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    I would think that this forum should encourage out of the box thinking about how to modify or create better machines.

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    Quote Originally Posted by EmanuelGoldstein View Post
    As a Maag-lover, I'm not sure why ZK wants a Sunderland ... except that they can do herringbones in a single operation. That's kind of neat, if you need to do herringbones. There are newer versions of the Sunderland that don't looks so antique but they must be rare as hen's teeth, I've only ever seen one.

    But if you really want one, ZK, there's one I know of in Thailand that you could get for a song. Needs work. And it's maybe a 60" machine ?
    I've just got a thing for Sunderlands. Plus, tooling would be trivial for me.


    Quote Originally Posted by EmanuelGoldstein View Post
    I know of a 6" David Brown (same design as a Matrix) and there was a guy who was modifying Hoagland dressers to make little fine pitch grinders out of them.
    FFS. Now, you hate me...? Still... a 6" would be kind of nice for much of the work we do...


    Quote Originally Posted by EmanuelGoldstein View Post
    ZK, have you considered an SH45 or SH75 ? Pretty nice and easier to find than a Sunderland ....
    [/QUOTE]

    Actually, I'd _LOVE_ a small Maag.


    Quote Originally Posted by EmanuelGoldstein View Post
    What you are insisting upon is probably the worst possible way to do this, so I dunno what else to say.

    Quote Originally Posted by dazz View Post
    Hi

    For me the price of hobbs just eliminates them from consideration.

    If I was to make a non-production gear cutting machine I would use my FUS22 Deckel clone, which includes a slotting head.
    With this I would electronically gear the table motions to a horizontal rotary table.
    I would use a single tooth rack as the cutting tool.

    A single tooth rack would be an easy tool to accurately grind and very cheap. The tool cutting edges would be straight and flat.

    This type of gear cutter would be able to generate any involute gear form with any tooth count. It could cut to a shoulder and, unlike a hob, it could do internal gears.

    Dazz
    FINALLY. Someone gets it. The only thing I would add would be to make it use a multi tooth Rack for externals, to speed things along.


    Quote Originally Posted by drcoelho View Post
    This is an interesting idea. I've already got a slotting head accessory for my Deckel. It hadn't occurred to me to use a single tooth rack, I would have thought that multi-tooth rack would be required to get things right. There are some challenges in synchronizing the slotting head motion with the horizontal rotary movement. Also, I believe the rack needs to move incrementally along the tangent of the work piece as it rotates to get the curve right, which would require some tricky mechanicals on the slotting head, or I guess you alternatively are suggesting moving the milling table simultaneous with rotary index rotation....that seems to me to be a difficult thing to pull off with accuracy.
    This illustrates specifically why you are getting so much incredulity from those more experienced. Not only is this simpler, but easier to implement. And making it automated, simpler too.

    Quote Originally Posted by drcoelho View Post
    Unfortunately, I'd don't have CNC control of my milling table so this approach won't work in my case.
    I'm going to pretend I didn't read that.

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    So i'm looking at the Maag machines, and it appears to me that these machines are very similar to the Sunderland approach except the cutting action is vertical versus horizontal, am I getting this right?

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    Quote Originally Posted by implmex View Post

    ...
    So here's a snip from my post #65 in which I describe something similar:
    When I have cluster gears or plastic gears to cut, my GO TO machine is my Haas Minimill with a custom G code writing program done for me by a buddy years ago that allows me to make a single tooth rack profile shaper cutter, and use spindle orient to generate an involute gear using the same strategy as the now ancient and long obsolete Sunderland gear shaping process uses.
    ...

    Cheers

    Marcus


    The same but different.

    Exactly the same concept applied in 2 ways.
    If I had a Hass, i'd do it your way. I guess if you had a slotter, you'd do it my way.

    Dazz

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    ZK: so I'm looking at the Maag process which is very similar to what dazz had proposed. Here's what I see as complications presuming you are creating an accessory for Deckel manual mill:
    - you need to synchronize the rotary rotation with the x-axis movement of the milling table, therefor you need CNC control of both of these....in my case, this is difficult because I really don't want to go mucking around in the electronics of my brand new FPS 300 M mill to get control of the x-axis, and I certainly don't want to layer another x-axis on top of the milling table
    - depending on the number of teeth you've got, you need to stop part way through your cut, move the rack cutter back to beginning and restart the cut in order to avoid needing a super long rack cutter. This is a very difficult maneuver to do accurately
    - the cutter on the slotting head needs to engage on downward cut, and disengage on upward return, adding complexity
    - if you have multiple rack teeth, the slotting head must be robust enough to handle this wide cutter surface, the Maag machines have really substantial slotting heads, I won't have a slotting head of that stiffness or bulk

    I just don't buy into the idea that making that all that work together is easier than the approach I have been considering which simply needs to get the horizontal spindle to synchronize properly with the rotary.

    The one argument that I'll buy into against my approach is the need to inventory a quantity of expensive gear hobs to cover the various gears one might need to make....if money were not an issue, I just don't see the Maag approach being easier to implement than the gear hob approach.

    Ultimately, it seems to me the debate going on here is that my requirements are really unusual (the desire to be able to cut gears on-demand without having a dedicated machine to do so)...by far the easiest would be to just buy a used machine which is what 99% of the folks out there would do.....OR as you have said previously, just buy the gears and skip the in-house manufacturing........

    This whole gear manufacturing thing is a very interesting area of study though, love the differential geometry math associated with underlying gear theory....

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    Dazz, please see my concerns above regarding the slotting approach, am I missing something? Slotting approach still seems more complicated than gear hob approach to me....presuming of course that I have unlimited budget for gear hob inventory

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    Hi again drcoelho:
    You wrote:
    "Here's what I see as complications presuming you are creating an accessory for Deckel manual mill:
    - you need to synchronize the
    rotary rotation with the x-axis movement of the milling table, therefor you need CNC control of both of these."

    You are missing a fundamental principle of this process, and here is what it is:
    You do NOT need to couple the rotary motion with the rack cutter translation in a timed manner.
    You could increment the rotary table, go for a nice coffee, come back and then shift the rack and when you make your next cutter stroke, all will be well.

    This is fundamentally unlike hobbing in which the synchronicity between hob and blank is everything.
    Once you wrap your head around this concept everything else falls into place.

    There is another thing I've touched on a couple of times that no one seems to have picked up on or commented on:
    The Sunderland generating process DOES NOT REQUIRE the cutter motion to be a shaper stroke.
    It can just as easily be a spinning cutter taking a milling pass, just like a saw.

    I have Sunderland cut many gear profiles on the Bridgeport (before my first CNC mill) with nothing more than a rotary table standing up so the axis is horizontal, and a shortie rack profiled flycutter like I posted in a previous offering.
    I rotate manually by a given increment (say 5 degrees)
    I know how far a point on the pitch circle has moved over that 5 degree increment.
    I drop the Z by that much.
    I make another pass.
    I do it again a gazillion times bringing the rack back up to the top of its travel whenever I run out of rack to engage with my developing gear and hey presto; I have an involute gear (or at least a reasonable facsimile)

    It's a royal pain in the ass to do it manually like this and as Zahnrad Kopf and others can attest, it makes gears more suitable to drive a cement mixer than a precision instrument or turbine reduction drive but the principle holds.

    With respect to the number of teeth on the rack:
    For generating the involute it doesn't matter a single bit if it's one tooth or twenty teeth or a hundred teeth.
    The additional teeth are theoretically ONLY there to share the load of hacking out the tooth spaces of the gear.
    Yes, if the rack is perfect, they will pre-cut and shave the involute flanks of adjacent tooth spaces, share the wear, do all those useful things but they are not THEORETICALLY necessary to make the involute flanks of a tooth space.

    Zahnrad Kopf talks about making a rack cutter because he can do so easily and accurately.
    He has a wire EDM.
    Using the rack will be more efficient and it will produce slightly better gears because of shared wear, but the principle remains that he need not bother if he doesn't want to and is willing to accept a slow process.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 06-15-2019 at 02:49 PM.

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    Quote Originally Posted by drcoelho View Post
    I would think that this forum should encourage out of the box thinking about how to modify or create better machines.
    Before you can make something better, you need to know what already exists.

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    Quote Originally Posted by EmanuelGoldstein View Post
    Before you can make something better, you need to know what already exists.
    Yes, of course, I'm learning a lot from you all and also from all the reading I'm doing, and THANK YOU for that

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    OK here's a try at a video upload of Sunderland generating without a rotary using only spindle orient on a standard VMC.

    Well that didn't work...let me try something else.
    Hopefully I got it up on Youtube.
    Here's a link (I think)
    YouTube

    OK it seemed to work...let me know if it's good.

    The gear specs:
    48 DP
    36T
    20 deg PA
    PD 0.75"
    Material: black Delrin

    Setup:
    Blank turning: 15 minutes
    Cutter grinding: 1 hour approx
    Programming: 5 minutes
    Machine setup: 1/2 hour
    Cut time: 25 minutes
    Passes: 756
    Pass depth: 0.005"

    These gears are pretty crude compared to a properly made one...the spindle orient encoder on a VMC is not that great for counts, and the holding torque is not that great either (I can move it around a bit with pretty light force).
    I wouldn't dream of cutting steel gears with this...I think I'd beat the spindle bearings to ratshit if I tried.
    But the principle it illustrates is kind of neat, and it sure looks cool while it's running.
    I wonder if it would work better on a Y axis lathe with a C?


    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 06-15-2019 at 04:42 PM.

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    Quote Originally Posted by implmex View Post
    I wonder if it would work better on a Y axis lathe with a C?
    If you had a little fourth axis, say on a vmc, you could just rotate the part as the spindle traverses, i.e. rotate part in B while Z goes up and down. Then move over in X and take another bite.

    In fact, drcoelho could do it that way with a lot less effort. In horizontal mode traverse in Y.

    Haas 4th axis ? Cheaper than any other method and versatile ... with a universal table you could do helicals.

    btw, Marcus - when people want to make especially accurate gears on a Maag they use a one tooth cutter. Rough first then come back and finish with a single tooth. Not on fine pitch tho. That's a different world.

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    Hi EmanuelGoldstein:
    Your way is probably going to be a LOT more accurate than mine has turned out to be and way less head scratching hassle to write a program to create the code, but if the OP is going to adopt it, it will have to be on his Speedio, not his Deckel.

    As I alluded to, and I'm sure you can appreciate, the spindle orient doing it my way has to be dead nuts accurate for the method I show to work even reasonably well, and as the tool tip gets further from the spindle axis the problem gets worse and worse because the small angular errors become large tip position errors.

    BTW, my buddy and I developed this method because of a particular problem; we had to make a big fine pitch gear segment on a small CNC milling machine, so there was no effective way to rotate the part...it was a one sixth segment of a 30 inch diameter gear.

    Fortunately the specs were not that demanding, the material was Delrin, and the method worked very well, but I stole the idea from a video I had seen of an old old Sunderland shaper generating an involute profile from a straight sided cutter.

    It turned out to be useful enough that I kept the code generating program we developed and used it on a few other projects.
    It also meant that I didn't have to pony up 8 grand for a rotary axis for the Minimill and I'm such a cheap bastard that I counted that as a bonus.

    Moving on to your other comment on making particularly accurate gears on a gear shaper...I have to say I'm surprised that a single tooth rack turns out to be the most accurate way.

    I expected tool wear to be a significant factor in degrading the accuracy especially if the gear was coarse pitch or high tooth count.
    Do I assume correctly that inaccuracies of the pitch or inconsistencies of tooth form of the rack cutter are the root cause?
    In your opinion, would a wire EDM cut rack cutter as opposed to a form ground and relieved multi tooth cutter make this source of error go away?

    I can imagine form grinding a cutter like this would be a cast iron bitch back in the day when state of the art was still manual grinders with Acme leadscrews and Diaform wheel dressers, but with a good wire EDM and a knowledgeable operator it's pretty easy to get everything within a tenth or two virtually without any pain...just program it, and push the green button.

    I see now that there are CNC dressed form grinders that can dress an involute onto a wheel...how accurate are those, compared to something like a Maag that generates the involute from two wheels with straight sided flanks and rocks the gear with a base circle wheel and straps while it traverses in small steps across the face?

    Last, (back to the OP's problem) how do you feel about just tipping the rotary up so its axis is horizontal and then making a flycutter to knock out the tooth spaces as opposed to shaping them with a Z axis stroke, given that the OP has stated he only wants to make spur gears, not cluster gears.
    The accessories and the motions would be essentially identical, just an X axis substitution for the Z axis stroke your method requires, and a Z axis cutter shift instead of the Y axis shift you describe.

    It would certainly be kinder to the spindle bearings not to beat up on them by using them to support a shaper stroke.
    Some of those Maag shapers on Youtube look like they are working awfully hard.

    My biggest concern would be for the longevity of the cutters, but he could get custom ground multi flute carbide saws from any tool grinder for 200 bucks or so, and if he has one in all his favourite diametral pitches and pressure angles he'd cover most of his bases for a lot less money than the corresponding hobs, and if he wants a real oddball, he could still grind up a flycutter.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    I know you all think I'm nuts, but I have in mind to do some careful experiments to determine whether I can get the Deckel horizontal spindle to sync with great accuracy with the rotary. I'm still waiting for my FPS 300 M milling machine to arrive from germany, maybe in August, but once I've got it in hand I'll put the most accurate encoder I can aquire on the horizontal arbor, put a cutting load on it, and determine what fluctuations actually occur on this particular machine and with my particular utility power supplied.

    If the above looks reasonably stable, I'll rig up the rotary with simple PLC sync maybe keyed just to the rotary encoder only (not worrying about the motor velocity on first pass) and see how close I can keep the rotary in sync with the horizontal spindle with a very simple phase locked loop.

    Final experiment will be to introduce servo motor encoder to track the motor velocity with the aim of refining control of the motor speed.

    I intend on instrumenting everything with real-time tracking and full data analysis with capture of every encoder output over a period of hours to get this whole setup fully characterized.

    If I am not comfortable that I can achieve at least AGMA 8 tolerance I'll most likely abandon this idea. I'm hopeful I can beat this tolerance, we'll see.

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    Quote Originally Posted by drcoelho View Post
    Dazz, please see my concerns above regarding the slotting approach, am I missing something? Slotting approach still seems more complicated than gear hob approach to me....presuming of course that I have unlimited budget for gear hob inventory
    Hi
    I don't and won't have any hobs so that option is off the table for me. The wide availability of hobs indicates that they are commonly used by others. Even if I had hobs, I would still need to retrofit CNC to make them usable. I have never seen a gear machine available for sale in this country. They exist but are very rare here.

    I do have a slotting attachment, a mill, a rotary table, and the ability to retrofit CNC.

    Different people will take different approaches to solving the problem based on what they have access to.



    Dazz

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    Here is another solution to making gears.
    Although it's a home solution, the method could be applied to larger or smaller gear making.

    Dazz

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    Hi Dazz:
    I looked at the link you posted and here are my comments:
    This is the traditional way to cut relatively rough gears on a milling machine, and of course, the limitations of this process are very well understood and have been extensively described but I'll recap them here.

    There are two main points:
    1) Since the involute profile is different for each tooth count within a DP and pressure angle, you either need a truly huge cutter inventory or you have to accept a compromise on the tooth profile and this is what the standard B&S eight cutter set does.
    2) The indexing method is a common source of pitch errors.
    Of course this is true of ANY indexing scheme, whether electronic or mechanical and is simply overcome with a better indexer.

    The whole purpose of generating a gear as opposed to form cutting it is to eliminate the need to compromise on the tooth form (Point #1).
    There are a few ways to do this all of which have been in use forever.
    Sunderland and Maag gear shapers as well as hobbers and some Maag gear grinders recognize that a straight sided rack of the correct PA and DP will mesh perfectly with an involute of any tooth count provided you can get them to move in the proper relationship as you generate the gear.

    The hobber differentiates from the shaper because the generating motion is continuous so it's more time efficient.

    However, the practical consequence is that hobbing cutters are hard to make with sufficient accuracy whereas shaper cutters are relatively easy to make with sufficient accuracy, and single tooth shaper cutters are easy enough to make that you don't need much in the way of expensive gear to do a creditable job.

    The second way to generate an involute tooth form is to recognize the principle that a gear of any tooth count will mate perfectly with any other tooth count gear again provided DP and PA are a match.
    That is the principle that Fellows shaper exploits, and is probably the source of the OP's misunderstanding that a Fellows shaper needs a master gear from which it makes copies.
    It in fact uses a cutter shaped like a gear but with front rake and side relief, and is almost as hard to make accurately as a hob, hence the comments made by Zahnrad Kopf on how much effort it took to make such a cutter in his own shop. (he has a custom spline application and cannot get a custom cutter made in a reasonable time)

    So there you have it; the basis for elaborate machine movements to generate a gear rather than form cutting it , and a basic (very basic) discussion on how the generating process works and the justification for doing it.

    Of all the processes, the rack form shaper cutters are by FAR the easiest to make...the demands on the precision of the motion control are roughly similar for all generating processes by contrast, so overall, a rack shaped cutter is the easiest solution when all is considered together, but it is relatively inefficient and has limitations which is why the other processes evolved.

    to add to the mix, the OP's stated goal is to be able to do all this to better precision than he can get by indexing and milling with B&S involute cutters, and to be able to do off-standard gear forms, and do them fast.
    That's why those who have experience gearmaking have been so adamant about discouraging him from investing heavily in a process that will not meet either of these goals quickly or economically.

    Interestingly EmanuelGoldstein DID recommend a forming approach (at least I believe he did) when he talked about a gear grinder capable of grinding small fine pitch gears from the solid.
    I'm assuming here that the wheel dressing is the secret, and that there is a good way to dress these wheels so you get whatever involute profile you want, dressed quickly right into the wheel.
    This is also a good approach since you can solve the major problem of getting your involute profile that way, but you need to know the magic of how the wheel dresser works.

    I have no idea, but I have used a pantographic dresser called a Diaform to make involute profiles.
    These follow a 10:1 pattern traced with a stylus manually and a super accurate (and expensive) diamond does the wheel dressing.
    You make the pattern on the CNC mill.
    With skill you can profile a wheel to within tenths.
    But you need a grinder and you need the wheel dresser and crucially you need to be able to re-dress the wheel in the same position you dressed it in the first time so you can restore the wheel to true form when it wears.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    I'm going to make another stab at stating my requirements:
    - I want to make quality relatively standard gears "on demand"
    - I am able and willing to purchase ahead of time a whole bunch of commercially made gear hobs
    - I don't have room in my small shop for yet another machine dedicated to gear hobbing
    - I'm theorizing that my new FPS 300 M manual mill is stout enough and accurate enough to make quality gears using the hobbing process
    - I'm theorizing that I can successfully sync the horizontal spindle to the rotary sufficiently well to get quality gears using electronic means

    The last two points are theories yet to be proven through experimentation.

    I'm smart enough to understand all the points that have been made on this forum, and to understand the idea that rack form cutters can be easily constructed and can cut a variety of gears whereas gear hobs are specific to a particular gear and are expensive. Other than the practical concern about costs associated with my little venture I have yet to hear a good technical argument about why what I'm attempting won't work. I'm never going to do this for production purposes, this is just part of my adventure to do small prototyping work and learn about machining in general.

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    Hi drcoelho:
    Yeah I guess we've let this thread kind of run away from what you asked for in your original post.
    But you must admit it's been fun (I hope) and instructive.

    Motion guru's advice has probably been of most direct use to help answer your original question which makes sense given that he does this kind of stuff for a living.

    I think you should go for it!
    You clearly want to do it, and I think you'll enjoy it.
    If it doesn't fully meet your expectations when it's finished, well I certainly, and probably most of us, have "projects" we dreamed big dreams about, now gathering dust in our closets too.
    But please do let us know how it's going...it would be cruel to leave us hanging having gone so far already.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    Quote Originally Posted by implmex View Post

    <-snipped->

    Interestingly EmanuelGoldstein DID recommend a forming approach (at least I believe he did) when he talked about a gear grinder capable of grinding small fine pitch gears from the solid.
    I'm assuming here that the wheel dressing is the secret, and that there is a good way to dress these wheels so you get whatever involute profile you want, dressed quickly right into the wheel.
    This is also a good approach since you can solve the major problem of getting your involute profile that way, but you need to know the magic of how the wheel dresser works.

    <-snipped->


    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Marcus,

    Actually the form created by dressing is the same form as on a hob (rack profile). And the gears are created using a generative process just like hobbing. It's a really neat way to quickly create your on hob of sorts without gashing, relieving and heat treating.

    Best regards,

    --david

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    Hi David:
    That's a very interesting concept.
    So the challenge would be to make a dresser that could put basically an Acme threadform onto the periphery of a grinding wheel.
    How did they do that back before the days of CNC dressers?
    A dresser built something like a miniature Excello thread miller?


    However what I was thinking of was the method shown in this Youtube link:
    YouTube

    Making a CNC single point diamond dresser would not be too much of a challenge, and if you could mount it over the wheel spindle like some models of the Diaform were set up, making any involute profile would be easy.
    Of course this video shows spline grinding and the machine is a tool grinder, not a dedicated gear grinder, so I don't actually know if this method is ever used to make gears, but I can't see why it wouldn't work rather well.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining


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