Used HMC decisions, full 4th ?
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  1. #1
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    Default Used HMC decisions, full 4th ?

    I am in the market for a used 500mm HMC.

    I currently have an older 3 axis VMC and I have never had any hands on experience with a 4th.

    I am trying to figure out when a full 4th would actually be beneficial. The only way i can really think about it being beneficial over a 1 degree indexing B axis is if you have the part located on center and then you can use it do continuous contouring on the outside profile of the part.

    An older generation of the same machine has 1 degree indexing while the newer version has full 4th capabilities and is a direct drive servo on the B axis so there would be no worrying about that.

    How much of a price premium would you pay to have that option? Between tombstones, tooling, etc... there will be alot of places i could spend the money if its not something that will be very beneficial to me.

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    Quote Originally Posted by blkaplan View Post
    An older generation of the same machine has 1 degree indexing while the newer version has full 4th capabilities and is a direct drive servo on the B axis so there would be no worrying about that.
    This is outside of my swim lane a bit, but I did recently have an experience that might be beneficial to know. Working on a large part volume order with simultaneous work, and an outside vendor with a full 4th Mori NHX had nothing but issues getting a quality cut on the part, despite the machines being quite recent and well optioned. DMG Mori was brought in and the best they could do was quote $20k per machine to install inverse time feed + higher grade look ahed, but (even with all that) they would not guarantee that it would fix the problem. In the end, they had to have a bunch of meetings and do some geometry changes on the part to make it work.

    I got to talk to a lot of folks and do some learning here, my takeaways:

    1- The number of parts that need full 4th axis motion are very rare, as it is a very narrow target. Anyone designing/engineering a component is likely going to target 3 axis or 5 axis. Very few engineers/designers are thinking simultaneous 4th axis.

    2- The industry focus is really 5 axis on the machine, controller, and CAM side. Slap a full 4th on an intrinsically 3 axis machine (or HMC), and you aren't getting features like tool centerpoint or inverse time feed, glass scales, etc that make simultaneous axis motion truly successful. Even the CAM tools for 4th axis motion are really kinda tacked on afterthoughts as software developers focus on making amazing 5 axis tools.

    3- Everything above comes from a project with complex swarf geometry, and probably doesn't apply to something like pockets or line engraving around wrapped cylindrical surfaces. Once you get into work from designers playing with curvature continuity and high-spec surface finishes driven by splines? That is when basic 4th axis setups will really start to shit the bed and you'll want something from Germany with a Heidenhain control on it.

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    My personal opinion differs from above.

    I ran\programmed a Makino a51nx and Haas Multigrind for a few years, before becoming self employed.
    Now, I will say, those machines spoiled me. Also taught me to think differently.

    A good quality full 4th machine, horizontal OR vertical can be a real weapon. IF you can program it.
    Add in tcp, twp, and tool\part probing, life is a breeze.

    All depends on where you want to be price point wise.

    I do quite a bit of simultaneous 4 on my Fadals, and find it really yeilds the opportunity to get creative with fixturing and processing. All it is, is 5 axis toolpaths with an axis locked out.
    You have to learn to think outside of the 3ax constraints.

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    Quote Originally Posted by macds View Post
    My personal opinion differs from above.
    We aren't really in disagreement.

    The point I am making is very narrow - a basic HMC with just the full 4th axis option does not make that machine fully capable of performing every 4th axis simultaneous cut you can throw at it. Simple, linear code for a pocket or text, wrapped around a cylinder concentric to the B axis is not a problem.

    ... what is a problem is if you expect to do complex geometry, often at funky locations off of the rotary concentricity, with long strings of surfacing code or fussy machine motion requirements. These are the kind of cuts that drove 5 axis programmers fucking bonkers until things like TCP/glass scales/kinematic calibration became standard. If you want to do that kind of work, you will want a machine that has those aforementioned features (in which case, this kinda stuff is a breeze). If that kind of work is what you are after, just be cautious when shopping for an HMC because there is more to the equation than the full 4th option - you need to make sure it has all that other stuff.

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    IME, the importance of full 4th has more to do with the ability to index in increments finer than 1 degree.

    For the parts we make, we're happy with 1-degree and it's bulletproof.

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    I don't have much experience with full 4th axis, except very basic on a vertical with rotary, so not sure it applies to an HMC or not... I doubt it would be worth the extra cost in the long run. If you find a used HMC with it, and the price isn't a dealbreaker, sure get it. But I think when you really need it is going to be at a minimum. If you have that work currently (full 4th) yes by all means look for it, but if you are just trying to "future proof".. eh...

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    Quote Originally Posted by blkaplan View Post
    How much of a price premium would you pay to have that option? Between tombstones, tooling, etc... there will be alot of places i could spend the money if its not something that will be very beneficial to me.
    What kind of price range are you looking to spend for your used HMC? 30k? 100k? That will change the "how much more" answer.

    We have 3 horizontals, all have .001 on the rotary, and let me tell you that, while doing vise work at 0/90/-90 degrees on tombstones that never leave the machine, 1 degree should be fine. Even when you need a feature at 45 or something. There are certainly times that you have a stupid feature at stupid angle, 34 degrees 12'22" or something like that, but usually not.


    Where I appreciate the fact that our machines all have .001 the most, is when putting a stupid fixture down on the pallet with no tombstone on it, I can pretty much plop it anywhere, tighten it down, put it in the machine, indicate it in, and set B to whatever angle it is at. Don't have to "tap it in" to the nearest degree. Super nice.

    I am running a job where I do segments of an "impeller blade" type part (not an impeller, but a similar looking feature) where I move xyzb all at the same time, in 1/2 degree segments. Couldn't have done that without it. But I agree that it is pretty rare to require full 4th interpolation.


    Now I have a question, is 1 degree indexing a "good feature"? I don't know how to phrase what I mean. I guess what I am asking is, how are these 1 degree machines driven, motor-wise, and why is it seemingly common? Does the pallet lock into 1 degree increments (like a curvic coupling or similar) or does the motor/worm/gear hold it there? It just seems like with motors having lots of pulses on them, and rotary gear ratios, I don't see how .001 isn't the absolute norm. What am I missing?

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    Most, maybe all, indexing rotaries on HMCs use a curvic coupling. HBMs typically use shot pins at 90 degrees and sometimes at 45 degrees. Indexer drive systems vary widely. I've seen servo motors, 3 ph motors, hyd. motors and probably others that I've forgotten. The drive mechanism in an indexer is far less accurate than what is used on a full 4th axis. It only has to get the rotation close to the index and the coupling or pins do the final alignment. 5 and 15 degree indexers are pretty common too.

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    If you do seven-sided parts or drum cams, .001* (contouring 4th axis) would be necessary. Otherwise, 1* is normally plenty. Even 90* is all right for most work.

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    You can always dedicate a pallet to a stand-alone rotary table and controller, if you purchase a machine with 1 degree and down the line have a need for it.

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    Quote Originally Posted by dandrummerman21 View Post
    What kind of price range are you looking to spend for your used HMC? 30k? 100k? That will change the "how much more" answer.
    I'm expecting the 1 degree older generation to be around 75k and the full 4th direct drive to be around 120k.

    They both have the same control, newer version has a 14k spindle vs 12k spindle.

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    Quote Originally Posted by macds View Post
    My personal opinion differs from above.

    I ran\programmed a Makino a51nx and Haas Multigrind for a few years, before becoming self employed.
    Now, I will say, those machines spoiled me. Also taught me to think differently.
    .
    I am basically looking at a Pro5 Makino A51 vs the Pro5 A51NX

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    If it was a 5 degree index, I'd be thinking really hard.
    But for a 1 degree, I'd go for it and the money saved I'd tool the thing right up.

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    We run 5 HMC. Only one has the full 4th. When we need it, we really need it. But it isn't very often.

    We mostly use it for work that has funky angled cuts. Like 22.5°.

    If you don't have a need for it already, I would skip the full 4th and use the money for accessories that will be needed.

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    Quote Originally Posted by blkaplan View Post
    I am basically looking at a Pro5 Makino A51 vs the Pro5 A51NX
    If you can swing it in the budget, the nx all day long.
    Once you get your head wrapped around it, youll be in love.

    Check the options list, if you want (or can) forward it to me... I can tell you exactly how its optioned\what it means.
    Makino support is excellent, and I can put you in touch with one of THE best applications guys in the northeast.

    Heres my lost love...


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    Quote Originally Posted by macds View Post
    If you can swing it in the budget, the nx all day long.
    Once you get your head wrapped around it, youll be in love.
    Thanks for the video, thats pretty much exactly how i was thinking you might use something like a full 4th on a HMC beyond being able to index less than 1 deg.

    Its a tough call because the reg A51 has the extended ATC (~130 tools) and probing built in.

    I think the NX is just the 60 and no probing... After getting a quote of 23k to get TLM and part probing installed from Makino I am weighing heavily preinstalled options.

    I sent you a DM

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    23K for tlm+PP is pretty decent in my opinion.

    For part probing, you want to talk to PQI.
    Not cheap, but its renishaw hardware, with PQI's custom macros setup how you want.

    Our tool check\guaging was Blum laser.

    We did a lot of high end "job shop" type stuff with the a51nx (not production), and found the 60 tool magazine to be almost enough.

    Keep in mind, for 120K + setting up probing, youre getting a hell of a machine (optioned, it was north of 500K USD when we got ours).

    Again, its going to come down to budget, and ROI.

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    I prefer 1 deg indexing on the HMC's.

    Full 4ths on a vert for sure, but you can run shaft type work on those.
    It's kind'a tough to mount a tailstock on a Horizontal in most apps.

    I have one of each, and MUCH prefer the 1 deg!
    I have had issues with thrust loads the further that you get from center on full B's.
    Not so on the 1 deg.


    As was posted further up - if I had 5 of them, I would expect 1 of then to be a full B, but not the rest.
    There's just not many times that you are likely to find yourself in need of one on a Horizontal.


    -----------------------

    Think Snow Eh!
    Ox

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    Ox is right, seldom is a full 4th needed or used on a horizontal.

    Ox also mentioned rigidity, which can be a factor between a 1-degree machine versus full 4th. The 1-degree machine will most likely have a curvic coupling to lock the index in position (probably clamped down with hydraulics), whereas the full 4th is held in position only by the servo motor and related gearing.

    Could make significant difference in cutting performance, espcially higher up on the tombstones...

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    We're maxing out the X-axis travel on this tombstone, about 11" from centerline to hit the chamfers.

    The centerline of the bores are roughly 8.5" from the B-axis centerline.

    This is a 1-degree machine.



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