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jpcnc
07-01-2011, 08:45 PM
Need these, or need pointing in the direction of the cheapest place to get them-

* Power table feed ( universal type will do ) for my x axis
* 16mm ball screw + nut 2000mm long with ends machined with supports
* 12mm ball screw + nut 600mm long with ends machined with supports
* 2 x universal handles for my x + y axis

Could do with a decsent engineering supplies for other bits and bobs in the nottinghamshire area.
Cheers
Jay

Jonathan
08-01-2011, 01:16 AM
i bought my screws from this fella, end machined with supports, if you look through his shop..., does any size to,although i havent actually used mine yet,ive not come across any complaints from others.
http://cgi.ebay.co.uk/3-ballscrew-1610-250-550-1050mm-C7-end-machined-/250694865242?pt=LH_DefaultDomain_0&hash=item3a5e94115a

Agree with this. Used him twice for rails and ball-screws and the service has been excellent. Got the ballscrew machined slightly differently to standard, and I think he didn't charge any extra :)

Make your own handles? Surely a good first project for your new machine!?

By the way I hope you're not intending to spin that ballscrew, unless it's under lots of tension... 2m screw that diameter will whip a LOT severely limiting your rapids. You want to rotate the nut ideally, not the screw. That's what I did on my build with similar length screws.

jpcnc
08-01-2011, 09:43 AM
The 2m ballscrew should be fine there isnt going to be any rapids just a steady feed, as for making handles, I have my own cnc machining business but its not worth all the hassle of making them when I can buy them pretty cheap, same goes for most of the other bits I need, unless it needs to be a specific shape.

Jonathan
08-01-2011, 10:26 AM
The 2m ballscrew should be fine there isnt going to be any rapids just a steady feed, as for making handles, I have my own cnc machining business but its not worth all the hassle of making them when I can buy them pretty cheap, same goes for most of the other bits I need, unless it needs to be a specific shape.

The critical speed for that length of screw is 290 to 650rpm - depending on what bearings you use. That's 1450 to 3250mm/min assuming 5mm pitch screw. I guess 3250 is ok - why are there not going to be any rapids?

I generally go on the if I can make it cheaper I do philosophy!

M250cnc
08-01-2011, 11:15 AM
The critical speed for that length of screw is 290 to 650rpm - depending on what bearings you use. That's 1450 to 3250mm/min assuming 5mm pitch screw. I guess 3250 is ok - why are there not going to be any rapids?

I generally go on the if I can make it cheaper I do philosophy!

I'm gonna agree with Jonathan, you will soon get sick of going at those speeds over a large distance, plus going too slow with a fixed high speed spindle means you will burn cutters/material and wear them out quicker.

I generally go on the principle that i make it as good as possible, so it will last indefinitely. An example is my lathe in the video on the home page you will see i used telescopic ballscrew covers they are very expensive and i had to wait 6 weeks for them to be made. The inbuilt seals will not keep out contaminants so a few months down the line they would all be ruined.

Phil

jpcnc
08-01-2011, 12:02 PM
Its only going to be turning rubber off tyres at around 1000mm/min, and it will only be doing one cut at a time, rapid will only be used to return it to the start point, ive sourced a supplier that is going to be issueing me what I need for beer tokens so I can get what I want, so I may upgrade to 25mm for the extra rigidity

Jonathan
08-01-2011, 12:12 PM
25mm would get roughly 2500 to 5700mm/min depending on what bearings you are intending to use on the screw?
I found the formula to be pretty accurate in my case. It suggested that the Y axis screw would whip over 6000mm/min, and it does. I'm running it at 4000 to be safe.

jpcnc
08-01-2011, 12:25 PM
My y axis is only going to be used to wind out by hand to a position then locked off, ballscrew is overkill really but I want the anti backlash etc
If im only needing 1000mm/min with a 5mm pitch then its only gona be turning at 200rpm wich I think will be fine

Jonathan
08-01-2011, 12:32 PM
My y axis is only going to be used to wind out by hand to a position then locked off, ballscrew is overkill really but I want the anti backlash etc
If im only needing 1000mm/min with a 5mm pitch then its only gona be turning at 200rpm wich I think will be fine

Yes I'm sure 200rpm will be fine, so long as your happy waiting 2 minutes to traverse the whole bed.
Surely if you're operating the Y axis by hand then you can compensate for the backlash by hand, as one would normally when using a manual machine? I suppose not having backlash helps get a good finish as you can use climb milling...not sure if that's an issue cutting rubber.

You might want to consider the drive mechanish I used on my Y axis - very very cheap, and very little if any backlash.

http://www.mycncuk.com/forums/showthread.php/2288-1.7*0.74*0.4m-Mill-Router-building...?p=16365&viewfull=1#post16365

(post #7)

jpcnc
08-01-2011, 01:22 PM
Its a lathe set up theres no climb milling, as for the ballscrew if i get it for free i might aswell do it for the optimum set up