[CallumRD]

Hi,
consider also that a 400w servo (1.27Nm@3000rpm) or a 750W servo (2.4Nm@3000rpm) will exhibit a great deal more thrust than the acceleration alone.

A 5mm pitch ballscrew exerts 125kg (1250N) thrust per 1Nm applied torque. Thus a 750W servo will easily exert a thrust of 2500N. Acting on a 32mm screw results
in 2.25um flex whereas the same servo operating on a 20mm screw results in 3.3um flex.....and that's the screw alone, not counting the fixed end bearing mount.

Craig

Thanks for all the info. Just one point, the servos can't exhibit more thrust than the force required for acceleration plus the force necessary to sustain the cut plus the force to overcome friction. Force is a conserved quantity in this context.

[joeavaerage]

Hi,
my training is in Physics and Engineering, and I would agree that the max thrust is acceleration plus cutting thrust plus friction.......and that's fine until you are standing in front of the
machine. The transient forces are many times your calculation.

My estimate, from personal experience having built and operated a machine of similar size and capacity to yours, is that 20mm is marginally to small, 25mm is about the best balance and that 32mm
is marginally larger than need be. That's not a theoretical calculation but an observation of reality.

Your money, your choice.

Craig

[CallumRD]

Hi,
my training is in Physics and Engineering, and I would agree that the max thrust is acceleration plus cutting thrust plus friction.......and that's fine until you are standing in front of the
machine. The transient forces are many times your calculation.

My estimate, from personal experience having built and operated a machine of similar size and capacity to yours, is that 20mm is marginally to small, 25mm is about the best balance and that 32mm
is marginally larger than need be. That's not a theoretical calculation but an observation of reality.

Your money, your choice.

Craig

I appreciate the insight. My background is in physics myself. The fundamentals are all simple enough, it's figuring out the realities of imperfect parts coming together that's hard.