View Full Version : Z-zero Routine

07-28-2003, 11:03 PM

I took a few minutes to work on the bot today and ran across an issue. Our shopbot has the z-zero plate. I have tested it to insure it trips the switch per the manual.

Here's the issue. When I go to run the z-zero file, it comes down and touches the plate and stops. The screen says the tool has hit the plate and tripped the input switch and then it doesn't do anything else. I went back and opened the file and read through it again to see if I was missing anything. It appears that the machine should pause, then move z up .5 then slowly jog back down to hit the plate, set z-zero then raise up 1.0. But it's sitting there. I saw on the screen, in the comment area that it pauses without time indicator, waiting for a keystroke command to start the second target hit. I tried hitting a key but nothing happens and I have to quit out of the file.

What am I missing?


Chris R.

07-29-2003, 07:03 AM
is it tripping input switch # 1, and is the machined screw that is in the side of your router mounting plate screwed into the router so it completes the circuit

07-29-2003, 10:06 PM

Should I be looking for a "ground" wire that goes from the columbo spindle housing to the router mounting plate?

As for the input #1, I don't recall it being tripped. I'll double check.


07-29-2003, 10:13 PM
No it is more of a set screw that project directly out of the housing. Take your Z-Zero plate and with the keyboard control NOT OPERATING touch the bit and see if it trips the #1 input switch this will indicate if the circuit is complete.


07-30-2003, 08:17 AM
Be sure and check your Z_Zero file and see what swithc SHOULD be tripping.

07-30-2003, 08:43 AM
Hi Chris,

From your prox switch posting it sounds like you have a used ShopBot...could the previous owner have modified the Z_zero routine or hooked up the wire to a different input switch? If it's hooked up to input #4 for instance it will act as an emergency stop switch and not move after contacting.


07-30-2003, 09:43 PM
Bill, we did purchase our SB used. I don't know if the previous owner modified the z-zero routine. I'm going to delete the shopbot.ini file and then re-open the SB software.

Dale, I'll also check out the results by performing your test.

Ron, I'll have to check and see what the z-zero file indicates as the switch to be tripped.

Thanks everyone. I'm trying to do this and actually "work" at the same time. It might be Saturday before I have any answers.



07-30-2003, 11:16 PM

If you have an older one that came with "Vector" as the CAM program, check about upgrading your Vector License. But first, check and see if you can live with Vector.

Some of us adore Vector others hate it. All will admit to a poorly written manual and not much support.

I'll probably upgrade to the latest program in August as I am back in the "8's" and the new one is 9 1/2 or so.

08-13-2003, 12:39 PM
Anyone mic their z-zero plates?

I'm trying to chase down persistant error(s) that seems to have me cutting 1 to 2mm too thin when doing double-sided work in my homebrewed flip jig. My z-zero plate seems to mic out at 0.120. Curious what others are finding (not using a high quality micrometer here, but I've got a little guage from Lee Valley that goes from 0 to 1" in increments of 5 thou).

The z-zero routine uses a value of 0.131 so I've changed that for now.

Hopefully that accounts for at least some of the error.... (double sided work is a pain... any z error is also doubled!)


08-13-2003, 12:43 PM
How clean is your bit tip? I've found that if there is residue on the tip of the bit, the Z will keep plunging until contact is made. This has introduced errors of .5 mm or more in my experience.

08-13-2003, 02:40 PM
Our check method for z-zero is to lay a sheet of paper between the job and the bit, then creep the router down (using "K" keyboard cursor) until the paper cannot be slid around (trapped by the bit). That is the definitive "z=0.00" in our book . . . . more reliable than measuring the thickness of a dirty old plate that is approached at high speed by a dirty old bit.

08-14-2003, 09:46 PM

Today, I took the time to insure that the bot was properly grounded. This fixed the z-zero routine issue.

But I didn't fix the x-axis prox issue. While tracing the wire from the prox switch, I appears to be spliced into a larger wiring harness. Is this typical? I'm trying to get a game plan on tracking down the wiring issue.



08-15-2003, 02:19 AM
Chris, I guess it would be typical, because all the proxies that I know of, only come with about 2m of wire as standard.

08-15-2003, 01:46 PM
As I was filing off the burrs left on my support clamp by my .5 mm too deep Z depth error, it occurred to me that a good verification of Z-zero plate routine would be to use part of Gerald's paper based technique. Plunge down to 0 + the thickness of your paper, then test the gap with your paper.

I still like the Z-zero plate as there never seems to be the right kind or amount of light at the bit in my shop

08-15-2003, 04:06 PM
Sheldon, we don't measure the thickness of the paper and then plunge to 0+thickness. We lay the paper under the bit, with the left hand on the keyboard we creep the bit down, with the right hand we slide the paper around a little until the bit pinches it. We assume that reading is 0.00 because the bit has probably dented/penetrated the paper. Calculating paper thickness would really be splitting hairs too much.

Yes, we also love our zero plate and that is our routine way of setting zero. But, when in doubt, we check with paper. (Also when we want to zero on to a small area where the plate does not fit.)

08-15-2003, 11:56 PM
I once knew a Shaolin Master Shopbotter who could plunge a bit down until it contacted rice paper and held it in place. When he would raise the bit there would be no evidence that it ever contacted the rice paper.

Oh by the way, this was while he was blindfolded.


08-16-2003, 12:43 AM

08-16-2003, 10:56 PM
newsprint was .002" about 30 years back when I used it to set up Roots style blowers

08-17-2003, 12:39 AM
Don't you mean papyrus Ron LOL

08-17-2003, 02:06 PM
No Dale,

paprus is thicker and one would need to ask their mummy for a sample.

08-21-2003, 07:38 AM
Mystic zero routine #4.

Insert bit into collet and hand tighten to remove clearance between collet sleeve and upper seat. Leave cutter extended out slightly farther than you envision it's final resting place.(.2517 should be fine). Using the mystic keyboard commands plunge z down untill bit makes contact with surface. Using your one good eye, and your 30w incandescent shop light on high continue the z plunge which will overcome the slight friction fit, moving the cutter up into the collet an unspecified amount but yeilding the approximate desired total cutter extension. Exit keyboard command and zero z. Here's the tricky part. TIGHTEN THE COLLET! JOG Z TO 1 INCH! ( or whatever distance your mystic advisor deems sufficient clearance). You have now acheived z axis heaven in a dimly lit room with one good eye and a z plate that wouldn't fit down in the surface you were praying could be zeroed. If you do not beleive the miracle mz to .002 and insert your .002 papyrus feeler gauge and be amazed.

I would never recommend that you insert a bit without fully tightening it immediately, I am just bearing witness that I have seen the above mentioned miracle of Z.