Glass scale (DRO) problem

[David ColwillParticipant @davidcolwill19261]

Hi All,

I have noticed a problem on the Z axis ( lathe carriage ) of my Sino DRO. When moving near the chuck a random error of between 1 mm and 8 mm is added or subtracted from the true value. I have 2 bed stops and have set these up to do the tests. The scale is fine further up the bed. I do use coolant when parting and although the scale has a protective cover I doubt this is 100 percent effective.

So, I suspect that dirt has got onto the scale. Has anyone any experience of cleaning these scales? Or any ideas as to how to proceed?

The DRO is about 8 years old so it certainly doesn't owe me anything and I am prepared to buy a new scale if necessary but would rather spend the money on something else.

Many thanks in advance.

David

[David ColwillParticipant @davidcolwill19261]

[MWParticipant @mw27036]

The rubber seals eventually will perish/encumber with swarf in the long run i guess, its a good question because my lathe glass scale, similarly on the Z axis is only protected by the rubber seal but is only over a year old, i always worry about the collection of dirt that might be mounting up inside it. Sorry i cant be of help with regards to cleaning.

Michael W

[Michael GilliganParticipant @michaelgilligan61133]

David,

I confess to the 'armchair' position on this [all the scales I currently use on machines are purely mechanical], but you might find it interesting to read my exchange with Jon, on this earlier thread.

Jon did not report back, so I have no idea what results he achieved.

MichaelG.

Edited By Michael Gilligan on 18/02/2016 11:12:05

[Anna 1Participant @anna1]

Hi, David,

I have Sino scales on my mill and had a similar problem recently on the y axis with misreading. (after machining C.I.) Since it wasnt working properly like you I felt there was nothing lost in taking it apart.. the small end cap is bonded in place quite firmly, I guess to seal it, and takes some gently encouragement to remove and break the seal Slide the reading head out very carefully taking note where the very tiny bearings and lever run. The reading scale on mine is bonded in along its length at about 45 degrees although I seem to remember someone else talking of being able to remove their scale ( may have been a different make or model). Attach a piece of lense cloth to cover the end of the a long piece of obeche strip or similar and soak cloth with isopropyl alcohol very very gently wipe scale and reasemble You probably wont have the original quality of seal but the seal still seamed good. It worked for me and no further problem, but I might have just been lucky.

Kind regards

Anna

[Clive HartlandParticipant @clivehartland94829]

Use Ether for cleaning glass scales if you can get it. attach very thin chamoi leather to a wooden stick and make it about 3mm wide by about 10mm..

Wash the leather a few times in ether and shake to get any pieces off and then use that to clean the scales with a lightly moist chamoi. Dip in ether and shake  till almost dry.

A pegwood stick can be thinned to size and the chamoi glued with super glue, let dry thouroghly before use.

Edited By Clive Hartland on 18/02/2016 14:26:00

[JonParticipant @jon]

Posted by Michael Gilligan on 18/02/2016 11:06:00:

David,

I confess to the 'armchair' position on this [all the scales I currently use on machines are purely mechanical], but you might find it interesting to read my exchange with Jon, on this earlier thread.

Jon did not report back, so I have no idea what results he achieved.

MichaelG.

Edited By Michael Gilligan on 18/02/2016 11:12:05

As I have to do almost yearly, take the end caps off scale and slide out the glass, clean soapy water and dry off, job done nothing more. This usually happens on the mill vertical scale only none of the others on X and Y plus almost continuous X axis lathe with coolant.

Also add if sporadic upon install earth the readout it will have a tag for that purpose.

 

Edited By Jon on 18/02/2016 15:45:54

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Jon

Good to know that they appear more robust than theory might suggest.

MichaelG.

[Johnboy25Participant @johnboy25]

Is this the same construction of Heidenhain dro slides? I have a couple – the longest one has the rubber seals completely disintegrated. I haven't found any info on the web regarding stripping them down to repair or clean them as yet. I did want to start the job without an idea how they came apart. 😳

John

[KWILParticipant @kwil]

This might help

**LINK**

[Johnboy25Participant @johnboy25]

KWIL – thanks for that… Just found some clips on YouTube featuring Hiedenhain encoders.

J.

[MuzzerParticipant @muzzer]

Dunno if the Sino scales are like my Chinese glass ones (Sino = Chinese?) but I was able to dismantle and shorten one of mine without issue. Pictures here. I found a several fine sets of fingerprints from the person who assembled it and was able to clean them off easily.

The mounting orientation and protection from flying swarf and coolant is critical. Although the scales and read heads are fitted with lip seals, they are a long way from being sealed.

Murray

[JonParticipant @jon]

Fairly similar Muzzer except the Sino glass is at 45 degrees.
Just a lip seal on underside the read head parts but these should be covered over any way. Flood coolant masses of swarf theyre fine.

The Sino on the mill that plays up is only the vertical scale well above the cutter and to the side immune to coolant but gathers a grey powdery substance on the glass. Does get some use perhaps 1 week the average model engineers use in 12 months so much so its worn the quill casting years ago for compare.

[David ColwillParticipant @davidcolwill19261]

Just a quick follow up to this.

I removed the scale, took off the end caps and removed the reader head. I then stuck it in an ultrasonic cleaner (it had to be turned round as it wouldn't fit). Finally I poured about 2 litres of clean hot water (about 70c) down it.

Result, it now works fine.

Regards.

David.

[JonParticipant @jon]

Good to know David, it usually works for me.

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