hot to remove the Z axis?

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daveeps
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hot to remove the Z axis?

Post by daveeps » Fri Aug 11, 2017 4:20 pm

Hi everyone ,
I am trying to use QCAD/CAM to create Gcode files to use on my machine ,
My machine is a custom built X,Y with no Z axis.
My problem is , how can I make the tool path follow my drawing lines and the drawing lines only ?
For example : if I would like to create a doughnut from a square piece of material how can I tell the drawing to follow my lines though a part on the main circle though to the middle circle follow the line round and then back through the same line with out the draiwing thinking it can lift away the material .
As my machine has no Z axis the tool is always in the material so running though and across the drawing will not work with my machine .
Hopefully I have explained this enough ,apologise if I haven’t , I am new to QCAD and forums!
Any help will be much appreciated .
Thank is advance
DaveEps

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andrew
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Re: hot to remove the Z axis?

Post by andrew » Fri Aug 11, 2017 8:46 pm

Can you provide a simple example drawing file and the G-Code output you would expect for your machine?
Most likely a post processor can be made for your machine with a minimal effort.

daveeps
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Re: hot to remove the Z axis?

Post by daveeps » Mon Aug 14, 2017 10:28 am

hi Andrew ,

thank you for getting back to me .
i have attached a pdf of some screenshots for example of some letters .
the top image is how the QCAD plots the gcode.
the bottom image is how i need the tool path plotted .
i hope this makes sense ?
also the gcode output and post processor are custom made not by myself so i could not answer that.

thanks
DaveEps
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toolpath.pdf
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andrew
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Re: hot to remove the Z axis?

Post by andrew » Mon Aug 14, 2017 10:32 am

I'm afraid, I would really need the actual G-Code (the textual code that is fed to your machine) to help you any further. Thanks.

daveeps
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Re: hot to remove the Z axis?

Post by daveeps » Mon Aug 14, 2017 10:40 am

would the dxf be any good ?
as if i create the gcode it will be like the first picture which is no good for me ?
if attached the dxf file .

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andrew
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Re: hot to remove the Z axis?

Post by andrew » Mon Aug 14, 2017 10:56 am

daveeps wrote:would the dxf be any good ?
No. The G-Code is a kind of a text file you would send to your machine. It contains the commands your machine needs to know where to move and in which order, etc. A post processor for QCAD/CAM can only be created if that exact code is known. If you don't know what code your machine needs, than this is what you would have to find out first.

daveeps
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Re: hot to remove the Z axis?

Post by daveeps » Mon Aug 14, 2017 11:15 am

hi Andrew ,

please see attached gcode .
the co-ordinates are minus due to my machine being upside down so my 0 is at the top .

hope you can help ?
thanks is advance
DaveEps
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test.txt
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andrew
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Re: hot to remove the Z axis?

Post by andrew » Mon Aug 14, 2017 11:19 am

Thanks.

What are the Z and A values used for? Where do these values come from? Other than that, the format looks more or less like standard G-Code.

daveeps
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Re: hot to remove the Z axis?

Post by daveeps » Mon Aug 14, 2017 11:46 am

Hi Andrew ,

to explain a bit more
my machine is a hot wire XY machine so i have 2 sides the same which both move at the same time in the same direction .
i have 4 steppers which are connected to ports that are labelled X,Y,Z,A
X and Z are up and down , Y and A are left and right .
but when it comes to the drawing i only need a 2D drawing, the post processor duplicates the X,Y to the Z,A
hope this makes sense and hopefully im not pointing out the obvious !
just trying to give you all the information.

also as there is a wire from one side to the other side, i cant have the tool path jump across what i would like to cut as this will make the wire cut though the parts i want , if you get what i mean e_confused
thanks
Dave

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andrew
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Re: hot to remove the Z axis?

Post by andrew » Mon Aug 14, 2017 8:07 pm

daveeps wrote:but when it comes to the drawing i only need a 2D drawing, the post processor duplicates the X,Y to the Z,A
hope this makes sense and hopefully im not pointing out the obvious !
OK, no problem to duplicate values in the output.
daveeps wrote:also as there is a wire from one side to the other side, i cant have the tool path jump across what i would like to cut as this will make the wire cut though the parts i want , if you get what i mean e_confused
How would this be handled? Is there a code that stops the machine and lets you disconnect the wire, then restart somewhere else?

Or is the G-Code expected to navigate around the work pieces? If so, I'm afraid QCAD/CAM does not have a logic / algorithm to make sure that the rapid moves (moves between pieces) are or aren't in any specific area.

You could draw the entire toolpath (including moves between pieces) as one single polyline to control all movement from beginning to end. Would that be acceptable? Or do you have any other ideas how to handle this?

I've also seen that the geometry and arcs in particular are rather imprecise in the G-Code you posted since there are no decimal places. Is this desirable or can decimal places be used for coordinates?

daveeps
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Re: hot to remove the Z axis?

Post by daveeps » Tue Aug 15, 2017 9:23 am

we have used a very old program called TurboCad for 20 to 30 years which has worked perfect with our machines, but we are now upgrading the machines and computers all to work with newer software as all the old equipment is being fazed out !
the XY has been upgraded and everything on the machine side is working fine, as i have used the machine and QCAD to cut, but only lines that dont cross each other ? as soon as i draw a line that crosses another line the toolpath goes all over the drawing .

please use the link below to one of my videos on youtube which will give you an indication on how the hot wire cuts .
https://www.youtube.com/watch?v=uqKuJeADu9s .

i have tried the polyline as this is how the old TurboCad works but it works for the singular cut line but again when i cross a line it gets confused !
to be honest im not to sure about the G-Code, i had a friend work on the gcode and post processors to make the drawing work with our machine, which worked fine for cutting a line or a square or a diameter but when something a bit more complicated like someones name for instance the tool path just doesnt want to follow my drawing lines ?

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andrew
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Re: hot to remove the Z axis?

Post by andrew » Tue Aug 15, 2017 11:10 am

The single polyline approach should definitely work. QCAD/CAM will follow the polyline from start to end in one go.

I've attached a simple post processor which outputs to the format you have posted above. This might still be far from perfect and might not even work, but should be considered a starting point.

To use the post processor, please save it into the "postprocessors" directory of your QCAD/CAM installation. Then start QCAD/CAM and choose "Expanded Poly" in the toolbar at the top left.
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ExpandedPoly.js
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daveeps
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Re: hot to remove the Z axis?

Post by daveeps » Tue Aug 15, 2017 3:29 pm

hi Andrew ,

thank you for the post processor,
before i went ahead with using the post processor,
I had a thought relating back to you saying to use poly lines,
I didnt want to use poly lines at first as this is what we used on TurboCad and wanted to get away from clicking around the lines to plot the tool path which is a nightmare in TurboCad!!
so i have had a play with the drawing and some research and found on another one of your posts, make existing lines poly lines !
" poly lines > Create from segments "
this has worked great as long as i show the poly line which way its going if a line crosses itself " for example: cutting the hole in the middle of an A"

But then another problem occurred which is once i make all lines a poly line , it chooses its own start point from the one i am asking it to ?
i have tried the change start point but and error message reads > POLY LINE MUST BE CLOSED <
i have tried closing this but it does not seem to work and also i have tried what you posted on here https://www.ribbonsoft.com/rsforum/viewtopic.php?t=4591
Any suggestions ?
oh or a thought does my start line need to be in a loop ? or can it just be a line ?

sorry for all the questions :D
thanks in advance
DaveEps

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andrew
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Re: hot to remove the Z axis?

Post by andrew » Sun Aug 20, 2017 9:08 pm

daveeps wrote:But then another problem occurred which is once i make all lines a poly line , it chooses its own start point from the one i am asking it to ?
i have tried the change start point but and error message reads > POLY LINE MUST BE CLOSED <
i have tried closing this but it does not seem to work and also i have tried what you posted on here https://www.ribbonsoft.com/rsforum/viewtopic.php?t=4591
Any suggestions ?
A polyline can either be closed (start point same as end point) or open (start point different from end point). For your machine, you very likely want to create one single, open polyline.

If the polyline is closed, you can set the start point to be anywhere on the polyline by right-clicking and choosing "Relocate Start Point".

If the polyline is open, you can see the start point highlighted in red if you select the polyline. To reverse the polyline (and swap the start and end point), choose Modify > Reverse.

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