Re: [CAD_CAM_EDM_DRO] Building EMC software

Concerning EMC.

What is called "brain dead install" (BDI) CD which has the linux operating system and EMC has been created by list members and will
be available at the North American Model Engineer's Show I think the last weekend in April. This is what I plan on starting my EMC
adventures with.

To answer your question about supporting the sheet I have seen it several ways. There are little ceramic pyramids that you can buy
for this purpose and this I have seen on really big flame cutters. An easier way is to just use .125" Hot rolled flat bar (whatever
thickness you need for strength I.E., 2" or 3") that is standing on end. You make a grill out of these and make them easily
replaceable. For long spans you may need to support them in the middle. There are also several variations of this method.
Underneath you lay down fire brick or a shallow tub of water. Water will help with the dust control.

I made a 12" by 24" plasma gantry that had a wooden frame and .125" by 2" flat bars that fit into Dados cut in the wood frame. This
worked very well. The resolution was .015" and feed rates of up to 200 inches/minute. I strongly suggest that you KNOW what your
requred cutting speeds will be and design your system to run at these speeds. I found the .015" resolution to be totally
acceptable, but the first machine I built ran way too slow and just melted the material I was trying to cut. If you are cutting
thin (.060" or less) sheet then you need to move really fast.

I'm sure you are aware that a 9 by 25 foot plasma cutter will probably occupy a space of about 12 by 30 feet or more.
I also think that if you are spending enough money to build that big of a gantry that you go with CNCpro as the controller. It's
only 150 bucks and has excellent performance on contouring (which is critical for consistent cutting), it has virtually no learning
curve and works on any old PC without having to learn a new operating system.

You may also want to investigate gap control. On a machine that big it will probably become an issue. If your sheet stock is wavy
or has turned up edges then you get inconsistent flame gap which makes inconsistent kerf, slag, burned up tips, etc. The one I have
seen uses a proximity sensor and controls the height independant of the x,y control.



OUTWATER ~ KEITH J /5G3110 wrote:

> Greetings all -
> I am trying to evaluate EMC as a controller for a large plasma cutter (25' x 9'
> capacity) that I want to build for cutting metal for a (large) boat.
>
> I have successfully installed rtlinux-3.0 with linux kernel 2.2.18 under
> redhat 7.0.
>
> emc-1.17 dosen't want to build under this setup. I have a couple of questions:
>
> 1. EMC seems to be heavily dependent on the specific versions of the kernel and
> rtlinux. Is there any future plan to use the 'standard' GNU
> autoconf/automake/configure tools to make the build process a little easier?
> for example, I see a lot of copying and linking going on to a platform specific
> directory and there appear to be separate spec/definition files for each
> platorm, OS and rtlinx variant.
>
> 2. If not (or in the meantime), is there an EMC package that will copile with
> rtlinux-3.0 and kernel 2.2.18?
>
> 3. Finally, for anyone out there who knows a lot about plasma cutters (I don't):
> a. For a large (25 x 9 foot capacity) plasma cutter, how is the plate to be
> cut supported? What issues are involved with the plate support as far as
> not interfering with the plasma jet, not welding to the workpiece, etc... ?
>
> b. What is the generally acceptable accuracy of cutters today?
>
> c. has anyone out there built a large (or small) plasma cutter with EMC?
>
> Thanks!
> Keith
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