Re: Newbie cuts wood, feels empowered...

[Ray <rehenry-at-up.net>]

Dean

Fantastic!  Thanks for the pics and the report.  I'll mix comments in your 
post.   

On Wednesday 02 January 2002 12:14 am, Dean wrote:
> I cut the NIST logo!  Feels like a "right of passage"
> or something.   Thanks to all that assisted me in this endevour.
>
> BTW, For any other newbies out there, steppers are sloooow.
> Probably took about 8-10 minutes to cut that little logo.
> For my steppers,
> MAX_VELOCITY = 0.05 and
> INPUT_SCALE = 1920  (steps / inch )
>
> My steppers start loosing it at about 0.08
>
> The steppers are NEMA 34  5V 1.25 amp driving 5/8"x11 lead screws.
> I am using the UMC5804 and I am driving the steppers directly
> from this chip.  The motors will take 1.4 amps but the driver will only
> handle 1.25 amps so I have installed current limiting resistors (and
> heatsinks, and a fan...)
>
> None-the-less, the wood cut cleanly (soft pine) and I don't think that
> I would want to go much faster while cutting hardwoods which is what
> I am shooting for.  So for now everything is fine.  Maybe later I will
> install some FETS so I can drive the motors at full current.

I drive smaller steppers than you have at 30 ipm but I use Gecko 210 
drives with a 50 volt supply.  I also have ballscrews.  I think that the 
trick here is to get the voltage up to around 10x the rated so that the 
motor quickly builds the magnetic fields that it needs.

> That emc.ini file was a bugger.  Took some head scratching to
> get the axis/homing/limits etc..worked out.
>
> Anyway..for those interested here's the pics of my home-brew router
> mill...
>
> http://web.starlinx.com/dhedin/dcp00462.jpg
> http://web.starlinx.com/dhedin/dcp00463.jpg
>
> OK Ray. I'm now ready to start probing.
>
> Had another brainstorm.  Virtual probing.
> At work I've been playing around with OpenGL.  Here's what I was
> thinking:
>
> 1) There is some open sourced code to read in VRML 3d models into
> OpenGL display lists.
> 2) Create a cylinder inside of the "scene" that represents the tool bit.
> 3) Move this virtual tool across the model just like probing as we
> discussed before.
> 4) Each iteration as you move the tool, perform a brute force, polygon
> intersection test between the model's polygons and every polygon
> comprising the cylinder.  Each time the tool hits, store the
> coordinates.
> 5) Once you have a sectional slice of the model, (and you know the
> section of the unworked piece) it should be easy to derive multiple tool
> paths to whittle it down a little at a time.
>
> The idea here would be to allow one to import VRML files into G-code. 
> Should work for simple models that are not to complex.  May take some
> time to calculate but heck, processing power is pretty cheap and it
> would go faster than "real" probing.

Matt Shaver has been working on a g-code builder that starts from 2D 
bitmaps and derives z depth from grayscale.   His notion is to create 
carvings from pics.  Your ideas here sound like it would be a terrific 
complementary kind of programmer for carving a 3D shape from a 3D block.   

Your understanding of the relevant software is way over my head but I can 
imagine where you are going with it.  All of the moves outside of the 
intersections of the stock and the part drawings, allowing for a finish 
pass, would be considered roughing cuts.  The math that computes the 
roughing cuts could produce some fairly complex and optimized cutting 
paths.  

One thing that I can do is encourage you.  A second would be to help with 
some underlying gui that might tie together all of the g-code approaches 
into a single interface.  This might make it possible to apply several 
approaches to the same file.  

> If you check out www.3dcafe.com they have a whole bunch of free models.
> Or maybe do it just  to take advantage of open-source 3d editors?
>
> Oh well, gotta walk before I can run.  Maybe I should just break down
> and buy a decent CAM package :)

There was quite a bit of discussion on CAD_CAM_EDM_DRO about cad and cam 
packages recently.  A bunch of good resources came to the front from it.

> BTW, are any of you folks out there using machinable wax to test out
> your g-code?  I was thinking of other alternatives like some kind of
> cheap foam.
>
> One more item..  Is there anyway to make the EMC gui fit on a 640x480
> desktop? If possible, it might be wise to set up the BDI to default to
> this as many are using old equipment for controllers.

There are two approaches.  It looks from your monitor like you may have 
found the first which is to edit the TkEmc file and use smaller font 
sizes.  You can go as low as 8 for the default font if you don't mind some 
ragged lettering.  I use about 36-40 for the position font size but some 
recent changes to tkemc make smaller font here of little value in reducing 
the overall size of the display.

The second approach is to download and install the EMC that I put into the 
linuxcnc.org/dropbox about 10/21/01.  In that set there is a tkemcex gui 
that I wrote specifically for my Viewsonic model 1 monitors.  I know that 
several have tested that release and can offer helpful comments on it.  It 
may be that we need to build a new experimental release with the recent 
bug fixes and some modifications to that gui.

Thanks again for the report.  Hope this helps.

Ray