3 Axis Foam Cutting Mill

3 - Axis Foam Cutting Mill - Part 1

PCB Layout

Finally the Lathe is far enough along that I can start on the Foam Mill. In an effort to avoid some of the more common mistakes that have plagued earlier projects. Namely not determining the critical components and having to design/revise essential parts around lessor items that were just easy or fun to do first...

In the Case of the Foam Mill, my weakest suite is the concept of 3D drafting, CNC (Computer Numeric Control) GCode and the controller electronics. That being identified, I want to make the controller, interface it to a PC, draw a cube, and feel confident that the X, Y and Z axis motors turn as I would expect, before building sliding tables, gantries and plunging router mounts.

There are numerous CAD (Computer Assisted Design) packages available, possibly even more CNC Gcode conversion programs to chose from. Before I even consider all the possibilities I need a controller that will be able to drive the motors to act as a test jig for the software evaluation phase.

After browsing the web for the various designs, and PC Interface methods, I settled on the Allegro 5804B a Uni-Polar Stepper Motor Driver/Translator per Axis connected to a PC Parallel port. The Allegro IC is very cost effective, readily available and appears to require minimal support circuitry for this application.

A circuit that appeared on at least 3 different sites was the CW Technologies 3 Axis controller. I've tried to Email CW Tech, unsuccessfully, and will continue trying to reach the circuit designer, as I'll be posting the design and layout for now (and would like to be able direct potential sales traffic to this most deserving of individuals) for having made the design available in the first place. The contact info the I've found is listed below, but I haven't verified it's accuracy...

CW Technology
7328 Timbercreek Ct
Reynoldsburg, OH 43068-1181
800-547-7479 - COD Orders Only 24 hrs. ($5 COD Charge applies)
cwtech@infinet.com

More circuit details are currently listed at the URL below.

http://users.auth.gr/~mixos/projects/pcb/pc/015/index.htm

I use Corel Draw to scale and edit final circuit board layouts, in this case all of the work was already done.

The image is printed onto HP Hi-Gloss Photo Paper, from a toner-type Laser printer (all laser printers use Toner). The printer properties are set to the darkest level to get the highest density of toner onto the paper.

The image is reversed, as if viewed in a mirror, as the components will be placed from the top (non-copper side).

The blank copper clad fiberglass board is cut to size with either a hack saw or the bandsaw.

The copper side is scrubbed with an SOS or Iron wool pad to remove any oils or oxidants from the copper, and carefully handled to ensure it stays clean.

The laser printout is placed face down into the copper side of the board and ironed at high temp for at least 30 to 60 seconds, while applying steady pressure.

The heat from the iron, melts the toner onto the copper and bonds the paper to the copper sided board.

The next step may be repeated 2 or 3 times as required.

The boards are soaked in a stream of cold tap water and the paper is brushed vigorously with a fingernail or tooth brush, until the paper backing has started to disintegrate into pulpy globs.

Still with cold tap water I use a soaked cloth or just my fingertips to gently rub the last of the paper and the thin plastic gloss coat from the exposed copper parts of the board.

If the toner is heavy and there was enough heat to bond it to the clean copper, the masked areas will be quite resilient and remain intact.

Once I start to loose more than a couple of traces or pads of the circuit I scrub the board clean and iron on a fresh pattern, I always print spares for that reason.

This little ECO-Disaster is Ferric Chloride Acid. I use an acrylic tub and cup for the acid bath. Every thing that I use for PCB production is securely stored and clearly labeled as poisonous and corrosive.

I just broke my glass fish tank heater that normally would heat the acid to accelerate the etching process. Without the heater, the acid is about 5 degrees celcius (shop Temp) and took over 30 minutes to etch the boards... if heated to 25 to 30 C it should be 5 to 10 minutes.

As you etch more boards the acid does become weaker, I'm sure that there is an electrolysis type process that would extract the copper and rejuvenate the acid, but I don't know what it is... if you do, please don't hesitate to email me...

Here are the boards fresh out of the bath, ready to be washed with warm soapy water and have the SOS treatment to remove the toner mask from the remaining copper traces and pads.

The boards are removed and carefully checked during the etch to ensure that all of the smaller areas have had the copper removed to avoid short circuits between parts.

I personally wear safety glasses for the entire duration that any acid is out of the container, until it is returned and capped. I should wear gloves, but definitely avoid any skin contact with the acid.

Here is the finished board, washed and scrubbed.

I've been making boards like this and using variations on this theme since I was 14 yrs old, and still get a major thrill when their polished up and ready for drilling and soldering.

Notice on the bottom centre there is a trace that didn't make it and will have to be jumpered with a small wire.

I made 2 (two) brds, in under 90 minutes, from cold start to finish. One for myself, and the other for a chum in Farmington Missouri.

Once the boards are drilled, I'll stuff them with the parts, solder them up, and begin testing... In Closing, again I have to thank CW Technology, the rightful designer of the above circuit (to the best of my knowledge) and will post up to date contact info when I find it... This process is not for everyone, and CW Tech should be your first choice of vendor if you opt to purchase the board.

Support theworkshop.ca

Back to Machining