cut meshes from each other ('difference').
•  MeshLab was used mostly to merge ('flatten') meshes together
• My code 'hollowed' out the initial model and generated the internal structure

The neck in slightly see through plastic

Todays result: A new A.B.S. x-motor end

Wednesday is my self-funded project day, ie I choose not to work Wednesdays so I have time to do my own things. I was disappointed to realise the day of printing I had hoped couldn't happen instead I needed to fix my printer again. During my last print the stepper motors got very hot, hot enough to soften and warp the PLA brackets they were attached to.

Printed a new ABS x motor end and fixed Mendel 90

Looks crap coming off of my old printer. Printed at 0.3m layer height, waves in the walls, very top deformed but repaired with soldering iron. Respect to Nophead for a good printer and model design. Notably easier to repair than other printer

Printed partial neck model missing walls

Eventually I did get one print in before bed time. I printed it to see the result of specific internal structures, but they didn’t even print. Otherwise looks good at 0.2mm layer height & 20mm/s print speed, much better than 0.3mm layer height 50mm/s print speed.

Simple mesh differencing algorithm unusable

The algorithm tries to cut one mesh from another. It works for the tests I have written and can a cube from a Pyramid successfully. However fails on even simple real meshes. It results in backwards triangles, hollow shapes, sharp corners, but there is evidence that it was trying to do the right thing. It assumes that shape is convex and hole cut can be simply filled over – rather than taking shape of cutting mesh. In my case this is acceptable even desirable as all the meshes intersect equally, along corners of the structure. Think of walls of a box where each wall is a rectangular prism, the walls intersect as each rectangle is the full length, width, and or height of the box.

I have looked for some existing functionality that I may be able to use, but haven’t anything that I can use quickly from c#. There are a couple potential libraries in c/c++ but I figured in my simple-ish case it would be quicker to hack together something that will get me across the line than to deal with all the silly problems caused crossing language boundaries and wrapping existing code. I may be wrong on this point.

Motor out of place because of warped PLA

 

Pink Panther woman neck with (incomplete) structural fill

Todays result: A second chance

I have decided to get back to this blog after several months idle. I stopped because after spending months working towards a new ‘better’ printer and then constantly failing to print anything reasonable I spat the dummy. I lost interest and hope in 3d printing and the printer was condemned to the corner.

...but after a break and some work on other neglected projects I found several motivations that lead me back into printing and eventually this blog. 

Reasons to resume blogging:

• ·         I want to document my results, I realised that I need closure on projects
• ·         I also want to get known a little outside of my immediate friends and colleges
• ·         I want evidence of skills and work I have done for employment reasons
• ·         It’s a good excuse to practice writing.

The plan is to focus on short results oriented posts, documenting methods, tools, results that are interesting and relevant, and include pictures

 

The printer in question, (not the real corner it sat in)