[BPE3976]

Hi,
why do you think it essential that you have encoder feedback for your spindle?

Is it position capable or something?

I use 750W Delta B2 servos, it was the first time I'd used AC servos so I had a current monitor on each of them .Waste of time. 99.99% of the time they draw next to no current at all and only
for a tenth of a second or so do they draw any real current. My estimate is that the closed loop steppers (being variable reluctance) will draw more than AC servos would.
I personally would discount the 'current draw' argument if that is all that is stopping you from getting servos.

Personal experience is that servos EAT steppers, any stepper for breakfast!

Craig

Hi Craig,

The spindle motor is a fanuc servo with a pulse generator encoder. If I wanted to do position monitoring for an atcdown the track, its helpful. Also, being able to monitor real time rpm and set torque requirements through the vfd will be advantageous.

I also agree, servos should outperform closed loop steppers, no argumentat all. That being said, i've not played with servos alot (a little in my job, but that's about it) I'm only going off the amperage draw charts that the manufacturers supply. I agree that the manufacturer usually will put worst case full load capacity on any chart they send out, so I was working with that.

The closed loop steppers I currently use, are 12nm nema 34's, they draw about 2 amps each on full load on single phase 240v. I'm curious as to what anyone has measured on a 1kw servo on a machine of similar size.

Thankyou,

Shane Barnett

[joeavaerage]

Hi,
my 750W servos draw about 100mA from a 230VAC supply. Only when they have to supply torque do they start using current. My machine weighs 800 kg, so the X axis table weighs about 200kg.
The X axis servo never goes over an 1A or so in my observation.

Craig

[BPE3976]

Hi,
my 750W servos draw about 100mA from a 230VAC supply. Only when they have to supply torque do they start using current. My machine weighs 800 kg, so the X axis table weighs about 200kg.
The X axis servo never goes over an 1A or so in my observation.

Craig

Hi Craig,

Thats what I needed to hear. My machine weighs close to 3200kg, the x+y table weighs about 350kg and can take about another 350kg on the table. It is running linear bearings, so its very light to move considering its weight.

I'll have another look at servos. The original dead dc servos were rated to 6nm and Max at 12nm, they were also mounted to reduction gearboxes of a 4:1 ratio. I'll see what's available to replicate the same torque rating. I know modern AC servos will eat 40yr old DC servos all day, every day.

Thanks,

Shane Barnett

[joeavaerage]

Hi Shane,
I use Delta servos on the basis of performance and cost.

There are cheaper Chinese made servos, and while I have no doubt they work, they have poor documentation, questionable backup and often no set up and tuning software....not recommended.

Delta is a Taiwanese brand made in China, and DMM is a Canadian brand made in China. Both are good quality, performance and backup and most importantly with good setup and tuning software
at fair prices. To be sure they are more than el-cheapo Chinese, but neither are they eye-watering Yaskawa or Siemens.

750W Delta B2's I buy for $438USD/kit (servo, drive and cables) and are pretty good value for money. 2.4Nm rated and 7.1Nm overload, 3000rpm rated, 5000rpm max.
You might be tempted to go bigger, although I can attest to how damn fast and powerful these 750W units are, but these 1.5kW B2's are 130mm frame for 7.2Nm rated, 21Nm overload
at 2000rpm rated and 3000rpm max for $750USD/kit

https://www.fasttobuy.com/cnc-router...le_p28102.html

These are the 750W units, I've bought ten of them over 3.5 years at this price:

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

Craig

[BPE3976]

Hi Shane,
I use Delta servos on the basis of performance and cost.

There are cheaper Chinese made servos, and while I have no doubt they work, they have poor documentation, questionable backup and often no set up and tuning software....not recommended.

Delta is a Taiwanese brand made in China, and DMM is a Canadian brand made in China. Both are good quality, performance and backup and most importantly with good setup and tuning software
at fair prices. To be sure they are more than el-cheapo Chinese, but neither are they eye-watering Yaskawa or Siemens.

750W Delta B2's I buy for $438USD/kit (servo, drive and cables) and are pretty good value for money. 2.4Nm rated and 7.1Nm overload, 3000rpm rated, 5000rpm max.
You might be tempted to go bigger, although I can attest to how damn fast and powerful these 750W units are, but these 1.5kW B2's are 130mm frame for 7.2Nm rated, 21Nm overload
at 2000rpm rated and 3000rpm max for $750USD/kit

https://www.fasttobuy.com/cnc-router...le_p28102.html

These are the 750W units, I've bought ten of them over 3.5 years at this price:

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

Craig

Hi Craig, thanks for that, I can get delta's locally for relatively cheap pricing (I'm in Melbourne Australia) the only Chinese servos I've seen with any tuning software are from Hanpose. That being said, I've used yaksawa in my job (very expensive) and fanuc (you better believe they are expensive! Lol) both are great, but my behind would hurt for some time after purchase.

Deltas would be my go to.

Thankyou,

Shane Barnett

[pippin88]

How much do they want for Deltas locally? (I'm in NSW)

I bought mine OS, really just assumed they would be super expensive in Aus

[BPE3976]

How much do they want for Deltas locally? (I'm in NSW)

I bought mine OS, really just assumed they would be super expensive in Aus

I'll get a quote when I'm back home (another week) and let you know.

Cheers,

Shane Barnett

[epineh]

Hi all been a while, so I've been doing some testing lately, late last year my MESA card in the wood router I built died. Long story short I retrofitted it with a Tang Nano FPGA running Riocore firmware, I made a simple PCB that holds the Tang Nano and plugs directly into my existing Breakout board, and it was up and running fairly painlessly.
The idea was to use the same setup in the mill with step/dir drives. Riocore has an encoder plugin that can be used to provide position feedback to servo motors.

I had removed the resolver and tacho generator from the X axis servo and added an encoder some time ago. Now I've temporarily wired the a and b signals to my breakout board Z pulse pins using very dodgy dupont wires, sent pwm and dir to a cheap ebay hbridge running on 30 Volts DC, configured linuxcnc for a one axis machine and bingo ! Closed loop to the controller servo control.

With hardly any tuning and motor voltage way under its rating the servo is surprisingly stable and is impossible to turn by hand when energised.

The best part is when the machine enable is off you can turn the servo by hand and see the DRO update...it's the little things!

I've designed new PCB's to run in the machine, will provide 4 axis closed loop to the controller servos, 3 axis control and one for the spindle - Riocore can use encoder input for speed regulation as well so that should be interesting. PCB's should turn up in a week hopefully so once I populate them I can integrate all this into the machine and do some real testing.

[epineh]

Bit more progress, the new HBridge and new controller boards turned up, I spent some serious time getting them going, including fault finding a few design issues. Happy to say it's time to go from the bench to installing them into the machine control box.
I've got one HBridge complete that I was testing with, I need to do a parts order for the remaining ones so for now I am concentrating on getting the X axis up and running. Estop is now installed and working, next will be sorting the servo power supply.

[epineh]

Had a good day in the shed today, finished off the servo motor cabling, including encoder, powered up and after some truly scary servo oscillations with the servo untuned and sitting on the machine bed, I am happy to report the X axis is done!
I still need to properly tune it but its good enough for now to jog the machine around slowly, I've limited the max speed to about 2000mm/min for good measure.

[epineh]

Quick photo of the cheapskate encoder cover I built, two plumbing pipe end caps, one machined out with my CNC wood router to match the mounting holes and fit over the encoder, one short piece of pipe, fits together nicely. Made another for the next Axis.