Ditron D80 DRO linear compensation...help?

Winegrower

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I only entered 3” in mm actual, whatever that is. It figures out one of the parameters, what it thinks the move is, and figures S. I recall having to follow EXACTLY the sequence the manual describes, even though it seems to be more free form. Later, I verified S computation with the formula, it checked.
 

A watkins

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I only entered 3” in mm actual, whatever that is. It figures out one of the parameters, what it thinks the move is, and figures S. I recall having to follow EXACTLY the sequence the manual describes, even though it seems to be more free form. Later, I verified S computation with the formula, it checked.
I posted the entire text of the manual on this subject; I don't understand what sequence you are referring to. Could you point it out?
 

Winegrower

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A watkins, my shop is covered up for a few days for reroofing. Honestly, you have it there, these are the steps I went through, lots of trouble until I set the DRO to metric. It just worked after that. You only have to enter the your standard’s length...in mm. The rest is automatic.
 

Winegrower

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Ok, here is what works for me:

Press C to enter linear compensation. Select Axis with arrows. Move lathe per the reference block. Select the “L” field, enter the reference distance in mm. Press Enter. Then exit by pressing C again.
 

A watkins

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Right, and the last part is not mentioned in the manual at all, including that there is an S field that you can also enter or edit. So insisting that all I have to do is follow the sequence in the manual is nonsense and is why I posted the manual in the first place. I love going in circles. And no, that manual is NOT any better thany any other garbage Chinese-product manual.

Where this all goes south is if you turn right around and run the calibration again. Imagine that you realized something moved during the first time attempt. So you enter a new L. The DRO’s reaction is to refuse to accept what you entered, and instead displays some other number different from the actual length. In addition it changes S a little. I have not figured out what it is trying to do, but I have figured out that if you want to redo a calibration from the start, you first have to go in and set S to zero. Somehow that convinces it to accept your gage block’s actual length.

And by the way, it makes absolutely no difference whether you enter the lengths in metric or inches. If you look at the formula for S for a second or two you’ll see why. S is simply the percentage difference between L and L1 (with the decimal point shifted) and as such is unitless.

What about other DROs with linear compensation? Do they allow you to edit the compensation figure itself?
 

Winegrower

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I struggled to calibrate my Ditron system too, but got it eventually, doing just as I said. Bummer you're having trouble.

You do not have to calculate S. You only input the actual length, but in mm. You are correct, it’s a dimensionless number, but you don’t know how the software computes internally. Note the manual shows the range acceptable only in mm/m.
 
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maticulus

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I struggled to calibrate my Ditron system too, but got it eventually, doing just as I said. Bummer you're having trouble.

You do not have to calculate S. You only input the actual length, but in mm. You are correct, it’s a dimensionless number, but you don’t know how the software computes internally. Note the manual shows the range acceptable only in mm/m.

I purchased this Ditron 5 axis DRO for the PM728 mill for $161 and the price immediately went up on the website by $100 afterwards. I suppose the marketing strategy is to get one person to buy and mention it before going to the intended price point. I found this thread while looking for more info on the DRO;


I mounted a Harbor Freight digital caliper in a vise to check accuracy against the DRO and found the "Y" axis was off by +.0015. I tried to correct it using my understanding of the instructions and two value entries (L & S I believe) unsuccessfully and noted that "S" changed with just one value entry. After doing what you described, entering one value, the error corrected to within a few .000X as far as I can tell since the HF caliper only reads down to 5um increments, vs the 1um scales I'm using. The thousandths position is uniform and the overall measure probably more accurate than I suspect given the temperamental HF caliper.

The DRO works great so far as I can tell and is a lot more user friendly than the first DRO I purchased, which was returned under the impression of being defective as only two of the four visible axis would read correctly using the same scales. It turns out after the ease of adjusting the settings in the D80 I have now, that the problem may have been a combination of awful instructions which gave no info on how to get into setup, and no info on the password code it appeared to want. nothing I tried from existing procedures on the net worked and an ebay seller that had no clue as to how to get into setup and make crucial foundational changes didn't help either.

It was a great looking piece of equipment, but without the ability to access all of the parameters a bad deal. This is a heads up for others who might be drawn into it. SDS5-4VA.

 

ddickey

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Do you have any jo blocks or even 1-2-3 blocks? Using a caliper is not the way to check a scales accuracy.
 

JimDawson

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My question is, is there a failure mechanism with magnetic scales that debris can cause temporary and localized errors? That is the closest summary of my problem that I can give at this point.

I have noted that by pressing with a finger on the magnetic strip a few inches away from the read head will show a change in the DRO reading. Putting some wipers on either side of the read head might be helpful, but I have not seen a problem on my mill with the strip exposed to everything.
 

maticulus

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Do you have any jo blocks or even 1-2-3 blocks? Using a caliper is not the way to check a scales accuracy.

I do have the elementary blocks and will check calibration formally using the absolute method of measure. It actually escaped my mind that the comparison between the DRO and caliper is relative and both need to be checked against a calibrated length for individual accuracy.
 
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