4 axis wire foam cutting programs. - Page 15 - RC Groups
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Jan 11, 2013, 07:58 AM
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dpot's Avatar
its is great when it all comes together have fun
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Jan 12, 2013, 07:37 AM
The wheels touch down FIRST??
BJ64's Avatar
This may sound like a dumb question, but when you set these things up, do you have the horizontal axes with the stepper motors facing you - or are the steppers meant to be at the rear of the machine?

Jan 14, 2013, 05:42 AM
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dpot's Avatar
it depends how long the plug will reach and what machine you have
and set it up to suite you and were it will be place in work shop
Jan 17, 2013, 09:08 PM
The wheels touch down FIRST??
BJ64's Avatar
Well... I've more or less got my CNC hotwire set up now - I think

It all runs nice and smooth during axis test runs, and I downloaded a neat set of 'Foam Cutter' screens for Mach3. Just have to make the mental adjustment of thinking/talking X/Y and A/B axes instead of X/Y Z/A, but that's ok. In fact, I can better visualize XY & AB anyways


When I do a test cut, the cutter makes a hell of a noise. There's an enormous amount of harmonics and resonance going on

I've set my Mach3 up to run "mm" as the native units instead of inches. The cutter runs 3/8-12 ACME threads, so my 'steps per unit' are 94.49 instead of 2400, with a velocity of 600 (i.e. 600mm/min = 10mm/sec). As I said above, that all runs really sweetly when I jog the motors around the axes at 600mm/min, but when the Feed Rate is set to 200 in the G-Code, the cutter makes horrible noises when moving the axes.

Is this normal?

Do I perhaps need to change the steps per unit, or the axis acceleration?

The NEMA24's on the cutter are rated at 200 steps/revolution - and I'm pretty sure that that's full steps (no half-step, micro-step etc. options).

Jan 17, 2013, 09:40 PM
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p901P901's Avatar
Those steppers should "sing" with a nice pitch. So what is the parameters when you jog?
Jan 17, 2013, 10:09 PM
The wheels touch down FIRST??
BJ64's Avatar
Unit Of Measurement= mm
Steps/Unit = 94.49
Velocity = 600
Acceleration = 9 (I think - I'll have to check when I get home)

All 4 axes have the same stepper motor and are set up the same way.

And you're right - she really sings nicely when jogging fwd/back, up/down on the axes

But when cutting, it sounds really awful - and you can feel the vibrations quite strongly.

Jan 18, 2013, 12:16 AM
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p901P901's Avatar
I am new to this also so I would like to see DPOT's comments-----

How did you get 94.49 for your steps?
3/8-12 ACME thread pitch is .083". So to move 1" it would be 1/.083" = 12 revolutions, full steps = 12 x 200 steps = 2400, 1/2 steps = 2400, 1/4 steps = 9600.
Jan 18, 2013, 12:26 AM
The wheels touch down FIRST??
BJ64's Avatar
Ahhh...yes...you are quite correct P901...but...

See the "Unit of Measure"? That 'mm' means millimeters, not inches... LoL

So on 3/8-12 ACME, that's 1/12 inch per turn = 0.08333" * 25.4 = 2.1166mm per turn.

To turn 1mm, we get 200 steps per turn = 2.1166mm per turn => 200/2.1166 = 94.49 turns per mm.

Jan 18, 2013, 12:28 AM
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p901P901's Avatar
1/12 = .083, .083 x 25.4 = 2.1mm
1 rev = 2.1mm so 200/2.1 = 95.23 steps per mm.
Got it
Ref: http://www.machsupport.com/forum/ind...;topic=14073.0
Jan 18, 2013, 12:54 AM
The wheels touch down FIRST??
BJ64's Avatar
Yah - now you're cookin

I read in the manual that fractions of a step are ok (as are decimal velocities and accelerations etc.)

It just makes a Gawd-awful racket when DevFus Foam inserts the F200 G-Code to slow the cutting down to 200 units a minute. And it mean it really is horrible - and LOUD.

I might set a second Profile up, using Inches as the native format with 2400 steps per inch. It shouldn't make any difference, as that Unit Of Measurement only applies for jogging (from what I've read).

It's the G20 & G21 G-Codes that tell it to use either imperial or metric when doing the actual cutting.

And yah, it would be interesting to hear DPot's comments.

I'll see if I can put up a short vid of the smooth singing sound it makes while jogging compared to the tear-your-fillings-out noise it makes doing an actual cut...

Jan 18, 2013, 03:18 AM
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dpot's Avatar
yes it should sing not scream but when cutting very small parts it can get loud

when it is jogging is the noise the same as cutting

in devfuz just to check the size is right draw a block of 100mm x 100mm and cut then check the size you must allow for the kerf but it should only be 2mm or 3mm out

if Wong

in mach3 just mark start of cut and G0 X100 Y00 A100 B00 and check size

if all is ok then it is the setup in devfuz if not then recirculate your screw

sorry have not replayed before it is now mark email notification
Jan 18, 2013, 05:09 PM
EDF rules... :)
AirX's Avatar
Sorry I had been under the weather for the last week and have not been following the forums.
Mine makes a lot of noise when the machine was cutting small parts like Dpot wrote. Mine does cut rather slowly because of using 1/4-20 allthread. It was handy and cheap what can I say.
The only other times I had problems with it is trying to cut a lot of intricate movements which makes a lot of noise as it makes the steppers change direction and speeds a lot and noise.
My previous driver program was GMFC and the end result is similar to any other cutter as for the ammount of noise.

Eric B.
Jan 19, 2013, 10:59 PM
The wheels touch down FIRST??
BJ64's Avatar
Finally got to do a test cut with my rig, now that I know the weird noises are pretty much normal.

I'm quite impressed - now all I have to do is to figure out how to configure all the pre and post cut settings in DevFus Foam so that it starts and ends where I expect it to.

I think trying to read the 'help' will be fairly useless, so I might be in for some trial-and-error...

Thanks heaps again for all your help in getting me to this stage, guys. Much appreciated

Jan 20, 2013, 02:49 PM
Registered User
dpot's Avatar
the setup is in mach not devfuzfoam
in devfuzfoam
you have kerf setting you will have to play with it depends on heat of wire and speed.
then your machine size right and left carriage distance max horizontal run and vertical run.
then safe return height

in mach X Y A B =+or-
system hotkyes
motor home and soft limits
limit switches and more
i use a screen set for my foam cuter it is not my work not sour how wrote it but it may come in handy for you it is in zip when you load it you must copy the image folder in to the folder image in mach
Jan 20, 2013, 09:42 PM
The wheels touch down FIRST??
BJ64's Avatar
Thanks DSpot - that's exactly the same screen set I'm using

I think I still haven't set something up correctly - and it's probably in DevFus Foam rather than Mach3. I've played around with the offsets etc. in DFF, but it still doesn't behave like I want it to.

I set everything up, bring the wire down until it's just above the foam block, and when I start the run, the wire goes up and a away from the foam instead of down into it.

I suspect it's something simple again - but no matter what I've tried so far, the darn hotwire wants to cut the pattern in fresh air above the foam instead of down into it. It's almost if up is down and down is up - but everything goes the right way when I use the jog arrows on the Mach3 screen.

C'est non tres amusant...


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