BuildingAfloat

[Ricardoco]

I'm sure he's going to waste more yet. Prime example is the ballscrews he used. Only 5mm pitch over than length, plus he's used expensive ones not cheap ones from china so no excuse.

Hey Jonathan, the 5mm pitch over that length, is ithat likely to cause him problems, I only ask because im building a similar size steel machine at the moment
.

Rick

[Jonathan]

Hey Jonathan, the 5mm pitch over that length, is ithat likely to cause him problems, I only ask because im building a similar size steel machine

Not sure what length he's actually used, read about 5 pages and got bored, so I'll just comment in general...
As a rough guide any axis about 1m will benefit from using greater than 5mm pitch and over about 1.5m rotating nuts become more economical. The reason is by going to 10mm pitch the RPM of the screw is halved for a given feedrate, so if the limiting factor is the critical speed (speed at which the screw starts whipping) using a 10mm pitch screw will get twice the feedrate of if you had used 5mm of the same diameter.

He's been forced to used driven nuts no doubt due to the critical speed being too low over that length, however he's starting with the wrong ballscrew and has made the shafts on the mounts far larger than necessary which will add a huge amount of inertia to the system so I'm not surprised they've not made much difference.

The other problem is using 5mm pitch has forced him to use 25mm screws, which is a massive disadvantage since their inertia is 2.44 times greater than for instance using 20mm diameter. This will greatly reduce the possible acceleration.

I believe you're X-axis is 8'? If so with sufficiently powerful motors (Nema 34 ideally with mains drivers) you could use RM2510 ballscrews and get up to about 5m/min which is nothing special, but adequate. Alternatively RM2020, which is significantly more expensive, which will get up to about 8m/min and you would probably still need Nema 34 motors but may get away with cheaper drivers. Either of these configurations would excel with a driven nut and 3Nm Nema 24 motors.

[BikerAfloat]

Hi All,

I'm after drawings for both the 1.5 & 2.2 kW Chinese spindles if someone has them, could you post them for me please?

Cheers,

Geoff.

[Ricardoco]

Hi All,

I'm after drawings for both the 1.5 & 2.2 kW Chinese spindles if someone has them, could you post them for me please?

Cheers,

Geoff.

Thats the best i can do so lets hope someone else has the other...

[Jonathan]

They do vary a little. Just had mine out of the spindle mount anyway as I'm investigating dynamic balancing and it's slightly different to that drawing. The main body is 80mm diameter for 200mm, then 11mm more at 68mm diameter, then the chuck protrudes by 39mm. When a tool is installed you need to add about 8mm to the length to account for the collet nut. It shouldn't make much difference to the Z-axis design...

[Ricardoco]

They do vary a little. Just had mine out of the spindle mount anyway as I'm investigating dynamic balancing and it's slightly different to that drawing. The main body is 80mm diameter for 200mm, then 11mm more at 68mm diameter, then the chuck protrudes by 39mm. When a tool is installed you need to add about 8mm to the length to account for the collet nut. It shouldn't make much difference to the Z-axis design...

The drawing has a few innacuracies in it and in fact is the same size as yours i suspect, take a look and see if you can spot the mistakes..lol

[Ricardoco]

Thats better..