Closed loop Step Servo Drive Driver 2HSS86H + 4.5N.M Motor + Encoder

[george uk]

hi Jonathan.

Originally Posted by george ukTwinning an X, Accurate Z position over large time running jobs



If those are causing a problem, then it should be solved by setting up the system properly.

understood, i have been reading up on what experiences people are haveing using twin X, and i notice that a few were having problems homing them both, i just thought that these may be an easy way round that, but, yes defiantly, if people are lossing steps on X, its machine problems or bad design .

Z Axis, for what i want to do, thats more important, some of the jobs we are looking at have run times going over 5 hours plus, ( am doing 2 machines ), so it seems to be a reliable way of making sure any lost steps in Z dont compound themselves, as they would be corrected immediately.

You can only gain anything below this speed, since whether the position is inferred from an encoder, or the back-emf, doesn't change the rest of the algorithm. That's the reason why the stall detect feature, e.g. on the AM882 driver, only works above 300rpm - it can't sense the position below that speed.

Thankyou for this, i like information put this way, short sweet and direct,

[Boyan Silyavski]

What i meant was that closed loop steppers are still steppers, low torque at high revolutions, which in my case meant i should have compromised with the gantry weight on the 2300x1300 machine i started building or buy a really big closed loop steppers, which in price surpassed second hand AC servo system. The other solution was to make all the gantry from aluminum, but as DIYers like me normally don't have access to machine 1 1/2 meters long pieces of aluminum, this would have raised again considerably the price.

I don't know if i am to obtain another level of headache. But maybe its the time to learn. Reading from the manual of the Samsung servos i have bought, the tuning seems quite simple in fact. If i drive them from the motion control in step mode. According to the manual you introduce some simple parameters, home your machine, push the button and the servos start some test moves and adjust to the machine itself. If that works, it certainly is a non brainer. If doesn't work, there is always something new to learn on the way. Plus i can control them in a couple of different ways also from the motion control board if desired so.

In short i prefer to be free with the design of the machine to be able to construct it the way i like, with the budget i like, to be heavy as necessary, and to drive it as its necessary :-) . As a DIYer i wanted a commercial machine for the money of DIY. That meant some second hand components.

[Boyan Silyavski]

In the spirit of this constructive discussion i want to say something more. When looking for motors after i decided i will go with cheap Chinese servo. Then i saw a Leadshine AC 220v servo at ali axpress. As leadshine seemed at that time to be a better choice i was ready to buy until i read this review: 06/01/2009 - Servo Drive Review and Comparison

It seems the jump should be straight to good brand servos, as the cheaper servos have some inherent problems and lacking of their own.

What i wonder after i read the review for the Leadshine servo is about the closed loop stepper and its control. It seems quite good on paper, but i still couldn't find a review from a real life implementation on a machine. I mean, would it stand well to what it promises?

There is also one possible combination that i believe will be nice, better and maybe even cheaper. Closed loop stepper/ stepper with encoder/ + second hand motion control board with its brand stepper drives , usually in the form of tight fit daughter boards or in the same enclosure. That sounds better to me , if one is ready to jump in the head ache world :-)

[george uk]

Again, this is a totaly out there question,

Have been reading of people using servos as spindles, can not quite get my head around the pros and cons. Am wandering if i large one of these closed loop stapper motors, might be usable as a spindle under certan curcumstances.

What am i missing ?

[Jonathan]

What am i missing ?

Torque and speed.

[george uk]

HI Jonathon

would that be the same problem with a servo as a spindle or just these type steppers. I was considering options for slower cutting speeds for stone, and i can not find a reasonably prices spindle that has the torque at lower speeds,

[Jonathan]

Normally servo motors have a constant torque rating up to a particular speed - often 3000rpm. For the stepper motor system that speed will be lower, however you can't really make a decision without comparing the available systems. Work out what torque vs speed curve you require, then just look which type of motors gets it for the least money.

[EddyCurrent]

A Vector drive will give full torque at zero speed, but with an asynchronous motor not a servo or stepper.
Have a read, look at the vector drive section.
http://www05.abb.com/global/scot/sco...14482_RevG.pdf

[Jonathan]

A Vector drive will give full torque at zero speed, but with an asynchronous motor not a servo or stepper.

Using vector control (also known as, FOC - field oriented control) also gets rated torque to zero speed with synchronous motors. Servo motors are generally permanent magnet synchronous motors and they will use FOC and hence can output rated torque down to zero speed, so long as the motor cooling is sufficient.
Stepper motors are less well defined in their ratings - with FOC they will output some value of torque between zero speed and some value, however this torque value isn't generally quoted in the datasheet, so it is unwise to make a general statement except that this value will be lower than the holding torque.

[Boyan Silyavski]

Some servos i have seen go to 6000 rpm or even more, so 3000 is not the limiting speed, when speaking about servos. But the answer to your question is the people use them on mills, belt driven , not cnc for wood. Some use them belt geared also for bestial rotary axis, where at the same time the axis can perform lathe function.