Friday, August 28, 2009

How is this going to work?

Before I get too much farther I guess I should discuss how I intend to make this work.
Let me start by listing my liabilities;
  • I don't have the first clue how to program a pic.
  • Python might as well be a really big snake.
  • Scripting is something i do to make my handwriting look nice on Christmas cards.
  • Everything I know about electronics I learned from the Radio Shack " Getting Started in Electronics" book.

OK , now that that's out of the way, this is the plan.

  • I will use software obtained elsewhere to "slice" my .stl file into images that will be sent from my laptop to the printer. ( more on this later)
  • I will use the inkjet's firmware to handle the printing and the motion of the gantry (formerly the paper feed, now the x axis) during the printing phase
  • Another PC (a worthless old PIII running TurboCNC in DOS) will control all other actions via g-code, steppers, optical sensors, switches, and a tanlge of wires. (don't worry I'll have more details when the time is right)

That's the basic idea anyway, The best part is that I didn't need to learn a whole new skill set. I was already familiar with TurboCNC, available here , and G code is no more difficult than old school BASIC (I think I just gave away my age).

One important note about TurboCNC. It allows the use of a PLC handshake (both input and output) that is vital. I didn't see the same command listed among the codes in Mach3. Be sure that whatever program you chose has the ability to pause and wait for a handshake. The importance of this will become clear when I explain the control sequence later. Oh yea, It also runs in DOS so you can use that old dusty computer you never got around to throwing away, and best of all It's Shareware.

The powder spreader

The next logical step might have been to mount what remained of the inkjet on some rails or slides.... But instead I decided to jump ahead and mount the roller for the powder spreader (I figured it would be much easier to do while I could still move the inkjet around) even though I would not be able to test it until much later. The idea here is that a spinning roller pushes powder in front of it while leaving behind a very thin smooth layer. The roller is scavenged from an empty HP laser printer toner cartridge. The shaft, bushings, and dc motor I scarfed from some discarded office equipment. The gears I had left over from another project. This is where being a scavenger/pack rat really pays off. I fabricated one mount from a scrap of Plexiglas and the other is a piece of metal from my " Big box o' bits". I decided that the roller should be placed higher than the paper so it wouldn't drag across the just printed layer. It also had to be lower than the print heads so they would clear the edge of the build bin. And lastly it had to be level (easier said than done). I bolted my mounts to the sides of the inkjet and mounted the roller and motor. I now had my completed carriage assembly. As it turns out I had to tweak the roller assembly later when I got to the powder trials... but I'm getting ahead of myself.

Thursday, August 27, 2009

The donor printer

The first thing to do is strip down the inkjet to the bare essentials. You should probably start by removing the covers and observing how it works. Print a few pages and see how the paper sensor works. On my lexmark there is a little plastic lever that is lifted by the paper as it is fed into the printer. This lever moves a plastic flag which is blocking an optical sensor on the circuit board. The sensor is blocked when there is no paper/ unblocked when paper is present. Once you have figured out how it works, you need to remove anything that is under where the paper would be. This includes any paper feed rollers, guides, or housing/framework. Don't forget to measure the distance between the print head and the paper (I did!). The paper feed motor on my printer is a stepper motor (On HP printers it is a dc motor with an encoder). I separated the motor and gearbox so they could be relocated to a stationary location. Some people remove the pcb so it can also be relocated. The the idea is to lighten the carriage but I decided it would be too much hassle to extend the ribbon cables to the print heads so I left it where it was. What I was left with was a carriage that I could mount on some linear slides so that instead of feeding a piece of paper under the print head, the printer would move over a bin of the build medium.

Getting started

I will be building a 3d printer around an old Lexmark Colorjet printer that I had collecting dust in my closet. The basic idea is to build a 3d object by "printing" a series of slices onto a medium. After each slice is printed, annother layer of the medium is added on top of the previous one and the next slice is printed. In this way the object is created slice by slice from the bottom up.

Here is a basic list of what is needed:
- an old inkjet (my lexmark 5700)
- some linear slides (the higher quality the better, but you can start with drawer slides)
- 3 stepper motors (make sure they are strong enough for the job)
- 3 axis driver board (Xylotex, Gecco, Stepmaster, or similar)
- a power supply of the appropriate amperage
- an assortment of switches, optical-interrupters, relays, wire...
- some timing belts, pulleys, lead scews and nuts
- a variety of construction supplies (lumber, corner braces, screws, epoxy, wood glue, aluminum angle...)
- an old pc (I'm sure you have an old Pentium II or III collecting dust next to that old inkjet)
- software to make it all work

I'm sure I left a bunch of stuff out but I'll go into more detail with each step.

There are, as they say, "Many ways to skin a cat" (apologies to cat lovers). So my solutions are just one of many possible. Please feel free to improve on my humble tinkering.


Where to begin...

This past Spring I attended the Wonderfest model and toy show here in Louisville. (Awesome show if you're into model building/ toy collecting) Anyway, one of the seminars was dedicated to rapid prototyping. After about 10 minutes I was like "This is so cool! I must have it!". Unfortunately I didn't have $15 G's burning a hole in my pocket. What I did have however was a basic mechanical and electrical aptitude and a new obsession. Oh yes... It will be mine!!!(insert evil scientist laugh here)

A few hours research on the web convinced me that I not only could do it but I already had much of what I needed for the project . I'm already well on the way to having a working 3D printer but I'll start at the beginning and chronicle my successes (and failures) and hopefully inspire others along the way.

If you are interested in building a 3D printer or just curious, be sure to check

I also want to thank A. Fogassa for his help and inspiration. Check out his blog at