DRO PRO UPDATE

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

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Mr Ron
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DRO PRO UPDATE

Post by Mr Ron » Mon Aug 24, 2020 11:21 am

It has been a little bit more than 2 years since I installed my 2-axis DRO PRO to my 6x26 mill. I was able to mount the X axis encoder to the front of the table as there was not enough room at the rear of the table. I had to make new brackets to keep the table locks accessible, but all worked out great. I still get readings "jitter" when I apply the locks, but I have figured out how to get around it; by going past the target reading, when I tighten the lock, the table moves to the correct reading. This seems to only affect the X axis, not the Y axis. Overall, I am very pleased both with the product and the way it operates. My machining "skills" have much improved. I would recommend that a DRO is a necessity on any mill and should be considered when getting a mill. DRO PRO has proven itself to be a great product for the money. It is not the easiest to install on any mill, but requires some ingenuity. You may consider this an endorsement of the DRO PRO from a happy user.
Mr.Ron from South Mississippi

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Bill Shields
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Re: DRO PRO UPDATE

Post by Bill Shields » Mon Aug 24, 2020 8:03 pm

question about the 'jitters'...which I see on the X axis of my lathe down in the .0001 digit fairly regularly..

what happens if you tighten up the gibs on the X axis a bit? do the jitters come and go?

I have found that when I get this problem (other than when drinking beer), it is because the 'head' is moving 'away' from the scale when the clamp is tightened.
Too many things going on to bother listing them.

Harold_V
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Re: DRO PRO UPDATE

Post by Harold_V » Tue Aug 25, 2020 1:25 am

I've commented about that movement before, which manifests itself when applying locks on mills. It's common when dialing in a hole, or sweeping the exterior of a round object. Makes it hard to end up on center unless you don't lock the slides.

You can consider this issue a design problem, as the lock works by loading the gib, which, in turn, deflects the slide. Not much you can do about it unless a different type of locking system is employed, or you operate the machine with the gib snugged up unreasonably tight, and even that doesn't work on an older machine, which has uneven wear, loose in the middle, as is so common.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

armscor 1
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Re: DRO PRO UPDATE

Post by armscor 1 » Tue Aug 25, 2020 1:44 am

I also mounted the scale encoder to the front of the table and can easily access the table locks.
The only downside I had to remove the table stops and the Power Feed stops.
My display also move slightly when locking the the table which is normal as Harold explained.

John Hasler
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Re: DRO PRO UPDATE

Post by John Hasler » Tue Aug 25, 2020 8:22 am

Harold_V wrote:
Tue Aug 25, 2020 1:25 am
I've commented about that movement before, which manifests itself when applying locks on mills. It's common when dialing in a hole, or sweeping the exterior of a round object. Makes it hard to end up on center unless you don't lock the slides.

You can consider this issue a design problem, as the lock works by loading the gib, which, in turn, deflects the slide. Not much you can do about it unless a different type of locking system is employed, or you operate the machine with the gib snugged up unreasonably tight, and even that doesn't work on an older machine, which has uneven wear, loose in the middle, as is so common.

H
I'm going to have to develop locks for my new mill table. It has no measureable backlash or freeplay but the table moves too freely to use unlocked. It came off an old Burgmaster CNC machine where they probably relied on the servos to lock it. I guess I could add brakes to the screws but I'd rather not load the nuts that way. Besides, it certainly has some backlash, even though I can't measure it. It uses shafts running in linear ball bearings: no gibs.

pete
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Re: DRO PRO UPDATE

Post by pete » Wed Aug 26, 2020 3:48 pm

I'm glad you started this thread Ron since I'm curious about what others are seeing for table movement on the display as those locks get tightened and what's normal. That 10th digit number on a dro can bounce around between two numbers sometimes unless that axis is fully locked and I'm guessing that's not at all unusual. Many I've seen on Youtube just use a piece of black electrical tape and cover that last digit since it's a bit distracting, or they change the dro's resolution range. But the dro display moving a few thou as the table locks are tightened probably isn't something that can be adjusted out on any machine no matter what type of gib or common table locking design it uses. Mine uses the usual tapered gibs and when new after I pulled it apart, thoroughly cleaned, relubed and adjusted it as closely as possible so there was no tightness, it also had no noticeable looseness that I could detect as the table moved. And I got the feed screw backlash down to right around .004" which was about half what the factory had it at. And that's apparently the same number Bridgeport's are quoted as having when new. So I think mine's about where it should be.

Mine has roughly .002" in the tables X axis and a bit less in Y as the locks get tightened. So far I've never seen a Bridgeport number for those yet. If the gibs are adjusted even a fraction more on my mill then there is noticeable drag starting to happen right away. I highly doubt I could gain more than a couple of 10ths better than that without creating much more slide and feed nut wear. I'm sure no expert in machine design, but any sliding surface has to have enough clearance for both the oil lubrication and to allow those surfaces to even move. So just like Harold said it should be considered normal and something that needs to be compensated for just as your doing if your location accuracy's are tight enough. This BP clone is the only one I've ever operated, so up to now I thought I could be missing something obvious. My mill only has ground way surfaces with no oil flaking at all. So part of that table movement might be from squeezing out the oil films a bit thinner. Maybe upper end machines with proper high precision scraped and flaked surfaces can be adjusted a lot tighter without creating any more drag? Even then I suspect there would still have to be at least some measurable table movement as the locks are applied. Fwiw my display is a bit more stable with that bouncing between two numbers when there's two vices on the table verses having one on it, so adding more weight does show some change. But I've never noticed that making any difference while locking a slide.

Mr Ron
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Re: DRO PRO UPDATE

Post by Mr Ron » Mon Oct 12, 2020 9:09 pm

I might also add that the most table movement I get when tightening the table locks is 1 or 2 tenths. When working to thousands, a few tenths isn't anything to worry about.
Mr.Ron from South Mississippi

jcfx
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Re: DRO PRO UPDATE

Post by jcfx » Sat Oct 17, 2020 9:22 pm

I'm with Pete about this thread, while I don't have a DRO Pro unit I have also noticed a number float when
locking the tables axis' I basically chalked it up to flex in my method of mounting the Y axis reader,
just finger tightening the Y axis lock I get .0005 movement but if I push on the reader mount I get a .0015
readout. I can zero it out again by nudging the Y axis mount to and fro .
Pushing the table doesn't change the reading from zero, but if twist the table by grabbing the ends
I do get a reading change. This is a Precision Mathews 932 mill.

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