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  1. #41
    The press fit as bad as it may look does not concern me as much as the steppers holding ballscrew in place. The reason being is I can measure the shaft of the motor moving along the motors axis as the load on the ballscrew changes. Inside the motor is a spring washer, if you pickup a stepper and try pulling and pushing the shaft you will see it takes very little force to move it. Maybe your lathe has different types of steppers with thrust bearings built in, or maybe its designed to work within the range of the spring washer inside?
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  2. #42
    john this machine has a working area of around 300mm by 500mm
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  3. #43
    Quote Originally Posted by gavztheouch View Post
    The press fit as bad as it may look does not concern me as much as the steppers holding ballscrew in place.
    But it should do because it's only a matter of time before that's floating around more than screw and stepper do.!!

    Think I'd be putting at least a Grub screw of 2 thru the profile has a minimum precaution.?

  4. Quote Originally Posted by JAZZCNC View Post
    Think you'll be hard pressed to any commercial or even serious Hobby CNC machine that press fit Ballnuts or run ballscrews without some form of end fixing.?? . . . It's Bad practice pure and simple and proper manufacturer wouldn't do it.!

    I wasn't actually meaning specifically CNC machines! I was thinking about any machinary in general.
    The fact is though, in this particular application, I doubt the steppers/ballscrews will generate enough force to move the ballnuts in the extrusion. It's quite smart, in that it does the job while reducing parts count and the amount of machining needed. Maybe not the ideal way to do it, but perfectly functionable.
    Large CNC machine builders won't do it because of serviceability. Pressing something into something easily handled is a bit different from something pressfitted into a lump of iron weighing several hundred kg. There's also the manufacturing issue. A few tapped holes, with a locating boss is easier than a single tight tolerance pressfit.

    I'm not defending MD though, especially given the prices. I'm just saying the methods used are maybe not ideal, but they're still perfectly functional.

  5. #45
    Quote Originally Posted by m_c View Post
    It's quite smart, in that it does the job while reducing parts count and the amount of machining needed. Maybe not the ideal way to do it, but perfectly functionable.
    Erm.!!. . . . I'd be more inclined to call it lazy arse bodging fueled by greed.!!

  6. #46
    John S's Avatar
    Lives in Nottingham, England, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,073. Received thanks 141 times, giving thanks to others 45 times. Referred 1 members to the community.
    An anteater is also functional but I wouldn't want to take one out on a pub crawl and bed it afterwards.

    Mind you if they are serving Old Rosie scrumpy it might stand a good chance.
    John S -

  7. #47
    Quote Originally Posted by John S View Post
    An anteater is also functional but I wouldn't want to take one out on a pub crawl and bed it afterwards.

    Mind you if they are serving Old Rosie scrumpy it might stand a good chance.

    Yes but it you met an anteater at the end of your pub crawl you might take the sexy young thing home to bed with you, then in the morning you have to gnaw your arm off to get away without waking it up !!!

  8. #48
    Looking at this it seems the machine isnt getting any better. Press fits are normally ok with certain materials but not pressing steel into aluminium especially when its not actually been machined to fit it in the first place and its supposed to be a permanent fit. The more I read this the more I'm glad I managed to send all my stuff back to them and get a refund although it was a struggle to get it.
    I would go with Jazz recommendation and get a grub screw through the side of the alu to hold the nut in place. Remember you just want to dimple the casing of the nut for the grub screw to locate into and get some thread locker on it.

  9. #49
    Can't see how a grub screw would help much in this case, no where to put it really, with the centre of the profile rail machined away the fit is only relying on 4 very small points of contact so you would need at least a grub screw either side but there is a big gap between the profile rail & the ballnut which would probably make the grubscrew ineffective.

  10. #50
    Our designs have been through many years of development as our business has grown, we have automated many of our processes using our machines, to produce components for sale via eBay and worldofcnc. Any issue we would evaluate and redesign.

    As the majority of our customers have business interests and therefore purchase a machine that is task related, we can adapt one of our many designs accordingly.

    Press fit ballnut?
    The ballnuts are not press fit….we use RSW ballnuts with an external V thread, the centre aluminium profile is bored and threaded to accept the RSW ballnut…
    This range of machines are supplied to the world's leading probing manufacturers, in tests we achieve an accuracy of less than 0.010mm/300mm of the whole machine.

    Later this year, all our Ballscrew driven machines will be fitted with thrust bearings this will align our product with our Class 5 preload Ballscrew driven machines and coincide with our 5 axis CNC being launched.

    Finally
    The floating end of a Ballscrew….
    What happens if the Ballscrew spindle became warm? The spindle would need to expand along its length, hence the term floating.

    If anyone would like to discuss in more detail please email admin@marchantdice.com or call us 01805 628222 (phone line currently down however will be working again in the next day or so)

    Many thanks
    Kevin Marchant

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