V plotter and pyrography machine

This misleading title is actually correct. Out-of-square distortion has been cured by software modifications. There is a small slant of the entire image to the right, but I think that is easily fixable. In other news I started soldering the components for new control board which is supposed to support up to 3 stepper motors (3rd motor will be used to lift the tool off the work). 

Here is Lauren Bacall in glorious 200x204 resolution:

Well, Hackaday prize is off, and I'm not too surprised. I reckoned I only had 5% chance to get in because of late entry. Project will nonetheless continue, because I have other goals for it as well. Last week saw mostly work on software, to permit drawing of raster images. Once that was succesfully completed, there was a big problem with image distortion. I tried three approaches to solve this, and only the 3rd one worked. It was a lot of effort to get it done. Software is still not finalized, so it will not be published for now. But I have 3 images to illustrate my trials during last week, so I'm posting those.

Image bellow is one of the first ones to be drawn from raster PGM file. Distortion is obvious:

Third attempt to solve distortion succeded, this was a test pattern bellow:

This was the biggest image attempted while distortion was not yet solved:

Machine is also to be capable of pyrography (wood burning art). Here is the art I created with my existing machine. It is only 30 cm high, and imprints are somewhat imprecise. This will change on this machine: it must be capable of minimum 1m x 1m work area, so very intricate detail artwork will be possible. Previous machine was limited to about 200 pixel x 200 pixel area. New machine will be capable of 1000 x 1000 pixel art, although it must be admitted straight away that such large drawing area will require long running times, sometimes days.

My cobbled together control board is, obviously, put together from different projects. It is only capable of driving 2 stepper motors (8 output lines in pport). Entirely new board will be needed for full 3 stepper motor complement required. This is probably the first element of the system to be improved, thereby permitting tool to disengage from the workpiece as required. This will mean new toolholder design, much better than just a marker holder.

I made a huge progress in the last two days. First, I decided to use as many existing components from previous projects as possible to arrive at basic working design fast. In this I suceeded, but I didn't have time to finish the toolhead, which is just a marker holder at the moment. What I did use is: my old parallel port breakout

board with screw terminals, my old motor driver board from an earlier cnc machine, and some code snippets that I had made years ago. I had to make motor-spool-motor assemblies, two of them, and then I mounted them on the wall. Those larger stepper motors were also used in my old machine, so they had connectors and cables. Other steppers are idlers, used as bearings. Piece of broom handle in between them acts as a pulley, and this is where the fishing line is actually being wound and unwound from. Working feverishly, I managed to hand code series of commands for JollyWrencher and Hackaday printout. As can be seen, straight lines are actually curved, and there are some oscillations of the toolhead, but I'm just delighted with my progress.

Well, this project doesn't show in kackaday prize entries, probably because the tag was wrong. We will see now. In other news, tomorrow I plan on start building the toolhead or toolholder platform, that will be supported by 2 fishing lines. Preliminary design for that is given in video I uploaded today. Also, I will definitely try latches to increase output capabilities of parallel port to 12 outputs. Latches won't require any programming, so in this sense design will be simpler.

I spent one hour preparing and making the video required for prize entry. I needed a wooden rod, clamp, bracket, and a 1/4 in bolt to attach the camera, but after that all went well. I essentially shuffled the papers with my sketches around and talked about the project. Camera batteries died and now I'm just hoping that video got saved... In other developments, I checked my 7400-series component  stash and discovered that I don't have the type of latch that I will probably end up using, 74HC573. I will have to order that.

Ten geared stepper motors, with ten driver boards based on uln2003 chip, arrived this morning by mail. I tested some of them and they are really excellent little motors. Almost noiseless, a lot of torque, and the whole package for just $20! One of those motors will be used to lift and lower the tool platform (where marker or wood burning tool will be attached).

A lot of stuff needs to be clarified. For sake of low cost, PC with parallel port will be used. I have a lot of experience with this setup controlling various devices, and old computers are practically free. Linux and GNU tools are also free. Things get a bit murkier at the end of the parallel port cable though. Options here include latches, PICs, AVRs, or Arduino like boards. I have experience with all of those, except latches - old school design. Driver part is also questionable. Prefab solutions are not free, and individual transistors are maybe too low approach (12 needed for 3 unipolar motors). Mechanical setup is even murkier, because spools, toolhead, and tool lifting are unresolved for now.