Re: Marchant Dice router no thrust bearings?
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?
Re: Marchant Dice router no thrust bearings?
john this machine has a working area of around 300mm by 500mm
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
gavztheouch
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.?
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
JAZZCNC
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.
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
m_c
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.!!
Re: Marchant Dice router no thrust bearings?
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.
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
John S
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 !!!
Re: Marchant Dice router no thrust bearings?
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.
Re: Marchant Dice router no thrust bearings?
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.
Re: Marchant Dice router no thrust bearings?
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 [email protected] or call us 01805 628222 (phone line currently down however will be working again in the next day or so)
Many thanks
Kevin Marchant
Re: Marchant Dice router no thrust bearings?
Quote:
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.
In this situation you can see how thrust bearings may be of less importance, but these kits are being sold as cnc routers with the ability to cut material. Try yanking on the stepper shaft and feel the washer inside, unless I have misunderstood again this is the only part resisting axial motion.
1 Attachment(s)
Re: Marchant Dice router no thrust bearings?
http://i59.photobucket.com/albums/g2...ps59919348.jpg
Attachment 7962
This is a quick mock up to mount my thrust bearings. This will fix in place the normally floating end, this means the spring in the motor will soak up the expansion of the screw and the motor side will effectively become the floating end, if it need more I can use a oldham coupler.
Il need another 4 holes that will be tapped to fix the bearing to the mount which will be made of aluminium.
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
marchantdice
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
[email protected] or call us 01805 628222 (phone line currently down however will be working again in the next day or so)
Many thanks
Kevin Marchant
I'm sorry Kevin but you will win no supporters on here for your method of construction.
I bought a copy cat of one your machines that was actually better in some cases than yours but still inadequate. In this case at least it correctly captured the ballnut but still had similar issues with the ballscrew mounting that you have engineered into your designs.
Its sloppy, cheap and has serious question marks for the long term accuracy of the machine. You're basically knocking these out as simply as humanly possible to maximise profit. It wouldn't be so bad if you were charging a suitable amount but 4 series extrusions with the most basic and barebones mechanical make up possible? Not acceptable in my opinion.
You talk about selling to businesses? Your going to cost them money in the long run because they'll have to fix or replace what you should have done right to start with.
Please go back, redesign and come with something fit for purpose and stop inflating the capabilities of your machines. They're very very lightweight machines capable of only light cuts in soft materials. And your accuracy figures mean little. Is that the accuracy of a part, if so what material? Or is it more likely the accuracy of the machine with no load ie. cutting air?
Re: Marchant Dice router no thrust bearings?
Just reading through older stuff and saw this, I always thought their stuff looked particularly shonky for the price on eBay but it looks like they manage under-engineering on a scale that would put professional bodgers everywhere to shame!
Boring and threading the "Liquorice Extrusions" was the high point of the BS excuse for me!
Anyone seen any of their more recent contraptions?
1 Attachment(s)
Re: Marchant Dice router no thrust bearings?
I had the problem of the floating acme screw and I put in a small thrust bearing from ARC Euro held against the motor mount extrusion by a collar with a grub screw to remove the end float on the screw. I did similar on the X axis, but the Z axis was a slightly different bodge as I needed to prevent it pushing upwards, so I put in a couple of thrust bearings to space it out (1 bearing and washers would have done !) and used the coupler to act as the retaining collar.
Attachment 19137
The machine is now (just) adequate for hobby use.
But I have to give a big thank you to Marchant Dice for opening my eyes to CNC. I now have the great desire to make a decent machine.
This quote from MD amused me 'in tests we achieve an accuracy of less than 0.010mm/300mm of the whole machine' I would have expected better than rather than less than, but Hey Ho maybe ?
Cheers,
Rob
BTW Nick, I have not seen any of their recent excrences - I believe their machines should be labelled 'For amusement only', they certainly make me smile :shame:
AND I like your use of the word 'contraption' - very apposite.
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
cropwell
I believe their machines should be labelled 'For amusement only'
And perhaps "A Learning and Growing Experience"? :D
Re: Marchant Dice router no thrust bearings?
Quote:
Originally Posted by
cropwell
I believe their machines should be labelled 'For amusement only', they certainly make me smile :shame:
AND I like your use of the word 'contraption' - very apposite.
Now that was funny
