NordicCNC's build log

[jarjar]

A 400W servo (rated at 1.2Nm @ 3000rpm) is plenty enough. 200W is also probably enough.
I will be using a Yaskawa 400W servo with brake for a 60kg Z axis (moving part only), driven by a 5mm pitch ballscrew @ 1g accel and 20m/min.
The servo has a peak torque of 4Nm, and moving this axis will only require about 2Nm peak.

[NordicCnc]

A 400W servo (rated at 1.2Nm @ 3000rpm) is plenty enough. 200W is also probably enough.
I will be using a Yaskawa 400W servo with brake for a 60kg Z axis (moving part only), driven by a 5mm pitch ballscrew @ 1g accel and 20m/min.
The servo has a peak torque of 4Nm, and moving this axis will only require about 2Nm peak.

In post #2 http://www.mycncuk.com/threads/13448...672#post114672 you said that these 180W servos that I had bought were only toys and that 400W would be the bare minimum. I think you were talking about a little bit different design in that case so I can just ignore it, correct? Anyway the price difference between a Delta 200W servo and a Delta 400W servo is minimal.

Will you be using direct drive for that Z-axis? I checked that those servos are rated at 3000rpm, so direct drive with 5mm pitch would result in 15m/min. Also what diameter will that ball screw be and is it possible to spin it that fast?

Your moving weight sounds extremely heavy! Are you designing it in steel? How did you calculate how much Nm will be needed to move the axis?

Wow, this turned into a lot of questions, lol!

[jarjar]

A JMC 180W might be enough power wise, but industrial servos are much more sophisticated. Encoder resolution, motion smoothing (much needed for high accel when the controller doesn't handle S-curve motion profiles), vibration suppression, ...
To be honest I also had a different machine in mind from what you're planning when you stated your requirements :)

For calculating the required motor, I simply plugged the numbers in Yaskawa's calculator (SigmaSelect).
It's a 2005 ballscrew coupled with 1:1 pulleys (I would have liked to go direct-drive, but didn't have enough space to inline the motor). The axis can reach 30m/min because servo max speed is 6000 rpm. Ballscrew critical speed is not a concern since it's short (400mm) and could in theory handle 13'000rpms.

Yes the axis is all steel, but the spindle is only 2.2kW ISO20 30krpm. The goal is high-speed aluminium milling.

[JAZZCNC]

A JMC 180W might be enough power wise, but industrial servos are much more sophisticated. Encoder resolution, motion smoothing (much needed for high accel when the controller doesn't handle S-curve motion profiles), vibration suppression, ...
To be honest I also had a different machine in mind from what you're planning when you stated your requirements :)

For calculating the required motor, I simply plugged the numbers in Yaskawa's calculator (SigmaSelect).
It's a 2005 ballscrew coupled with 1:1 pulleys (I would have liked to go direct-drive, but didn't have enough space to inline the motor). The axis can reach 30m/min because servo max speed is 6000 rpm. Ballscrew critical speed is not a concern since it's short (400mm) and could in theory handle 13'000rpms.

Yes the axis is all steel, but the spindle is only 2.2kW ISO20 30krpm. The goal is high-speed aluminium milling.

Nordic be careful here because it's like comparing apples with oranges when comparing Yaskawa motors with Cheaper Chinese motors. The price difference is big and so is the quality. I'd also guess to get those speeds the Yaskawa will use an absolute encoder system with high count encoders requiring a high-frequency controller.

When you move up into these levels then everything else attached to them needs to move up in quality with it, else no point fitting expensive high-quality servos.
Your 8K budget will soon get eaten up with motors and ball-screws.

[jarjar]

Delta is Taiwanese and they make proper cheap servos. Also 400W Yaskawa servos can be found rather cheap (~$400 motor + drive + cables). Most similar sized servos have the same ratings. 6000 rpm is nothing special, same for absolute encoders.

I asked a quote for the latest ASD-A3 drives from Delta with a 750W servo, 24-bit incremental/absolute encoder. Price was $350.

But Jazz is right to warn you. Servos are more complex than steppers. I went Yaskawa just because their manual is more comprehensive than the Delta one.

[JAZZCNC]

Delta is Taiwanese and they make proper cheap servos. Also 400W Yaskawa servos can be found rather cheap (~$400 motor + drive + cables). Most similar sized servos have the same ratings. 6000 rpm is nothing special, same for absolute encoders.

I asked a quote for the latest ASD-A3 drives from Delta with a 750W servo, 24-bit incremental/absolute encoder. Price was $350.

But Jazz is right to warn you. Servos are more complex than steppers. I went Yaskawa just because their manual is more comprehensive than the Delta one.

I wasn't referring to Delta when I said Chinese servo's it was a general point between Cheap and Expensive Servo's. Regards the Yaskawa motors -drive-cable package then can you post a link to where your buying because that's a very good price. What model is that.?

Regards the speed I don't see many that are rated at 6k rpm in the lower price ranges, 3K rpm is a typical rating with incremental encoders. Yes, they can be run up to 5-6K rpm but they are not rated to run at that speed constant.!

[jarjar]

I wasn't referring to Delta when I said Chinese servo's it was a general point between Cheap and Expensive Servo's. Regards the Yaskawa motors -drive-cable package then can you post a link to where your buying because that's a very good price. What model is that.?

Regards the speed I don't see many that are rated at 6k rpm in the lower price ranges, 3K rpm is a typical rating with incremental encoders. Yes, they can be run up to 5-6K rpm but they are not rated to run at that speed constant.!

There are currently tons of offers on Ebay for SGM7J-04AF + SGD7S-2R8A00 at $450 new. I bought one like this a while back for a little less. I just asked for cables and they included them with no extra charges.
You can even buy the model with absolute encoder separately for less (SGM7J-04A7 $160 + SGD7S-2R8A00 $260)

I didn't say 6000rpm is the nominal rating, but it's still useful for short rapid moves.

[NordicCnc]

Nordic be careful here because it's like comparing apples with oranges when comparing Yaskawa motors with Cheaper Chinese motors. The price difference is big and so is the quality. I'd also guess to get those speeds the Yaskawa will use an absolute encoder system with high count encoders requiring a high-frequency controller.

When you move up into these levels then everything else attached to them needs to move up in quality with it, else no point fitting expensive high-quality servos.
Your 8K budget will soon get eaten up with motors and ball-screws.

Thanks for the heads up JAZZ. I am set on using chinese servos anyway because of the price and their good reputation.

Regarding the controller pulse output then I don't think I need to worry. The ESS SmoothStepper can output up to 4MHz according to its specs.

Would you also have time to check my questions in post #44? I would really appreciate it man! http://www.mycncuk.com/showthread.php?p=114834

Skickat från min SM-A530F via Tapatalk

[NordicCnc]

A JMC 180W might be enough power wise, but industrial servos are much more sophisticated. Encoder resolution, motion smoothing (much needed for high accel when the controller doesn't handle S-curve motion profiles), vibration suppression, ...
To be honest I also had a different machine in mind from what you're planning when you stated your requirements :)

For calculating the required motor, I simply plugged the numbers in Yaskawa's calculator (SigmaSelect).
It's a 2005 ballscrew coupled with 1:1 pulleys (I would have liked to go direct-drive, but didn't have enough space to inline the motor). The axis can reach 30m/min because servo max speed is 6000 rpm. Ballscrew critical speed is not a concern since it's short (400mm) and could in theory handle 13'000rpms.

Yes the axis is all steel, but the spindle is only 2.2kW ISO20 30krpm. The goal is high-speed aluminium milling.

Thanks for the link to the calculation software, this will be very useful to me.

Myself I think I am going to consider a 2005 ballscrew for the Z-axis. My ball screw length is also 400mm long and who would not appreciate a 15m/min rapid feed rate! Originally I planned for a 1605 with a 2:1 reduction, since I worried about whip (ball screw critical speed) and increased inertia (180W servos). These things are no longer an issue!

Skickat från min SM-A530F via Tapatalk

[NordicCnc]

Some design progress has been made.

X-axis design



- L-shape gantry with 120x80 (heavy) Item profiles 1200mm long, with approximaterly 950mm travel length . The profiles for the L-shape are bolted together from the bottom. I plan to use aluminium plates as guides in the T-slots. Should these guides be fastened somehow or is it enough to insert them into the slots and shim away the clearance?
- High side gantry profiles with 120x80 (heavy) Item profiles, 160mm long. These are bolted to the bottom profile of the L-section, from the top of the bottom profile.
- 20mm aluminium gantry side plates, bolted to both the L-section and the high side gantry profiles. It is also bolted to the bottom plates, that will be mounted to the Y-axis bearing plates. The purpose of the bottom plates being separated from the Y-axis bearing plates, is to allow some adjustment later when squaring the gantry.
- 20mm HIWIN linear rails.
- 2010 ballscrew, 1150mm long.
- Delta 400W servo motor with a 2:1 reduction, to limit ballscrew RPM.



Y-axis design will continue from here!