Siff' Build Log

[Jonathan]

Will be welded to an aluminium frame when complete

Why aluminium? Will be interested to see it welded ...

The Z axis isn't completely finished yet..

Good, as it wont work like that!

Y-axis: You need to have the 4 plates that make up the 'box' round the linear bearings configured such that the plates with the bearings on can be adjusted to get the bearings precisely parallel. Look how I did it ... just don't copy my mistake - making two of the plates 10mm too short! At the moment it relies on the two plates in the YZ plane being machined very very accurately which just isn't going to happen.

X-axis: End supports for the ballscrews look a bit bendy? Remember that all the cutting force in the X direction will be resisted by those plates, so they want to be strong to stop the tool deflecting much. That's why I made mine the odd looking shape out of bar. The easiest solution I can think of is to replace them with box section then put a smaller plate/disc on that to mount the bearing. Have the holes slotted on both so you can align the ballscrews.
If you rotate the ballnuts by 90° you can get the ballscrews slightly closer to the tool...probably not significant.

The way your Y-axis box section is mounted to the X-axis is a bit bendy as the vertical plates only have a line contact with the X-axis bearings. That's why I used box section...

You could get the gantry even further down? Debatable if it's worthwhile.

Other than that looks good (but obviously I'm going to say that as you copied mine )

[everyreasonto]

Using aluminium because I can get it cheaper than steel and my rails are sitting on ally extrusion. That would mean I could then weld the ally extrusion to the base.

I'll add something in to make the bearing adjustable.. something I never thought about, so thanks!

I've reinforced the joint between the x and y axis, but I believe the bearing plates will be strong enough. I know some builds don't even use bearings on the 'floating' side and they will be made from 15mm ally.

Wish I could lower gantry but i'm trying to avoid using timing belts/pulleys where I can, so I had to raise it so the motor would clear the ballscrew :sad:

Also, quick question, where do i get pulleys from with a 10mm bore to fit the ballscrews? And can I get the belts in any length? Should I add a tensioner further down the line?

Finally, once I have bolted together all of the y axis and confirmed it is square/smooth etc, If I weld along the seems (lack of a better word) will it cause the ally to distort at all?

Cheers, Joe :naughty::naughty::naughty: (looking forward to getting it built)

[Jonathan]

I believe the bearing plates will be strong enough. I know some builds don't even use bearings on the 'floating' side and they will be made from 15mm ally.

That sounds reasonable as long as they are mounted securely.

quick question, where do i get pulleys from with a 10mm bore to fit the ballscrews? And can I get the belts in any length? Should I add a tensioner further down the line?

I think this is the cheapest place (HTD is the best):
http://bearingstation.co.uk/products...HTD_Pulley_5mm

You could drill it out to 10mm, but that's very hit and miss unless you have a set of drills in 0.1mm increments and even then I'd bore it. Or use a reamer, but then it's still not likely to be concentric.
Get them delivered to me and it's only about a 10 minute job for me to bore them to 10mm accurately.

There's various length belts at that site ... you'll soon find the formula to work out the belt length for a given centre distance (it's pretty simple). If not I can send you a spreadsheet with it. I just made it so that the 4 holes that mount the motor are slotted so that you can accommodate different length belts and different pulleys.

Finally, once I have bolted together all of the y axis and confirmed it is square/smooth etc, If I weld along the seems (lack of a better word) will it cause the ally to distort at all?

It defiantly would with steel, ... this implies it's worse with aluminium:
http://www.aws.org/wj/2003/02/028/

You need to design it such that there is adjustment designed in to the relevant parts such that it does not matter if it distorts. Obviously clamp it well when you weld it... I did that with mine and didn't really notice any distortion.

[everyreasonto]

Ill probably do that then when I order if thats ok. Can you send me the spreadsheet please? I really can't be bothered to work it out, Just got back from work and i'm knackered!

Anyway, I've been buying today. I haven't ordered anything structural yet because i'm still working on it but I have bought:

Power supply, 3 x 3.1NM steppers, 3 x 4.2A drivers, 3 x couplings = £264
Breakout board = £13.99
4 x ballscrews, 6 lengths of rail, 12 x bearings, er11 collet set = £350 (exc import)
1.5kw spindle and inverter = £201 (exc import)

Still need to order belts, pulleys, extrusion, ally and some milling bits. Can't wait!

Oh, I also picked up a dedicated PC today for the workshop... 2.6ghz P4, 512mb ram, 40gb HDD, old ati graphics card and 15" monitor for £30!! Not bad eh?

Jonathon, what are the dimensions of the spindle mount that you made?

Regards

[Jonathan]

Ill probably do that then when I order if thats ok. Can you send me the spreadsheet please? I really can't be bothered to work it out, Just got back from work and i'm knackered!

Found this, http://www.sdp-si.com/cd/default.htm ... simples.

Jonathon, what are the dimensions of the spindle mount that you made?

This:



Or:



(but with more rounded corners...)

Or whatever you need really...the 150mm wide ones are 1/2" thick and the 125mm wide are 5/8" thick.