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Author Topic: zero doesnt equal zero?  (Read 6190 times)

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Offline Hodges

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zero doesnt equal zero?
« on: September 25, 2007, 06:47:56 PM »
 First off, I am VERY new to CNC and the Mach3 software. I purchased the full working version because it looks so simple to use.


I have everything set up, I finally was able to get the software working and talking to my equipment, and figured out that all of my motors needed to be reversed in order to work. A BIG thanks to everyone who posted replies in the forum's previous posts for your excellent explanations on how to solve these common problems!!

I have an issue that I cant seem to find a solution to with a search:

I can set my Z to zero, set the work thickness, and tool offset and  then manually jog the Z up and down to 1, then to -.01 (several times) and when the machine is at -0.1 ( running the roadrunner.set file) starts to run, the tool is actually much too deep (around -0.4) and immediately breaks my tool.  For the life of me I cant figure out why the tool is deeper when running the program than it is when I manually jog it to the same depth.

I have already tried setting the tool offset to 0.66 , and also setting it at zero. I have tried setting the work height at zero with no offset and also setting it to the actual offset height. I have tried setting the tool height to zero while touching the top of the work.

I'm stumped...

Can anyone offer a solution?

Hodges Handcrafted Guitars
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Offline Chaoticone

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Re: zero doesnt equal zero?
« Reply #1 on: September 25, 2007, 07:19:03 PM »
Hey Hodges,
Could be lots of things. Are you skipping steps? Is it pulling the tool out of the collet making it longer in effect? Do you have any mechnical slip? Are your steps per right? What kind of machine is it? Can you post a picture? Post your G-code for us to see. Shhhhhhhhhhh, thought there for a minute all I was going to do was ask questions.  ;D

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

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Offline Hodges

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Re: zero doesnt equal zero?
« Reply #2 on: September 25, 2007, 08:12:08 PM »
Here is a picture of the mill. As I said, it is a home built hobby mill that originally came from someone on ebay.



I am not skipping steps and there is no hesitation or skipping in the process. The program starts at zero. This is a file that came with mach3 named roadrunner.tap and if you notice the first thing that the z does is to drill a hole that is .2 deep, then it lifts, moves a bit, and lowers again to -0.1 and begins the outline of the roadrunner. When the Gcode says it is at -0.1, it is actually much deeper (guessing somewhere around -0.4 or -0.5). I have broken at least 20 tool bits so far trying to figure this out. The bits are secure and not slipping in the collet.
attached is the roadrunner.tap file.

Thanks!
Ken
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Offline Hodges

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Re: zero doesnt equal zero?
« Reply #3 on: September 25, 2007, 08:23:16 PM »
One thought just came across my mind...

Is it possible that when the Gcode is drilling that initial hole at -0.2 that it is resetting my zero to that depth? It would make sense since the next step after that is much deeper... I dont know enough about the gcode to know if this is even possible...
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Offline zealous

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Re: zero doesnt equal zero?
« Reply #4 on: September 25, 2007, 09:36:38 PM »
Seems you're offset by 0.4....try this

1. Reset all the Tool Offsets to zero

2. Refer all axis Home (if you have home or limit switches)

3. move X and Y to its' starting point on material

4. Drop the Z to material thickness

5. Zero all axis (hit Zero X, Zero Y,Zero Z)

6. Bring up the Z axis to a reasonable height above material

7. Cycle Start Gcode

Offline zealous

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Re: zero doesnt equal zero?
« Reply #5 on: September 25, 2007, 09:45:29 PM »
Cool Guitars!

Offline Hodges

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Re: zero doesnt equal zero?
« Reply #6 on: September 25, 2007, 10:02:11 PM »
Thanks Zealous!  I'll give it a try and see what happens.

Thanks for the compliments ont he guitars too. I hope this mill will help to speed up my inlay work on the guitars.

Stay tuned, I'll let you know if this works.
Hodges Handcrafted Guitars
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Offline Chaoticone

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Re: zero doesnt equal zero?
« Reply #7 on: September 25, 2007, 11:10:41 PM »
Yup, they look nice, better than nice even. They look real good.  ;) Hodges, you should see some of Zealous's guitars he made. Unreal. I sent you a personal message.

Brett
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My guard dog is not what you need to worry about!

Offline stirling

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Re: zero doesnt equal zero?
« Reply #8 on: September 26, 2007, 03:46:58 AM »
the first thing that the z does is to drill a hole that is .2 deep

Hi Ken - Are you sure that your Z is not working backwards somehow - according to the gcode, the first thing it should do is RAISE the Z axis to 0.2 (for clearance) i.e. there is no hole 0.2 deep at the beginning of the gcode.

Offline jimpinder

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Re: zero doesnt equal zero?
« Reply #9 on: September 26, 2007, 06:40:33 AM »
I'll go along with Stir;ling - having looked at the road runner file you posted, there is only two z positions, one is Z0.2 and the other is Z-0.1. This is the first time I have looked at this file, and I am suprised to see that there is an entry for X,Y and Z on each line.

It doesn't actually matter, though, because the tool should only move if it is different to the previous entry for that axis.

As Stirling says - and you can check this - the first movement is 0.2 and should be up, the only other movement is -0.1 which is 0.3 down from its upper position.

When you have jogged your axis, I assume you put the x and y at the start position, touching the work, and the Z axis is positioned with the tool just touching the surface of the work. DO NOT FORGET to ZERO the Z at this position.

The first move should be up - away from the work, and the second movement should be down. If it is the opposite way check your ports and pins and check the direction pin for the Z axis. If it is checked for active 0, uncheck it, and vica versa, and the direction will alter.

I read you first post again, and I think where you are going wrong is messing about with the Z axis at all. Clear all your offsets, particularly tool depths etc. To get going, merely touch the tool tip on top of the work and set Z DRO at 0. This will tell the machine where it is (in relation to the depth). As we said - from there it should go 0.2 up, move, then go down to position -0.1 which is 0.1 into the work (since you set the top of the work at 0).

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