Plasma and BACON!

Well, no bacon but we did fire up the plasma cutter tonight and have some interesting results.

Aluminum bad.  The current supply doesn't seem to have enough power to cut through AL.  Seems the heat conduction is too much.  It cuts, but verry, verry slowly.  See photos.

Next up was 0.035" steel, cuts quickly and easily.  Clean on top but dirty on the bottom.  cut width is 0.030" with the head contacting the surface and 0.50" raised up 0.125".

Finally we tried the 0.075".  Slowest of all, but does give reasanable cutting action.  Tilting the work head up to 45 degrees seems to provide much faster and cleaner cutting.  Not sure how to make the CNC head do this.  Estimate 12" / min with the head tilted, slower with head perpendicular.  Higher air pressure might help this, but the available compressor can't keep up to much more than 60 psi continuous.

Arc needs to be started at 30 PSI, then raised to 50 for cutting.

Arc must be started by grounding the tip, which will start the plasma inside.  This could be problematic for the CNC version because we don't really want to automate the third axis if we can avoid it.  One idea would be to build a circuit that momentarily connects the outside of the tip to positive to start the arc.  This circuit can then be removed and the arc will jump to the material to be cut.

A general problem with flame cutting flat material is warping.  This may not be a problem with our setup because the heat input is quite low, but if it is we could add a caster to the cutting head and let it ride up and down with the material as the machine moves.

The wiring is pretty kludgy at this point, but we can clean it up a bit as we start to pull the system together.  It's in proof-of-concept phase now.

We'll need to get some shade 6 welding glasses.  The shade 11 welding helmet was just too dark to see much, and there's loads of UV and too much light to do without protection.

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An example of someone doing something similar to what I have in mind

Rcpowers.com is a website run by a couple guys who mess around with foamie radio control airplanes.  Iterative experimentation is the name of the game here.  The principal behind it seems to have no real background in anything technical, and amusingly, seems to skip the 'research' phase of any project, preferring to just go ahead and 'do'.

They've actually made a number of  interesting models, and sell plans and kits online.

I'm not suggesting that going about things in such an unscientific way is an ideal approach to accomplishing anything, what impresses me more is how this guy has parlayed his regular updates to his Youtube videos, an 'everyman' approach to things, and the willingness to share his work into what looks to be a successful hobby business.

I think he's successful on multiple fronts.

1)  Looks like he's having fun doing it

2)  His website and videos provide entertainment/inspiration for people

3) It sounds like his website actually generates some revenue to pay for his hobby spending.  Whether it's enough money to cover his time from a $/hour perspective or not is another matter.

Nigel's summary of meeting #1

Here's the contents of a followup email that Nigel sent to the gang:

Here's what I think we need (more or less):

1. CAD software - I have an old version of Solidworks kicking around
which will work fine for creating models of the parts we want to cut out.

2. CAM software - Mastercam is a popular commercial product. I don't know
if there are freeware alternatives out there. This takes in a solid model
and generates a set of tool paths in "G code" format. Someone will need to
scope this out and get something functional up an running. Any reasonably
recent PC will work for this, and it doesn't need to be dedicated to the cutter.

3. CNC software - Freeware TurboCNC from DAK engineering should work. This
will need to be installed on the dedicated cutter PC. http://www.dakeng.com/turbo.html

4. Dedicated control PC - something with a built in printer port, a monitor,
and a keyboard. Only really needs to run DOS. We may need to pull 5V power from the PC
to run the processor on the linistepper motion control board. Marc will pull this together,
if I understood correctly.

5. Motion control boards. I have three Linistepper version 1 boards.
Documentation is here: http://www.piclist.com/tecHREF/io/stepper/linistep/index.htm There
are lots of links to follow and lots of good info on how to make these things go. Another
link: http://www.romanblack.com/lini.htm

6. Stepper motors able to handle 1 amp at some voltage up to 50V. I have two:
6.1: 1.8 deg/step, 3.1V, 1A. May be a bit weak and a bit too fine for this task.
6.2: 15 deg/step, 12V/phase, current unknown. Physically bigger than the other one,
but I don't know how much torque it will generate.
We may need to find other motors - someone needs to assess these ones and try to
come up with a rough idea how much torque/speed/power we'll need overall.

7. Control Wiring. We need PC to driver and driver to stepper wiring. Ideally we
would also have PC-controlled plasma starting, but we can use manual control for now. I have
a parallel cable with conductors big enough to solder to, but not much else of use. We'll
also need female connector bodies - check the linistepper page from item 5 for details.

8. Mechanicals - bed, rails, motor mount, drive screws/belts/cables, bearings, torch
mount bracket, etc. I likely have enough bearings kicking around, but I haven't done
a full inventory. I'll spend a bit of time soon looking at what I have and don't have.
Some ideas: http://www.youtube.com/watch?v=Lm_TvPSdGDI
http://majosoft.com/engraving/html/home_made_plasma_cutting_machine.html
http://www.cncinformation.com/CNC_Plasma/CNC_Plasma.html
http://www.youtube.com/watch?v=l9kvH5OxM7Q

9. Plasma cutter - I have a lower power machine for now, but I'm willing to upgrade if
this works out nicely.

Nigel

The next meeting will probably be at Nigel's place so that we can all get a look at things, and figure out our next steps.  Hopefully Marc will have put together a computer for it.

I mentioned that it would be nice if we could end up controlling things via USB, making it much more versatile (use any laptop etc.) but that's not how the controller circuits that we all ready have are set up to work.  Possibly something to add in V2?

First meeting

We had a productive and somewhat filling first meeting Whisper's.

It looks like the first project we work on will be a CNC plasma cutter table.  Nigel already has much of the hardware necessary, so we'll see if we can't make something which will be useful for future projects.

I also tried to sell people on my ideas of logging our planning and work progress.  The blog is obviously the first step, but doing progress photo galleries, posting meeting minutes/email discussions and maybe even podcasting meetings/conference calls is something I think might be interesting to try out.  Obviously the content we produce in a fairly straightforward project like the first one won't be that compelling, but I'm interested in laying down the framework for us to record any future, more interesting projects that we do.

Something else I just thought of:  Use bug tracking/project management software?  Bugzilla?   A good way to break down tasks, check what depends on what, manage bug lists as well as future features etc etc....  Probably overkill for now, but might be nice for the future?

Project updates

This is where we'll post project updates, photos and video of the stuff we're working on.