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Thursday, June 10, 2010

Rockets!

Space X made it and so can you (not) with this rocket! I designed this because I wanted to try out different shaped rockets and see which flew the best. I'm a bit stymied right now though because the rocket isn't airtight enough! It's quite tight, but in order to build up enough pressure to take off I think it needs to be really airtight. I've got some theories about how to improve it, but right now the 3D printing is leaving little holes in the build.


Rocket Fuel
This rocket doesn't burn Ammonium Perchlorate Composite Propellantkerosene or liquid hydrogen. No this uses the power of Arm and Hammer along with vinegar as an oxidizer (correct?). I've had a lot of experience with this fuel mixture resulting in a lot of frothed upon clothes, heads and hands. It's simple and fun but when the explosion goes off with you around you end up smelling like a Fish & Chip shop!


Next Steps
The rocket printed out well and a lot of people like the design. It could almost do just as a toy, although I need to trip the fins to be less pointy. What I need to do next is get the rocket airtight. My plan is to print an inner combustion chamber that is a simple cylinder. Based on previous prints of this shape it ends up very airtight. This will either fit into an expanded rocket shape, or maybe part of the design. Back to the drawing board!



Tuesday, June 8, 2010

Patents and 3D printing

I'm an inventor and I have at least 9 patents to my name, so I was interesting in what patents are out there for 3D printing. It looks like Stratasys has been working in this area for a while, but I noticed that their original patent is now no longer under patent protection:


5121329 Apparatus and method for creating three-dimensional objects was filed in Oct 30, 1989 and issued Jun 9, 1992.


For patents issued before June 8, 1995, the patent term is either 17 years from the issue date or 20 years from the filing date. That means this one ran out in 2009. And it's a doozie too because it basically covers CNC based plastic deposition printing!

Pro 3D printers

I started this thread on the MakerBot Google group as a discussion about how to improve MakerBot and what might be added. I've been looking at pro printers and one problem I can't work out is why they are so expensive! Are they particularly difficult to make, or do they just not sell that many?

Saturday, June 5, 2010

Rillakuma Bears Multiply

http://www.thingiverse.com/derivative:2635
I was very pleased to see someone else had printed out my bear model. It's actually quite difficult to get it to look good, but I think the pink one works! I made this bear for my daughter and based it on one of the many bears she has. She is リラックマ nutty!

Friday, June 4, 2010

Self-printed Makerbot

This is very awesome. Someone very patient took the time to design, print and assemble a MakerBot made out of parts a MakerBot had printed. I'm not sure if he gutted the old one or built a copy. I think the time to do this is probably not worth it given the fact that laser cutters can punch out the case quickly and cheaply, but if the only tool you have is a Makerbot, then this is very cool.

Thursday, June 3, 2010

Jigsaw Cookie Cutter 2

I printed out the cookie cutter and learnt a few things:

  • It would be better to print upside down because the bottom layer on the heated build platform tends to be squashed and as such doesn't make a good cutting edge
  • The cutter is too small for a good sized cookie (yum, cookies...)
  • The edge at 1.5mm is way too thick and according to a cook I asked, not good for making cookies
Also, a tip to anyone doing printing of objects that have thin walls with a fill in between: print from SD Card! If you ever see a zigzag fill going on in the output of Skeinforge between two walls that translates to a whole load of GCode and the serial link is just not fast enough. As a result, your walls are going to get over full and pudding out. Using the SD Card will give you a zippy fill.

So, now I've redesigned my cookie cutter to have really thin walls. In fact it's 67 layers, one layer thick! Let's see how that prints out!
Screen shot from netfabb showing the new STL file. I use netfabb for quick and dirty STL file fixing. It is very good at it.

Wednesday, June 2, 2010

Jigsaw Cookie Cutter

This took me a lot longer than I thought it would! My first attempt ended up with the protrusions and indentations being different sizes. This was all due to the wall thickness not being zero (a perfect cookie cutter). The wall thickness is 1.5mm which seems thick to me, but I took it from another cookie cutter on Thingiverse. I think it may be possible to thin it down considerably, but I want to see how it performs first.
The other element I added was a curved taper to the Z-axis. I did this to add a bit of style but it also enables, or should enable multiple cookie cutters to be stacked. I'm dying to print this out and see how it performs stack-wise and cutter-wise. It was also a terrific learning experience on Rhino. I found out how to extrude walls to make solids and how to use the Taper function!

Saturday, May 29, 2010

Simple pot

This is a little pot that I'm quite proud of. It's a variation on a circular pot I made with a fluted top, but I applied the maelstrom
command in Rhino 3D. Since having the MakerBot I've really got into Rhino and feel quite comfortable with it, although it's complicated. I am sure beyond doubt that some of the ways I do things are sub-optimal and would make more experienced designers laugh!
However, the real reason I'm proud of this pot is that it was only by printing it that I found out how awful it was. It twists in your hand when you pick it up, which makes it fiddly. It looked great in 3D though!
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CNC Music!

About 22 years ago, I was doing a day-release Engineering course at a college where they had a CNC machine. After using it to make some parts for the robot we were building, the technician brought out a cassette tape (the code was stored on tapes) and pushed it into the machine. He hit go and the machine started to play music! The cool thing was that it was using the stepper motors of the table to form the notes by spinning at different frequencies.
I wanted to replicate this on the Makerbot and I found some sample code from here that had what I was looking for. Unfortunately, it didn't work for the Makerbot so I had to hack it. This resulted in Tetris Music!

12 interlocking rings

This is a print I did of this part . I printed this on a Heated Build Platform (HBP) with a double layer raft. The HBP is one of the latest additions to the Maketbot and took me only about an hour to build from the kit. As you can see, the two middle bolts almost impinge on the build and they actually did knock the plastruder head a bit when the raft was printing, so I think I might remove them for future builds.
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Finishing the whistle

The printer finished the whistle. It didn't work unfortunately due to there being too many wisps of plastic left inside the cavity. I used a pair of pliers to pull most of the out and the whistle blew loudly, but to date I've never managed to get the ball to roll around inside cleanly.
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Printing!


This was one of the first things I wanted to print - a whistle I downloaded from Thingiverse. The printer not only prints a fully working whistle, but prints the ball inside it!
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Naked plastruder parts

Stripped!
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The Plastruder


Here are all the parts of the Plastruder (plastic extruder). Each part is covered front and back with protective paper or blue plastic polythene. It was a pain to get off, but kind of satisfying too!
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Z-axis drive bolts and X-axis motor


This is a close up of two of the z-axis spindles and the bolts that go on them. You have to make sure that each bolt is the same height so that the plastruder platform is level. Also in this picture you can see the X-axis motor pulley. One problem I have with the Makerbot is how loud this motor is. It vibrate the whole of the bottom of the cabinet.
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Z-Axis Drive Mechanism

All four spindles are driven at the same time by one stepper motor via this long belt and four pulleys. The Makerbot operator can also yank the belt to raise or lower the z-axis manually. This is done:

1. At the beginning, when you are centering the build platform and putting the nozzle right a 0,0,0
2. During the raft printing, to squish down the plastic.
3. At the end, if you haven't programmed in a lift at the end of the build.

To make sure I never made a mistake, I drew an arrow on the cabinet showing which way I should yank to raise the printing head!
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Z-Stage

The Z-axis stage is made of plastic / perspec / plexiglass and mounted on four spindles. It moves up and down and sits on four bolts. It's a reasonable approach, but prone to wobble if the spindles are not 100% straight. I found this out after crashing the z-stage into the build platform and warping some of the spindles.
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Cabinet Completed

Everything is fixed together with nuts and bolts and it took a lot of them to complete the cabinet! My arm was aching from all the Allen Key (hex key) twisting.
The MakerBot is powered by a 400W PC power supply. I had visions of using ducting the fan from the PS up around the back to blow on the hot plastic at the end of the build. This isn't really needed, but now that I have a Heated Build Platform that might help it cool down quicker.
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X and Y Stage complete


The X and Y stage are now complete!
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Y-stage

This is the Y-axis stage. I just finished putting the hot glue onto the bushes. Now to move on.
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Making the MakerBot

The Makerbot came as a laser cut kit. The instructions were in Wiki form on the Internet. Exciting stuff!
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