28-04-2013 #31Mmmm! not sure what you mean here?
Just to make it clear thought that its only because open bearings and supported rail are being used with a small bearing centre to spindle nose distance ratio. Ideally the bearing centres (on plan) should be increased but given Mike has already redesigned it a few times I didn't want to offer any more changes without justifying them with calcs.
If you are making a box to encompass the supporting rail then you are actually increasing rigidity.
This is free movement just to take up play, if you add any deflection due to load then this will obviously increase further. for cutting Ali the open bearings can run close to the max load capacity and as rigidity is a function of imposed load and load capacity then deflection will be high.
On the face of it 10 micron is a very small amount but remember this is only One element and doesn't include deflection in the part. if you lose 10 micron at every junction then it all adds up to a considerable amount.
Any way that's my take on it!
Ross i did say that the plate could be moved further back. In this design there is no reason why the ballnut could be more central and the spindle moved closer to centre. There is no need to have the nut pushed further away from centre.If the nagging gets really bad......Get a bigger shed:naughty:
You can get the ballnut in a more optimal position with the current design - it doesn't have to go behind to do that. Similarly the current design could easily have a 'box to encompass the supporting rail' added.
like these, either side of the ballnut and the swarf is wiped off easily. They're working well for me and not showing signs of wear, although admittedly I've not been using them for long.
Last edited by Jonathan; 28-04-2013 at 05:47 PM. Reason: spelling
28-04-2013 #34Ross i did say that the plate could be moved further back. In this design there is no reason why the ballnut could be more central and the spindle moved closer to centre. There is no need to have the nut pushed further away from centre.
If you look at the Z axis drawing in post #18 there is barely enough room to flip the plate over. if you then centralise the ball screw you will have to move the Z axis assembly further away, making the situation much worse.
As I said there are other more pressing issues with the design but as the parts are bought and he wants that size working envelope then there's not much that can be done other than maximise the other components. Another reason for not moving the ball screw is that despite the large plate on the back the y axis could still twist if Mike decides to cut larger pieces of Ali. with the ball screw in the front it is a simple case of widening the y beam to increase its torsional rigidity.
Anyway I think we will just have to agree to disagree on this one. We all have different ideas and its up to mike to decide as ultimately he knows what is needed from the machine.
Right, I have made one small change to the Y axis to tie it all together. So no more changed till it is built. I ordered some 6082 aluminium plate and have started to construct the Z axis.
I can only do a little at a time before the pain is to severe and I have to stop, It will be a slow build but I will get there. Anyway one drawing of the change and two pictures to keep you going.
looks like some good progress Mike. that back plate will help stiffen it all up.
glad all the comments didn't put you off. keep it up
Looking really good. Any estimations on how much you think this project will cost?
Just wondering.... Where did you source the aluminium extrusion from? Thanks
Bit late now but a chop saw would have been a good investment for you if you have problems using a hacksaw.
With the right blade you could have cut all the aluminium both plate & profile yourself which would have made things a bit easier, plus it would also be handy for cutting aluminium to size before machining it once the router is up & running.
Last edited by Bush Flyer; 30-05-2013 at 08:49 AM.
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