Page 2 of 4 FirstFirst 1234 LastLast
  1. #11
    slow down a bit irving!! it will take me all night to take all that info in!!!:confused:
    only joking, thanks for the calculations.
    does this mean i could fit the 10 toothed pulley directly onto stepper motor with out reduction?or am i missing something,i would like to go for bigger motor just incase i was going to do some alloy or do you think this would just be overkill??
    i was also thinking of making my own v bearings with twin bearings inside round bar turned down to suit angle iron or do you think this would be to much friction??
    sorry for all the questions but its your own fault for being so knowledgable!!:naughty:
    thanks again Tom

  2. #12
    my plan is to build router that can take 8x4 sheets so the belts would run full length of table crossing over gantry to other side,both being driven by toothed gear reduced down from stepper motor then the back of the belts would go round idler then down the other side of router. Hope that kind of makes sense:confused:
    I wish i could just draw a bit faster and better but am just learning autocad
    Understood perfectly. Have you priced it up tho? as Irving said belts arnt that cheap espesially as you'll need them 12' or more in one run as it also goes thro the Y axis.

    I think that once you get to 8'x4' belts arnt a cheap option, just cheaper than ball screws

    I wouldnt have thought belt sagg would be to much of a problem as they will be on their side, and if you use collar less pulleys you could put a small ledge for the belt to sit on.

    If you make our own Vee bearing will you save that much? Have a word with vic66, hes using vee bearings and angle, look at his thread and theres a link to the mechmate stuff which sounds simillar to what you want.

  3. Quote Originally Posted by dickieto View Post
    slow down a bit irving!! it will take me all night to take all that info in!!!:confused:
    only joking, thanks for the calculations.
    does this mean i could fit the 10 toothed pulley directly onto stepper motor with out reduction?or am i missing something,i would like to go for bigger motor just incase i was going to do some alloy or do you think this would just be overkill??
    i was also thinking of making my own v bearings with twin bearings inside round bar turned down to suit angle iron or do you think this would be to much friction??
    sorry for all the questions but its your own fault for being so knowledgable!!:naughty:
    thanks again Tom

    dont take these as gospel, its a frst cut. I may have missed something, or my approach to estimating how forces giving rise to motion of the gantry translates to torque might be wrong. I dont want to diss your idea, but can't help but think if it was that easy why hasn't someone done it before? I do think the limiting factor might be belt width/torque handling and availability in the lengths you need. One or two suppliers do continuous belts larger than 3.7m which could be cut open, but these tend to be in the 8mm not 5mm HTD and the pricing is >£50 per belt. With 8mmHTD a 10t pulley is 25mm dia so the torque needed at 200rpm is 0.3Nm, and the resolution at 1/4step is 0.1mm. 8mm belts come standard at 30 and 50mm widths

    I was working on the assumption that the steppers drive the pulleys directly, but in practice you can't because the shaft length is too short. You will need the two drive pulleys mounted on a shaft in bearings which is driven by the motor via a coupling.

    Before embarking on the big build, I would trial a small version of the X say 200 or 300mm square using 5mmHTD and cheap drawer slides from B&Q to measure the loads/forces/etc. operating load could be added by a bit of string running over a pulley to a pan that can be filled with sand or other stuff to see how it performs under load.

  4. However open-ended belting is only available in 100m rolls, so this might not be as cheap as you might think!
    A grovelling appeall to the afore mentioned Mike Everman might be worth a try :)

  5. #15
    Is a 10 tooth pulley big enough to hold the belt on a quarter turn? That's 2 teeth.

    Is it small enough to get any kind of resolution on a stepper?

    A 15mm PCD pulley moves it 47mm per rev.

    0.12 mm/step before you start springy microstepping, will that work for cutting alloy?

    If you microstep can you rattle the PUL pin on the driver fast enough to get the top speed?

    If you gear it down, do you move beyond the top speed of the motor?

    Beginners don't usually play with the numbers, they just look for massive torque motors and hope that will make it right. That's why steppers are usually sold by the Newton meter rather than by the torque to speed graph.

    130kg belt tension may exceed the permitted side loading on the motor shaft.

    Can you actually get a big enough shaft inside a 15mm aluminium pulley without severely under cutting the teeth? I think you will need a bearing either side of it.

    A little maths and understanding to find the best compromise before you build can save a lot of disappointment later. (Please assume a big grin smiley, the new editor restricts my smiley selection, sometimes it shows, sometimes it doesn't).

  6. Quote Originally Posted by Robin Hewitt View Post
    Is a 10 tooth pulley big enough to hold the belt on a quarter turn? That's 2 teeth.
    I was assuming that both pulleys on the shaft were driving, thats 4 teeth and the torque is fine on that...

    Is it small enough to get any kind of resolution on a stepper?

    A 15mm PCD pulley moves it 47mm per rev.

    0.12 mm/step before you start springy microstepping, will that work for cutting alloy?
    Probably not, but I don't think you would realistically do alloy on an 8 x 4 router

    If you microstep can you rattle the PUL pin on the driver fast enough to get the top speed?
    Needs 200rpm for rapids, thats fullstep = 670steps/sec, then microstep for final positioning... needs a morphing driver really but its doable at fixed microstepping 2600steps/sec.

    If you gear it down, do you move beyond the top speed of the motor?

    Beginners don't usually play with the numbers, they just look for massive torque motors and hope that will make it right. That's why steppers are usually sold by the Newton meter rather than by the torque to speed graph.

    130kg belt tension may exceed the permitted side loading on the motor shaft.
    It would, thats why it needs the pulleys on a bearing supported shaft (skate bearings OK to 1700N radial force) and the motor coupled in.


    Can you actually get a big enough shaft inside a 15mm aluminium pulley without severely under cutting the teeth? I think you will need a bearing either side of it.
    Thats an interesting one, and not one I'd considered. The standard 10tooth pulley is a 6mm dia shaft. the upper pulley and lower pulley are in opposing tension so can a 6mm shaft stand a shear force in the middle of 2600N?
    I suspect it will need a bigger (more teeth) pulley and the motor will need to be geared down to drive the shaft to get the resolution without too much microstepping. A 20th tooth pulley and a 2.5:1 gearing would give a 30mm dia pulley (good for a 10 or 12mm shaft). One turn of the pulley = 100mm so 0.1mm resolution needs 1000steps, geared down 2.5:1 is 400steps/rev which is 1/2stepping and 10m/min rapids = 100rpm of pulley = 250rpm of motor which is still feasible at 1666steps/sec.

    A little maths and understanding to find the best compromise before you build can save a lot of disappointment later. (Please assume a big grin smiley, the new editor restricts my smiley selection, sometimes it shows, sometimes it doesn't).
    mine doesnt! :naughty:

  7. #17
    Quote Originally Posted by Robin Hewitt View Post
    Is a 10 tooth pulley big enough to hold the belt on a quarter turn? That's 2 teeth.

    Is it small enough to get any kind of resolution on a stepper?

    A 15mm PCD pulley moves it 47mm per rev.

    0.12 mm/step before you start springy microstepping, will that work for cutting alloy?

    If you microstep can you rattle the PUL pin on the driver fast enough to get the top speed?

    If you gear it down, do you move beyond the top speed of the motor?

    Beginners don't usually play with the numbers, they just look for massive torque motors and hope that will make it right. That's why steppers are usually sold by the Newton meter rather than by the torque to speed graph.

    130kg belt tension may exceed the permitted side loading on the motor shaft.

    Can you actually get a big enough shaft inside a 15mm aluminium pulley without severely under cutting the teeth? I think you will need a bearing either side of it.

    A little maths and understanding to find the best compromise before you build can save a lot of disappointment later. (Please assume a big grin smiley, the new editor restricts my smiley selection, sometimes it shows, sometimes it doesn't).
    hi robin
    looks like i will need to go back to school,maths was never my strongest subject
    i was thinking more along the lines of a 40mm pulley!!!.and driving the stepper with a reduction to the shaft.would this work or would the stepper be running to fast when the ganty is moving at high speed
    as you have said i am just a beginner and speed,torque,force applied etc are all new to me.
    i was thinking of making a prototype using chains and sprockets (my works got plenty)just to try out the theory,measuring pull needed to turn drive shaft with spring scales!!
    thanks for your input
    Tom

  8. Quote Originally Posted by dickieto View Post
    hi robin
    looks like i will need to go back to school,maths was never my strongest subject
    i was thinking more along the lines of a 40mm pulley!!!.and driving the stepper with a reduction to the shaft.would this work or would the stepper be running to fast when the ganty is moving at high speed
    as you have said i am just a beginner and speed,torque,force applied etc are all new to me.
    i was thinking of making a prototype using chains and sprockets (my works got plenty)just to try out the theory,measuring pull needed to turn drive shaft with spring scales!!
    thanks for your input
    Tom
    Tom,

    See the inline answer I gave to Robin's questions. He is quite right, there is the 'suck it and see' approach or the 'model and calculate' approach (and then usually an element of suck it and see!) - with something this complex its worth spending some time getting a basic appreciation of the numbers to try and see if things look reasonable...

    If you want a more detailed description of the torque/forces/etc to help you understand the number just ask...

    A 40mm PCD dia pulley is approx 120mm circumference (24 tooth). Therefore 1 rev moves 120mm. Set 1 rev = 1200steps then 1 step = 0.1mm. At 10m/min rapid the pulley turns at 10,000/120 = 83.33rpm, geared down 3:1 (12teeth/36teeth) the motor turns three times as fast = 3 x 83.33 = 250rpm, in 1/2step mode this is 250/60 * 400 = 1667 steps/sec which is no problem.

  9. #19
    Quote Originally Posted by irving2008 View Post
    the motor turns three times as fast = 3 x 83.33 = 250rpm
    That's over 4 revs/second. If we start straying beyond the capabilities of the cheapy 40 volt stepper drivers he needs to be warned, but maybe we have already confused him enough for one day

    Thanks for fixing my smilies

  10. #20
    The first part of my router design arrived today a 4.4m drive belt for £6 cant be bad but the teeth on the belt are not uniform so will not lay back on itself in the the teeth are larger than the gaps.
    Oh well back to the drawing board it may do for the design on this thread.
    The belt is designated as RPD8 the 8 I assume is the tooth root, tried a search but nothing I could recognise but cheap enough.
    Now for some pulleys.

    peter

Page 2 of 4 FirstFirst 1234 LastLast

Similar Threads

  1. Belt drive on a router
    By John S in forum Rails, Guideways & Bearings
    Replies: 23
    Last Post: 10-09-2012, 09:39 PM
  2. WANTED: wanted drive belt and pulleys
    By oadamo in forum Items Wanted
    Replies: 2
    Last Post: 13-05-2011, 09:00 PM
  3. any one know where to get a belt drive convertion for x2
    By Scott in forum Sieg Milling Machines
    Replies: 15
    Last Post: 27-09-2010, 08:44 PM
  4. Standard Drive Belt Size ?
    By Lee Roberts in forum Belt Drive, Pulleys & Timing
    Replies: 2
    Last Post: 19-05-2009, 10:56 AM
  5. Re: Standard Drive Belt Size ?
    By HS93 in forum Belt Drive, Pulleys & Timing
    Replies: 0
    Last Post: 18-05-2009, 03:30 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •