Can you Zzero to the top of material on indexer?

[myxpykalix]

I am trying to work on a project that I need to Z to the top of a rounded column but everytime i try when i run the cut file it starts air cutting about an inch or so above the surface.

I bring the Z zero plate to the rounded surface and set my z. Is the Zzero for the indexer hardcoded to the center of the material and no way to change that?
It looks like it thinks the top of material is the center and moves up.
I want to set it so that I set my Z to the surface then am able to set a depth of cut just like i would a flat piece on the table. Any experts out there?

[cmagro]

Jack,

I zero to the top of the material a lot...I find that it's not as accurate but for works for many things. I say it's not as accurate just because even if you have the center of the head and tail dead on the blank itself might be slightly off from head to tail (like if you mark a center and use a spur).

[cmagro]

Jack,

Clarification....if your entire blank will be round than rounding it first will of course make it quite accurate...but if you have a square blank and only want a portion turned it might be slightly off right where the square meets the turned area.

Simple visual...draw a circle inscribed in a square...move it just a tiny bit and you can visualize the problem.

[ed_lang]

When you ask for the experts, that left me out but I'll still try.

The last time I saw an indexer, was in your shop. I do recall that the Zzero is the center line of the work, which is the center of the chuck. My suggestion was to put the Zzero plate on the top of the stepper motor that drives the chuck and zero off of that then knowing the distance from there to the center of the chuck you can tell the control software that the Z is located at that distance right where it is positioned by using the VA command. The other way, which I would use would be to copy the current Zzero routine that you use to zero with regular cutting and modify the variable for the Zzero plate thickness to the distance from the top of the plate to the centerline of the chuck. Then when you Zzero with the plate on top of the stepper, the proper distance will be added for you each time.

If I recall right, you do no remove and replace your Indexer. With that known, you can zero from anyplace on the machine that will not change in relation to the center of the chuck. Your spoil board would not work for example because of surface it.

Here is another thought- How about using the chuck itself? Just touch off to the chuck. Making sure the ground clip in attached to the chuck and you are centered over the chuck since it is round.

Good luck.

[bill.young]

The Indexer Virtual Tool uses the center of the blank as the z-zero point for exactly the reason that Christian mentions....if you don't have your blank perfectly centered, or if it's not perfectly round (or square or octagonal or whatever), then your Z-axis zero point will be different in different points in the rotation. Zeroing to the center of the blank solves that problem.

The distance from the center of the blank to the top of the stepper motor or chuck is always the same, and Ed gives a bunch of easy ways to do your zeroing that way. If you're using the Indexer Virtual Tool but really need to zero to the outside for some reason, though, you could zero to the outside of the blank and then accurately measure the radius of the blank. Then use the [VA] command to add that measured radius to the current Z-axis value. It won't be as accurate as zeroing to the center, but should be close.

Bill

[myxpykalix]

Here is my train of thought, and please tell me if i'm off track.
I'm working on trying to do some spirals. Because many of the bits have different depths of cut, rather than make this more complicated than it has to be, what i wanted to do was to take a bit (knowing the profile is 3/8" deep) zero the tip to the top of the material. Then have it do a 3/8" depth of cut.
This is the way it is done manually on the Legacy and that works fine it seems to me it should work similar to doing a flat cut on the table of the bot if you were making a 3/8" depth cut from the top of material you would Zzero to top of material set your depth of cut in the part file and go. The difference is the rotation.

Using the current method for using the center to work from for a 3d file (like the 3d skull) in virtual show and tell is the way to do it but I think using center, calculating radius, taking router bit profile depth (dividing that in half),
along with calculating pitch, rotation, number of starts, bit diameter is making it harder than it needs to be.

So Bill is correct for maybe most situations his way is the way to do it, but I don't think that a whole lot of complicated math is necessary for this. PLEASE tell me if there is some flaw to my logic here as many good minds are better than one.

In so far as finding the center of the material I wrote a long post with pictures long ago detailing how i used a laser line to center on the dimple in the stepper motor shaft to find absolute center, then lowered the bit till the tip met the line. I zeroed out there, then took a block of wood and cut it to that height and use the wood as a template off of to center any bit.

[bill.young]

John,

If you're not using the Indexer Virtual Tool to do the spirals and are going to do them manually by entering the commands or writing a file, then you can zero the Z-axis any where you want...there's no hardware or software reason not to zero at the blank surface. That's the neat thing about this CNC stuff...you can do it whichever way makes the most sense to you.

Bill

[cmagro]

Jack,

In my opinion you are right on track...I always do my spirals from the top of the material (never from the center). Simply put...you have your turning on the indexer and you want to just put whatever radius you want and put in the spirals. I have a newel or baluster stored away and want to add flutes or spirals etc. I put it on the indexer and eyeball the z from the start point and from the end point (if it's tapered). I've got the distance and z-heights. Experience has put me in a position to visualize which bit I need and rotation amount quite well but usually will run it off the material while holding a pencil loosely in the collet so I can draw a light line on the blank (to get my blood pumping I wear a long sleeve flannel shirt, no goggles and the router is plugged in...I also rest my other hand on the rail).

Lucky you...I am turning some newels with spirals in the upcoming week. I will be happy to document step by step. Here is the design...spirals not shown.


8468

Christian

[myxpykalix]

Yes the way it will be written is not with indexer virtual tool but something different and I am programming in the surface as the 0 point.

For these purposes of a constant depth of cut all the way around it makes more sense to me to zero from the surface. If i was doing some type of 3d file with varying depths that would not be the right way to do it.

I was concerned that there might be some type of hardcoded Z zero for the indexer. At this point there is far more unknown than known so while i'm working on this its better to know than not.

[myxpykalix]

Christian,
yes yes the more pictures and documentation the better! Maybe we can start an "Indexer" thread in the "designing and cutting the sbp cutting file" section that might inspire more contributions.

[knight_toolworks]

here is a file you can use to do the zzero automatically. just put in the location of what you want to zero from use the zero plate. you get the normal zzero routine then type in the thickness. but you can replace that part with the thickness and have it zero again.
like change it so after you zzero with the plate leave in the part that zero's it after the plate thickness then jock where you have clear room jog down the thickness or up depending on where you zero and zz again. or you can use this as is and type in the thickness.
'zero for tabletop.
jh
j2 -1.407, 29.009
c2
jz .121
zz
INPUT "What is the material thickness?" &thick
JZ,&thick
VA,,,0.0 'Set Z to zero if the material surface is to be zero.
jz 1
jh

[myxpykalix]

Is there a way to manually control the X,Y,Z axis while the B axis is spinning?

When i input a manual command (MB360000) the B spins but won't let me do anything else. I would like to be able to just do a simple plunge manually to achieve this.

8469

[scottcox]

Jack,

Just use M5 commands.

M5 0,0,-1,0,36000 will spin your indexer as your z drops to -1.

M5 0,0,1,0,0 pulls the z back up as the indexer spins backward to B=0