Turning with micron precision

[jscpm]

This is pretty cool:


It's a two ton copper roll used to produce films for large screen TVs. The spindle, made by the Swiss company TDM SA, runs so true that it can turn sub-micron finishes and micron level concentricity, no grinding involved.

The spindle has a plain journalled bearing. Kind of surprising it works because we know journal bearings are for "cavemen" who need to "stop using 19th century technology" and real machinists use roller bearings.

 

[Halcohead]

This is pretty cool:

View attachment 369798
It's a two ton copper roll used to produce films for large screen TVs. The spindle, made by the Swiss company TDM SA, runs so true that it can turn sub-micron finishes and micron level concentricity, no grinding involved.

The spindle has a plain journalled bearing. Kind of surprising it works because we know journal bearings are for "cavemen" who need to "stop using 19th century technology" and real machinists use roller bearings.

Pretty cool machine, thanks for sharing. One of the larger lathes of this type I’ve seen.

I’m almost certain it’s not a simple “plain journaled bearing”, but an air bearing spindle. Aerostatic spindles are the gold standard for precision spindles (eg commonly used in semiconductors where they seek roundness in the 10-nanometer range), and pretty incomparable to the hydrodynamic spindles that are considered “19th century technology”.

With that said I wouldn’t be surprised if my 1960s south bend’s plain bearing spindle had lower radial error motion and asynchronous runout than the brand new Okuma turning center at work.

 

[jscpm]

...
I’m almost certain it’s not a simple “plain journaled bearing”, but an air bearing spindle. Aerostatic spindles are the gold standard for precision spindles (eg commonly used in semiconductors where they seek roundness in the 10-nanometer range), and pretty incomparable to the hydrodynamic spindles that are considered “19th century technology”.
...

It's not an air bearing. Air bearings cannot hold up 4000 pound rolls. It's a plain journalled bearing with pressurized oil.

 

[jscpm]

High load applications are usually not done with air spindles. The spindle and tailstock shown in the photograph at the beginning of this thread are journalled bearings supported by pressurized oil, which economically enables high precision turning with heavy axial loads.

 

[Robert R]

Hydrostatic bearings are not journal bearings. Journal bearings require relative motion between the shaft (journal) and the bearing shell to produce the fluid pressure supporting the shaft. Hydrostatic bearings have a external fluid pressure source and do not require relative motion.

Air spindle bearing lathes such as the Precitech Nanoforms use hydrostatic slides with built in linear motors and encoders to support the cutting tool. The spindles are capable of supporting the cutting forces needed for turning optical surfaces to 0.1 micron accuracy with .001 micron surface finish. The bearing clearances in a aerostatic spindle are smaller than those in a hydrostatic spindle. The clearances are a function of the working fluid viscosity.

Nanoform 700 ultra – Multi-Axis Ultra Precision Machining System

Lathe machine with large swing and load capacity to produce optical lenses, optical mold inserts, mirrors, and mechanical components

www.precitech.com

A hydrostatic spindle lathes such as the Hemburg Mikroturn also uses hydrostatic carriages with linear motors similar to the Precitech design. A hydrostatic spindle is used in this application because, with the same dimensions of a aerostatic spindle, it can support much higher loads.

These lathes can produce parts much faster than grinding and still maintain dimensional accuracies of 2. microns and surface finishes of 0.1 micron that approach those of grinding. For some applications, the combination of faster machining and good enough accuracy can provide significant manufacturing cost savings.
A copper plated barrel shaped roll would be a challenge to grind. Diamond turning machining is a better choice.

Mikroturn® | Danobat

Hembrug Mikroturn® horizontal ultra-precise hard turning lathe for hardened workpieces up to 70 HRC. Visit us for more information.

www.hembrug.com

The Hemburg lathe has a very large oil chiller (not shown in the product description) that is required to control thermal expansion in the spindle. A small difference in temperature between the spindle and bearing shell would cause the assembly to lock up. The air bearing spindles are self cooling as long as the inlet air pressure and temperature is within specification.

For the copper roll machining application JSCPM describes above a hydrostatic spindle is a lower risk choice for a custom made machine tool. A equivalent load capacity aerostatic bearing would be much larger and much more expensive, The aerostatic bearing is working with fluid pressures in the 100 psi range. The hydrostatic bearing is working with fluid pressures in the 1000 psi range.

 

[MCritchley]

Anyone consider asking the manufacture about their spindle?

 

[TGTool]

Anyone consider asking the manufacture about their spindle?

Much more fun to piss and argue. Why stop the party?

 

[Bill D]

Anyone else notice this thread is just before the which $1,500 China lathe should I buy thread?
Bill D

 

[Halcohead]

For the copper roll machining application JSCPM describes above a hydrostatic spindle is a lower risk choice for a custom made machine tool. A equivalent load capacity aerostatic bearing would be much larger and much more expensive, The aerostatic bearing is working with fluid pressures in the 100 psi range. The hydrostatic bearing is working with fluid pressures in the 1000 psi range.

Thanks for the well-informed post Robert. My mistake you’re definitely right, this is using a hydrostatic spindle, not aerostatic. Another point in favor of a hydrostatic spindle here is it needs load capacity over speed. Aerostatic tends to favor higher speeds and lower loads, hydrostatic being the opposite.

Also, FWIW TDM mentions copper roll turning hydrostatic spindles on their website. No mention of aerostatic anywhere. http://www.tdmspindles.com/hydrostatic.html

Relatedly, I recently encountered a bearing manufacturer who makes custom ABEC-7/P4 bearings using hard-turned races, no grinding involved. I thought it was pretty cool to find out hard turning has reached that level of quality.

 

[jim rozen]

New hampshire ball bearing has been hard-turning all their parts for years.

 

[GregSY]

I'm kinda surprised it doesn't use magnetic bearings.

As for journal bearings, the vast number of serious machinery uses non-rolling element bearings...they all use hydrodynamic bearings. By 'serious' I mean high load, high RPM rotating equipment like turbines, compressors, motors, generators, etc. Go tell a manufacturer they need to build a 50MW 3600RPM generator that meets API vibration specs and you want ball bearings. They'll show you the door.

But...I have to wonder if that lather really uses 'plain' journal bearings or something like a tilt-pad journal. I guess the RPM is pretty low so a plain journal might work OK.

 

[fmari --MariTool-]

My Toyoda CNC cylindrical grinder has hydrodynamic bearings for the wheel head. When pressurized and belts removed from the electric motor just one little nudge of the 20" grinding wheel will make it spin for several minutes. Tech who installed the machine said as long as you maintain the oil bearings will last forever. They pulled a machine running 24/7 for 25 years in automotive plant. Bearings measured like factory new.

 

[Robert R]

Toyoda uses a combination hydrodynamic - hydrostatic bearing on their belt driven wheel heads. The external pressure source is sufficient to float the spindle while the spindle is stationary . This eliminates bearing wear when the spindle is brought to a stop. During operation the hydrodynamic pressure generated by the moving journal provides the additional pressure required to support grinding loads.

Three Pillars of Toyoda Grinding Machines

Our grinding machines legacy is founded on the TOYODA STAT® BEARING, FLOATING PLATE BALL NUT and CONVERSATIONAL CONTROL. These patented technologies optimize performance of Toyoda grinding machines and long-term machining accuracy.

www.toyoda.com

 

[Robert R]

Hello Barbter:
The lathe can be purchased from Moore Tools. It is called the Nanotech HDL-2600
There is some product information in the PDF. Keep in mind that many of these diamond turned products are made up of a stiff substrate with a thick plating of nickel, copper, or gold. The diamond turning lathe is machining the thick film. The substrate was machined to the required geometry by conventional machine tools.
The accessories for these lathes include a piezoelectric driven single point cutting tool.
The 2005 model:

https://www.nanotechsys.com/wp-content/uploads/2010/08/Nanotech-HDL2000_HDL2000-HD-Machine-Features-Rev-0914.pdf

The current model:

HDL 2600 | Nanotech Ultra-precision Machining Systems

nanotechsys.com

https://nanotechsys.com/hdl2600-large-scale-drum-lathe-machine-accessories/

And a video of it in operation:

https://nanotechsys.com/hdl-2600-drum-lathe-machine-videos/

The lathe is being used as a ruling engine to engrave the copper drum. The drum will be used to print ( emboss) the grating on a roll of plastic film
The film can be purchased in small quantities on Amazon. The search phrase is diffraction grating film

 

[jscpm]

The lathe I linked is not a Nanotech lathe. The Nanotech lathe does use a hydrostatic bearing like the one I linked, however.