Ballscrew Thickness!

[AdCNC]

thanks tribbles for that info, 25mm OD is some fair chunkey stuff!

[Ross77]

Gary (from Zapp) gave me a website which allows you to calculate the whip speed based on the diameter and so forth

As Tribbles said the diameter required to reduce whip is fairly easy to work out. The pitch is not so. You mentioned speed and accuraccy..... I dont think the two are easily achived without lots of money.......

You havent said what you are cutting or what accuraccy you require. But if you are using steppers when 200 steps per rev at 5mm pitch gives 0.025mm resolution. With a 25mm pitch you get 0.125mm resolution.

Also given that for your 1829mm travel you will probably need 20mm + dia. then motor torque will be an issue, lots of mass and inetia to control.
I may be corrected by others but you are probably in Servo Motor terratory for the distances and speeds you require.

See the attached pdf that I got from Cnc-zone.( hope its ok to repost it. cant remember who its from. {Lee any probs just remove it}

Goes in to detail about designing motors, screws and feeds.

[Ross77]

Sorry. Gary and your self posted whilst I was writting...
30mins to post. Must be time to go to bed....:heehee:

[AdCNC]

You havent said what you are cutting or what accuraccy you require.

Well i was planning on cutting woods and none ferrous metals!

Ive been looking at the 25mmOD ballscrew and im leaning towards that! as for the motors being not power full enough i can gear them to something like a 5:1 or more and get a 20-25 pitch ball screw!

What do you guys think!

[Ross77]

Well i was planning on cutting woods and none ferrous metals!

Ive been looking at the 25mmOD ballscrew and im leaning towards that! as for the motors being not power full enough i can gear them to something like a 5:1 or more and get a 20-25 pitch ball screw!

What do you guys think!

Did you mean none or some? Gearing will definatley help with the motor power and accuracy (200 steps at 5:1 is 0.025 resolution) but will also slow the travel time down. Max stepper RPM is 350 ish I think

If your using belts then you might also want to check the 5:1 ratio, sounds a bit high. the small pulley will not have enough teeth in mesh if the bigger pulley is to large. Ive got a calculator at work so if its any help I'll post it tommorow.

Hope you dont think I'm being negative but I had to make the same decisions for my build. I chose Slow and accurate because Im only using it to build the fast machine :heehee:

Have you concidered rack and pinon? its cheaper and very fast.

[Ross77]

Ok I've had a rethink, Have you already got your steppers and drivers yet?

If not then the better drivers have micro stepping. if you get the correct size motor then u can direct drive it and use the micro stepping to get the accuracy/ resolution you need.

Give gary a ring. Im sure he will help you and is much better qualified then me. Im just trying to cover all possibilities to help you make the right decision.

[tribbles]

thanks tribbles for that info, 25mm OD is some fair chunkey stuff!

I was looking at 40mm before realising the motors wouldn't go as fast as the speed I was anticipating, so Gary suggested using the 25mm pitch stuff instead - and it's worked out great (thanks!)