Bridgeport Knee Mill Stepper to servo upgrade

I want to upgrade to servos and I was wondering what is the lowest torque I should avoid. I have been looking and all seem low to me.

Or upgrading to a closed stepper would be just as good?

0.75kW or 1kW servos would be my choice. Much better than closed loop steppers.

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Originally Posted by Jim Dawson

0.75kW or 1kW servos would be my choice. Much better than closed loop steppers.

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Thank you. What about torque?

Hi,
I use 750W Delta B2 series servos. They are rated at 2.4Nm (cont), 7.1Nm (overload) at 3000rpm.

https://www.fasttobuy.com/flange-80m...er_p28084.html

When a stepper gets overloaded it misses steps or stalls, no ifs or buts. When a servo gets overloaded it just digs into its three to four-fold overload rating. It can only do this for
brief periods but it results in a servo often appearing way more powerful than the numbers would suggest.

Steppers have a great deal of torque....at low speed....but above a few hundred rpm they fade badly. Closed loop steppers are still steppers and a closed
control loop changes the diminishing torque with speed not at all.

If you are going to get steppers ensure they are low inductance, as that is what determines how quickly and badly the torque fades with speed.

For 23/24 size 1mH -2mH, 1mH preferred and reject anything over 2mH.
For 34 size 2mH-4mH, 2mH preferred and reject anything over 4mH.

Closed loop stepper manufacturers would have you believe they are faster, more powerful, never miss a step.....all BS.If a stepper is marginally overload it will miss a step.
A closed loop stepper drive will insert an extra step to catch up, but guess what, the extra step is just as likely to be missed as a regular step.

Closed loop stepper can an do interpolate between steps in a way that open loop steppers cannot, and a closed loop stepper can determine if its lost too many steps
and signal a 'following error' fault to your controller. You are paying dearly for these features.

If you want genuine closed loop performance get decent AC servos, they'll eat any stepper ever made.

Delta, a Taiwanese brand made in China, and DMM a Canadian brand made in China are both good quality, good support, good documentation and most importantly free set-up and tuning
software at fair prices. There are cheaper Chinese brands but the documentation is poor, support questionable and no set up software. To be fair to them they do work and the prices are compelling, but
if you've never set up servos before you'll want, even need, setup and tuning software. Avoid them like the plague.

Craig

Quote:

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Originally Posted by usajet

Thank you. What about torque?

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What Craig said

Quote:

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Originally Posted by joeavaerage

Hi,
I use 750W Delta B2 series servos. They are rated at 2.4Nm (cont), 7.1Nm (overload) at 3000rpm.

https://www.fasttobuy.com/flange-80m...er_p28084.html

When a stepper gets overloaded it misses steps or stalls, no ifs or buts. When a servo gets overloaded it just digs into its three to four-fold overload rating. It can only do this for
brief periods but it results in a servo often appearing way more powerful than the numbers would suggest.

Steppers have a great deal of torque....at low speed....but above a few hundred rpm they fade badly. Closed loop steppers are still steppers and a closed
control loop changes the diminishing torque with speed not at all.

If you are going to get steppers ensure they are low inductance, as that is what determines how quickly and badly the torque fades with speed.

For 23/24 size 1mH -2mH, 1mH preferred and reject anything over 2mH.
For 34 size 2mH-4mH, 2mH preferred and reject anything over 4mH.

Closed loop stepper manufacturers would have you believe they are faster, more powerful, never miss a step.....all BS.If a stepper is marginally overload it will miss a step.
A closed loop stepper drive will insert an extra step to catch up, but guess what, the extra step is just as likely to be missed as a regular step.

Closed loop stepper can an do interpolate between steps in a way that open loop steppers cannot, and a closed loop stepper can determine if its lost too many steps
and signal a 'following error' fault to your controller. You are paying dearly for these features.

If you want genuine closed loop performance get decent AC servos, they'll eat any stepper ever made.

Delta, a Taiwanese brand made in China, and DMM a Canadian brand made in China are both good quality, good support, good documentation and most importantly free set-up and tuning
software at fair prices. There are cheaper Chinese brands but the documentation is poor, support questionable and no set up software. To be fair to them they do work and the prices are compelling, but
if you've never set up servos before you'll want, even need, setup and tuning software. Avoid them like the plague.

Craig

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Thank you