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Offline jevs

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Still having trouble with Z offset
« on: March 21, 2015, 04:57:11 PM »
No matter what I do my part seems to be high or low and gives Z soft limit warnings.
I loaded all my tools and set the offset from the table previously (and I did run a part successfully).
Now I tool change to my longest tool.
Jog over the center of my stock.
Go down until it just pinches the 1" height of my 1-2-3 block
Have gage block set to +1.000
Hit set Z.

I try this both with the Tool offset on/off button lit and unlit and one throws the part way up out of the work area, and they other just seems to put it about an inch low. Not sure how to do this right!

Offline jevs

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Re: Still having trouble with Z offset
« Reply #1 on: March 21, 2015, 05:05:07 PM »
Could it be that I set the height of my tools wrong?
They are all at a -Z distance from home. Basically what it would take to make them touch the table.
However, some of them cannot reach the table in real life. I used 1-2-3 blocks up to 3" to set the offsets.
The difference of offsets between the tools is right, because I ran a part, but maybe the overall way I am setting it is offsetting them overall in an incorrect way??

Offline jevs

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Re: Still having trouble with Z offset
« Reply #2 on: March 21, 2015, 06:35:39 PM »
So everything looks good in the code up until this:
N06 G43 H1 Z1. M08

The G code list in mach says that it expects all the heights in the tool table to be positive. Mine are all negative. So when it calls H1 it is offsetting by my tool one at -10.99

This is making me think the tool offsets are being done incorrectly. Confusing.
 

Offline jevs

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Re: Still having trouble with Z offset
« Reply #3 on: March 21, 2015, 07:13:44 PM »
Is there a walkthrough for this!!! This is wasting my whole day. It makes no sense to me. I am not sure how it worked the first time with all negative values. I must have got lucky
Re: Still having trouble with Z offset
« Reply #4 on: March 21, 2015, 07:43:53 PM »
I haven't used this much, but what I have used worked well. I'll try to help.

First, I took the shortest  tool (or empty holder) and touched it on anything near the full stroke of the Z- and with tool 1 selected, make that Tool 1, Z zero.
Then put all the other tools in on at a time , select the appropriate tool #, jog to touch and hit Set Tool Offset.
Do this for every tool, they will all be offset from the empty Zero tool #1 and all offsets will be positive, meaning that the Z will need to be more positive for the longer tools as they are referenced from the shortest tool with the Z fully extended.

Then, you can put any tool in that you want, make sure that the correct tool is displayed in the DRO, touch that tool and Zero the z and all others are then in reference and ready to go.

I hope I said that right, as it worked like a charm here before.
HTH,
Russ

Offline jevs

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Re: Still having trouble with Z offset
« Reply #5 on: March 21, 2015, 09:23:25 PM »
Using the shortest tool makes more sense......

I finally got the part cut. I think the Mach instructions for the G code on the H value being positive, must just mean that the number of the tool table location has to be positive. I still cut and all my offsets are negative (since I used the longest tool).

I finally just hit the button and ignored the Z soft limit message. I think it is somehow looking at my tool change operation, which does have to go beyond the soft limit of Z home. My tool change happens by moving above Z home and my macro for it turns off soft limits temporarily to do the change. The state of the tool offset on/off button and how you do things is still a bit foggy. I just kept messing with it until Z said what I wanted and ran it.

It worked, but my profile is still cutting too deep for some reason, or the part is lifting when the material gets thin....oh well. I may never make this part again. I got two and that is all I need :)

I wish I had more time to devote to learning my machine better, but right now I just need some parts to finish up another project.

Thanks

Offline BR549

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Re: Still having trouble with Z offset
« Reply #6 on: March 21, 2015, 09:38:23 PM »
Using the shortest tool creates a problem with Z travel. IF you are at the top of Z and setting with the shortest tool AND you then switch tools to the longest tool then there MAY not be enough Z UP travel left to do the comp and you will hit the limits.

Using the Longest tool the Z can only comp in the DOWN direction of Z and you CANNOT hit the Z up limits.

IF you are going to use the longest tool THEN it MUST be set as the master with 0.000 offset.


The reason for the Soft tlimits warning IS you are moving BEYOND the range of Z travel that you set in soft limits.

Just a thought, (;-) TP

« Last Edit: March 21, 2015, 09:44:13 PM by BR549 »

Offline jevs

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Re: Still having trouble with Z offset
« Reply #7 on: March 21, 2015, 10:18:44 PM »
Using the shortest tool creates a problem with Z travel. IF you are at the top of Z and setting with the shortest tool AND you then switch tools to the longest tool then there MAY not be enough Z UP travel left to do the comp and you will hit the limits.

Using the Longest tool the Z can only comp in the DOWN direction of Z and you CANNOT hit the Z up limits.

IF you are going to use the longest tool THEN it MUST be set as the master with 0.000 offset.


The reason for the Soft tlimits warning IS you are moving BEYOND the range of Z travel that you set in soft limits.

Just a thought, (;-) TP
I actually ended up doing exactly what you said. I made my longest tool 0.000 and then the rest had negative offset. Your statement makes sense, the only thing that was throwing me is this statement:
To use a tool length offset, program G43 H~, where the H number is the desired index in the tool table. It is expected that all entries in this table will be positive. The H number should be, but does not have to be, the same as the slot number of the tool currently in the spindle. It is OK for the H number to be zero; an offset value of zero will be used. Omitting H has the same effect as a zero value.

This is not the case. All my table values are negative as far as offset goes.

Again, I don't know about the Z limit. Nothing in the program goes out of Z when cutting the part except a tool change. This is in a macro and turns off the soft limits. I am not sure what mach is looking at when it gives the Z minus warning since nothing actually trips a soft limit during cutting......unless ignoring it and clicking go anyway is turning off soft limits completely? I didn't look to be honest. My hard limits are not far off from the soft limits though and that will kill my machine. They don't get hit during cutting either.

Offline BR549

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Re: Still having trouble with Z offset
« Reply #8 on: March 21, 2015, 10:30:46 PM »

G43 H1  means to invoke the tool height offset of TOOL#1 as defined in the tool table. What ever offset you have set for tool #1 is what it uses to COMP the tool height. Take a pen and scratch out things that you find to be wrong. The manual is not 100% correct (;-) as you will find.

NOW remember you can call ANY tool# from there whether it is right or wrong.  (;-) Rule #6 pay attention to what you tell the machine to do Cause it WILL do it reguardless of how big a hole it bores in your table.

I would practice with a piece of styromfoam over and over again to get it drilled into your head. THEN it will become habit and easy peasy for the rest of your cnc days (;-)

Another thing concerning the soft limits. In order for them to be correct every time you MUST refhome the machine to the same exact spot every time when you start up the machine.
Re: Still having trouble with Z offset
« Reply #9 on: March 21, 2015, 10:36:15 PM »
Using the shortest tool creates a problem with Z travel. IF you are at the top of Z and setting with the shortest tool AND you then switch tools to the longest tool then there MAY not be enough Z UP travel left to do the comp and you will hit the limits.

That's why I mentioned   "First, I took the shortest  tool (or empty holder) and touched it on anything near the full stroke of the Z- and with tool 1 selected, make that Tool 1, Z zero."  in my previous post.  :)