Some ideas...

discussion of design changes / improvements / suggestions
Max Metz
Posts: 240
Joined: Sun May 20, 2012 11:55 am

Re: Some ideas...

Post by Max Metz » Mon Jul 30, 2012 2:47 pm

Thanks northbear.

Some have found that cutting close to the x axis Makerslide yields a more accurate cut for harder materials like aluminium, perhaps because the lever arm has less effect when the weight of the spindle is close to the where the v wheels slide on the z axis, so the top stage will be for shallow 2 dimensional work. Sometimes however one might want to cut the top of a tall object or even a deep object so the bottom stage will allow this. The Shapeoko allows a healthy depth of cut compared to many cnc machines so it seemed a good idea to be able to capitalize on this.

Best regards. :D

cvoinescu
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Joined: Thu Jul 19, 2012 6:50 pm
Location: Camberley, UK
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Re: Some ideas...

Post by cvoinescu » Mon Aug 13, 2012 9:58 am

I am considering the shaft idea for my ShapeOko (batch #3, so no hardware yet).

From your experience, do the 5 x 13 x 4 mm bearings fit the holes in the Y plates exactly, or did you have to enlarge them? Or, worse, was there any play?

Also, did you have any trouble from the shaft not being stiff enough and twisting a little (elastically, of course) causing the left end to lag behind the right end during heavier cuts? Or is it more likely for the motor to skip steps before the shaft twists significantly? I have no appreciation of the forces involved vs. how flexible the shaft is in torsion.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Max Metz
Posts: 240
Joined: Sun May 20, 2012 11:55 am

Re: Some ideas...

Post by Max Metz » Mon Aug 13, 2012 12:03 pm

Thanks cvoinescu.

My machine is currently sitting in the Chicago mail sorting facility waiting patiently to begin its long journey to Western Australia so all this stuff is just drawing at the moment.

The 13mm motor holes are likely very accurate as they are cnc cut, as for the flanged bearings one can only hope! If the bearing are slightly smaller than 13mm it will be a matter of pushing them back in the same direction and holding them in place with super glue before tightening them with the two nuts either end of the shaft - the nuts hold the bearing flange hard against the plates from the centre of the bearing so as to minimize lateral movement while jamming the bearing flanges hard against the plates. I don't expect any problems - the bearing have not arrived as yet.

As for the threaded shaft, to honest there is not enough room for much more, even now one will have to pack out the z axis at least another 2mm so the shaft will fit at 5mm diameter - otherwise it will be in the path of the 8mm z axis shaft as it lowers. A wider shaft powering the y axis, tube rather then solid, would be better for torsion (say 8mm) though that would need further packing out of the z axis. Hopefully the solid nature of the threaded rod will compensate some, you may be better to wait till I get mine going to see how well it works.

The threaded shaft rather than a plain rod will introduce some play, as it will be narrower than 5mm, this will however alleviate the need for a bearing puller which with such a narrow shaft could be destructive, so same as before push the shaft to the back of both centre bearing holes before tightening up the nuts that hold the flange and rest of the dual pulley assembly in place.

Best regards mate. :D

cvoinescu
Posts: 4442
Joined: Thu Jul 19, 2012 6:50 pm
Location: Camberley, UK
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Re: Some ideas...

Post by cvoinescu » Mon Aug 13, 2012 6:33 pm

Thank you for your answer, I appreciate that. I'll order a pair of flanged bearings to have them on hand when the kit arrives, but I may try a dual-motor design first (I have all the parts I need for that).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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