Film-Tech Forum ARCHIVE: How are star gears machined?

This is topic How are star gears machined? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002650

Posted by Josh Jones (Member # 447) on 09-18-2001, 10:21 PM:

What type of shop machines are these gears made on? Also what type of metal are they made of, and what type of hardning processes are used. I have been curious about if these could be made by a regular machinist. Supposively they had precision on the order of 1/10,000 of an inch.

Josh

Posted by Richard Fowler (Member # 893) on 09-18-2001, 10:51 PM:

Josh, most intermittent parts and sprockets that U.S. manufactuers use are supplied by Lavezzi.....they have a website....www.lavezzi.com...an average machinist does not have the neccessary skill or tools to harden and grind down proper tolerances.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

Posted by Will Kutler (Member # 770) on 09-18-2001, 11:24 PM:

1st, ther are books that give all kinds of tech data about metals and heat treatment so that a designer/engineer can select the approperiate materials for a given application.

the basic shaft od (outside diameter) profile is turned on a lathe between centers. The shaft is then taken to a mill where it can be inserted into a made fixture for mass production--or a rotary table. and the star to cam and star to cam pin profiles are milled with approperiate dia end mills . Rough milled parts are left about .010 oversized to allow for grinding. The part is then heat treated. After heat treatment, the shaft will be ground between centers on an od grinder. Then the star to cam and star to cam pin bearing surfaces are located back into a made fixture or rotary table and ground on a jig grinder. Finished part needs to be precision inspected. Tolorances for these parts is about + or - 0.0002 or so -- a quarter inch is 0.250 --so this shows you just how precise these parts are! Yes, I can make these parts--I just dont have my own shop! Fun projects. About 3 days work to make one star and cam (including heat treatment) So making one is expensive! Shops like LaVezzi have special set-ups and tools for mass production. This explanation is very basic, I have not discussed all of the tools and fixturing needed. These would have made excellent projects for my machine tool classes--we just did not have a jig grinder!

As for sprockets, LaVezzi has designed their own special tools and processes for making sprockets--these are their own patented secrets that they will not discuss--they do not give tours of their shop.

Posted by John Pytlak (Member # 331) on 09-19-2001, 01:33 PM:

Here are some links to LaVezzi's website:
http://www.lavezzi.com/Pages/AboutLaVezzi.html
http://www.lavezzi.com/Pages/Quality.htm
http://www.lavezzi.com/Pages/FAQs.html
http://www.lavezzi.com/Pages/LavSprocket.html

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by John Anastasio (Member # 607) on 09-19-2001, 05:40 PM:

Josh, I'm convinced that if you'd been born about 70 years ago, we'd all be arguing now about how the Jones projector is the best one ever made! Your inquisitiveness and inventiveness are amazing.

Posted by Josh Jones (Member # 447) on 09-19-2001, 07:55 PM:

Thanks John

But just for the record, The company would be called RCA

Josh

Posted by John Anastasio (Member # 607) on 09-19-2001, 09:13 PM:

The Sarnoff Research Center is practically in my back yard and I've been in it many times, including the old "General"s office...actually had the chance to peruse his personal picture books one day, courtesy of an old friend. RCA did make some nice equipment, but they also had some spectacular bombs. You're probably too young to remember the CED videodisc that actually used a stylus sitting in a groove. You should have seen the video games they were working on with that dog! Fortunately, they never made it to the public. And yet, their unique "video engine" computer has enable other companies to produce some amazing new technology. They also made a few radios that were amazing for their really crazy circuitry, especially in the 1930's. They did a lot of really nutty things to get around other people's patents. What they couldn't get around, they stole and then ran people into the ground in court....like Edwin Armstrong. Those Brenkerts might have an RCA logo on them, but they weren't designed by RCA. It was an interesting company. Watch a tape called "Empire of the Air" and you'll get a good feel for how Sarnoff made the company in his own somewhat seedy corporate image. They had a very large presence in New Jersey, both here in the Princeton area and also down in Camden.

Posted by Paul G. Thompson (Member # 655) on 09-19-2001, 09:41 PM:

John, David Sarnoff was quite the person. He and Frank Sinatra were very good friends, too. I have heard that Frank Sinatra composed a song for Mr. Sarnoff, and sang it at a party that included Mr. Sarnoff. Name of the song (I think) was "That's Why You're A Champ".

Josh, have you seen the video tape PBS had about these old radio guys? The title was, "Empire of the Air". I have that, and if you would like to borrow it, I'll send it to you. I think it is out of print, and can't buy it anymore. It includes the history of all these guys from Marconi, Armstrong, Deforest, Sarnoff, and a few others.

One weird funky circuit RCA had was known as the "Syncro-Guide" Oscillator. It was used as the horizontal sweep circuit in the old RCA TV sets, and it was nothing more than a mdoified Series Hartley Oscillator.

I never ever did figure out how his horizontal drive circuit worked. And, I have heard many TV techs say, "Oh, those ***** syncro-guides - grrrrrrrrrrrrrr" And, I have said the same countless times.

Paul

Posted by Mark Gulbrandsen (Member # 72) on 09-20-2001, 04:53 AM:

Will and others,
I have been very fortunate to have been on a tour of LaVezzi with Al LaVezzi a number of times. At both the old plant in Elmhurst and the new one in Glendale Heights. He's a very gracious host when time allows him to conduct what is usually at least an hour plus long tour of the plant in Glendale Heights, IL. No 10 minuite tours there! The following is a generalized write up about how stars and cans are made....Sprockets are a whole other thing that involves many. many operations, some that are similar to the description below. The only thing proprietry as far as sprockets go is the VKF and posi-trol teeh thata re ground into various sprockets, other wise sprocket making is a pretty straight foreword process. Its the making of Stars and cams that LaVezzi has many secrets about, however they never hesitated to show me, or any other people I brought with for a tour. Quite frankly, one could not set up easily to produce the parts, they are the only one in the country making them to the precise dimensions thata re requires....so why would they worry about someone steeling any secrets........
Century cams are turned down to a rough dimension in one or two passes from 3" diameter alloy steel bar stock on Swiss made CNC lathes. Huge, deep cuts are done on these automated CNC machining centers that have automated bar stock feeders. I remember Al saying that the CNC lathes have burst into flames a couple of times in the past as the cuts they take are so large and generates so much heat. Century cams were being roughed out on my last tour and smoke was pouring from the machine due to the 1" deep cut that was being taken off! From what I remember he told us, if they had to take too many extra passes to turn the bar stock to the proper diameters it would not be economically feasible for them to even make the parts. The next step is to mill out the slot for the star wheel to turn over in,and any other holes and set screw flats, and oil spirals needed. After the rough cut operations, the roughed out cams are sent out for heat treatment and black oxide coating and then the shaft, and then the raduis for the star ground to proper diameter. Next the hole for the pin is located, this is after heat treating due to slight dimensional changes in the part as a result of the heat treat, and a finished cam pin is pressed into place.

Starwheels are another matter as they involve more operations, but are roughed out in a similar way as the cams are. After rough cut the star end is round rather than like a star. Next operation if memory serves me is to rough out the star radiuses first on CNC milling machines and to turn any oil spirals, etc into the shaft end, and then the stars go out for hardening and Black oxide for corrosion prevention. The black oxide also aids in visual checking during machining operations. They come back from heat treatment and are sent through a number of different grinding operations such as shaft diameter, star slot rough grind, etc. of which the final operation is a final grind on the slot. This is done in a soundproof booth(talk about working in a padded cell!) with an air bearing Studer grinder which is manually operated. On my last trip there were two of these rooms set up for this. On my last trip through there Al LaVezzi said that there were only two people that worked there that could do this final grind operation properly. The final slot grind operation is something that has to be heard and cannot be felt as in other grinnding operations and thats why the sound proof room. Even the grinder barely makes any noise of its own when its running.

After any part at LaVezzi is manufactured it goes into a temperature controled room for QC and each and every parts critical dimensions are checked to meet specification. Reject ratio is low due to the many long time employees experience in this type of manufacturing. Employee turn over is not something he worrys anout much.
They also make parts there for other companies such as Imax, Cinemeccannicca, Strong, and also movement parts for many motion picture camera manufacturers.
They do have a web site at http://www.lavezzi.com/
There is an on line slide show of the plant and some of the parts that they produce, however, one has to actually go there and see the operation to appreciate the craftsmanship that goes on there. Also, keep in mind that Motion Picture parts are only a small amount of what is produced there anymore. LaVezzi also makes many other parts such as medical items(many from from Titanium!), aerospace parts and anything else of a precision nature. All in all an amazing place to tour.
Mark @ GTS

Posted by Mark Gulbrandsen (Member # 72) on 09-20-2001, 05:27 AM:

Paul, John,
There is a great book Titled "Vladimir Zworikin, Father of Television" that gives a really good but brief account of General Sarnoff. He was quite the guy and a hellish buisness man. His buisness tactics resulted in several people committing suicide, Major Edwin Armstrong, the inventor of FM radio, among them. Anyone interestd in reading about how TV was commercially developed should check into this book.
Another mind boggling very detailed book is "Distant Vision" which is the true life account of Philo T Farnsworth. It was written by his wife. This guy had so many firsts that it really boggles the mind plus he operated alone with only funds from private investors. From this he managed several hundred patents including the most basic television patents which RCA had to liscense from him to produce television sets and cameras. much to Sarnoffs dismay. This all involved a lawsuit from each side of amazing proportions that went on for a decade till a high school teacher came up with evedence in Farnsworths favor. Farnsworth was also well on his way to making self sustaining fusion a reality and had he not died early it would probably already be with us today. Both books are highly reccomended and are far more accurate that the book "Tube" which is a more generalized account and far less accurate.
Also see this web site: http://www.farnovision.com/chronicles/
Mark @ GTS

Posted by Oscar Neundorfer (Member # 458) on 09-20-2001, 07:07 AM:

Mark,

It is absolutely amazing how much we take for granted. I bet no one will ever look at these parts in quite the same way again after reading your detailed description of LaVezzi operations in making these parts.

------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.

oscar@smartdev.com

Posted by Will Kutler (Member # 770) on 09-20-2001, 05:00 PM:

Hi Mark and all!

Just to give you a little background info about myself. I have been a licensed FAA Aircraft Mechanic since 1988 including both civilian and military service. I am currently completing my AAS in Machine Tool Technology CNC Option from Pima Community College (need to finish English 102 to graduate) and am working on a BS in Manufacturing Engineering Technology from AZ State University. Yes, I have job shop machining experience--not to mention my experience as a Projectionist. So I found your post about LaVezzi interesting.

I guess Mr. LaVezzi wants to ruin his expensive CNC machines--1" cuts!? And machines bursting into flames? I'm speechless! And needing to hear the gringing operation because feel does not cut it? This is what precision inspection equipment is used for during and after the machining and grinding processes!

Posted by Mark Gulbrandsen (Member # 72) on 09-21-2001, 10:17 AM:

Will,
There are no after machining touch ups at LaVezzi that I was privy to seeing done in the inspection room. The inspection room is a clean, temperature controled room and would not be doing this sort of thing. Any final stuff is done in the shop, which in itself is so clean it could pass a use for food service inspection easily. The final grind on the star wheels slots are indeed done this way and perhaps this is LaVezzi's method of final inspection for this part, but this is out in the shop in an enclosed room for each grinder.
Personally, you could never learn what these guys know in any school, anyplace, ever, or even around the normal type of precision CNC machine shop. You have to remember that they have been doing this stuff since the mid 30's, perhaps earlier. You'd have to work there to learn how to make the sort of things that they do. Also keep in mind that they are just about the only place in the country that has this sort of experience, the facility, and knowledge to make these high perecision parts to such tight tolerances, and to keep reject rates as low as they do. I have been to other precision shops to have parts manufactured that claim they can do similar work but the overall quality of the finished product is normally no comparison to what LaVezzi cranks out. When you are shown the parts sample collection that resides in the clean room you are literally blown away. There are parts for Panavision and Arriflex camera movements, Imax camera and projector parts, and the normal lot of high precision projector parts, plus other interesting complicated aerospace parts. These guys are definately in a class all by them selves. When the star slots are getting their final grind sometimes it can be heard and sometimes not, although the final few hundred thousandths or so that is removed definately comes off. The old fashioned way to do this is to lap the slots out to final size. Final inspection of critical dimensions are then performed in the clean room. Anything bad is rejected there and destroyed, although that is rare.

As far as these guys taking such heavy cuts are concerned I'm quite sure that they know what they are doing with the lathes that perform this task. I can't remember the depth of cut exactly but it is very large. My last visit there was about 6 years ago and I'm sure those lathes are still humming along quite well today. These lathes also do alot of Titanium machining rough out for medical instruments so one could assume that they're made for this sort of work day in and day out. As I'm sure you kow, it all has to do with spindle speed and cutting tool feed plus proper lubrication of the cutting tool to clear away debris and keep the cutter cool. Any high quality lathe of sufficient size can do this if properly set up, day in and day out.

Will, Probably after you have about another 20 years experience in making ONLY presision parts you can then start to think about making parts like those that come out of LaVezzi. If you have the facility to do it in. Keep studying!
Mark @ GTS

Posted by Will Kutler (Member # 770) on 09-21-2001, 06:16 PM:

Hey Mark!

If you are offering me a challenge about making these parts, then give me a copy of the prints! I'll take you up on it! There may be a few operations that I may not be able to do because I dont have the tools. I can present the challenge to my instructors and maybe I can use the shop!

Most of my classmates are/where people with a lot of experience behind them! They went back to school to get a little piece of paper so that they can get promoted at work!

About some of my instructors:

They are just not "schoolroom" instructors--all work in industry and teach as a side. If I spent the time here to tell you all their credentials, it would blow you away! Keep in mind that Tucson is very high in the aerospace industry. Several of my instructors were in charge of the tool room at Hughes Aircraft. One of these people was also a tool maker at Los Alamos! Several of these guys are injection mold makers. Several are also precision instrument makers at the University of AZ involved with NASA related projects! We have one injection mold shop in town that is known for taking on the difficult jobs in the country that no one else will touch!

As for me, ya, I am used to working with tolorances of 0.0000! And ya, I am good!

Another piece of info for you--if one decides to become a machinist, one will never stop learning! The worst machinists are those with egos who are know it alls!

Posted by Will Kutler (Member # 770) on 09-21-2001, 06:27 PM:

Dont get me wrong--I am not by any means bad mouthing LaVezzi! I am just looking at these parts and finding it interesting projects!

Posted by Richard Fowler (Member # 893) on 09-21-2001, 06:36 PM:

Wil,
my key machine shop contractor, who has NASA and several major airlines for clients, was blown away on the quality of the Lavezzi parts we had modified by them for an O.E.M. account.....he asked for spare samples to show his staff what level of quality they should be going for.
Richard Fowler
TVP-Theatre & Video Products Inc. www.tvpmiami.com

Posted by Mark Gulbrandsen (Member # 72) on 09-21-2001, 07:16 PM:

Will,
The idea here is not to make just a few parts but to make hundreds in one run and keep all the tight tolerances. Making a few is easy, making hundreds at a run is far more difficult. I would urge you to attempt a tour at LaVezzi if you get to the Chicago area. You'll see what I mean.
I do have a 32 tooth Alumnium VKF sprocket blueprint I had drawn up(and also made)that I can send you if you want to tackle a hundred or so of them for me. My sprockets were made by Worral Grinding in Californis. They work great and have good tolerances. They only made six of them for my VV machine. Of course one thing you could do is to design and make 35/70m VKF sprockets for the Phillips DP-70. You'd actually sell bunches of thise so it would be a worthwhile project(venture)for you to tackle. I'd be first in line for several sets of them. Your target price cannot be over 250.00 List price per sprocket. My cost has to be at least 40% less than that.
Mark @ GTS

Posted by Greg Mueller (Member # 17) on 09-21-2001, 08:17 PM:

Wil
Probably a lot of what you're seeing in shop class are conservative "beginning" speeds, feeds and techniques. Once you get in to the real production world lots of things change. I have no doubt that lavezzi has been running these parts long enough and has pushed the envelope on production of each part to the point where they can manufacture each of them for a profit. I'm sure you'll be somewhat shocked by some of the things you'll see as you go along and get further from the class room and more into the competitive world of production. I had an instructor that although he taught us the numbers and formulas for material removal also made it very clear that these were only beginning points. Another instructor (not mine) would come out and yell at us if he saw us pushing the envelope. The difference was that my instructor was a successful machinist who was teaching during the great Boeing crash and the yelling instructor was never more than a teacher (I'm not dissing teachers). There's quite a difference between the class room and the competitive world of production machining, and you're right, you never quit learning.

------------------
Greg Mueller
Amateur Astronomer, Machinist, Filmnut
http://www.muellersatomics.com/

Posted by Gordon McLeod (Member # 33) on 09-22-2001, 09:58 AM:

An old phrase I once heard "when you quit learning you are dead"
Also Mark Twain waid "Never let your schooling interfere with your learning"

Posted by Will Kutler (Member # 770) on 09-22-2001, 12:51 PM:

Hi everyone!

I guess you did not all read everything I wrote--yes, I do have a good amount of "real world" shop experience!

Now, Duh! CNC is for production--but duh! there was a time before CNC when duh--turret lathes, tracer mills, etc, etc were used for mass production! and yes, I have experience with both CNC and manual tools. Actually I love manual machining more than CNC!

So, duh, none of you really know me, or the type of work I am capable of, so send me a print of a star and cam! I'll see what I can do!

Posted by Mark Gulbrandsen (Member # 72) on 09-22-2001, 01:19 PM:

I also have quite a bit of machining experience, enough to make a star and cam or two but not hundreds at a time. Apparently you didn't read all of my posting either. Let me know when the first batch of new VKF style DP-70 sprockets are available. Will, also... you have to do your own drawings as I did for my 32 tooth Internittent sprocket(on autocad or what ever works for you). I still have enough of the 32 toothers left as the machine is still on it's first sprocket.
Mark @ GTS

Posted by Will Kutler (Member # 770) on 09-22-2001, 03:15 PM:

So what is so difficult about mass production? There are special machine tools for this, and no, you don't need to rely on CNC! Unfortuantely, I do not have my own shop. Maybe I could make a Star and Cam in the college shop if I get permission. No, I do not have access to the special grinding machines needed to make sprockets! Yes, I am very experienced with Autocad, in fact I would like to purchase a computer for that purpose as I would love to get into photoetching--do you know what that is, Mark?

Posted by Greg Mueller (Member # 17) on 09-22-2001, 04:41 PM:

Wil
Quick, go start your own shop and put all of the stupid "duh" shops out of business. All you have to do is make a better product and sell it for cheaper than the competition. I have the equipment necessary to make just about anything on a projector, but I buy stuff from manufacturers who are already making the stuff. Why? Because they have already done all the R&D and all the leg work, made all the mistakes and know how to do it right. It is more cost effective (a term I'm sure you will become acquainted with in the near future) for me to do what I do and make money and buy the product of people who know what they're doing with their product, than it is to make one from scratch. Unless your time has absolutely no value, you simply cannot make a star gear (by hand) better and cheaper than one that is in production. Guess why turret lathes and tracer mills have been replaced by CNC equipment. As far as the difficlties of production go, guess you have to be there to appreciate that one. Good Luck in your new vocation.

------------------
Greg Mueller
Amateur Astronomer, Machinist, Filmnut http://www.muellersatomics.com/

Posted by Gordon McLeod (Member # 33) on 09-22-2001, 04:46 PM:

Photoetching is more accurately called chemical milling and is the basis of much precision work in not only printed crcuit board fabrication but other areas. Mark is well familiar with it as he has seen dimmer boards being etched in my shop from designs we did in Protel

Posted by Mark Gulbrandsen (Member # 72) on 09-22-2001, 06:59 PM:

Yes Will, I do. It is a process of making parts by masking and then etching away the unwanted areas of metal. In fact that is how printed circuit boards are made. I just got done etching a pair of boards for a class A line stage preamp for my home "high end" stereo system. Been making my own pcb's for years.
There are Photos of in the works audio projects at this site for those interested: http://albums.photopoint.com/j/AlbumIndex?u=51304&a=13785415&f=0

If you ever make PCB's be sure to get PCAD for doing this. Its the best PCB CAD program there is. You can download a free trial version at: http://www.pcad.com/downloads/utilities/p-cad2001/viewer2001/p-cad2001viewer.exe
Enjoy and have fun with it.
Mark @ GTS

Posted by Gordon McLeod (Member # 33) on 09-22-2001, 08:11 PM:

Actually the old Dos Protel pack of Autotrax pcb and router and schematic schematic editor do up to 7 layer boards very nicely.
The latest Win version is very powerfull as it has a Spice module that also checks the finished board for possible induced signals
A freeware version is available called Easytrax from http://www.cia.com.au/rcsradio/index2.htm
as well they have the source code for writing your own drivers

Posted by Steve Guttag (Member # 268) on 09-23-2001, 12:16 PM:

Ok you PCB people you...I'm a proud user and supporter of Design Computation's DC/CAD...aka Draftsman-EE...it will out route just about any other router I've seen. It will do from 1 to 48 layers or so and around 8 common layers (aka planes). Too bad they went out of business but you tend to like what you are used to.

I'll stay out of this machinist bickering though.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Gordon McLeod (Member # 33) on 09-23-2001, 12:29 PM:

I tried HiWire 2 and found it the best router out there but was too expensive to buy Also they make a low end one called Smart Work

Posted by Josh Jones (Member # 447) on 09-23-2001, 12:54 PM:

Your quite the photographer, Mark

That ferris wheel picture looks nice

Posted by Mark Gulbrandsen (Member # 72) on 09-23-2001, 06:07 PM:

Thanks for the compliment Josh. I've been taking pics since I was seven years old. I've pretty much retired my 35mm slr's for the larger format stuff. There is alot to photograph here in Utah and since I hike and do photos I might as well haul around the best I can afford to. I also do most of my own color darkroom work....time permitting. The ferris wheel picture is a digital shot taken at Lagoon and thats what I have been using for about 3 years now for general photos.
Mark 2 GTS

Posted by Will Kutler (Member # 770) on 11-02-2001, 05:18 PM:

A topic back from the dead machining and metalurgy!

Anyhow, I was watching the Annenberg CBP channel the other night and caught a show called The World of Chemistry produced by the University of Maryland. This particular show was devoted to metalurgy and was excellent! One of the producers/sponsors at the end credits was Eastman Kodak...kudos, kudos--!

Posted by John Pytlak (Member # 331) on 11-05-2001, 02:50 PM:

Will said: "One of the producers/sponsors at the end credits was Eastman Kodak...kudos, kudos--!"

Thanks. Kodak tries to be a good corporate citizen, and has sponsored several PBS series. I'll pass the thanks along to those who make it happen.