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Hi all,
I am finalizing my first CNC router and have a few questions (total newbie of course)
I have three SH5618C3508-B motors with TB6600 drivers and I would like to know if they will work together well ?
Also, if someone can advise what is optimal external power supply voltage for the mentioned motors?
Thank you
Regards
Hi,
looking at the specs of the motor and they are not too bad. The inductance is a respectably low1.7mH and the bipolar-parallel wiring
config has 1.84Nm torque. Very useful.
Those TB6600 drivers are rubbish.....and likely to blow up. I think the TB6600 are only 36V, not enough to 'pull the skin off a rice pudding'.
You want some decent drivers, preferably 80V units with an 80V power supply, Gecko if you can afford them, but there are plenty of perfectly good 80V
Chinese made drivers which are cheaper than Geckos.
Craig
Completely agree with Craig....... Rubbish!.Quote:
Originally Posted by satman1w
I would also go with the bigger 80V type drives but 60V supply will be plenty for those motors and leave headroom in case of back emf.
However......
I would have a look at stepperonline and get some drivers that can take AC voltage and use a toroidal transformer of around 55Vac instead.
This will futurproof you for quite a while.
Such as:
https://www.omc-stepperonline.com/di...or-dm860t.html
https://uk.rs-online.com/web/p/toroi...rmers/2238358/
Wire those motors in PARALLEL according to the datasheet, for best performance.
Also. you don't supply voltage to the motors. The drive does. You supply your psu voltage just to the drives.
:-D
did I mention that except 35+ years of IT and electronics experience, I have none with CNC... that is why TB6600 are in the game, but... I will certainly look for better ones..
Thank you guys, I will have more questions in the future...
regards
Hi,
I disagree with the idea of running drives at a lower voltage than their rated voltage, presumably for increased reliability.
Any drive capable of 80VDC, or 55VAC, or higher is not a toy and I would expect to run them AT their rated voltage without demur.
If you were concerned about over-voltage damaging the output MOSFETS then you would do better specifying a more moderate
acceleration in your CNC software. Its the voltage spike that occurs at deceleration that can, and with toy/rubbish drives, that will kill
the MOSFETS.
I have five-phase Vexta steppers and Vexta drivers on my mini-mill. The drives are direct off-line, that is 230VAC supply. The incoming
AC is rectified and smoothed to 320VDC and then buck-regulated down to 150VDC. Its the 150VDC that is applied to the MOSFETS of the drive.
My wee steppers sing along at 2400rpm under normal conditions but have had them up to 3000rpm. These motors and drives were second hand when
I got them, and expensive at that, but they have run lickety-split for six years ever since. This rather proves the point that with quality drives you CAN
run them at rated voltage without problem.
If you are new to CNC there is a basic dividing line with respect to axis motors, steppers or servos.
Steppers are very much cheaper than servos, although as years have past the best steppers and drives are approaching the price of the cheaper AC servos.
All steppers lose torque the faster they go. Low inductance is critical to minimising that torque degradation. The steppers you have already have low to moderate
inductance and should when paired with the highest voltage driver you can afford still have 20% of its rated torque at 1000rpm. If you think that 20% @1000rpm
is paltry, it is! You can only operate steppers up to a certain speed, depending on the torque load requirements of the machine, before is starts missing steps.
No doubt you have seen/will see closed loop steppers being advertised with the claim 'that they never miss steps'....total BS. The idea is that if the encoder
detects that a step has been missed, invariably because of torque overload at that speed, that the drive will insert an extra step to catch up. Guess what....the extra step
is just as likely to be missed as a regular step.....the stepper is marginally overloaded which is why it missed a step in the first place. There are a couple of advantages
that closed loop steppers do offer but scarcely worth the premium you pay. When all said and done closed loop steppers are still steppers and suffer from
degrading torque as speed increases and closing the loop alters that not one jot.
Modern AC servos on the other hand have constant torque up to their rated speed, and typically have short duration torque overload capacity of three to four times their
rated torque.
I have three new 750W B2 series Delta AC servos for my new mill. They will EAT any stepper ever made! They have a rated torque of 2.4Nm, which is modest by comparison
to a similar sized stepper, but unlike a stepper when the load comes on my servo will deliver 7.1Nm whereas the stepper will just stall. They retain that torque out to rated
speed, which is 3000rpm, but I'm running them up to their max of 5000rpm for fast rapid traverses. These servos, drives and cables cost $438USD plus shipping each from
China. Delta is a Taiwanese brand manufactured in China, good quality, good back up, good documentation and most importantly, good set-up and tuning software at very
fair prices, certainly much cheaper than Japanese/US/European made stuff. There are even cheaper Chinese brands but questionable quality, support, crap documentation and
critically NO set-up and tuning software....avoid like the plague.
A good stepper and high voltage drive might set you back $150-$200 per axis where an AC servo from a decent manufacturer will set you back about $300-$400 per axis,
so servos are still more expensive but 'by crikey do they ever go like hell!'
Craig
That's where I'll be going later if my machine can make the money to pay for them. Servo's. Either A4 or B2 for the axis. Not fussed really.Quote:
Originally Posted by joeavaerage
I already have an A4 Lichuan servo drive, 1.8kw servo for the mill spindle upgrade. Basic but a very nice set (once I figured out the IO with Craigs help).
Paid roughly $320 for them from Aliexpress
I looked at closed loop steppers but they do seem like a waste of money. A bit like putting a band aid on the machine.
Hi,
the cheaper Chinese servos like Lichuan are good value, and as dazp1976 attests work well. I don't have a problem with either their quality OR their performance, but
they have shocking documentation and no set up software.
If they were to be your first experience with AC servos then you're in for a real battle trying to set them up.
If you have had experience with other AC servos, especially those with good set up software, then you will know that most servos a set up very similarly, maybe with different
terminology, but otherwise the same. With that experience under your belt then deciphering and interpreting Lichuan documentation and set up would be fine.
Craig
dazp1976 and joeaverage - thank for your answers. I have already made some changes as you suggested...
I got the DM860 motor drivers which will be supplied with 66VAC from toroid transformer (that could be also changed in near future if not adequate) and driven with Planet-CNC MK 3/4 controller
(https://planet-cnc.com/hardware/#products-hardware).
Specifications for SH5618C3508 stepper says that motor "can survive" 4.95A when connected in parallel.
Does it mean that I have to setup drivers dip switches to adequate current (4.86 / 5.83 peak) in case of parallel connection, or something else?
Does it make any sense to setup motors with DPDT switches and to be able to switch between serial and parallel or is it stupid?
Also, what "Pulse/rev" setup should I choose for starters (400-40000) ?
Thanks for your time.
Regards
Hi,
the current of a stepper is the maximum the manufacturer believes that won't overheat the stepper dangerously. You can run a stepper up to that current
level but risk burning it out if you go higher.
You might decide to run the stepper at less than its rated current, while it will produce proportionately less torque it will also stay cooler. If your steppers are
more powerful than your machine requires at your chosen maximum speed you should do it.
No, set them up in parallel and be done with it. You did not pay a premuim to get good steppers and drivers only to flush all that performance downQuote:
Does it make any sense to setup motors with DPDT switches and to be able to switch between serial and parallel or is it stupid?
the toilet by running them in series.
That is called microstepping. It allows a stepper to do part steps, although beyond 1/2 or 1/4 steps it does not work that well as a means to increase resolution.Quote:
Also, what "Pulse/rev" setup should I choose for starters (400-40000) ?
What micosteppig does do however is make the motion much smoother than full-stepping. If you increase the microstepping too high you controller will struggle to provide
the pulses required at high speed, it just won't be able to keep up. What you need to do is balance smoothness and resoluton on the one hand, and increased pulse rate
on the other, and about 8 microsteps per fullstep or 1600 steps per rev is a good compromise. I wouldn't go below 800 or go above 3200....anywhere in that range will be fine.
Do yourself a favor, once you make a choice of microstepping, say 800 or 1000 steps per rev, set it and leave it. Many newcomers bugger around with microstepping
for hours/days/weeks instead of getting on with the real problems.
Craig
Excellent, thanks for now.
I'll be back with results and/or questions as soon as I put it all together...
regards