Need some tech knowledge that missing (or hiding real good)

[Human2]

Hi there,
I've been looking around for days, hopefully somebody here will know.
Is there any difference in the tolerance (the error range of the cutting) between the neumann vms machines? And scully? What is the tolerance of them any way? What do you think is the upper border of the tolerance that can be, without sound digrade? (Listening by human ears in very good shape).
Have fun (:
Me.



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[Human2]

Nobody knows??? Im impressed.

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[markrob]

Hi,

You received no answer because your question is not answerable. What cutting tolerance are you talking about?? There many parameters that could be variable in the system. If you want a serious answer, you need to pose a question that makes sense.

Mark

[Human2]

If you make 2 lathe cuts of the same master in the same machine (let say vms 80) .
There is a so little differences between them, micro one, But still there is a difference. The lathe is such machine that has to be a tolerance, no lathe existed that will do exactly to the 0.000001 mm the same work again and again.
The amount of the difference available is the tolerance.

The same question in another words:
Let us say the groove width at contact point is 0.0254, what will happend if it will be 0.024 for example? And 0.023? What is the error limit that will not be noticeable by hearing?

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[markrob]

Hi,

Seems like you are asking what the tolerance is for the depth control system. I don't know the answer, but I don't think it matters within reason. If the cut depth at a given point in time is a bit different than another cut made under the same conditions, the playback stylus will just ride a bit deeper or higher in the groove. That should make no difference at playback unless the depth gets so large that the stylus bottoms out or is so shallow that is can't track the groove.

Mark

[Greg Reierson]

And it would be swamped by lacquer variations.

There are probably 100 terms to define to get closer to an answer. You have defined one so far (width/depth.)

What is the goal of your question? Are you building, buying, re-designing, just interested?

[markrob]

Hi,

I wanted to make a correction to my last post. The stylus will never bottom out. In fact, it will always find a level that is the same distance from the bottom of the cut groove. As the groove widens, the playback stylus will ride lower referenced to the top surface of the record, but the distance from the contact point to the bottom of the groove will remain the same provided the cutter and playback stylus have no change in their geometry.

Mark

[Human2]

Thanks a lot mark! I think you have answer my non so simple question.
Greg, does it matters who am I? Will the answer be different to each person you have mantion? (: well, im not just interested, I was really interested (: now im full.
Thank to all of you guys!

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[Greg Reierson]

Who you are doesn't matter at all but understanding your goal would help us figure out how much detail you are looking for in an answer.

The more time you put into presenting clear questions, the better and more useful the answers will be.

[Human2]

There is no clearer question on lathe machine then "what is the tolerance?" every lathe machine in the world has this info in her preferences. only this way, the costumer know what he buys.
You can check it out. Just for. Knowledge, most of the lathe machines in the world have a 0.05 mm tolerance. The means, that if you want 2 meters of a shape, it possible to get between 1995 mm of a shape to 2005 mm.

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[Human2]

Sorry, its wrong. I mean, between 1999.95 mm of a shape to 2000.05 of a shape.

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[concretecowboy71]

The question makes no sense at all. Other lathes cut material like metal that does not deviate from a norm. The lacquers that we cut on vary in thickness and flatness all of the time. A dashpot is used to try and compensate for some of the inconsistencies but we see deviation from lacquer to lacquer. We have the ability to set our pitch and our depth. Time and experience are what drive my decisions in regard to cutting depth. If you work with a mastering lathe, you will know that NOTHING can be taken as "standard".

I would say that the skill of the cutting engineer has more to do with results than any kind of standard we might toss around about these machines! Some are over 50 years old!

[audiocarver]

I'm not sure if I understand the OP question exactly either, but I think what he's asking is if manufacturers of disk cutting lathes had a repeatability tolerance from one manufacturer to another.

IMHO, audio disk cutting lathes were never really sold like a milling machine or engine lathe found in a machine shop where you could, and needed to, get direct process repeatability from cutting one part to the next part within a certain tolerance range and achieving certain level of throughput weather you made 1 or 5,000 parts with the same machine or a machine made by another manufacturer.

With audio disk cutting lathes, from disk to disk, you can get close with settings, but the tolerance variance between blank disks as well as the actual audio being cut and limitations of individual cutting heads and amplifiers used and such.

In other words, unlike with an engine lathe or milling machine, with disc cutting lathes, you're not just machining a groove, you're making the groove to give a level of quality to the audio signal being cut.

[mossboss]

Well the question most likely arises from the term " lathe" it is a fair question if one is comparing lathes
It would also be fair to say that on a DMM machine with carefully controlled copper masters an answer could be given
So say that we cut a 1 k tone at a fixed pitch having set land and depth of cut one could determine the tolerance of repeatability.
Add a modulated signal to the mix than the answer will be the same by taking as a previous poster indicated a whole host of parameters so as to provide an answer
At the end of the day we are dealing with microns a far better tolerance standard than any engine lathe can produce consistently
On the other hand we are playing back with microns so it becomes a complex case of, yes this is the tolerance under such and such conditions and the tolerance will be X
Not sure what this knowledge would achieve in any case, suffice to say that it will be an extremely close repeatability within microns given the parameters are set exactly the same in each test with the copper masters checked for flatness as well as thickness so as variations can be accounted for
The task will have another level of complexity when it comes to lacquers which are so variable as every cutter knows no doubt about that.
Could we say it is an academic question, do they ever have an answer?
Best
C

[Sillitoe]

One could use a C0 rated ballscrew (aerospace grade) for the carriage drive, producing a lead accuracy/ cut reproducibility with 3.5um fluctuation and 4um travel distance error (specs for 200-300mm screw length)... Also dependant on pitch motor accuracy.
Expensive stuff!

Then there are all the other variables...

Cheers
James

[Voxster1965]

Sounds like my old job - getting deja vu - I think the appropriate methodology would be to conduct a gauge repeatability and reproducibility study to determine the percentage of variation attributed to AV (Appraiser Variation - the operator or metrology person) and EV (Equipment Variation) attributed to the tolerance width. Essentially 3 operators would conduct three trial cuts per lacquer and repeat this experiment 10 times (i.e. 10 lacquers in total with 90 trial cuts in total). From this the Grand Mean per lacquer (average of the average) can be obtained for each lacquer and each trial, and the Average Range can be obtained for each appraiser. You would still need to select arbitrary specification limits (e.g. groove width). Usually a result of less than 10% of tolerance attributed to R&R is acceptable in my old world of automotive and defence engineering.

https://www.spcforexcel.com/knowledge/measurement-systems-analysis/three-methods-analyze-gage-rr-studies

Another methodology is to use Cpk (Process Capability) indices. This is how well 100 or 300 samples of, again lets say groove width, satisfy normal distribution rules (68% of the data within +/- 1 standard deviation of the mean, 95% of the data within +/- 2 sd's from the mean and 99.7% of the data within +/- 3 sd's from the mean) within a tolerance band and are of a sufficient distance away from both specification limits. Usually a Cpk of >1.67 is adequate for most processes.

http://www.isixsigma.com/tools-templates/capability-indices-process-capability/process-capability-cp-cpk-and-process-performance-pp-ppk-what-difference/

Again, with any statistical analysis, you need to be sure what you are measuring is worthwhile in obtaining fit for purpose product (i.e. the definition of "Quality" is complex as it was initially defined by Deming as "Quality is determined by the Customer" (or satisfying continual improvement requirements). So - what are the key factors that determine good vinyl - measure that - that's worthwhile.