Aluminium CNC log.

[Robin Hewitt]

Thoughts and constructive criticism welcome.

I like the triangles, you get a lot of strength from a triangle.

Can I suggest 2 small changes.

The X axis rails have a lot more vertical separation than there is separation on the ball bushings. This introduces an awkward turning force on the nut which the bushings are poorly placed to resist. Suggest you lower the top rail and screw somewhat. Allow the Z rails to overhang at the top you are only going up there for tool changes, keep the strength at the bottom where you need it.

Bolt the vertical risers to the sides of the Y axis aluminium sections. Connect the diagonal braces to the vertical risers with a lap joint not a mitre. Using an offcut from the vertical riser as packing, lap joint the braces to the aluminium sections. Maximise the rigidity the diagonals have to offer.

Incidentally, 1/2" thick aluminium bar is a lot easier to find than 10mm.

[Jonathan]

I think the Y-axis rails should be mounted on something stronger, ideally both on a single piece. At the moment they're on something that will twist easily, so they will still deflect downwards...
Having them far apart is good I think, though I agree the ratio of the Y and Z rail seperations should be closer to one. Perhaps make the Z axis wider?

[jcb121]

I have just received my DIYCNC Breakout board! :D

this may sound silly, but this is the first serial item I have ever used! I have to find an old PC now!

Also took delivery of some M6-M12 taps.

Exciting stuff.

The supported rails in that picture were 250mm Long and the screw was 350mm, this allowed me to mount the screw supports above and below the supported bearings making it thinner.
I'm now getting 300mm supported rails, this means that the screw supports will have the be inline with the rail and that the Z axis will be wider.

would changing the ratio of Z and Y closer to 1 make it more rigid? I thought it was a bigger the better situation!

the ratio of the new design is about 2:1

the 2 being the Y axis.

[Jonathan]

I think that ratio is fine as both of the distances between rails are reasonable, so it surely can't be worse than if they were both the same as the 1.

What are you mounting the Y-axis rails on?

[jcb121]

probably one large bit of Alu. due to the cost of this, i'll have to make the Y Axis rails closer together to make it cheaper! then it probably will be very close to 1:1

[Jonathan]

One large piece is best, otherwise the rails will twist.

Try www.aluminiumwarehouse.co.uk

Imperial dimensions are more common, so you're after about 7"x3/8"... these are the nearest:

http://www.aluminiumwarehouse.co.uk/...ducts_id=29030

http://www.aluminiumwarehouse.co.uk/...duct_info.html

[jcb121]

Pictures!
Attachment 4591Attachment 4590

I've milled most of the big blocks of alu in college so the edges are straight.

Just need to start mounting everything and it will soon be done :D

The Mill in college is complete crap, there is a MM of backlash on the X axis! really screws up my work :(

The Y is ok though.

Some of I2I's masterclass machining above.

[jcb121]

It's all working :D!!!

but it's too late to do anything :(

big thanks to 2e0poz and i2i, Couldn't have done it without you guys!

[jcb121]

PCPPS v3.0

I was planning on getting the 4 axis one from Zapp but he was out of stock. I'm sure this one will do just as well. I'll be using DIYCNC drivers as well.