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leaveme
09-04-2010, 09:59 AM
I built a fixed gantry hybrid (aluminium & MDF) machine.
I haven't installed any limit switches yet and planning to use the soft setup for the time being. One thing I can't configure is Z axis: don't really understand whether I'll configure "0" at top or bottom.

For instance, if I set zero at top then bottom (base plate) will be -6.10.

| (0.00)
|
| (-6.10)
---

Please advice, what you guys are configuring for you case?

Phife
09-04-2010, 10:28 AM
that is correct, typically the Z home is at the top of the Z, and as it travels down it goes into the negative.

leaveme
09-04-2010, 11:16 AM
Thank you, Phife. It helps me for Z setup.
I also need some help on material setup (since I'm first time with CNC).
For instance, my base plate is at -6.10 and I put the material (i.e height 0.75") there for curving. How do I configure it in Mach3?

Thanks in advance.

M250cnc
09-04-2010, 11:30 AM
I also need some help on material setup (since I'm first time with CNC).
For instance, my base plate is at -6.10 and I put the material (i.e 0.75" dia) there for curving. How do I configure it in Mach3?

Thanks in advance.

The norm is that the top of material that you are machining is set at zero then any cut is then a minus number. So to machine 1/4" deep then the cutter is -0.25"

I do not understand the last paragraph i.e. 0.75" dia you need to explain this

Phil

RomanLini
09-04-2010, 12:12 PM
Interesting views.

I run the opposite, the Z axis is at 0 when the tool is at the deck, which is set by my Z tool height setter.

Then if I make a cut at Z=2mm it makes the material 2mm thick etc. I can't imagine any Z system better than that, but maybe there's something I missed. ;)

Phife
09-04-2010, 08:13 PM
Interesting views.

I run the opposite, the Z axis is at 0 when the tool is at the deck, which is set by my Z tool height setter.

Then if I make a cut at Z=2mm it makes the material 2mm thick etc. I can't imagine any Z system better than that, but maybe there's something I missed. ;)

That may work for you, but I use a vacuum table and sometimes I use vacuum fixtures of various thicknesses. I find it easier to have my Machine Z 0 at the top of the Z travel, and then I set the Job Zero to the top of the work piece. The program then doesnt care if the part to be machined is on the bed surface or on top of a fixture.

hemsworthlad
09-04-2010, 08:42 PM
Interesting views.

I run the opposite, the Z axis is at 0 when the tool is at the deck, which is set by my Z tool height setter.

Then if I make a cut at Z=2mm it makes the material 2mm thick etc. I can't imagine any Z system better than that, but maybe there's something I missed. ;)

Ye but your in OZ so everything is upside down. . Lol

pointcloud
09-04-2010, 09:40 PM
I got a shovel, see I am standing on the ground at sea level... I dig a hole 1M deep, is that I added a meter hole? or I subtracted a meter hole? I dont know go figure?

Safe "Z" covers the tallest trees in the forest? is that 100M 0r is that -100M?

I guess I am saying I want my submarine to go -
and
I want my airplane to go +

I'm just saying?

leaveme
09-05-2010, 04:30 AM
Thanks guys, I got some useful info.
Seems it will be bit easy if prepare a probe plate for zero setting. But material top (height) will be zero in this case.
Is my understanding right?

hemsworthlad
09-05-2010, 05:20 AM
I would defiantly recommend probing for material height.

I use Machblue screen set with a few mods to the probe scripts to suit my needs and wouldn't be without it, must save me 30mins a day compared to messing with slip gauges etc.
The other probes such as edge finding and hole centering probes are very useful when needed as well.

I always work in the negative and my Z Machine zero coordinate is at the top and homes to this.
I think you'll find this is the more common way people work.

cyclestart
09-05-2010, 07:41 AM
For instance, my base plate is at -6.10 and I put the material (i.e height 0.75") there for curving. How do I configure it in Mach3?

Use the 'touch-off' feature. Bring the tool to the surface of the part and designate that position relative zero. Really easy if you're only running one tool. Beware of entries in the tool length offset register. I'm not a Mach user but those general rules should apply.

If the finish height on a part is 2" I might measure to the table top and factor in the 2" in the touch-off dialog box. Depends if the unfinished top surface is irregular. (That's assuming the part is clamped directly to the table.)

If you're running multiple tools there are more decisions to be made.

pointcloud
09-05-2010, 09:55 AM
yes stock or material should be Z0, and Z-1 will be a cut equalling -1 for measuring system your machine is set to use.

RomanLini
09-05-2010, 10:32 AM
...
... Depends if the unfinished top surface is irregular. ...
...

I think that is the crux of it. If I'm making a widget that has varying heights then it suits my needs to have the deck at 0 and the cut heights all positive. Especially so if the widget is being machined from a piece of irregular stock like a casting etc, that has no proper "top surface".

But people who mainly are doing engraving down to a set depth on flat sheet stock might benefit from having the stock top surface as zero I guess.

It still seems a little funky, most of the acrylic I get has very poor thickness, ie 10mm sheet can be 9.9mm at the edge and 9.2mm thick near the middle. So setting to the "top" of the sheet is going to cause issues but setting to the deck means the parts made will have correct dimensions.

pointcloud
09-05-2010, 11:12 AM
as you can see it doesnt really matter if you plan to work around all the other problems you might have. as you see others make a real effort to do things a dificult way sometimes...

Just be sure that your safe Z is set up to clear all these hurdles people are talking about..

Normally Z0 is the top of your stock, even if it is irregular...
Normally SAFE Z is Z0.25....
Some programs allow a skim clearance, which I use and have it to output Z0.0625

Keep reading and you'll weed out all the BS, if not by reading then you'll figure it out with your machine... Which normally needs to be videoed for thers to watch, cuase if you dont get it right.... Its a crash now and be one hell'ova laugh later...

One good thing about setting Z0 the correct way... You NEVER EVER have to watch it and say OMG that's 4+6-8+4..... as it crashes? you can CLEARLY see that Z0.25 is CLEAR for rapid moves? Go FIGURE?

I do agree that MATH is GREAT but why would a person want to even second guess where the stock top is?

is it Z0 plus stock of 3.0625 and plus safe Z .250? equalling Z3.315 for a rapid move? or you could say Z0 is TOP so Z0.250 is SAFE? either way....


outa heree...