Newall DRO Adjustment

[MetalhackerParticipant @metalhacker]

I have a Newall dp700 fitted to my Boxford VSL. It has never given accurate readings on diameter. If I move the cross slide 10mm inwards to give an overall cut of 20mm dia, it reads 17.68. This was measured with a mitutoyo dial gauge so should have been accurate. I have followed the recalibration instructions to no avail. I have tried earthing the output screen to the lathe, which has not improved things. Does anyone have any ideas about how to resolve this. While I work in metric it is less of a problem but it makes imperial dimensions rather difficult!

Andries

[Peter Cook 6Participant @petercook6]

Is the error consistent, i.e. every time you move 10mm you get the same 17.68 reading? Does the error vary depending on the starting point? If it’s consistent it would seem to rule out noise/earthing issues. Those would tend to give more random  errors. Is the Error linear, i.e. if you move the cross slide only 5mm is the error halved?

When you say you have followed the recalibration instructions, have you checked that the encoder choice is correct? Have you looked at the linear compensation screens to make sure that no corruption has crept in.

The fact that it has never worked correctly points to either a faulty or mismatched encoder.

What happens if you swap over the channels so that the other channel sees that encoder. Do you get the same errors?

Edit – there is what appears to be a fairly detailed user manual here

[ZanParticipant @zan]

I’ll check mine in the morning. but just a current thought, is the resolution of the controller set to the same as the scale.? I seem to remember that is one of the  important early setting during “set up”

[MetalhackerParticipant @metalhacker]

Thanks Peter, sorry to take so long to get back to you. Yes the error is consistent and is half for a half distance. Have been through the set up and error correction instructions with no effect. Could try the alternative setting for the scale to see if that helps though. Will keep you posted, but don’t hold your breath, I don’t get out to the workshop as often as I would like!

[Peter Cook 6Participant @petercook6]

No problem. From this distance my best guess would be that the encoder type is set wrongly. There is little technical information on the web about the signalling Newall encoders use. They do make specific types that use industry standard quadrature encoding, but they also make others specifically for their head units, and I suspect they use different signalling.

The fact that you get a consistent error suggests a decoding issue where the head unit is expecting more signals/mm of movement than your scale is generating. But its not a simple 1 micron vs 5 micron deviation or similar but something more subtle.

Good luck.

[Nick HughesParticipant @nickhughes97026]

Also (As Peter posted previously) beware that the “Microsyn” and “Spherosyn G2” are different and also the range of resolutions available, vary between the types (See page 9 of the manual)

[Clive Brown 1Participant @clivebrown1]

MachineDRO, who have a good reputation are Newall dealers. Might it be worth asking them nicely, they could be helpful on this rather strange problem?

https://www.machine-dro.co.uk/pages/about-us

[Neil LickfoldParticipant @neillickfold44316]

Check the settings page, that you have selected the correct scale type selected. Also check, that at this stage there is no error compensation added .

[Neil LickfoldParticipant @neillickfold44316]

https://www.machinetoolproducts.com/content/Newall/DP700%20Manual.pdf?srsltid=AfmBOooApwpj4NwYalJ2BBAaHR-wkEzOM_WJpYkXpKO5MfmKtAMramsB

The link is to a pdf manual that you most likely have.

Page 3 has the input scale type and resolutions that the Display is compatible with.  This is them here.

Only Spherosyn or Microsyn encoders can be used with the DP700 DRO
Input and Resolutions
Spherosyn 2G or Microsyn 10  ,5µm (0.0002″), 10µm (0.0005″), 20µm (0.001″), 50µm (0.002″)

Input & Resolutions
Microsyn 5 , 1µm (0.00005″), 2µm (0.0001″), 5µm (0.0002″), 10µm (0.0005″)

Page 7 has the setup information.

You need to enter the 4 digit code to get to the setup. The default 4 digit code is 1937

Then goto the Setup encoder, and toggle through the 3 options,

SPH 2G (Spherosyn 2G),

USN 10 (Microsyn 10),

USN 5(Microsyn 5)

Then set the SetUp Resolution and toggle through to match that of your scales.

By default there is no linear compensation set.

The most common cause for the scale reading being out is an incorrect scale setting.

We have the power go out at work, and sometimes it does not save the encoder information. So every once in a while  it requires to go back into the parameters and needs to be reset to the actual units. We have the Microsyn 5, 1um for the cross slides, and the Microsyn 10 , 5um for the carriage. We also have  the DP1200 on some lathes too.

1937 is the code required for all of them at work for any changes that need to be edited. Each has it’s own little book of Settings and the encoder type fitted to that machine.

None of the 4 lathes are requiring to use the error compensation.

This should get you in the right direction.

 

 

 

 

[PeteParticipant @pete41194]

Your DP 700 is from what I can find a current and still in production model Andries. If it’s never worked correctly, the first thing I would have done would have been to contact Newall directly within at most a day or two of first noticing any errors. I’d still do exactly that after writing down the displays serial number and all the data on each of the reader heads. Whatever the real issues might be or possibly due to the initial dro set up, almost for sure Newall can talk you through the possible causes in a very few minutes. I’d also guess there dro’s might have built in diagnostic screen displays that aren’t detailed in the users manual. So talking with there own tech support might be the only way to get the correct input codes to even access that feature.

Newall has from my own experience extremely good technical support. I’m unsure about what those DP 700 models have, my own DP 900 came with a USB port. Maybe unlikely I suppose, but it’s still not exactly impossible yours might have some partial or corrupted data programming. However I’m also unsure if that’s the case, your dro might or might not be capable of being double checked and reprogrammed while linked into Newalls tech support. I do know any dro updates can or at least could be done using that method at one time, and as far back or maybe further than the Newall C80 models. I used a very good set of gauge blocks to double check all 4 axes for my own Newall and it’s error compensation. Fortunately mine didn’t need any adjustments. But much of it might be due to how well the scales and reader heads were aligned since I spent a lot of time on that.

Afaik, Newall reader heads use multiple pickup coils, 6 if my memory isn’t faulty? They generate and detect the signals for each of the ball bearing positions along each of the radi and for each ball bearing. A quite clever method that’s far more complex than I’d first thought when buying mine. Fwiw, this is still only a rough and best guess, but if one of those pickups isn’t working. That might also be a cause of your error?

[MetalhackerParticipant @metalhacker]

Thank you Peter.
The DRO was already fitted when I bought the lathe from Hugh Gilhespie, almost 10 years ago. They were allegedly installed by Newall’s initially. However initially I never got round to doing anything substantive about them. However now my eyesight is failing their proper functioning is more important. I will do as you say and contact Newall for some help.
Thank you for your detailed help and information
Best Wishes, Andries
Sent from my iPad

[PeteParticipant @pete41194]

Your more than welcome Andries, but like I said, anything I might suggest are a best only guesses. With a used lathe and dro, then you have some viable excuses for putting the problem off. But it’s somewhat logical that the reader head might also have suffered an impact while moving the lathe. I’ve never really examined my own microsyn reader heads, so right now I’m still unsure if they can be taken apart just to visually check the wiring into each one of those pick ups. I’d suggest that double checking the multiple connection pins on the reader head cable for any that feel a bit loose compared to the rest might not be a bad idea either. Are you 100% sure that the reader head hasn’t moved or the problem scale might have been bent a bit? Newall dro’s have some fairly precise requirements for the concentricity between the reader heads and the scales.

Your user manual should give the maximum allowable deviation for your scale alignments. If I recall correctly I think that’s all supposed to be within or under .001″. Once your dro is working as it should, I’d want to indicate each scale in both directions to be sure everything is still aligned as well as possible. Even more so since the lathe has been moved at least once since the dro was installed. The Newall scales and reader heads are in theory almost impervious to swarf or contamination, but that’s true and only in a mostly static position. Moving a used machine and dro? It’s hard to say for sure that’s 100% true. Even less so if the machine and dro were moved and exposed to winds at highway speeds if it wasn’t already inside an enclosure. My mill for example, somehow gets metal chips up and inside the table casting, and that seems impossible it could ever happen. A tiny piece of metal swarf in the wrong place might also be just enough to block one of those pickups? Fortunately this seems to be a consistent issue for your dro, so hopefully it shouldn’t be that tough to find the cause.

 

[SillyOldDufferModerator @sillyoldduffer]

My brain is stewed again, so this may be nonsense!

17.86 on a travel of 10mm is:

1768      221
——  =  ——
1000      125

A denominator of 125 suggests a power of 2 relationship  (1000/125=8), hinting this a partial fault with the digital number sent from encoder to head.  The fault could be the number generated by the encoder OR a bad connection in the plug/sockets OR a problem with the cable, OR a problem in the decoder in the DRO electronics.

I suspect something mechanical, damage caused when the lathe was moved, dirt, or maybe old age.

Unplug the cable, check both ends for a bent pin or dirt, give the connectors a squirt of switch cleaner and reseat.

If that fails try and isolate the fault, for example, does the DRO measure correctly if the other encoder is plugged in (swap X and Y)?  Swap the cables and check end-to-end continuity with a multimeter.  If no joy, not something simple, job for an expert.  This being a pricey DRO, at least one firm repairs them.   Seems to be Price on Application…

Dave

 

 

 

 

 

 

 

[Neil LickfoldParticipant @neillickfold44316]

Did you find the solution to this DRO problem.?

Cheers Neil

[MetalhackerParticipant @metalhacker]

Sorry to have been quiet for so long, been away. I had always been suspicious that the measuring  scale(rod) was not parallel to the cross slide, but had been reluctant to take off the protective shield ( ali angle) because it was so convoluted to get an allen key in to take it off. When it was off my fears were justified as it was 0.15 mm further from the cross slide at one end than the other. I machined up a small gauge block which I used to match the distance at each end, and then re setup the scales. Now about .02 mm out on length and similar on diameter, which is fine. Also found out it has a microsyn 10 scale, which is useful to know for any further adjustments that may be necessary. Thank all of you for your help.

Best, Andries

[Author]

Posts