Selecting motors for the MechMate

[skippy]

I just got a quote on the PK296A2-SG7.2 here in Australia at about AUD $ 620 each which is about USD $510 and I need five for a four Axis

WE can not get PK296A2A-SG7.2 in Asia and it's equivalent is PK296A2-SG7.2

below is the link for the USA

http://catalog.orientalmotor.com/ite...=prod&filter=0

Which are USD $257 each. I might need someone int the USA to send me them instead

Regards

Paul

[anton]

You can order straight of the Oriental Motor website, and have it couriered with UPS to Aus.

Anton

[skippy]

You can't order from the USA Oriental Motor website outside of the USA. Someone PM me suggesting to try a different region that maybe able to send to Australia that I'm looking in to.

Regards

Paul

[domino11]

Paul,
Check out the marketplace area. I posted a link for a distributor in Canada, He might be able to ship to you. Very helpful. I got my motors from him. He is an authorized distributor.

[Ticapix]

Hi,

This is my first post and my english is not very good.
I have read with a great interest major part of posts concerning : the choice motors.

I have understand that a big motor is not a good choice.
My question is:

With the new drivers who can make µsteps, is it possible to use bigger ( i.e. nema 34 - 7 amp - 1200 oz ), direct drive motor, without disadvantages ?

[Gerald D]

Drivers making µsteps are not new. Most of the things written in this thread: Why a stepper motor should not be too big were written by people who only produce drivers that make µsteps.

[Ticapix]

Ok, thank you Gerald.

I thought , that drivers technology, had changed the past two years.

Regards

Thierry

[Polder48]

Gerald and all interested.

In my efforts to complete our preparation for the MM build, I had an interesting discussion with a familiar supplier of drivers. He is the distributor of STÖGRA drivers. These drivers start with a Nema 58 size and they calling them "small" drivers.

After informing me that he could supply me a driver similair to the PK296AE-7.2, he advised me against his driver, because it wasn't "explosion safe", which was definitly the case with the OM driver!

This gave me sort off a blow on the head, because I never considered explosion safety an item, while never read anything about it on this and other fora. Contact with OM confirmed me that the PK series are explosion safe.

Is this of any interest for you? I stop searching for an alternetive driver and definitly go for the OM.

cheese from polder

[Gerald D]

Polder, you have me confused!

1. I think you used the word "driver" when you really wanted to say "motor"? The whole discussion is about motors and Stögra makes motors. (The drive(r) is the electronic circuit that gives power pulses to the motor).

2. This is the very first time that I see "explosion proof" mentioned in relation to CNC routing in the typical woodwork workshop.

In electrical terms, "explosion proof" means that the device is completely enclosed so that a spark inside cannot cause an explosion of the gases around the device. If you think of the coal mines with methane gas, or the fuel pumps at the gas station, there you need explosion proof motors and other electrics (such as lights and switches). However, in our workshops we normally use routers, saws, grinders, drills which are definitely NOT explosion proof. I see no need for our MechMates to be explosion proof if the other equipment is not.

[Besser]

Skippy, dont waste your money!
Look here: http://www.oceancontrols.com.au/ocean_catalogue.pdf page 56. You get the whole kit (four sets) for $1600 AUD

They are 630oz ,motors, power supplies and drivers (all matched)
While I think it's still expensive, it's the best I've found so far for us OZI's

Who can beat that?

[KenC]

The Chinese...

[Polder48]

Gerald, excuse for the confusion.

You're right ofcourse, I meant motors, not drivers, my English thinking is not straight yet. Glad you consider explosion proof not to be an item in a typical woodwork workshop. In my relation with the Stögra salesman there where a lot of chemicals (nasty stuff) involved, that's why he probabely made a point of it.

Never the less if the OM is a good thing on this point I'am not going to argue against it. Last weekend a ship in our harbour burnt down, due to an electrical circuit breaker that didn't do what it supposed tobe doiïng, breaking the electrical circuit. I hate fire.

cheese polder

[Gerald D]

Hey, that ship burnt on 30 July! (unless you have these electrical ship fires every week?)

I am sure that you are talking of the Prins Willem fire

[BartDeckers]

Gerald,

You mention a price of about 250 USD for the PK296A2A-SG7.2 stepper motor.

I got a price quotation of 391 USD in Belgium for the PK296AE-SG7.2.
This price is tax included (+25%). Price without tax is 314 USD.

Is your price of 250 USD tax included?

Regards,

Bart

[Polder48]

Gerald,

The Prins Willem burned down on august 8! A remarkeble day since I was in Den Helder that day returning from a sailing trip with my wife to the Shetland Isles.

The yacht I talked about was also a historical wooden ship, an one of build from 1923, based on a "gauntlet". A big loss because it was a very fast sailing yacht, 18-22 knots with 7 bgt winds, and steady as a rock. Loved it like a MM.

happy sailing polder

[Polder48]

Bart,

Wait 2 more days. I will have a confirmation on a offer for the PK296AE-SG7.2, which is the European equifalent of the PK296A2A-SG7.2. Its less then 250 euro if everything works out right. Will keep you informed if you wish so.

cheese polder

[BartDeckers]

Polder,

That sounds like a very good price. Please keep me informed.

Thanks,

Bart

[Greeny]

I am currently sourcing items and came across this Stepper motor for sale in the UK.

http://www.arceurotrade.co.uk/Catalo...Stepper-Motors
Item Number: 160-010-00450

Specs are (for parallel): Current=4.2 A/Phase, Resistance=0.8 Ohm/Phase, Inductance 3.5 mH/Phase, Holding torque=3.5 Nm
Supply Voltage would be, using 20xVoltage= 20*(4.3*0.8)=69V or 32*Sqrt(3.5)=60V, so lets say 60V
Corner speed would be (0.191*60)/(0.0035*4.3)=761 rpm, geared 3:1=254 rpm, which compared to other motors mention here, seems ok.

It is pretty cheap at £35 (~60 $US) and i am thinking it should be ok with a 3:1 Belt drive.
It only has a 10mm shaft with no flats, but apart from that it seems pretty good for the price.

I would be very grateful if anyone would comment on it's suitability and/or check my calcs
Cheers, Greeny.

[Richards]

You used a different set of calculations than I use, but the end results were almost identical. I figured about 60V for the power supply and about 250 RPM when using a spur gear that had 1.25" pitch diameter and the speed set to 5" per second.

Most of the stepper motors that I've tested work very well up to about 1,000 RPM, so, assuming that your motor is typical, you would still be in the high torque range of the motor.

[Greeny]

Thanks Mike,

I used formulas that i'd gleaned from this and other threads, but really know very little about it!
I'm sure yours are more up to date.
I appreciate you taking the time to run the calcs, it's a big help.

Cheers
Greeny

[octobpra]

Hello Anybody, can you explained to me about motion king spec that i dont understand 580 N cm Min - 18 N cm Max ? is spec require min for MechMate ? that i heard min 4.51 N m ? i still dont understand that convertion unit which one i use for checking min tourqe min or max ? hope anybody reply me soon thanks.....

[jhiggins7]

Octobpra,

Your question is not clear. However, if you want to convert from Newton Centimeters to Newton Meters, you simply divide by 100. So, 580 N cm would equal 5.80 N m.

For any conversion you need, simply do a Google Search and you will find links to conversion calculators. For instance, Google: "convert Newton Cm to Newton Meters"

[Richards]

580 N-cm = 5.8 N-m = 821 oz*in

"Holding torque" is the value that I normally use when checking a motor's torque. Holding torque is the amount of torque that the motor produces when the motor is NOT turning and the stepper driver is giving full current to the motor. Holding torque is usually much higher than running torque. Running torque is the amount of torque that the motor produces at a specific speed.

When you look at a stepper motor's torque chart, you'll normally see a graph that shows the torque produced at specific speeds. As the speed goes higher, the torque goes lower. At a certain speed, the corner speed, torque drops dramatically. The larger the motor, the lower the corner speed. Most mid-sized 34-frame size stepper motors (at least the ones that I've tested) have a corner speed greater than 1,000 RPM. Even with a 7.2:1 transmission, and a 1.25-inch pitch diameter pinion gear, 1,000 RPM will move an axis at about 540 inches per minute.

With a 3:1 or a 3.6:1 belt-drive, I would like to have a motor that produces between 450 oz*in holding torque and 600 oz*in holding torque. (450 oz*in = 3.18 N-m = 318 N-cm, 600 oz*in = 4.24 N-m = 424 N-cm). That means that an Oriental Motor PK296-F4.5A, if connected bipolar parallel would work, or a PK299-F4.5A, wired half-coil, would work. Any other motor with similar torque curves would also work (PK299-03AA wired half-coil, PK299-02AA wired half-coil, PK296-03AA wired bipolar series).

Also, motors that have an Inductance rating between 1.5mH and 6mH are best suited for use with Gecko stepper drivers.

[toad]

Don'r mean to be buttin in, but I am presently using nema 23, which are too small. If I go with the geared motors will my existing 24V power supply and breakout board work, or will I needd to replace it all? I am presently coming directly off of the breakout board with 4- 280 OZ NEMA 23 motors.

[Richards]

Toad,

There are normally four components in the stepper chain:

1. A power supply

2. A break out board (i.e. PMDX-122)

3. A stepper driver (i.e. Gecko G203v)

4. A stepper motor (i.e. Oriental Motor PK296A2A-SG7.2)

The inductance of the stepper motor determines the voltage of the power supply, i.e. 32 X SQRT( Inductance ) = MAXIMUM voltage. When wired half-coil, the PK296A2A-SGxx motor is rated at 1.5mH, so it can be used with a power supply up to about 39VDC. When wired bipolar series, that motor is rated at 6mH inductance, so it can be used with a power supply up to about 78VDC.

The stepper driver has a minimum voltage and a maximum voltage. You must stay within the voltage limits of the power supply, even when the formula computes a voltage out of the range of the stepper driver.

[Gerald D]

Toad, you also need to consider the currents (Amps) and load capacity (VoltAmps) of your drives and power supply. There is a strong possibility that your existing drives and power supply are also too "lightweight".

[KenC]

Toad, what is your PSU type & rating?
From what I learn here, in theory, if its a 300VA unregulated 24Vdc, then you will need to find a motor with 0.5625mH (from V=32*Sqrt(mH)). I wouldn't guarantee much but at least you will be near.
If its a switching mode power supply, & its regulated, then you need a lot more meaty one.

[toad]

sounds like I need to start all over in the drive department. just hoping what I had would work, but apparently not. Thanks for the info.
Does Gecko sell a kit with 4 motors and all necessary components, or will I need to find each one individually.
Where is the most inexpensive place to find the rack and pinion?

Toad

[domino11]

Toad,
Best place for rack is Standard Steel. Gecko only sells drives. You can order the motors directly from orientalmotor.com.

[iclazion]

I am having a really hard time selecting a motor. REALLY
I want the most precise cutting mechmate possible to cut High Density Polyurethane, now the question I have is: What is needed for precise cutting? Does it have anything to do with the motor, and if it is geared or not? I have been looking at http://www.orientalmotor.com/product....html#shgeared PK/PV Series 2-Phase stepping motor with SH Gear. Looking at the motors on my own is pointless, I have been looking at the criteria. But for me to know which motor is going to provide me with the most PRECISE cutting / working is really pointless. I have been going to-and-thro the forum, but really the only result is getting me more confused. Price also plays a role, but I want the pieces I am going to cut to be as clean as possible. Please I am a fish out of water here to be honest