hotwire post

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gfacer
Posts: 24
Joined: Sat Feb 14, 2009 11:00 pm

hotwire post

Post by gfacer »

Hello,

Weird question here.

I have just retrofitted an old hotwire cutter that is 2D with a grbl based controller setup made for foam wings and such. this controller is 4 independant axis, 2d on either side. Because this is somewhat normal in hotwire cutting, and this format doesn't allow for arcs, the hotwire specific software I bought doesn't output arcs and it sort of shows on the quality of the output. It does of course link up the inside of letters and outside of letters so that's good and it will be fine for some stuff but I'm hoping to expand my options.

For that, without changing the controller, I don't think will be getting arcs as the control software will only take 4axis code. But, I am wondering if I can get the same 4 axis code from cut2d.

What I need is esentially the Z axis value that mirros Y and a U axis that mirrors X. I am not sure that is possible with vectric's PP or not.

Any ideas on how to accomplish would be great! I'm assuming it's either fairly simple or impossible, but it's not clear either way to me.

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Adrian
Vectric Archimage
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Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: hotwire post

Post by Adrian »

Have you looked at the post processor editing guide on the Cut2D Help menu?

I would think it's possible from a "programming" point of view. You would need to redefine the Z variable so it's sourced from Y and create a new variable for U sourced from X. Then change the relevant move sections to use the new U value.

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TReischl
Vectric Wizard
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Joined: Thu Jan 18, 2007 6:04 pm
Model of CNC Machine: 8020 48X36X7 RP 2022 UCCNC Screenset
Location: Leland NC

Re: hotwire post

Post by TReischl »

There is a lot more to this type of cutting. It is very similar to EDM. The movement of the wires has to be coordinated between the top and bottom axis. It will work for straight up and down cuts, but coordinating feed rates for work with any taper requires a very different type of software.

Simple example: A cone. The top axis must have a much higher feedrate than the bottom axis, in addition the moves must be coordinated between the two. This is probably why you are not seeing Arc outputs. More advanced controls allow arc commands, but internally (as is the case in all CNC) those arc moves are broken down into incremental steps.

Since you are using Grbl, I would suggest you dig around on GitHub for foam cutting software. Pretty sure I have seen it there.
"If you see a good fight, get in it." Dr. Vernon Johns

gfacer
Posts: 24
Joined: Sat Feb 14, 2009 11:00 pm

Re: hotwire post

Post by gfacer »

I did see the guide, and thought it was like the doc included with cut2d, but a little ok through it might point me to how to make the fix whereas the included guide didn't (coloured letters!)

My system is always xy and can't do cones or tapers so no worries there.

gfacer
Posts: 24
Joined: Sat Feb 14, 2009 11:00 pm

Re: hotwire post

Post by gfacer »

Well, tried to follow the guide, but the problem seems to be that I am trying to use the x and y variables twice. If I can define my own variables, that would probably work, but if I try to use a new variable VAR U_POSITION (to follow the example of the other position variables), I can't.

Remapping Z to output an internal Y value seems to not throw any errors, but I haven't scrubbed all the U references to test if it's actually working yet.

Should I try to simply remove the output letter with the variables and hardcode them in the relevant lines of the post instead?

I guess so, that seems to have worked!

Since this method will not use arcs, is there a way to make sure the post doesn't try to use arcs?.... I deleted the arc sections of the post but not the I and J variable lines.

For what it's worth, I quickly decided I wanted something other than a GRBL control on this machine and will be changing to a UCCNC AXXB-E control box in the near future which will use more normal g code. GRBL board wasn't liking the connection with the PC and the benefits of a more robust control system became apparent quickly.

Greg

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