Check your Z-Zero Plate Thickness!

[Brady Watson]

Hey guys,
For the heck of it, I checked my z-zero plate with the digital calipers today. It checked in at .121" thick...By default the value in the Z-zero.sbp file is .131" thick. I believe this may be a typo in the file since the plate was bought directly from shopbot. I thought I checked it before...but I think I am mistaken.

At any rate, .01" can make a big difference in your cut quality. It might not be a bad idea to check yours out as well.

I'd be curious to find out if your ShopBot purchased plate is .131" or .121" thick just to give the crew at SB some feedback on the situation.

Thanks!
-Brady

[gerald_d]

I don't believe in measuring the z-zero plate. I do a z-zero routine, and then actually cut a piece of wood that has been clamped to the table to a specified thickness. Then this piece of wood gets measured - if it is too thin by (say) 0.015" then I add 0.015" to the theoretical thickness of the plate in the z-zero.sbp file. The value in our file does not correspond to the micrometer thickness of our plate (partly because we have some thin sponge under our plate). But, our zero comes out at zero, and the thickness of a job is precisely predictable.

[Brady Watson]

Well Gerald, that sounds to me a lot like shooting dice...and I realize that we all have different ways of doing things...AND if it works, great.

I posted to those that have a ShopBot purchased Z-zero plate to bring the potential error to their attention and to get feedback as to what others got when they measured.

-Brady

[paco]

ANY Z-plate should be check/gauge fisrt to assure accuracy of Z-zeroing... and then one should rectified, if needed, the value in the Z-zero routine file according to it's plate mesurment!
By the way, I use a combination of both your method Brady and Gerald; I believe the plate should be gauge... but the final adjustment are made, for me, with eye ball and finger touch! I actually use the Bot to gauge it!!! I have made me (actually, Ted helped me some...) a "gauge routine" that use Z-plate to gauge itself, material thickness and such. If any are interest, I'll be glad to share...

[gerald_d]

If one is cutting a lot of dado grooves, and you consistently find that they are all 0.015" too shallow, there is only one cure....adjust the value of the z-zero plate thickness in the file by 0.015". It does not matter how thick the plate really is. It is the final result that is important.

We realise that the z-slide cannot stop instantaneously when the electrical signal is sent - the z-motor does run on a couple of steps more. We can see the holes in our plates where the bits have "dived" in.

We also know that a conventional (up) spiral bit pulls the router and gantry closer to the table, while a down spiral pushes the router/gantry away. And that the gantry flexes the most in its center. All these things affect the depth of dados, and yet again we can only adjust the z-plate thickness in the file. There is nothing else we can do if we want to get dados that measure accurately at the end.

[waltie]

Brady, checked mine it also is .121, used a digital mike from work that I know is dead on

[waltie]

do you need to change any code in the ZZero
routine to address the thickness difference,
if so how.

Thanks

[paco]

Yes... at about line 23...

[gerald_d]

No...don't change any code.

....unless, your SB is cutting stuff at the wrong height (or depth).

[paco]

Yes! If you wish to... from what you wrote, you are 0.004" off... still, it's up to you!

[Brady Watson]

Ray,
Change the .131 value to .121, that's all.

I doubt that 99.9% of SB owners have either checked their plate thickness OR tested Z-movement with anything other than a tape measure and good eye.

After changing my z-zero file (apprehensively at 1st) I noticed that I wasn't eating into my spoilboard and still cutting cleanly through the material.

-Brady

[gerald_d]

Don't scratch where it doesn't itch.

Don't fix what isn't broken.

etc.

[paco]

After this change, or not, you can actually test your Z accuracy on your spoilboard WITH THE Z-PLATE AS A FEELER...

[gerald_d]

Paco, before we made our z-plate, we used paper as a feeler gauge to feel when the bit was just touching the reference surface. Even now we still sometimes use paper if there is not enough space to lay the plate down flat.

[cnc_works]

Until I set up my Z-zero, I used .001" brass shim stock to set zero. Still do with my small cnc. Doesn't tear like paper, is thinner than paper and doesn't dull the bit.

As an aside, since I set up the Z-zero, I've used it probably a couple hundred times with all kinds of bits including 1/4" mill and 90deg V bits and it has just a couple of the tiniest points where I can see that the bit contacted the aluminum.

Doesn't appear that it ever hit hard enough to break even the finest point off.

Donn

[wayne_walker]

I have been cutting some small parts and want to leave a thin film of material (ABS plastic) in place so it will hold the part in place. I have found that the Z-Zero reading, .132 and the thickness of Z Plate, .122 have created the problem so I have to adjust each file. I can not find where to change the thickness of the Z Plate. I had changed it when I first set the machine up but need some help.

Thanks in advance for any help.

Wayne

[gerald_d]

Look in the SbParts folder for the file Zzero.sbp - this is the contents:

'S_ZZERO2.SBP -- Example File showing how to zero out z axis on contact plate
'Copyright 1998-2001. ShopBot Tools, Inc.
'Zero Out on Contact Plate -- T.Hall 12/98,7/00,5/01,4/04
'-## Modified 9/10/01 to do a 2-speed plunge, jog down, back up a tad, then ck at move speed
'-## Modified 4/7/04 to alter plunge to designated speeds and reset to starting values at end
' Note that this means if you interrupt running the file, you will need to manually reset Z speeds
'User takes responsibility for the effects and outcomes of the use of this program.
' Wire up a plate (e.g. copper pc board, aluminum plate, etc., to an input
' line) to sense depth of a Z plunge and calibrate to zero or known depth
' this file currently set for a plate on Input #1
' **Test plate by tapping it to metal on the tool ... Input #1 display indicator should show
'Move Z to .25 - 2.5 inch above plate, then run this file

'Initialize
SA, 'Let's be in Absolute Mode
SF,0 'Turn off limit checking temporarily here
SC,0 'In general, it is probably a good idea to turn off stack
' creation in a switch-oriented program like this in order
' to prevent unexpected effects related to the pre-processing
' of all movement commands. Alternatively SC,2 could be used
' to break stack activity into chunks.

&ZBOT=0.131 'Put THICKNESS of your plate HERE ... NOW SET FOR 1/8inch Standard Plate
'Our plates seem to mic out at .131 these days ...

&ZUP=.5 'Put Z pull-up height here ... where you want bit to park after zeroing

'----------------------------------------------------------------Read the starting Z speed values to reset later

&start_Zmove_Speed = %(73)
&start_Zjog_Speed = %(78)
VS, , .25,,,, .65 '... and assign slower speeds

'----------------------------------------------------------------THE PROGRAM
'Make First Plunge... the following line will display first and wait for key stroke
' *** Hit ENTER When above plate and Ready to Zero ***
PAUSE 'Pause with no second value waits for key stroke and displays
'

'Set-up the contact switch action ... (Note- Set for Input Switch #1)
GOSUB TEST_CLEAR 'test to make sure there is no lingering contact on the zero plate
ON INP(1,1) GOSUB CONTACT1 'this is where we'll go on contact with plate

JZ, -5 'start continuous plunge (just a big number) ... looking for contact to occur
'Hope your plate is connected and tool & Control Box grounded,
' otherwise we're headed to China!

'Set-up the secont contact switch action ... (Note- set for Input Switch #1)
GOSUB TEST_CLEAR 'test to make sure there is no lingering contact on the zero plate
ON INP(1,1) GOSUB CONTACT2 'this is where we'll go on contact with plate

'Make Second Plunge
'
MZ, -1 'start continuous plunge ... looking for second contact to occur

END 'This END statement causes the program to end here without
' dropping through to subroutine

'================================================= ===============Subroutines
CONTACT1:
'This is our subroutine for action on hitting the plate the first time
'We hit the plate !
ON INP(1,1) 'First set switch to nothing to prevent secondary trigger
VA,,,&ZBOT 'Set the thickness
PAUSE 1
JZ, .50 'Pull-up SLIGHTLY ...
'Now We're Ready to Make Slow Move for Accurate Reading
PAUSE 1
RETURN

CONTACT2:
'This is our subroutine for action on hitting the plate the first time
'We hit the plate !
ON INP(1,1) 'First set switch to nothing to prevent secondary trigger
VA,,,&ZBOT 'Set the thickness
PAUSE 1
JZ, &ZUP 'Pull-up to designated height
'Now We're Back at the Pull-Up position and ready to work ...
'Reset the orginal Z speeds
VS, ,&start_Zmove_Speed,,,,&start_Zjog_Speed
PAUSE 2
RETURN 'Technically this RETURNs us to the next file line after the
' move that was interrupted by the switch ... eg. the MZ
' and we will then encounter the END and leave the file.

TEST_CLEAR:
If %(51) = 1 Then PAUSE 3
If %(51) = 1 Then GOTO NO_CLEAR
RETURN

NO_CLEAR:
'Reset the orginal Z speeds
VS, ,&start_Zmove_Speed,,,,&start_Zjog_Speed
'Z-Contact did not clear for some reason. Exiting.
PAUSE
END

Edit as necessary with a standard text editor like NotePad and save.

[richards]

Gerald has given some good information, but I think that we need to start at another point. Assuming that you're using the standard C2 command to Zzero your shopbot, look in the c:\SbParts\Custom folder for the Custom2.sbc file. Open the C:\SbParts\Custom2.spb file in your favorite editor and look at the file description. On my laptop it says C:\SbParts\Zzero.sbp. Assuming that you haven't modified the Custom2.sbc file, do exactly as Gerald wrote and modify the command.

On my real computer, I've changed the file name to mjr_zzero.sbp so that the Zzero routine always calls the file that I've already modified with the proper plate thickness for my shopbot.

To further complicate the matter, in later versions of SB3, look under the Tools Menu Item and you'll find an option where you can select your personal options for your shopbot. Since the current version of SB3 is 3.4.1 and the version that I have on my laptop is earlier than that, I can't give you the specifics; however, I do know that if you're running version 3.4.1, you can enter the parameters for your Zzero plate as well as the the parameters for your proximity switches, making the zeroing process much easier. In other words, let the shopbot provided programs do the heavy lifting for you.

[gerald_d]

Just for the record, we don't use the file that I pasted here. We work in millimeters and our working file is a hacked version of the one above.

[wayne_walker]

Gerald and Mike,

Thanks for the info, I do have the latest version. I will take the easy way out, if possible.

Thank for the quick response.

Wayne

[wayne_walker]

I looked in the tools section at the top of the tool bar in ShopBot, Ver 3 and it only has the Part Wizard, Typestter, Copy Machine, and Header Writer. I could not find any referance to the Z-Plate thickness adjustment. I must be blind. I know that it is here SOMEWHERE.

Thanks,

Wayne

[paco]

Wayne,

that's since 3.4.1 (latest).

[richards]

Wayne,

Paco's right. On version 3.4.1, click on Tools, then click on Shopbot Setup and then fill in the information requested. When you've finished, you'll find the file 'myZZero.sbp' in the SbParts folder. You'll also find the file 'my_variables.sbc' in the SbParts\Custom folder. The value that you entered for the Zzero plate's thickness will automatically be used.

[wayne_walker]

Mike, Gerald, and Paco

I found the file to change the thickness of the Z-Zero plate. Works great.. now!

A great forum and support group.

Thanks,

Wayne

[john_r]

I'm having troubles with my ZZero file or something else?
I used the SB set up file and entered my plate thickness. It runs to routine and moves Z to 1" above the material surface. I measured this it's as close to 1" as it can get.
When I try to run a file it thinks it's below the 0 surface. (i.e, Z shows it's at -.067 when it's actually above the material and not cutting)Does anyone have any suggestions?

Thanks,
John

[gerald_d]

Psst John, tell your SB a lie about your actual plate thickness - "adjust" it by .067" and everyone will be happy. (Well, nearly everyone. Some purists believe you have to measure the plate)

[drodda]

John,
Are you Zeroing on the table surface or the top of the material? Sounds like you are doing one and the SB thinks you are doing the other?

Dave

[john_r]

Hey Gerald, I thought about that one but I thought it should be more accurate. I measured my table surface, my material and my zero plate to make sure I wasn't going crazy. When I measured the bit to the top of the material it was right at 1".
Dave, I'm Zero'ing off the top of my material. My Plate Mic's out at exactly .125 with my Digital calipers. Is there somewhere else I should be putting this number into my ZZero.sbp file? It doesn't look like the one that was posted on this topic before. I also just updated the SB control software with ver. 3.24

[Brady Watson]

John,
If you are using the latest version, then the values that you need to change are in the 'myvariables' file in the Custom folder. Change it there and you should be good. I'm pretty sure that they supercede values for the &ZBot variable found in ZZero.sbp...so changing them in the .sbp may not have any effect & may be the issue.

-Brady

[john_r]

Cool Brady, Thanks. I'll look at it in the AM.

[john_r]

Hey Brady, that did the trick...Thanks.

[dvanr]

Hi guys,

you can change myvariables in the custom folder through the SB3 controller as well.
Goto TOOLS and select SHOPBOT SETUP and a whole series of questions get asked , including Z plate thickness.

cheers