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Calibration comes out incorrect
#1
Hi everyone,

I have a set of igaging (original) x, y and z scales which were set up and working correctly with touchdro on my old milling machine. I removed them and mounted them on my new mill, but am having issues with the calibration. The only differences in hardware are a new tablet, and I removed the 4th (w axis) scale as my new mill doesn't have a quill. 

I'm following the calibration routine as described in the YouTube series, using 2x 1-2-3 blocks and a test indicator. Everything goes fine until I change the CPI for the x-axis from 30,000 to the reading on the display (from memory, it's around 0.2997). When I enter 2997 as the CPI count, the displayed distance traveled is 1.04" rather than the expected 3.00". I've repeated it a couple of times and I get the same reading.

I'm not sure where to go next in terms of troubleshooting. I thought maybe it's the battery on the scale, but it repeats consistently which I wouldn't expect if the battery is dying.

Any advise would be greatly appreciated!

Lee
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#2
(10-16-2018, 07:58 PM)leeko Wrote: Hi everyone,

I have a set of igaging (original) x, y and z scales which were set up and working correctly with touchdro on my old milling machine. I removed them and mounted them on my new mill, but am having issues with the calibration. The only differences in hardware are a new tablet, and I removed the 4th (w axis) scale as my new mill doesn't have a quill. 

I'm following the calibration routine as described in the YouTube series, using 2x 1-2-3 blocks and a test indicator. Everything goes fine until I change the CPI for the x-axis from 30,000 to the reading on the display (from memory, it's around 0.2997). When I enter 2997 as the CPI count, the displayed distance traveled is 1.04" rather than the expected 3.00". I've repeated it a couple of times and I get the same reading.

I'm not sure where to go next in terms of troubleshooting. I thought maybe it's the battery on the scale, but it repeats consistently which I wouldn't expect if the battery is dying.

Any advise would be greatly appreciated!

Lee

Don't you want to start with your CPI set to 10,000?  That's the method Yuriy describes (I just calculate the ratios).
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#3
I'm confused - the YouTube videos show 30,000 as the setting to use. Where are the instructions calling out 10,000?

Thanks,

Lee
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#4
(10-16-2018, 08:49 PM)leeko Wrote: I'm confused - the YouTube videos show 30,000 as the setting to use. Where are the instructions calling out 10,000?

Thanks,

Lee

It's here on the web site, but it's in the method for using the lead screw, then dividing the displayed value by the distance in inches that you crank in.  I know that my Shars capacitive scales output 2540 CPI, and I just go by my lead screw and adjust the CPI by the ratio of the distance that I crank in to the displayed value.  CPI in TouchDRO takes floating-point numbers, so any systematic inaccuracy in the scale calibrates out pretty well.

So I don't know why 30,000 isn't working for you if you're using the 3" dimension on your 1-2-3 block.
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#5
I went back out to the garage and rechecked all 3 axes using the 1st method described by yuriy (no 1-2-3 blocks, just the graduated collars). I always end up with 2557cpi as the number to input in settings for the x and y axes. That was the case regardless of the distance travelled (1 inch, 3 inches, 10 inches).  Using that number doesn't give me anywhere near the correct distance travelled. 
The z-axis gave me 2560cpi, but I only checked that once before I ran out of time.
I'm stumped!
Lee
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#6
(10-16-2018, 11:37 PM)leeko Wrote: I went back out to the garage and rechecked all 3 axes using the 1st method described by yuriy (no 1-2-3 blocks, just the graduated collars). I always end up with 2557cpi as the number to input in settings for the x and y axes. That was the case regardless of the distance travelled (1 inch, 3 inches, 10 inches).  Using that number doesn't give me anywhere near the correct distance travelled. 
The z-axis gave me 2560cpi, but I only checked that once before I ran out of time.
I'm stumped!
Lee

ok.... it seems to be working now. All 3 axes are now agreeing with the dials within 0.001" over 4" or so. 2557 - 2560cpi appears to be the correct number. Not perfect, but at least it's in the ballpark now!

Not sure exactly what was going on. I dont think I changed my method - the tablet is running an older version of android, so maybe it was a (non-touchdro) software thing. It appears to be working reasonably well now... Thanks for the help.

Smile
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#7
(10-17-2018, 02:14 AM)leeko Wrote:
(10-16-2018, 11:37 PM)leeko Wrote: I went back out to the garage and rechecked all 3 axes using the 1st method described by yuriy (no 1-2-3 blocks, just the graduated collars). I always end up with 2557cpi as the number to input in settings for the x and y axes. That was the case regardless of the distance travelled (1 inch, 3 inches, 10 inches).  Using that number doesn't give me anywhere near the correct distance travelled. 
The z-axis gave me 2560cpi, but I only checked that once before I ran out of time.
I'm stumped!
Lee

ok.... it seems to be working now. All 3 axes are now agreeing with the dials within 0.001" over 4" or so. 2557 - 2560cpi appears to be the correct number. Not perfect, but at least it's in the ballpark now!

Not sure exactly what was going on. I dont think I changed my method - the tablet is running an older version of android, so maybe it was a (non-touchdro) software thing. It appears to be working reasonably well now... Thanks for the help.

Smile

Sorry, I'm a bit late to the party...
If you are getting to within 0.001", try tweaking the CPI by a fraction. I.e. 2557.1, etc. The config understands decimal numbers and having a whole number CPI is pretty uncommon from what I can see.


Calibration seems to be confusing to a lot of people, so I have a "ticket" to redo it in the app (i.e. have a dialog that just tells you to zero out the axis, move the scale some distance and tell the app what distance you measured), but that is in the 30's right now when it comes to priority order.

Thank you
Yuriy
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#8
(10-17-2018, 06:11 AM)Yuriy Wrote: Sorry, I'm a bit late to the party...
If you are getting to within 0.001", try tweaking the CPI by a fraction. I.e. 2557.1, etc. The config understands decimal numbers and having a whole number CPI is pretty uncommon from what I can see.


Calibration seems to be confusing to a lot of people, so I have a "ticket" to redo it in the app (i.e. have a dialog that just tells you to zero out the axis, move the scale some distance and tell the app what distance you measured), but that is in the 30's right now when it comes to priority order.

Thank you
Yuriy

It's good to see a response from you, Yuriy.  I enjoyed setting up TouchDRO on my lathe and mill, and am pretty happy with it, but I'm definitely looking forward to seeing the next release to see what kind of enhancements you've come up with.  I was watching Robin Renzetti demo the old Haidenhain DRO he has on his Hardinge HLV and thinking of how great it would be to see some of those features in TouchDRO.  I'm trying to finish up an Arduino-based electronic leadscrew app on my lathe and get it all buttoned up, and I understand how hard it can be to maintain your enthusiasm with life always getting in the way.
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#9
(10-17-2018, 03:00 PM)Briney Eye Wrote:
(10-17-2018, 06:11 AM)Yuriy Wrote: Sorry, I'm a bit late to the party...
If you are getting to within 0.001", try tweaking the CPI by a fraction. I.e. 2557.1, etc. The config understands decimal numbers and having a whole number CPI is pretty uncommon from what I can see.


Calibration seems to be confusing to a lot of people, so I have a "ticket" to redo it in the app (i.e. have a dialog that just tells you to zero out the axis, move the scale some distance and tell the app what distance you measured), but that is in the 30's right now when it comes to priority order.

Thank you
Yuriy

It's good to see a response from you, Yuriy.  I enjoyed setting up TouchDRO on my lathe and mill, and am pretty happy with it, but I'm definitely looking forward to seeing the next release to see what kind of enhancements you've come up with.  I was watching Robin Renzetti demo the old Haidenhain DRO he has on his Hardinge HLV and thinking of how great it would be to see some of those features in TouchDRO.  I'm trying to finish up an Arduino-based electronic leadscrew app on my lathe and get it all buttoned up, and I understand how hard it can be to maintain your enthusiasm with life always getting in the way.

Yeah, I'm still alive, and still working on TouchDRO. It's not  hard to maintain enthusiasm for me; I suffer from the opposite, actually - too many ideas and too little time to work on them. Last year and a half have been pretty intensive at work(s) - the startup that I worked for got acquired, so the workload jumped through the roof. Finally this spring I decided to bail and went to work for AWS (Amazon Web Services), so last 4 months I spend a LOT of time just learning the stuff I need for work. Haven't been in the garage since March...

I will take a look at that video. I'm always open to good ideas Smile
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#10
(10-17-2018, 05:34 PM)Yuriy Wrote: Yeah, I'm still alive, and still working on TouchDRO. It's not  hard to maintain enthusiasm for me; I suffer from the opposite, actually - too many ideas and too little time to work on them. Last year and a half have been pretty intensive at work(s) - the startup that I worked for got acquired, so the workload jumped through the roof. Finally this spring I decided to bail and went to work for AWS (Amazon Web Services), so last 4 months I spend a LOT of time just learning the stuff I need for work. Haven't been in the garage since March...

I will take a look at that video. I'm always open to good ideas Smile

I hope to wrap it up "soon" and do a video showing the whole thing in operation (with TouchDRO, too!).  The old Logan lathe that I have turned out to be perfectly suited to electronification.  It's very luxurious to just dial in an inch or metric feed rate or pitch.  I'm still on the fence about incorporating programmable stops.  Winter seems to have arrived early here, so I should be spending more time inside in my shop.
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