Request for ultrasonic cutting

[farmersplow]

Request for ultrasonic cutting ???

When I came across the post: "DMM questions" in the "Vinyl Mastering, Laquer cutting, Pro's and others" section of this forum a few days ago, I asked myself the following question:

How exactly does it work with ultrasonic support?

With the DMM (cutting in copper), there were numerous modifications to the cutting head, the stylus and the audio control. This was necessary because the copper layer (exact material composition unknown) is much harder than the lacquer layer that was cut and you cannot cut as deep.

Since the depth of cut must remain the same, the raked angle is increased (the farmer drives his plow more brutally into the ground) and thus one can penetrate deeper into the material. To do this, a diamond is used (instead of the sapphire used in lacquer) and the geometry of the diamond is modified. This modification also includes the omission of the phase cut on the cutting edges.

However, this creates a new problem: the side walls of the cutting groove will no longer be "clean" and as smooth as with lacquer cuts.

Exactly the same problem is experienced by all those who cut with diamond in Pet-G or PVC. The "silent-cut" is never as "clean" as with lacquer cuts.

At that time, the problem was solved by additionally using an "overlapping" ultrasonic signal! From now on it was much easier to cut into the "hard" metal and also the walls became clean again.

But how exactly was this done?

I also researched that ultrasound was used (experimentally) for lacquer cuts before the time of the DMM. Frequencies from 25kHz to 40kHz were used.

I looked around a bit on the Internet and found a wide variety of ultrasonic cutters for plastic, paper, wood, rubber, metal and composites. In fact, with the support of ultrasound, you cut into the material much easier than without and the cuts become extremely clean.

e.g.:
https://www.sonotec.com/en/column/cutting_quality.html
https://www.youtube.com/watch?v=9LjhsWh3ixw
https://www.youtube.com/watch?v=FA46h7Db1BY

Now I was thinking, "What if I support my cutting system with ultrasound?"

• Will the cutting stylus then be more protected or wear out faster?

• Will the cut really be better?

• And if I want to use the system, how should an ultrasonic actuator be applied?

• In the X-direction, in the Y-direction or in the Z-direction?

• Or completely differently?

X_Y_Z.png

I don't know if anyone has thought about this before, or even has experience with ultrasound assisted cutting?

Since I am currently very busy with my project, I currently have an excess of lack of time. But there is still room in my mind for such fantasies and I would like to test the system. At the same time, I don't want to start from scratch.

So if someone knows something about it, please for information.

Kind regards from Austria
Thomas

[farmersplow]

No idea yet?

Is it possible that a high frequency signal (35kHz) was simply oversampled onto the audio signal and then an amplifier was used that can amplify up to 35 kHz (40kHz)? Could the driver coils have done this?

Greetings from Austria
Thomas

[farmersplow]

I have written:
…Since the depth of cut must remain the same, the raked angle is increased…

But I cannot confirm this statement. Further research on the subject only revealed that the vertical cutting angle (VCA also corresponds to the vertical tracking angle VTA) was reduced from 20° to almost zero or 5° and was compensated electronically.

I have not found out how the "raked angle" was changed.

Regarding "ultrasonic" the legends go from overhead signal 60kHz (via amplifier) to "controlled squeaking" by mechanical friction on the copper surface.

It seems to be one of those secrets that only very few people know.


WIKIPEDIA writes:
…where the mechanical audio modulation is cut onto a lacquer-coated aluminum disc, DMM cuts straight into metal (copper), utilizing a high frequency carrier system and specialized diamond styli, vibrating at 60 kHz[1] to facilitate the cutting.
https://en.wikipedia.org/wiki/Direct_metal_mastering


en-academic.com writes:
…examination of early DMM discs revealed what appeared to be a high frequency modulation in the groove, thought to be caused by the use of an ultrasonic carrier tone. In fact, there was no carrier tone and the modulation was simply caused by the vibration (squeal) of the cutter head as it was dragged through the copper disc.
https://en-academic.com/dic.nsf/enwiki/11064174

gammaelectronics.xyz writes:

Helping to keep the rotational force within normal cutting-amp power limits is the shape of the new Teldec diamond cutting stylus (Fig. 1). This stylus has no burnishing facets and thus avoids the high-frequency amplitude losses that occur at the innermost grooves of LP records.
While a 5° cutting angle (VCA or VTA) is employed, the IEC standard playback angle for consumer phono cartridges is 20° (VTA), and this must be factored into the DMM process. In addition, the grooves must be cut to meet that standard; other wise, playback would be severely distorted. Teldec gets around this dilemma by adding a tracking-correction element to the cutting signal. Said Shelton, "The deviation from the usual value of the vertical tracking angle is corrected by means of an electronic delay equalizer that is part of the system's electronics. It is called a Vertical Tracking Angle Converter, and it pro vides the correct playback angle for a typical phono cartridge through time delays." Shelton went on to explain that there is a marked difference between the styli and between the procedures used in cutting lacquer masters and DMM masters. "In creating a lacquer master, the sapphire cutting stylus must be heated to reduce hiss noise during cut ting. The recording engineer must strike a compromise between too little and too much heat. Too little increases noise, while too much erases the highest frequencies as they are cut and generates 'horns' [crests on the groove edges]. Horns degrade the quality and complicate the production of stampers, and create molding problems at the record press that lead to waste and higher production costs." Styli designed for lacquer cutting in corporate burnishing facets which smooth the groove wall for a quiet cut (Fig. 2) but also erase and distort high-frequency content on inner diameters.

audio_1987-04_dmm-f1-2.jpg

(left) Fig. 1-Cutting stylus for Direct Metal; (right) Fig. 2-Cutting stylus for conventional Mastering. lacquer mastering.

https://www.gammaelectronics.xyz/audio_04-1987_dmm.html


Greetings from Austria
Thomas

[selectavision]

Hi Thomas,
the "squeeking" is a result of " the cutter head as it was dragged through the copper disc".
(https://en-academic.com/dic.nsf/enwiki/11064174)

How the squeeking ist "controlled":

Afaik this is like scratching with chalk on a blackboard, which normally gives some HF-noise of undefined /unstable frequency, thus unwanted. The main thing is how to generate a stable "carrier"-frequency in the unaudible range of 40 kHz and without an external electrical ultrasonic generator. This was accomplished by proper design of the cutterhead. Especially by means of one component: the torque tube. The torque tube of a DMM-head was properly redesigned in terms of wall thickness, diameter and length so that it could resonate with the desired frequency in the transverse direction. The torque tube is the actual oscillator component (almost like a quartz - the comparison is of course not entirely correct, but anyway).
The amplitude of this frequency is determined by the friction of the stylus when cutting the groove into the copper. A deep cut will excite a large amplitude and vice versa. So friction is greatly reduced in deeper cuts. By this means the frequency remains stable because the mechanical properties of the torque tube are constant.
This is why DMM-cuts won´t work with a SX68, SX74 or heads alike.
Moreover in my opinion there´s no way to apply a carrier-frequency via the drive coils. Because the required amount of energy to excite the ultrasonic vibration would fry the coils within seconds as it represents a high burden additionally to the modulation load. So Redlich, Dickopp and Klemp of Teldec abandoned the idea of electrical ultrasonic excitation.
I haven´t got the VMS80 manual with the schematics but I´m sure theres no electrical bias oscillator in there like e.g. in a magnetic tape recorders.

Martin

[farmersplow]

Hi Thomas,
the "squeeking" is a result of " the cutter head as it was dragged through the copper disc".
(https://en-academic.com/dic.nsf/enwiki/11064174)

How the squeeking ist "controlled":

Afaik this is like scratching with chalk on a blackboard, which normally gives some HF-noise of undefined /unstable frequency, thus unwanted. The main thing is how to generate a stable "carrier"-frequency in the unaudible range of 40 kHz and without an external electrical ultrasonic generator. This was accomplished by proper design of the cutterhead. Especially by means of one component: the torque tube. The torque tube of a DMM-head was properly redesigned in terms of wall thickness, diameter and length so that it could resonate with the desired frequency in the transverse direction. The torque tube is the actual oscillator component (almost like a quartz - the comparison is of course not entirely correct, but anyway).
The amplitude of this frequency is determined by the friction of the stylus when cutting the groove into the copper. A deep cut will excite a large amplitude and vice versa. So friction is greatly reduced in deeper cuts. By this means the frequency remains stable because the mechanical properties of the torque tube are constant.
This is why DMM-cuts won´t work with a SX68, SX74 or heads alike.
Moreover in my opinion there´s no way to apply a carrier-frequency via the drive coils. Because the required amount of energy to excite the ultrasonic vibration would fry the coils within seconds as it represents a high burden additionally to the modulation load. So Redlich, Dickopp and Klemp of Teldec abandoned the idea of electrical ultrasonic excitation.
I haven´t got the VMS80 manual with the schematics but I´m sure theres no electrical bias oscillator in there like e.g. in a magnetic tape recorders.

Martin

Hi Martin,
that's super interesting! I already thought that it was produced with "controlled" squeaking, but the dimensioning of the torsion tube and its own resonances is just as comprehensible as it is interesting and ingenious!
Thank you very much for this explanation and for passing on this knowledge! Now I can sleep better!

Greetings from Austria
Thomas

[selectavision]

post scriptum:

How can it be done in plastics, e.g. PC etc.?

The amount of friction in plastics is not high enough to generate the ultrasonic oscillation of the torque tube, regardless of its dimensions. However, a solution could be to replace the torque tube with a piezo actuator that is electrically excited. Its dimensions should be chosen so that it resonates at the desired excitation frequency in order to ensure maximum amplitude. Bimorph piezoelectric actuators may be usable here. But that's purely speculative...

Martin

[farmersplow]

That's a very good idea and a sensible approach!
I have already looked into this.

https://www.all-electronics.de/elektronik-entwicklung/prinzip-auswahl-und-design-von-piezoelektrische-aktoren-387.html

My fear is that the torsion tube will then be too heavy. But it will be worth a try! (Probably the most likely option).

I have also considered having a kind of "feed ball" rest on the record blank and transmitting the ultrasonic signal via this.
I have also considered attaching a piezo directly to the cutterhead housing (in the longitudinal direction - in-line with the torsion tube).

However, I won't get around to testing this this year.

Thank You
Thomas

[selectavision]

Hi Thomas:

maybe one could try this:

https://www.piceramic.de/de/produkte/piezokeramische-komponenten/rohre

They can manufacture those ceramic tubes in small dimensions and with different configurations of the elektrodes. Ceramics are stiff and lightweight. A possible direct replacement of the original torque tube. The only thing needed ist a cheap stereo-cutterhead to be cannibalized...

Martin

[farmersplow]

WOW! That looks very promising. It seems to be a good way to move the torsion tube 9µm back and forth. Since I develop and build my own cutting heads, I will adapt the torsion tube and its holder accordingly. The only thing that makes me a bit nervous is the required 500V voltage. But you're right, it shouldn't be a problem in terms of weight. And it is anti-magnetic!
If only I had a little more time... I would start researching tomorrow. But this way the seed can continue to germinate in my mind...

Thank you