The New Machine

[Jonathan]

I don't see the point of wanting a round number. As soon as you've entered it into mach3/EMC you won't need to know about it at all. I've forgotten what the value is per step on mine...

As fragger said, you will almost certainly be using 1/4 or 1/8 micro-stepping anyway which effectively changes the value but doesn't really gain accuracy.

By using pulleys you get
-another source of backlash
-drive flex(belt stretch)
-reduced top speed
-side load on the screw

1) no, unless your pulleys are awful. Mine have not added backlash.
2) negligible from my experience.
3) What! That's impossible to judge without calculating it properly. You need to get the motor running in the optimal region of the torque/rpm curve and to do that you need to get the ratio right which, unless you're very lucky, requires pulleys.
4) Surely the bearings in the mill are going to cope with that...if not add more? I'd be more worried about the bearing on the stepper motor.

On my router I've found that generally increasing the size of the pulley on the stepper motor has increased the top speed, but of course sacrificed resolution. It's less clear cut on a milling machine as it's heavier and the coefficient of friction is greater.

[Ricardoco]

I don't see the point of wanting a round number. As soon as you've entered it into mach3/EMC you won't need to know about it at all. I've forgotten what the value is per step on mine....

I had decided that for the way i wanted to position the steppers that belts and pulleys was the way to go and at a 2.5:1 ratio i would get that round '1' it was not a requirement i could have even gone 1:1 and still can ill just swap out the pulleys and belts if need be and i will probably forget about it as you have.

The little ratio and ballscrew tutorial I wrote down in the middle of the post was perhaps to make things easier for some people to understand as it was a source of many questions from me when i did the other conversion. Using round numbers just made it easier in my mind to see what was going on thats all..

As fragger said, you will almost certainly be using 1/4 or 1/8 micro-stepping anyway which effectively changes the value but doesn't really gain accuracy..

Shouted! :lol:

on another note what do you think of the idea of a counter balance on the Z... please dont shout your reply its only a question...:heehee:

Rick

[Jonathan]

on another note what do you think of the idea of a counter balance on the Z... please dont shout your reply its only a question...:heehee:

[whisper]I think someone on this forum is considering it / has done it...
As I'm sure you know it should improve your Z-axis feedrate, but when do you actually need a high feed there? Possibly small drills (definitely with PCBs) and maybe with 4th axis in some situations but that's about it?
You can use an 'oversize' (i.e. greater than the mass of the head) counterweight to eliminate backlash in the Z-axis.
[/whisper]

Are you using a rotating ballnut on Z, just out of interest?

[Ricardoco]

Are you using a rotating ballnut on Z, just out of interest?

Hmmm tell me more...

[Rogue]

[whisper]I think someone on this forum is considering it / has done it...[/whisper]

I'm playing with the idea, primarily because I think it looks good, effectiveness be damned! :twisted:

On a related note, I also asked similar questions about the under-table mounting, the consensus seemed to be that it wasn't a problem. The following thread might have useful things for you: http://www.mycncuk.com/forums/showth...or-under-table

[Ricardoco]

I'm playing with the idea, primarily because I think it looks good, effectiveness be damned! :twisted:

On a related note, I also asked similar questions about the under-table mounting, the consensus seemed to be that it wasn't a problem. The following thread might have useful things for you: http://www.mycncuk.com/forums/showth...or-under-table

I will be using the Double ballnut if needed when i fit the ground Ballscrew but for now with the rolled i will use just the 1 with the ability to encorperate a double in the design..

LOL well here is the Vcarve output for the endplate for the Z with a side mounted stepper, or if prefered it can be hung on the end infact ive desinged it so you could hang it on the left rignt or even underneath,Ive not included the tensioning system yet as im still working on it. I still think it looks bodged on the end but that is just my opinion lol




I will make the prototypes out of a non metalic material i suspect...

Oh and ive made it incorperate the ballscrew Double A/C bearing housing as well.

[i2i]

on another note what do you think of the idea of a counter balance on the Z...
Rick

Denford used to do this on the early triacs, they stopped it quite quickly.

[Ricardoco]

Denford used to do this on the early triacs, they stopped it quite quickly.

Hmmmm Your not the first to tell me that, i wonder if the bell is tolling for the counter balance idea!!!!

[Jonathan]

The ones at Zapp are close, but still more than Kelling. I'm surprised as I've spent ages looking for lower inductance motors, though only really Nema 23.
Either way the difference is insignificant if you're running the motor on a higher voltage with something like this:

http://www.zappautomation.co.uk/2m11...5669f8490a6970

Without that you'll never get a very high speed from that size motor, if you need it.