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Tidbit 14: Ground surfaces go together better than lapped surfaces Can anyone explain this?

Remembering a previous life, in the previous Century, in Silicon Valley. For the HP 5528 system, designing a custom 68K board to fit the mainframe, controlling a linear motor X Y stage on an air bearing platen to scoot wafers around, hopefully faster than the competition. Became the Ultratech Stepper model 2000. Great fun, commercial flop. Stumbled across it in the Tech Museum years later... But, watching the phase wiggle of the measurement channel on the scope, in response to the footsteps down the hall, was a mind blower to my young imagination..!

Sir how to make it?

I have an idea of how or what can be causing the blemishes. Wherever you are doing your maching (lathe setup location) could be getting vibrations from something as minute as a A/C unit on a house running could potentially cause blemishes on a micron level, so pretty much any other machines or appliances running or even talking to a friend in the vicinity of operation can result in acuastic resonance in the tooling or the oarts being machined. Thats why if you ever go to a professional manufacturer of these telescope mirrors they have clean rooms that are also acoustically cut off from the outside world that is if they are making mirrors in the same manner as diamond lathe, but there is also lapping of mirrors. But what im trying to get at is next time you machine a mirror turn off any other known electrical sources even the a/c on your house and see what the results are

Nice,thanks for sharing those books with us.I have one of them.

What were you studying formally?

hook us up with some cad bro!

Excellent list. Also worth checking out is... "Instruments and experiences: papers on measurement and instrument design" by R.V Jones. Hard to find a physical copy, but has recently appeared in digital form and can currently be loaned from the internet archive. Another worth mentioning is.. "Know your machine tool" by Tim Sheridan. All about using capacitive gauges to measure machine tools, can be downloaded from the Lion precision website for free.

Love this discussion-- My university is heavy on fluids theory and light on mechanism design, so finding a list of books like this is an great resource. Thanks again!

Supposedly the only copies of Precision Machine Design are actually on sale by Slocum himself.

1 book on your list I didn't have... hello book order. On the optics side a bit more: Optical Shop Testing by Malacara, Optical Methods in Engineering Metrology by Williams, Optical Tooling for Precise Manufacture and Alignment by Kissam. That leads to the rabbit hole of astronomy and lens/mirror making.

Machine tool reconditioning and applications of hand scraping by Edward F Connelly is a good reference on measuring and adjusting machine geometry for dovetail slideways.

Nice collection. I'm Jealous. Hope you keep your videos going there very interesting

Holy bank robbery Batman..... these damn books are expensive.

Prof. Alex Slocum is the GOAT

Also from me congratulations on your graduation!🎉

Excellent list, hit all the classics "Principles and techniques for designing precision machines" Layton C. Hale PhD dissertation is an excellent overview similar to Slocum. Some great examples "Precision spindle metrology" Eric Marsh is good too for anything that rotates. Surprised with your PI connection you weren't able to snag a copy In general any MIT PhD dissertation advised by Slocum or David Trumper is excellent

Congratulations man, it’s been incredible watching all your progress and we wish you the absolute best!

Great list Cyrus! I have a few to add to my collection for sure. My recommendations would be: Sensors and Actuators by de Silva - it's the textbook Dan Gelbart uses when teaching the class of the same name The art and science of engineering - Richard Hamming (stripe press) - Not about precision engineering, but about engineering and being an engineer. Can't recommend enough. Thanks for the video, good luck post-grad!

Nice collection Cyrus! The flexure analysis in Slocum's work is phenomenal. I would submit for consideration "Building Electro-Optical Systems: Making it all work" by Philip Hobbs. A fantastic resource for anyone considering design of precision optical systems, sensing, etc. Extremely technical yet relatable, and the author's humor is a pleasant side.

i would love to read every book, sad that 2 of them are not to get so easy or at all in germany and that they all are not cheap. But i have the Diamond Turning at least already

Great collection. Congratulations on your graduation, Cyrus. I hope you'll continue to make videos about your future activities.

Nice collection.

Great video! Looking forward to comparing these to what university has to teach me

That's cool AF!!

was the spindle and work holding balanced? could this be micro chatter? the center being dull looks like a velocity problem from my machining background(keep in mind that i have never tried to cut a mirror finish nor used diamond tools). sometimes, depending on the sharpness of the tool, when velocity of cut diminished forces can build because it becomes less plastic and or gulling can happen. for this reason we use constant velocity when turning. it might be worthwhile to implement an accelerometer on the spindle and tool to keep track of harmonics. also what kind of coolant are you using? there are no metallic deposits forming on top of your cutting edge are there? being from bar stock, could the rings also be from the tempering on the material as it cooled at the mill? it would be interesting to see what would happen with a piece of plate vs bar stock.

Lots of good tips in here: larger tool tip, optimizing air coolant to clear tool & just worked surface, optimizing air speed to minimize material tear away, checking x axis drive mount for debris, making sure you're actually cutting deep enough so your tool is cutting and not rubbing... have any of these helped yet? Your mirror mount seemed rock solid. When you started off with oiling the mirror, and showing us the flat line you had achieved when you ran the tool tip near the OD circumference, I was impressed... have you considered doing the same thing, feeding it inward on the X just as the tool tip would see? Maybe any machine introduced errors would be highlighted in this way. Regarding the tool holder/mount, rotational speed in relation to center, heat, and vibration: worst case scenario thinking here; tool is rubbing some, heat is transferred into material, vibrations picked up in the mirror resonate, material vibrations interfere at harmonics highlighted by the rotational speed at given circumferences. (What was the rotational speed at the break points we see in the interference scan? Are these always repeated?) Can you put a feeler Guage on the tool holder, independent of the tool mount, while making your next cut. (With another camera to record it.) The mirror mount. Is it mass dampened? Is the center of the mirror supported from within, or is it like a drum? You went to some effort to check your X dimensions and center. Check your Y. Account for tool tip size, and experiment with its cutting position. Experiment with its cutting angle.

I have just discovered this principle by mistake while experimenting with the first air bearing spindle I got my hands on and I thought I was going crazy as I didn't expect this was a result to me closing down the thrust bearing air gap and I am just so glad I found this video of yours as i thought it was locking up because of poor quality work anyway..I have been trying to find the documents/drawings of the model I have...it's a westwind model 70, which is the smallest air spindle that I could find and afford...another thing that makes it more rare is that it is an air powered spindle + aerodynamic bearing...the rotor/turbine design is another great alternative to electric motor. I can send you some plans if you want? You should make one for your Dan Gelbart lathe as I was going going to do the same project as that video of his completely changed my life of engineering..I am going to make a bigger version of the spindle that I bought...this little westwind spindle I bought to mount on my SIP...I was wondering if I am correct in guessing the reason for the turbine powered instead of electric, as my goal was to have the least jittery rotation spindle as I think the particular model I have is better than the other turbine designs that I have seen in that it doesn't work with a vane type propeller that has blades that ports guide the jetted air up against the blades. It's almost like a reverse principle type configuration. The next experiment I aim to get working is to combine something like this that you built into my westwind...I was wondering if you could answer some questions about it? Thanks for the inspiration 😊

Really amazing results! This is easily my favorite ongoing project on YT at the moment 🤩 I think Bath interferometers introduce a bit of astigmatism which maybe is contributing to your error. IIRC there's a way to null out the Bath astig in DFTFringe so you can see just the mirror astig

Can you lapping on them diamon and silicone carbide for like f2000-8000? For natural stones

I want to see you sharpen a knife with this kind of precision. I think you could make the sharpest knife on youtube. with the ultimate polished edge.

Very inspiring! Amazing work. I was getting into a direct laser lithography to produce photo masks for planetarium projector star plates. I wanted to use a high NA microscope lens and just pull the focus in and out to adjust the star diameter to expose the photo resist, while an XY table moved the plate to the proper coordinate for the star position. I was working with a precision stepper stage with a 1mm pitch lead screw. Still couldn't get reliable focus variation. So I was led into exploring a similar air bearing set up for Z with high resolution feedback. That quickly got way out of my technical capabilities and financial reach, so I am just going to pay a photomask company to make them on polyester film. Much cheaper, but not as much fun!

Fresh sub today, ROBRENZ and Stefan's channels got me interested in all this solid tool post game, and youve taken it a step further, love it mate👍👌🇦🇺

How deep did you drill into your cross slide? Did you use a thread insert or just drill and tap?

Centrifugal convergence and centripetal divergence.

The workpiece becomes a rotor in an open shaded-pole induction motor

Depending on the radius you're turning, could you mount the diamond tool on a pivot, so that it moves in an arc across the work piece?

Thank you for sharing this was very informative. You made it easy to follow you. Thanks again

The speed of sound goes down with a decrease in fluid temperature. The temp of the excaping air is so cold that the speed of sound is lower than its escape velocity from the can. Pretty cool

Outstanding work, as usual! I do R&D with an older Moore 450UPL at work. At one point I was investigating machining parameters (including constant surface speed [which is indeed over-rated for SPDT of aluminum], feed, tool geometry, alloys, etc). Decided to minimize variable by using 2" flats as my test standard, but found some residual power (PV error) much larger than expected. Thought it was vacuum pressure, but for these pucks that was an order of magnitude lower effect unless the mating surface wasn't lapped flat. However, one day I decided to chuck up a 6" 1/20 wave optical flat and ran a mahr electronic indicator across it (and clocked to rule out wedge) and found that there was waviness in the X-axis. During PM, Moore would adjust spindle axis perpendicularity with a test bar, but they'd only check one position along the axis so it went unnoticed by the production folks. So, if it's a geometry error, you should be able to find it without making a cut, unless it's dynamic. If that's the case and it passes the flat test, then find a high quality glass lens with a spherical curvature similar to yours to use as a "calibration artifact" and program a radial scan with an indicator and you'll get your answer. Measure it with your interferometer and make an error map of the artifact if you need to. That being said, if you can confirm with an artifact that it's not machine error, you still have many things to investigate. I've seen many befuddling errors due to material inhomogeneities, mounting interfaces, and residual stress from blank preparation. Heat treatment is important, as can be alloy selection. Obviously thermal can be a huge error source, and the longer the cut the more it can be an issue. There's also tool tip waviness - local irregularities in the tool's radius. Our supplier doesn't charge much more for a 1/10th wave tool tip waviness vs 1/4 wave and it helps on spherical parts when you're not using a B-axis to rotate the tool. Good luck!

Can you feed the inverse of the surface error into the Z axis setpoint?

Maybe your air bearing guide suface has some dirt on it? You might just wanna try cutting on a different part of your x axis and see if your error moved with your tool or if its in your axis?

I am not sure the surface will get better due to bearings at those scales. Metal doesn't cut the way you think. ruclips.net/video/aF7ltBT_atA/видео.html Taking a shallower depth of cut can actually give worse finish in some cases as there is not enough material being removed to produce a proper chip to evacuate. Instead it just mushes around. This might be what you are seing. The sudden change in cut at the inner area may be the stepover vs feed crossing some threshold causing it to suddently "bite" better. The speed of the main spindle would have to be controlled relative to the current cutting diameter to create a constant linear feedrate to eliminate such thresholds.

Is there any chance that some of the distortion is thermal? Some sort of latent stress in the base material that leads it to distort slightly with however many degrees the room temperature might vary.

Averaging over 90 degree rotations is a bit questionable since your coupling has order-3 symmetry. When you average over 90 degrees (order-4), you might end up cancelling out deformations that are induced by the shape of your coupling. Although I doubt that such deformations are a major effect, I think some mild order-3 stuff was showing up in your wavefronts in the previous videos.