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  1. #21
    Member peteeng's Avatar
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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - Now that's clear. No the integrated unit provides force not torque. So the N is correct. They don't quote the motors torque. The formula for force from a screw can be found on the Hiwin site. Peter

    somewhere here https://www.hiwin.tw/products/ballsc...crew_list.aspx



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Well, Belts are expensive.. lol
    For a length of 8ft, would I need a belt to be a full continuous loop, or could I use a belt clamped at each end, and driven pulley on gantry.
    Or, am I better off reconsidering Rack and Pinion



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    Default Re: Help a Newb Build an 8x4 Machine ????

    I'm 100% with you London, I wish ClearPath and most servos were through shaft. I'm seriously considering developing my own through shaft servos for driven nut applications up into larger screw sizes, that would not be integrated with a specific screw.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - try here for belts

    https://www.ebay.com.au/str/powgesyn...4aAnE2EALw_wcB

    It can be a U drive or a continuous belt. I prefer continuous as then the belt is not bent in two directions so does not fatigue as fast. Plus you can run it at higher tension so its more accurate. A U drive the motor moves with the gantry and is a bit stiffer as the belt is shorter but if the belt is correctly tensioned I think the continuous is better. I'd estimate your a year from making sawdust so make some decisions and start getting serious in CAD... Peter



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi Peter,

    Thanks for the link, it’s not working on my iPad atm but I’ll check it out when I get in front of a pc.
    My experience of belt drive things is Engines. I used to build a fair few 1JZ/2JZ engines, often used Kevlar Timing belts, which are not cheap, but they take a hell of a beating. I’m not going to be able to afford that spec of belt being ~5500mm x2, so looking at PU and Rubber belts 50-64mm widths with 5mm centres, as there is a lot of choice of pulleys and I think it’ll be accurate enough, if like you say, it has decent tension. How long it’ll stay accurate for remains to be seen, but should last a decent while.
    I’m still investigating driven nut, but really struggling to find an ‘off the shelf’ bearing carrier, and not sure I can be bothered to design one, get them machined, and hope it works. I still believe this system will be best for my application, just a shame there is not more products readily available.


    Hi StrawberryBoi, yeah I agree, it’s a great design concept, I’m surprised they’re not available in bigger sizes.
    The ideal motor would have, a big hole that a Driven Ball Nut would slot and bolt into. So you can spec and install the ballnut that suits the size and pitch of your chosen ball screw.
    Can you get them done by the end of the week? Lol



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - 50-64mm width is way too wide. 25 or 32mm PU with steel wire will do nicely. Belts settle in then stay stable pretty much forever. I like belts for longer machines. There is a grade called ATL which is stiffer and has zero clearance teeth for precision motion applications.. I general use AT belts... Peter

    https://www.gatesaustralia.com.au/ga...e-timing-belts

    Mectrol used to have a great catalogue/design guide now its been bought by Gates the documents aren't as good. see here for guides. Especially look at the stiffness spec...

    One thing I'm toying with is to have a motor at each end of continuous. Mentally one day I see the maybe advantages then next day I see potential hiccups. Will have to try to find out.... I'd use 5:1 precision gearboxes this gives a big output shaft with strong bearings and heaps of torque...

    Last edited by peteeng; 09-27-2021 at 06:24 PM.


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    Default Re: Help a Newb Build an 8x4 Machine ????

    Thanks Peter, going for a look at those belts.

    On the Driven Nut plan, found a company that make through shaft servo motors.. specs look promising.. but, they look really, really expensive.. Iv requested a quote so I’ll post back when they get back to me.
    https://www.stober.com/synchronous-servo-motors/


    Going back to the Angle Iron talk, I’m now thinking about H beam, 100x125 or 100x150. I’m thinking about making the machine basically sit on the floor, and then make my work table suspend from the roof and lower down over the CNC when it’s not in use.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - Consider making a machine with its bed vertical up against a wall or at say 10degs. Footprint is really small and you won't have the hassle of lifting your bench. I think your making things over heavy unless you really shooting at steel. But I think you will be disappointed in the end (if steel is in the wish list as stiffness not good enough for steel. Aluminium is doable at far less mass... Peter



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Yeah I do kinda go over the top with most projects..lol

    This is the kind of thing I had in mind..
    The top is 450+18mm off the floor

    Attached Thumbnails Attached Thumbnails Help a Newb Build an 8x4 Machine ????-704b2859-b671-4549-8b41-f2eef0d62888-jpg  


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    Default Re: Help a Newb Build an 8x4 Machine ????

    Quote Originally Posted by LondonBoards View Post
    Thanks Peter, going for a look at those belts.

    On the Driven Nut plan, found a company that make through shaft servo motors.. specs look promising.. but, they look really, really expensive.. Iv requested a quote so I’ll post back when they get back to me.
    https://www.stober.com/synchronous-servo-motors/


    Going back to the Angle Iron talk, I’m now thinking about H beam, 100x125 or 100x150. I’m thinking about making the machine basically sit on the floor, and then make my work table suspend from the roof and lower down over the CNC when it’s not in use.
    I'd definitely love to hear the pricing when they get back. The axial length of this kind of a solution is an issue in smaller machines, but smaller machines also benefit less from the inertial reduction of a driven nut application.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Quote Originally Posted by LondonBoards View Post
    Hi Peter, thanks for your thoughts, I take on board what you’re saying about a flat bed, I’ll do my best, I have a Fab shop behind my unit, they have a big engineers flat table I can use, hopefully be good enough.

    Just done a quick sketch of how I envisage this layout.. I couldn’t be arsed with anymore detail at this stage so excuse the primitive sketch.
    I just found this thread and it looks like an interesting project.I took a look at your gantry scheme and would offer one thought;the gantry legs have a wide spacing for the long axis and ought to restrict deflection well.If you are using similarly powerful steppers or servos on all axes,isn't there a risk that the gantry beam and upright can flex a bit?For no extra overall width you could add a triangulation web from the widest point of the motor mount to the end of the gantry beam on each side and it would add a good bit of resistance to deflection.

    I am a little curious about the hold down system you are intending as a vacuum system is ideal for sheet materials,but expensive and a real power hog.Threaded inserts in the table are all too often in the way of the cut but do allow for long bolts for the bigger beams you may find yourself cutting.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hahahaa.... ahahaaa.. hahahaaaa.. sorry StrawberryBoi, I’m still laughing from the quote I received today from Stober... £1500 gbp EACH. They are made to accept off the shelf sizes rotating ball nuts... but they can suck a massive di.. if they think I’m paying that. I will try blagging and seeing if they offer anything more cost effective, but not looking good.
    Back to the drawing board..

    Hi Routalot, thanks for your observations, the drawing is just a very basic drawing, I was thinking the same, I will most likely add some bracing, it’s ones of those things thatll evolve as it goes. I will Tig weld most the Gantry components, it’ll be hard as hell, I’ll soon feel whether it needs strengthening up or not. I’m cautious of adding more weight if it’s not needed, but there’s an argument to say more weight is better for stability, will see how it feels..lol

    I’m keeping on keeping on with the rotating nut method, or through hole motor.. I think it’ll be more user friendly in the long run.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - The ducks nuts is linear motors. Hiwin have them... Peter

    https://www.hiwin.us/products/linear-motors/



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi Peter,
    Do you mean the LMT series? That looks like witch craft to me...lol
    Also looks amazing.. I’m looking at LMT6T, does that look a suitable spec you you? Although it does say max stroke is 1050mm, not sure why it’d have a max stroke.

    https://motioncontrolsystems.hiwin.u...t-series/lmt6t

    Iv also seen the TMRW series of hollow motors. Can you take a look at the spec of TMRW13L and see if that would be suitable for driven nut system?

    https://motioncontrolsystems.hiwin.u...series/tmrw13l



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    Default Re: Help a Newb Build an 8x4 Machine ????

    I've worked on linear motors, odd challenges to make them and really large work space required vs traditional servos, so that is the main reason for high cost in them.

    Have to really make sure you are getting the forces you want when selecting one, if you go with a small "car" to utilize the stroke then you will reduce the force it outputs.

    C profiles which have magnets on both sides of the axial-flux stator are the strongest in terms of force, but the most PITA to build and so almost universally avoided by manufacturers.

    The one sided ones are great though still, but you have to support the "car" at a small gap, typically 1-2mm with +/-25% variation allowed, across the stroke. Shouldn't be an issue with linear rails.

    They come in induction and permanent magnet varieties typically. You can get separately excited varieties.

    The servo company I previously worked for made a lot of them in arc forms for antenna positioning on satellite receiver/transmitters in commercial aerospace. You know, so you can text your spouse while in the air or pay $24.99 for crappy internet.

    Almost all of our linear stages for semiconductor mirror control used linear voice coil motors. Super freaking fast response but low overall force.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    BTW not shocked on that pricing, it's a niche market and having a large through bore is a real challenge. For one, almost all go to encoders for small servos stick on the end of a shaft and the larger diameter ones sometimes have severe speed limits.

    That said, if I knew there were going to be orders for a hundred or so I could sell a one size solution for that in the range of $750 and be sitting fairly pretty. It would take 2-4 months to develop, proto, tweak, and then standard lead times after that of about 6 weeks in current market.



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - No look at LMX series. Peter

    If I were to make a driven nut design I'd use a stepper or servo motor with a belt to geared nut. There's a few on the forum. Need to sort the bearing & housing for the nut. But for your application neglecting metal, belts are the go, cheaper then R&P just use a big belt.. Peter



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    Thumbs up Re: Help a Newb Build an 8x4 Machine ????

    Hi Peter, I’m going to get a quote from Hiwin for the LMX, and LMC system, looks easier to implement and possibly cheaper.
    This is link to the specs page, which power would you suggest? If you have time.
    Really liking the look of this system, hard to find any prices online but possibly cheaper than those hollow shaft steppers, and more spec than you can shake a stick at, super quiet, while not wearing out. What’s not to like?

    https://motioncontrolsystems.hiwin.u...ors-lmc-series

    Many thanks



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    Default Re: Help a Newb Build an 8x4 Machine ????

    Hi London - What's not to like? Cost I expect... Typical ballscrew designs can apply well over 100kgf in any axis. Over 200kgf for metal cutting. The LMC series top sizes can apply 100kgf and 400 peak. Try LMC-EFE6? I've seen them used on laser cutters but not router/mill applications ask Hiwin about that. Peter



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    Default Re: Help a Newb Build an 8x4 Machine ????

    You really should consider the loads you'll actually apply though under cutting. A 1/2" cutter running at 10Nm of torque is requiring 160kgf, but this is a rather extreme example which is 2-3 times the real torque a solid carbine tool cutting >300HB steel, such as through hardened 4140, should ever see with real speeds and feeds.

    Are you going to hog hard steel with a 3" cutter using the LMX system? For sure not, but are you ever going to do that anyways? If you can think through the actual types of cutting you'll be doing, the speeds you want to move, the acceleration you'll need while under cutting load, then you can work out something with 2-3 times the force you'll need and have a solid setup.



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