Top and Bottom Z Zero CNC config

Top and Bottom Z Zero CNC config

Postby rablack97 » Tue Sep 15, 2015 7:55 pm

I'm working with a Mulicam Classic CNC machine.

If you select Z Zero for the bottom of the material, how would you configure the CNC surface/max depth.

When i set my surface at the top my material, and the max depth at the bottom of the material, the bit hoovers over the material similar to a dry run, when using the bottom Z Zero.

How should i go about setting the surface/max depth on the CNC to avoid driving the bit into the table or having it hover directly over the piece if i want to use the bottom Z Zero.

I'm guessing, and probably guessing wrong, set surface as the top of the table, and max depth as the top of the material?
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Re: Top and Bottom Z Zero CNC config

Postby Adrian » Tue Sep 15, 2015 8:35 pm

You don't have to worry about it. If you're machining a 1" thick piece of material and you're cutting, for example, 1/4" into it there is no difference whatsoever between the setup for the Z at the bottom or the Z at the top other than the obvious that you set the Z there in the material setup. Obviously you must Zero the Z to the same place on your machine.

If that's doesn't work can you describe your workflow as you've got something wrong somewhere.
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Re: Top and Bottom Z Zero CNC config

Postby rablack97 » Wed Sep 16, 2015 4:57 pm

Adrian wrote:Obviously you must Zero the Z to the same place on your machine.


I guess this is the part that i am not clear on. I am new to CNC, and want to understand the logic behind this option, and i am really green on the terms.

So when setting Z Zero on the machine, is this the set surface, set max depth procedure. If so, i am placing the surface tool on top of the material, to set surface, then on top of the spoilboard to set max depth.

If vcarve is creating toolpaths referencing the bottom of the block as the surface, but i've told the machine my material surface is the top of the block, this doesn't sound correct.
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Re: Top and Bottom Z Zero CNC config

Postby rscrawford » Wed Sep 16, 2015 5:07 pm

rablack97 wrote:
Adrian wrote:Obviously you must Zero the Z to the same place on your machine.


I guess this is the part that i am not clear on. I am new to CNC, and want to understand the logic behind this option, and i am really green on the terms.

So when setting Z Zero on the machine, is this the set surface, set max depth procedure. If so, i am placing the surface tool on top of the material, to set surface, then on top of the spoilboard to set max depth.

If vcarve is creating toolpaths referencing the bottom of the block as the surface, but i've told the machine my material surface is the top of the block, this doesn't sound correct.


On your machine, you have the option of setting the Z0 to the spoilboard (Table) or to the top of your material. All this does is tell the machine where Z0 is. But it is a 'local Z0', and you machine still knows where the machine Z0 is, so it doesn't affect your soft limits (if you set soft limits to the table top, then setting Z0 to the table or the top of your material will not affect that soft limit).

Now if you are using v-carve or Aspire, etc, you need to set the Z0 to the top or bottom of the material (and make sure to do the same with your machine). All this does is change the way it computes the toolpaths. Makes NO difference to the actual cuts. The most common way among experienced CNC users is to leave the Z0 to the spoilboard, because then you never have to worry about cutting into your spoilboard, and you never have to measure Z0, its just always the same at the spoilboard. The reason to set Z0 to the top of your material is if you don't know the exact thickness of the material and need your cuts to be an exact distance into the material (with fine v-carvings, for example).
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Re: Top and Bottom Z Zero CNC config

Postby Adrian » Wed Sep 16, 2015 6:50 pm

rablack97 wrote:I guess this is the part that i am not clear on. I am new to CNC, and want to understand the logic behind this option, and i am really green on the terms.

So when setting Z Zero on the machine, is this the set surface, set max depth procedure. If so, i am placing the surface tool on top of the material, to set surface, then on top of the spoilboard to set max depth.

If vcarve is creating toolpaths referencing the bottom of the block as the surface, but i've told the machine my material surface is the top of the block, this doesn't sound correct.


VCarve will create the toolpaths from where you tell it to in terms of the table surface or material surface. If you've set the Z to be the top of the material on your machine then you need to make sure that you've set VCarve to the same before generating the toolpaths. As long as you're setting the Z-zero position to be the same in VCarve AND on your machine you won't go wrong.
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Re: Top and Bottom Z Zero CNC config

Postby rablack97 » Wed Sep 16, 2015 6:56 pm

Image

Ok so is this where you can set z zero to the top or bottom?

If so, how would you set max depth, if you set this at the top of the spoilboard? Or would even set max depth on the CNC as this would be done in the vcarve software?
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Re: Top and Bottom Z Zero CNC config

Postby rscrawford » Thu Sep 17, 2015 4:18 pm

that is how you would set your z zero to the top of your material. The maximum depth of cut is set in your toolpaths in v-carve. You have to set the depth of each cut in the toolpath settings. I assume your machine has soft limits set, so in case you make a mistake in your toolpaths the machine will not cut deeper than the soft limits - these will not be affected by where you set your z zero, they are absolute machine limits.

I think you are over thinking this. You can test out a file by setting z zero 1" above where you want it and do a 'dry run'. The machine will cut in the air and you will be able to see what it is doing without danger of ruining your table or workpiece!
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Re: Top and Bottom Z Zero CNC config

Postby rscrawford » Thu Sep 17, 2015 4:26 pm

If you set z zero to the spoilboard, v-carve will warn you if any of the toolpaths will cut through the workpiece and into the spoilboard. So basically the spoilboard will automatically be set as the maximum depth of cut.

The bad mistakes come when you set z zero n v-carve to the top of your material, but leave z-zero on your machine set to the top of the spoilboard. Without machine soft limits set, your machine will now cut all the way through the workpiece and do all the cuts into the spoilboard.
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Re: Top and Bottom Z Zero CNC config

Postby rablack97 » Thu Sep 17, 2015 6:23 pm

:D

I know I probably am overthinking it, but its not my machine. I am not comfortable trying a theory without completely understanding it.

If the photo in my post is how you set the CNC Z-Zero at the top of the block, how do you set Z-Zero to the bottom of the block on the actual machine

rscrawford wrote:If you set z zero to the spoilboard, v-carve will warn you if any of the toolpaths will cut through the workpiece and into the spoilboard. So basically the spoilboard will automatically be set as the maximum depth of cut.

The bad mistakes come when you set z zero n v-carve to the top of your material, but leave z-zero on your machine set to the top of the spoilboard. Without machine soft limits set, your machine will now cut all the way through the workpiece and do all the cuts into the spoilboard.


This is what i dont want to happen, so i'm being really cautious.

What are the steps to set z-zero to the bottom of the material is the crayon answer i'm looking for, and its probably as simple as saying, instead of setting the surface z-zero with the grounding collar on top of your material, place the grounding collar on top of the spoilboard, set surface z-zero and done.

No one in my makerspace understands this function and wont use it, so i'm trying to understand how to set it up and the vectric tutorials advise setting z-zero to the bottom of the block for accurately cutting through materials.
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Re: Top and Bottom Z Zero CNC config

Postby Mobius » Thu Sep 17, 2015 7:18 pm

Im going to answer this question with a scenario:

Say you want to cut all the way though a piece of 1" material with a profile toolpath, 1/4" pass depth.

If your material is exactly 1" thick and perfectly flat, you can set your Z zero to the top of the material. When you run the toolpath, it will cut all the way through without cutting into your spoilboard.

But what happens if your material isnt perfectly flat and even? If you set your z zero to the top of the material in the wrong spot, you could end up with a cut that is too deep, or not deep enough.

So to solve that problem you would set the z zero to the spoilboard. Your machine would then start your cut at 3/4" above the spoilboard, regardless of your actual material thickness. The first cutting pass may be a little more, or a little less than a 1/4" depending on the uneveness of the material, but the end result will be a part that is cut out all the way without damaging your spoilboard.

Either method of setting the z zero is acceptable, it is just a matter of preference and job requirements.

Just be sure that whatever method you use is the same as you have set in the software.
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Re: Top and Bottom Z Zero CNC config

Postby rablack97 » Thu Sep 17, 2015 8:00 pm

Ok, I understand why you would use z-zero bottom.....but take vcarve out of the equation......vcarve has been set to z-zero bottom in the software....

I go to cnc machine, i place the grounding block on the spoilboard, set surface z-zero as the top of the spoilboard.

Will those steps set the CNC to Z-Zero at the bottom of my material?

All of the explanations are amazing, and i appreciate the feedback, but i'm looking for the steps to setup the actual CNC machine to z-zero bottom, as quoted below. I'm being told what to do but not how to do it.

So to solve that problem you would set the z zero to the spoilboard.


I really appreciate all of the help, i really do, and sorry if i'm not pulling the answer from all of the informative feedback.
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Re: Top and Bottom Z Zero CNC config

Postby Frunple » Thu Sep 17, 2015 8:07 pm

That is correct. Use the same procedure in the directions you posted, but place the "zeroing block" on top of the spoilboard.
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Re: Top and Bottom Z Zero CNC config

Postby rablack97 » Thu Sep 17, 2015 9:48 pm

Frunple wrote:That is correct. Use the same procedure in the directions you posted, but place the "zeroing block" on top of the spoilboard.


Awesome that's what i needed to know.

So would there be a need to set max depth on the cnc, and if so, would you set the grounding block on top of the material to set max depth or would you just leave it on the spoilboard and set both surface and max depth there?
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Re: Top and Bottom Z Zero CNC config

Postby Mobius » Fri Sep 18, 2015 12:26 am

Z zero is just a reference point to judge the height of your material.

If you set z zero to the spoil board using your grounding block and have it set up in the software that way, you need not do anything else. The software will automatically reference the height of your material by the value you have set in the material setup page.

So if you have 1" material and you set your z zero to the spoil board, the machine will compensate for the 1" material height and start carving from 1" above the spoil board. If you place a 2" piece of material on your machine and start again without changing the value in the material setup screen, the machine will still start cutting from 1" above your spoil board and you will run into trouble.
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Re: Top and Bottom Z Zero CNC config

Postby rablack97 » Fri Sep 18, 2015 1:45 am

OK perfect.....this is exactly what i needed to know, Thank you all for your input....
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