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  1. #201
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    Default Re: My CNC Router Build Adventure

    Hi Jayne - The next issue once you have the mech specs is how to measure the actual belt tension to establish if the motor spec is exceeded. I have been working on and off that one for quite a while. The belts definitely run better the higher the tension. You could use a luggage scale to pretension the motor then you will know the belt tension. Peter



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    Default Re: My CNC Router Build Adventure

    Grrrrrrrr........ I have managed to create some type of weird circular reference between the fixed bearing mount and the plate it's mounted on so any change made to one part messes up the other part. I really need to learn how to use Fusion properly after finishing this project. Time to redraw those two parts......



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    Default Re: My CNC Router Build Adventure

    Hi everyone,

    I got the circular reference problem sorted out by turning “capture design history” off and then back in again. To the best of my limited knowledge, that is the same as switching to direct modeling mode and then back to parametric mode in Fusion. Doing that has got me out of trouble a few times when the model starts misbehaving with a long and messy timeline.

    Stepperonline responded quickly to my email asking for max limits on the motor shaft. This is the response they gave me:

    The motor 23HP45-4204S can apply a maximum dynamic axial load of 15N and a maximum dynamic radial load of 75N to the shaft.

    That is for their Nema23 3Nm stepper with a 10mm shaft. So if I understand this correctly, 75N is roughly 7.5kg which would be the maximum belt tension I could apply, if I was to use something like a luggage scale to measure. So maybe tension the belt to 4 or 5kg to allow some safety factor. Does that sound about right?

    Jayne



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    Default Re: My CNC Router Build Adventure

    Hi Jayne - On my belt machine I tensioned by feel. Just kept snugging until it worked right so don't have a real number on it. A 12mm AT5 belt is recommended to have max tension of about 500N (this gives infinite life) so its not the belt to worry about its the bearing or the shaft. 5 - 7.5kg is easily achieved by hand tension so start around that and see how it feels. A 10mm deep groove bearing has a radial static strength of around 2000N(200kgf) so I think the loads are for an infinite shaft life... I expect tighter then 7kgf will be OK if needed....Peter

    also remember that 7kgf on the shaft is only 3.5kgf tension in the belt...

    Attached Thumbnails Attached Thumbnails My CNC Router Build Adventure-belt-1-jpg   My CNC Router Build Adventure-belt-2-jpg  


  5. #205
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    Default Re: My CNC Router Build Adventure

    Hi Peter,
    Thank you for the belt info.



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    Default Re: My CNC Router Build Adventure

    Quote Originally Posted by JayneV View Post
    Hi Peter,
    Thank you for the belt info.
    You don't want to be using any of those Timing Belts, in the chart, if you can get the GT-5MGT Belts and pulleys, these are the only Timing Belts that have almost zero backlash, all the rest have backlash.

    The 5 is 5mm pitch, and 15mm wide Belt would be all you need for your machine

    Mactec54


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    Default Re: My CNC Router Build Adventure

    Hi M54 - Unfortunately Gates bought Mectrol and Gates technical publications aren't as good as Mectrols where. IMO the GT and AT sections don't have much difference in performance from what I can read. If you want a true backlash free belt the only one I can find is an ATL spec. This is specifically made for linear motion applications not power transfer applications. They are twice the cost of an AT belt and have zero clearance teeth. But in this application with a 180deg wrap all belts at correct tension will have very very low backlash probably zero... Its more important to look at the specific stiffness of the belt to make a decision in this application, the stiffer the better and make it a medium size pulley not too small. I can't find this info in the Gates manual for the GT-5MGT series unfortunately... Plus we are in Austraaaalia which is at the end of the earth so we have limited sources of lots of things. Even though they are in the catalogues, distributors don't stock and importers don't import stuff...We can get stuff mail order from China to here faster then I can get stuff from Gates for instance, if Gates Oz have it that is.... Peter

    https://www.gatesaustralia.com.au/~/...us-nz-2018.pdf



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    Default Re: My CNC Router Build Adventure

    Hi M54 - I tried to send a request to Gates via its technical portal and Australia is not even on its country list. So I give up on Gates.... Peter

    Attached Thumbnails Attached Thumbnails My CNC Router Build Adventure-gates-jpg  


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    Default Re: My CNC Router Build Adventure

    Hi All - Its difficult to wad through the marketing hype vs the easy technical numbers. Gates (and other corps) prefers to sell propriety product vs std product. Once you buy a GT pulley you are committed to GT-Gates product into the future. If you use an AT pulley you can pick from many suppliers.. choose your poison.

    I can't find the specific stiffness of the GT belts so its hard to compare the GT to the AT. But Gates do say that the T & AT have "perfect" meshing vs the GT at "highest accuracy". Obviously hype, I'll leave it at that. Peter

    RE GT - carbon is used so the life of the belt is longer as CF does not fatigue like steel does. Steel and CF are the same stiffness so if the same volume of fibre is in each belt the stiffness is the same CF vs steel. The CF does not fatigue and is a smaller fibre diameter so the pulley size can be smaller. Also the CF is 1.8 SG vs steel at 7.8 so the centrifugal forces are much less. This all says the CF belt is better as long as its the same stiffness as the steel belt. In this application specific stiffness is really important so its worthwhile tracking that number down....

    edit - and KUKA use AT belts in their robots and I'm sure they are worried about backlash. So I don't think its about the profile, I think its about designing & implementing the system correctly...

    Attached Thumbnails Attached Thumbnails My CNC Router Build Adventure-gates-t-jpg   My CNC Router Build Adventure-gates-gt-jpg   My CNC Router Build Adventure-kuka-belt-jpg  
    Last edited by peteeng; 10-21-2021 at 07:00 PM.


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    Default Re: My CNC Router Build Adventure

    Quote Originally Posted by peteeng View Post
    Hi M54 - Unfortunately Gates bought Mectrol and Gates technical publications aren't as good as Mectrols where. IMO the GT and AT sections don't have much difference in performance from what I can read. If you want a true backlash free belt the only one I can find is an ATL spec. This is specifically made for linear motion applications not power transfer applications. They are twice the cost of an AT belt and have zero clearance teeth. But in this application with a 180deg wrap all belts at correct tension will have very very low backlash probably zero... Its more important to look at the specific stiffness of the belt to make a decision in this application, the stiffer the better and make it a medium size pulley not too small. I can't find this info in the Gates manual for the GT-5MGT series unfortunately... Plus we are in Austraaaalia which is at the end of the earth so we have limited sources of lots of things. Even though they are in the catalogues, distributors don't stock and importers don't import stuff...We can get stuff mail order from China to here faster then I can get stuff from Gates for instance, if Gates Oz have it that is.... Peter

    https://www.gatesaustralia.com.au/~/...us-nz-2018.pdf
    There is a very big difference in performance between the 2 belt designs, the power rating alone is more than double for the GT3 over the AT belt, of the same size, they are available in Australia as users here on the Zone, have used them in Australia, if you can't get them they are available to ship to Australia

    Not true the AT belts have backlash, does not matter how the belts raps around the Timing pulley, the tooth design has to have clearance ( Backlash ) for it to work, the GT2 / GT3 series have near Zero backlash, and can have Zero clearance, depending on the Timing Pulley Machining.

    Look under GT2 or GT3

    Here is another link, they can also be found on eBay, this is a good supplier also for Timing Pulleys and Belts. they have a design tool also to get your center distance with the Timing Pulley and Belt selection, so is easy to get the right parts, most you will have to do is bore and keyway the pulleys to suit you motors and what ever you are driving.

    https://www.sdp-si.com/products/Timi...leys/index.php

    https://www.gatesaustralia.com.au/ab.../contact-gates

    Last edited by mactec54; 10-21-2021 at 08:21 PM. Reason: added more content
    Mactec54


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    Default Re: My CNC Router Build Adventure

    Quote Originally Posted by peteeng View Post
    Hi All - Its difficult to wad through the marketing hype vs the easy technical numbers. Gates (and other corps) prefers to sell propriety product vs std product. Once you buy a GT pulley you are committed to GT-Gates product into the future. If you use an AT pulley you can pick from many suppliers.. choose your poison.

    I can't find the specific stiffness of the GT belts so its hard to compare the GT to the AT. But Gates do say that the T & AT have "perfect" meshing vs the GT at "highest accuracy". Obviously hype, I'll leave it at that. Peter

    RE GT - carbon is used so the life of the belt is longer as CF does not fatigue like steel does. Steel and CF are the same stiffness so if the same volume of fibre is in each belt the stiffness is the same CF vs steel. The CF does not fatigue and is a smaller fibre diameter so the pulley size can be smaller. Also the CF is 1.8 SG vs steel at 7.8 so the centrifugal forces are much less. This all says the CF belt is better as long as its the same stiffness as the steel belt. In this application specific stiffness is really important so its worthwhile tracking that number down....

    edit - and KUKA use AT belts in their robots and I'm sure they are worried about backlash. So I don't think its about the profile, I think its about designing & implementing the system correctly...
    You are not on the right page, you can spin as much Bs as you like about the AT series belts, The AT series Belts are the same as the HTD series belts in terms of Backlash and performance, but they don't compare to the GT-2 GT-3 series, the robots that use belts are not very accurate and don't have to be, any Robot that is supper accurate is using direct drive servos at each joint no belts are used

    Mactec54


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    Default Re: My CNC Router Build Adventure

    Hi M54 - The question for me is not about availability or power rating. Its about solid evidence that the GT has less potential backlash then the AT and what is its stiffness? I use readily available commercial parts so custom pulley clearance is not available to tune that out. The ATL series is the one to pick for zero clearance but cost & availability is always an issue in OZ. I have sent an email to Gates asking for the specific stiffness we shall see how that goes.

    I have spoken to the Gates people directly and via their distributors on and off over the last few years about the GT and they do not respond to this sort of question to a small operator like me very well. I have spoken to techs in Europe via optibelt and they were conversant and happy to discuss the belt type issues even without a possible sale. Different culture. The so called registration error is really small with a correctly tensioned belt. This is the error when the belt changes direction so the belt is loaded in the opposite side of the tooth that is engaged so potentially the belt can slip backward until the tooth flank engages in reverse but the preload of the belt means the "backside" of the tooth should be engaged at all times especially when there is a large wrap. I think this is a very small issue within the scope of the design. Many very expensive Mills use belts to couple to the screws so its a known reliable solution... Your in USA so Gates is easy where in Oz so AT and ATL is easy....

    If tooth backlash is a real issue then go with a micro V belt with no teeth. Technically we should be able to design a no slip system, but then we are very paranoid about slip. Peter



  13. #213
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    Default Re: My CNC Router Build Adventure

    Hi everyone,

    Peter and Mactec, you have both been kind of addressing my next question before asking. Where do I find a supplier for belts and pulleys. I sent an email request to ptparts.com.au yesterday and the response was a little disappointing. They don’t stock GT2/3 parts and they told me they can only supply from the T5/AT5 range, which I figured would be a suitable alternative for my machine. This is the email response I received:

    Hi Jayne

    Unfortunately, we do not have access to the T2/3 sized pitch.
    The smallest pitch we have available in this range is the T5 & AT5 range, which appears to be too large for your application.
    Unfortunately I do not believe we can assist with this request

    Kind Regards
    Stephanie Samsa


    I’m not convinced my request for information was understood correctly, so I may have to call or send another email. As Peter said, access to parts is often difficult in Australia unless we resort to importing directly with ridiculous shipping costs or buying from China through eBay or AliExpress which often leads to disappointment if the seller is not known. The amount of times I have received items that are not even close to what was advertised has made me vary wary of buying from those sites unless others have previous positive experiences. Having said that, eBay and AliExpress seem to have countless options if you are looking for belts and pulleys to build a 3D printer but anything larger is much harder to find. Mactec, I will have a look at the links you provided when I get home later.

    I’m starting to wonder if I have a unwittingly made things more difficult for myself by choosing to use belt drives rather than directly driving the screws with the motor. I like where my design is at right now but if relocating the motors outside the frame like they were before will save me the headache of sourcing decent belts and pulleys it might be worth sacrificing some additional floor space to cater for the increased footprint with the motors attached to the outside of the frame.

    Btw, I downloaded a belt product manual from Optibelt last night. It’s full of information and formulas for selecting the right belt for the intended application. Best part is everything is in metric which is my first language but it is also very detailed beyond what is easy for me to understand. If I’m bored maybe I will sit down (with LOTS of coffee) and work through some of the calculations to try and understand how to specify a belt on my own.

    Jaybe



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    Default Re: My CNC Router Build Adventure

    Hi Jayne- Yes I think PT misread your email somehow. You need a 16mm wide 5mm pitch AT belt and pulleys PT will have those. Mactec and I haver been "discussing" GT belts vs AT belts for some time on other threads. Unfortunately in OZ the GT is hard to get and even if its "better", on your type of machine I doubt you will experience a difference. So either buy from PT or from powge.... the preload is very important to get right but that's a snug up, use snug up use, until sweet. If you have a screw adjustment this is an easier & more reliable process then trying to do it by hand. I use a guitar tuner to match each side, plucked

    https://www.ptparts.com.au/products/...16-timing-belt

    https://powge.aliexpress.com/store/702327


    The optibelt manual is very good. But it is a bit dry, lubrication with coffee is a good idea and PU belts are easy to clean when you fall asleep and spill the coffee on them...

    The issue I have with the GT is that Gates have not been able to answer my questions on and off over the years. So until I have written evidence I have to say the AT is it in OZ. I have priced the GT and its very expensive through the distributors and they don't want to deal with someone that wants 2 belts and they can't tell me the stiffness of the belt so I can't compare it to others. Saying more - the issue of backlash is irrelevant in your simple motor/screw case. The correct preload means that leading and trailing teeth flanks are in constant contact so there is ZERO backlash in the belt pulley system with any belt tooth type. I'm sure I'll cope some flack with that one .... If there is backlash it is in some other component of the system not the belt/pulley interface... usually the belt chosen is too small so its a bit springy for positional accuracy so use as big a belt as possible. But your belt is short and stiff... onward to another subject. Peter

    and on the powge site and other Asian sites the 2GT section is not the GT2 or GT3 section.... its the original round section....



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    Default Re: My CNC Router Build Adventure

    Hi Peter,

    5mm pitch is what I pictured as being about right for my application. There was obviously a misunderstanding in my email request, I'll call them on Monday to try and get a clearer answer. Using a guitar tuner to adjust the belts is interesting, lateral thinking in action. It also seems appropriate to "tune" the machine that will make guitars with a guitar tuner.

    When you say "use as big a belt as possible" do you mean width? My non-scientific "that looks about right" approach tells me 15mm width should be fine, 20mm better. For the pulleys, I am thinking about 40-50mm diameter (however many teeth that equates to.......30ish teeth at 5mm pitch?).

    I was wondering about the 2GT sections. I have seen those advertised on the Asian sites and wondered if it was their way of marketing a clone version of the Gates section.

    Jayne



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    Default Re: My CNC Router Build Adventure

    Hi Jayne - Sorry by "big" I meant wide. 20mm may overhang the shaft a little but if it fits then use that. The asian 2GT is the first generation Gates GT belt. The patent and Gates interest has run out on that so the asians use it freely. As long as your clear of the minimum recommended size it will be OK. I have used minimum teeth count pulleys on Scoot-S1 to maximise force and they ran OK for years. U drives do get into trouble as the belt gets bent in two directions and the return pulleys are generally undersize for the flat side so fatigue could occur. But they seem to work OK once settled in. Peter



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    Default Re: My CNC Router Build Adventure

    Hi - This maybe my Xmas present, although it does explain the working formula so you could use a guitar tuner and the formula to calculate the tension. I can FE model this and check its accuracy... Peter

    https://www.gatesaustralia.com.au/~/...ter_manual.pdf



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    Default Re: My CNC Router Build Adventure

    I'm fascinated that there is a tool designed to measure belt tension by measuring the sound it makes when plucked. That is so cool. Hope Santa brings you your present.



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    Default Re: My CNC Router Build Adventure

    Hi everyone......again

    I have a few more questions about the timing pulleys. AT5 belts and pulleys are readily available locally, so I'm going to take that route. I can always change belts and pulleys later if these aren't performing well or if I want to experiment with something else.

    So my first question....is there a difference between pulleys for a T5 and AT5 belt, or are the pulleys the same and the difference is the belt profile and how ir engages with the teeth? I have seen lots of places advertising that their pulleys are compatible with a larger number of different belt profiles and I don't know if that is sales hype or the truth.

    My second question is about securing the pulley to the shaft. The motors have a flat machined into the shaft so that part is easy, but as far as I can tell, the ballscrew ends are cylindrical with no flat. I don't want the pulley to slip on the shaft so do I machine a flat on the screw shaft (or ask the vendor to do it if it's an option), or are there better ways? I found this old post by Mactec https://www.cnczone.com/forums/attac...6&d=1296941413 (image attached below) which seems like a great way to prevent slippage but I don't know how to drill a hole offset from the centre.

    Finally, ptparts has the right size pulleys but they only have a pilot bore hole which is not a problem to enlarge to the correct size, but what should I do with the set screws? Is drilling through the teeth a good idea (like in the attached image from the POWGE online store)? My concern is the belt prematurely wearing as it passes over the teeth with missing material where the set screw holes are.

    Oh, one more question....are 2 set screws enough, or are three better to evenly distribute the clamping force around the shaft?

    Sorry for all the questions, I thought I better ask them all now while we are on the belt topic.

    Jayne

    Attached Thumbnails Attached Thumbnails My CNC Router Build Adventure-motor-pulley-mount-gif   My CNC Router Build Adventure-i_12_at5_16-jpg   My CNC Router Build Adventure-screen-shot-2021-10-22-10-31-a  


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    Default Re: My CNC Router Build Adventure

    Quote Originally Posted by peteeng;247Hi 7626
    M54 - The question for me is not about availability or power rating. Its about solid evidence that the GT has less potential backlash then the AT and what is its stiffness? I use readily available commercial parts so custom pulley clearance is not available to tune that out. The ATL series is the one to pick for zero clearance but cost & availability is always an issue in OZ. I have sent an email to Gates asking for the specific stiffness we shall see how that goes.
    The GT series has the same positioning accuracy as the ATL, which you keep talking about but you have not used them. why have you not used them ???

    The link I posted https://www.gatesaustralia.com.au/ab.../contact-gates have the Synchronous PowerGrip GT series Belts and Timing Pulleys on there site, so there is no excuse to say that the information is not available in Australia

    Quote Originally Posted by peteeng;247Hi 7626
    I have spoken to the Gates people directly and via their distributors on and off over the last few years about the GT and they do not respond to this sort of question to a small operator like me very well.
    You are full of it. you can call Tec support at Gates and they will send you an Email of everything you want to know.

    Quote Originally Posted by peteeng;247Hi 7626
    If tooth backlash is a real issue then go with a micro V belt with no teeth. Technically we should be able to design a no slip system, but then we are very paranoid about slip. Peter
    Now you are being ridiculous

    The photo's I posted of the motor mounting, that was of AT-5 belt and Timing pulleys being used, I'm no stranger to the AT belts and Timing pulleys, I have the Hobbs to machine the timing pulleys, they have there place. CNC drives is not one of them. when you can have much better.

    This company uses the AT series for there servo belt design, he has a thread here on the Zone, and will tell you that the AT series has backlash, this is the only belt type that will work for there servo belt design, it is mostly being used for automation, not CNC machines, because of the backlash, I think a few zone users have tried this for there machines but have not seen anyone's feed back

    His whole business revolves around the AT series Belt

    https://www.bell-everman.com/resourc...rvobelt-linear

    Mactec54


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