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Thread: 6-axis Horizontal Machining Center for Education

  1. #161
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    Default Re: 6-axis Horizontal Machining Center for Education

    Me, I would question the idea of incorporating old-fashioned coolant. Many advanced aerospace and automotive companies in the USA and Europe have moved to MQL and pulsed misting - and are getting double the tool life. I do not use coolant myself.
    But yes, you do need good way-covers, possibly even sealed ones.

    Cheers
    Roger



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    Default Re: 6-axis Horizontal Machining Center for Education

    Quote Originally Posted by handlewanker View Post
    This build is going above and beyond the realms of credibility....too many variables...…….one micron?....try .02mm at best.

    If Kitamura have claimed to get repeatability of that figure it's because they've been in the game for years to achieve that claim.....you are not even near to getting anything off the ground this century.

    I did say you.....this is regarding the one off prototype build you are anticipating as any production models would no doubt be built by a fully competent workplace that had the equipment and expertise to get the specs right.

    Just cooling a ball nut does not achieve anything...…..cooling the ball screw itself would if you have a problem, but pushing a machine so hard to overheat the ball screws does not give you room to achieve 1 micron accuracy.

    You forget that the ambient temperature all year round fluctuates and that will make any dissimilar metal on your build also fluctuate differentially one to another...…..this will also affect the epoxy granite mix as it's not a good heat resistant material.

    BTW.....are you also going to temperature control the linear ways...…..being tied down at 60mm intervals will make them exert pressures longitudinally like a railway track in the sun.

    I realise you have high ambitions and expectations, even if not immediately achievable, given the very fullness of time no doubt you will get to where you are thinking of, so with my very best wishes.....go forth where not many men have been before and do your best but at the same time accept your failures too.

    BTW....I like the idea of the wood panel mock up to see if the design is actually feasible...….my exact mode d'employ…..though I don't aspire to the notion that if it looks good it is good......total BS......if it looks good it's a toy.
    Ian.
    "Success consists of going from failure to failure without loss of enthusiasm."
    —Winston Churchill



  3. #163
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    Default Re: 6-axis Horizontal Machining Center for Education

    Quote Originally Posted by RCaffin View Post
    A thought for you if you are going with a cast base and frame:
    Include some copper tubing for cooling water for temperature stabilisation.
    You will need water cooling for the spindle anyhow, so a good INDUSTRIAL pump will be needed. Do NOT buy a domestic water pump: they don't last.

    Cheers
    Roger
    Roger,

    We've been thinking about that quite a bit indeed. It's not very difficult, it does not change the rest of the machine's design, it's not really expansive, and it could bring significant benefits. The selection of the pump is chiller is the tricky bit.



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    Default Re: 6-axis Horizontal Machining Center for Education

    Quote Originally Posted by jkkmobile View Post
    There are no way covers? If you are locking the final travel now you need to add room for way covers specially between bed and upright colum..
    You're absolutely right. I have yet to being looking into that, and I fully expect the addition of way covers to shuffle the design one more time, but if we try to get everything in at the same time, we won't get anywhere. So, I'm approaching the design in the following sequence:

    1. Finalize overall dimensions.
    2. Finalize motors and ball screws placements.
    3. Design linear encoder placement.
    4. Select way covers and design placement.

    We're at #2 now.

    Any recommendations for a good supplier?



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    Default Re: 6-axis Horizontal Machining Center for Education

    Quote Originally Posted by RCaffin View Post
    Me, I would question the idea of incorporating old-fashioned coolant. Many advanced aerospace and automotive companies in the USA and Europe have moved to MQL and pulsed misting - and are getting double the tool life. I do not use coolant myself.
    But yes, you do need good way-covers, possibly even sealed ones.

    Cheers
    Roger
    Roger,

    We're definitely going for MQL, using this:

    CNC Machinery Lubrication System - Automatic Lubrication System - Quantum | Unist

    But we still need way covers. Not sure they need to be sealed though. Our roller guide, ball screw nuts, and linear guides are already sealed.



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    Default Base with Draft Angles

    Here is the new base designed as a mineral casting. For that purpose, it includes 5° draft angles for all vertical surfaces that require it. This draft angle can be 3° to 5°, per manufacturer recommendations. It might not look like it, but this makes the parametric design a lot more complicated that when surfaces are all square. I have also adjusted the design in such a way that parameters are more meaningful and can all be changed independently of each other. This as well is a lot harder than it seems at first and will clearly take quite a bit of practice before I can get it right at the very first attempt.

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-base-jpg   6-axis Horizontal Machining Center for Education-parameters-jpg  


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    Default Base Assembly

    We still need to verify that design with our mineral casting supplier, but I think we should mount our X-axis rails on a pair of ground steel beams instead of mounting them directly onto the mineral casting. This would have the advantage of ensuring much tighter tolerances and would make it much easier to machine the threaded holes for installing the rail shoulder plates. Furthermore, it would allow us to use shoulder plates instead of a weaker shoulder profile. This is due to the fact that threaded holes on a mineral casting cannot be too close to an edge, especially when a lot of torque is applied. Also, on the other side of the beam from where the rail shoulder plates will be mounted, we could have threaded holes for mounting our linear encoder (on just a single beam of course).

    Ideally, these beams should be bolted onto the casting after the top of the casting's ribs have themselves been ground.

    One thing I am wondering is the pros and cons of this approach from a thermal expansion standpoint, knowing that the thermal conductivity of steel is 25 to 40 times the one of a mineral casting, but its thermal expansion coefficient is about half. Any idea?

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-base-assembly-jpg  


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    Default Rail Shoulder Plate

    We've added a rail shoulder plate for the rails of the X axis. We'll do the same for Y and Z later as soon as we have them on the new design. These plates are 25mm x 10mm and have half as many bolts as the rails do, while having the bolts offset from the ones of the rail in order to make sure that we do not have interference between holes. The number of bolts was inspired from what we saw on this excellent video:



    I could watch that kind of stuff all day... And you've got to love the white gloves...

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-rail-shoulder-plate-jpg  


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    Default Machine Frame

    Here is the full frame for the machine, made of two separate mineral castings. I considered doing the whole thing as a single casting, but I think it will be easier (and possibly cheaper) with two. That being said, I don't think I'll be satisfied with just epoxy for attaching them together, which is the reason why I have added some flanges at the bottom of the vertical column, just so that we can put some big fat bolts as well. They might be useless, but I'll sleep better at night knowing that they're in there, just in case...

    The draft angles give the machine a really massive look, which I find kinda pleasing to the eye. I know this is purely cosmetic and subjective, but to be clear, these draft angles are required for the mineral casting. So, we get good looks for good mechanical reasons, not just because we like our machine to look good.

    Besides, look should never be underestimated. It falls into the category of marketing, but marketing sells, and sales help make cool machines...

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-column-jpg   6-axis Horizontal Machining Center for Education-machine-front-jpg   6-axis Horizontal Machining Center for Education-machine-perspective-jpg   6-axis Horizontal Machining Center for Education-machine-profile-jpg  



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    Default Hydraulic Cylinders for Z-Axis Counterbalance

    Here are the two hydraulic cylinders for the Z-Axis counterbalance. They're bolted into 220mm recesses within the base casting. 2" bore, 3,000 psi, 25"1/4 stroke. Just enough for 25" of travel on Z. Probably oversized, but I'd rather stay on the safe side.

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-4-44-a   6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-4-44-a  


  11. #171
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    Default Redesigned Column

    Once I looked at our new column, it immediately felt much less balanced than our new base. This is because the base is putting the motors on the outside of the carriage, while the column is putting them on the inside. By going outside, the rails get closer to each other (probably a good thing), and the motors will have more leverage over whatever they're trying to move. Therefore, I've decided to apply the same treatment to the vertical column, and I really like the outcome. This redesign will make it a lot easier to install and maintain the motors. It should also allow me to attach the hydraulic cylinders directly to the ball screw nut mount, which further simplifies the design and should make the overall assembly a lot more rigid.

    This is the first time I attempt a project of that kind, and I am struck by the sheer number of options that one has to consider before arriving to a half-decent design. The number of permutations and combinations is just mind blowing... But it's a ton of fun...

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-7-27-a   6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-7-27-a  


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    Default Frame with ATC Conveyor

    Here is the new machine frame with its ATC conveyor.

    I really, really like where this is going...

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-8-03-a   6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-8-04-a  


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    Default Re: 6-axis Horizontal Machining Center for Education

    Hi Ishi

    MQL is GOOD.
    But don't pay too much for it. You don't need all the bells and whistles. I made my system out of 'scraps', see 7724.
    The nozzle end is shown in 7721. The mist is sucked out of the micro-tube (see black arrow) by venturi action.
    The interesting thing about all this is that you CAN have the liquid valve quite some distance from the nozzle, for pulses down to a fraction of a second.
    I use M8 to turn on the air blast and M7 to turn on the pulsed mist. An electronic timer does the actual pulsing.

    OK, you may not want to DIY, but this does show that a very simple system works as well as the expensive ones.

    Cheers
    Roger

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-7724-jpg   6-axis Horizontal Machining Center for Education-7721b-jpg  


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    Default Re: 6-axis Horizontal Machining Center for Education

    Quote Originally Posted by RCaffin View Post
    Hi Ishi

    MQL is GOOD.
    But don't pay too much for it. You don't need all the bells and whistles. I made my system out of 'scraps', see 7724.
    The nozzle end is shown in 7721. The mist is sucked out of the micro-tube (see black arrow) by venturi action.
    The interesting thing about all this is that you CAN have the liquid valve quite some distance from the nozzle, for pulses down to a fraction of a second.
    I use M8 to turn on the air blast and M7 to turn on the pulsed mist. An electronic timer does the actual pulsing.

    OK, you may not want to DIY, but this does show that a very simple system works as well as the expensive ones.

    Cheers
    Roger
    Roger,

    That makes perfect sense to me. On the long run, we should definitely make our own system, because there isn't a lot of magic in there. And I really like yours. Very clean. But for the first batch, using something off-the-shelf will save us quite a bit of time and pain. At $5k, the Unist Quantum isn't cheap, but compared to the total price of the machine, it's only 2%.

    What we need to work on is the mounting of our MQL nozzle onto our 2-axis head. Of course, when doing so, we won't be able to get endless rotation on C. I need to talk to HSD to get an idea of how other manufacturers are dealing with this issue.



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    Default Going from 32 Tools to 36

    With our new design for the vertical column, we had to deal with some constraints related to the spacing of ribs for the linear rails, and without going into too many details, the easiest solution was to move from a 32-pallet conveyor to a 36-pallet one. This allowed us to put the conveyor's flanges on the vertical column further apart from each other, thereby giving us enough clearance in the column's canal for the spindle head and conduit profile as well as for the hydraulic cylinders' rods. The resulting design is even more imposing... I'll let you decide whether this is a good thing or not. Bud we got 4 more tools as a result!

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-9-36-a   6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-9-36-a  


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    Default Re: 6-axis Horizontal Machining Center for Education

    Easy enough.
    At the end of the spindle there is always a non-rotating outer bit, larger diameter than the actual spindle itself. Clamp onto that and adjust nozzles to point towards the tip of the cutter. Then use silicone rubber tubing to hook up to the hoses. Make the hoses long enough and you should be able to retain full rotation.

    I have in fact done something very similar to this to my spindle to add water cooling to it. It has rather large solid bearings, and they were getting hot after a few hours running 'fast'. Now I can run flat out all day and keep the bearings cool. Flexible Si rubber tubing is your friend.

    Cheers
    Roger



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    Default Re: 6-axis Horizontal Machining Center for Education

    Quote Originally Posted by RCaffin View Post
    Easy enough.
    At the end of the spindle there is always a non-rotating outer bit, larger diameter than the actual spindle itself. Clamp onto that and adjust nozzles to point towards the tip of the cutter. Then use silicone rubber tubing to hook up to the hoses. Make the hoses long enough and you should be able to retain full rotation.

    I have in fact done something very similar to this to my spindle to add water cooling to it. It has rather large solid bearings, and they were getting hot after a few hours running 'fast'. Now I can run flat out all day and keep the bearings cool. Flexible Si rubber tubing is your friend.

    Cheers
    Roger
    Fair enough. But we might need something a bit more advanced if we want to be able to deal with tools of different lengths. I think we'll need a small rotary actuator for the MQL nozzle. Nothing fancy, but this should make a big difference when dealing with very long tools, like the ones you use for the finishing pass on molds. It should be easy to add later on though (no ripple effect on the rest of the machine's design).

    By the way: thanks a lot for the encouraging words regarding MQL. This is *really* helpful.

    Ismael



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    Default Chip Evacuation

    Now that we have moved the motors for the X axis on the outside, we're left with a giant empty canal in the middle. So, how can we put it to good use? Well, maybe we could figure out a proper way to get chips out of the machine. I know that this was out of the original design requirements, but we're making some solid progress here, and I see no reason why we should slow down.

    The traditional method for chip evacuation is based on using some chip evacuation screw, but I'm not sure this would work best for us, especially when using MQL instead of traditional coolant. My intuition is that some kind of conveyor belt might work better, especially if we were to design our way covers in such a way that all the chips would gently fall in the middle. Thoughts?

    Attached Thumbnails Attached Thumbnails 6-axis Horizontal Machining Center for Education-screen-shot-2018-07-22-9-56-a  


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    Default Re: 6-axis Horizontal Machining Center for Education

    deal with tools of different lengths.
    A lot of systems deal with that by having the nozzle placed very close to the shaft of the cutter, pointed downwards. This config is fairly insensitive to the length of the cutter as the angle is so shallow. Also, the pulsed mist does spread out a bit, which helps as well.

    The traditional method for chip evacuation
    The trad method assumes a relatively low-velocity liquid stream. Air blast with MQL lets you clear the chips with the air blast. Works for me.

    Cheers
    Roger



  20. #180
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    Default Re: 6-axis Horizontal Machining Center for Education

    Hmmm.....lots of planning etc...….who was it that said "once the battle commences all plans are obsolete"?....some German guy, Bismark I think, last century or so....never a truer word spoken in earnest.

    No doubt you will continue to rationalise the plan as it further evolves......lets hope by the time it gets on the ground they haven't re-invented the wheel......that seems to happen with monotonous regularity with technology.

    So I would advise, get it together and make a mock up, then stand back and see where you're going to go next......seeing something in the flesh usually gives you a different perspective of the plan.
    Ian.



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