Another Aussie - Motors and Drivers Received - Pakenham, VIC Australia

[guerd87]

Hi Everyone,

Im John from VIC and am looking to start building a mechmate soon. Im still relatively new to CNC but I know how to use one. I currently have a basic JGRO design that I made to teach myself CAD and CAM software.

I Have been getting heaps of paid jobs to do on my JGRO, and its a great machine. But theres so many jobs I have had to knock back because of size and materials, the MM will change that! The JGRO is only good for Light timber, and even that is still pretty slow.

Planned size: To fit standard Aus 2400 x 1200 sheet

I will reuse the router off the JGRO first up, because its a good Makita one I brought for the CNC, Spindle one day *drool* The electronics are only Gecko G251's with 269oz Nema23's - way to small for MM, I will be selling these when I am ready to cut with the new machine.

I will be starting the build in around 3-4 weeks, Ive just been reading, reading and reading! Tax return will be here soon which should cover the base and gantry parts. A little Overtime coming up will cover the rest.

Currently only working out of my shed at home, But I hope to change that and get a small lockup to work out of. I have been doing alot of kids storage cubes and play kitchens out of Melamine on my table saw, which is tedious for a small saw and full size sheet. Im hopeing to get the files drawn up for these and then just knock them out when needed.

Will update when Ive got some parts and start building

1st question: I know how to weld (not a Pro but can make consistent clean welds) But I dont have a MIG. Will my Arc welder be ok for most of the parts? I have 2 options:

1. Use good quality Arc welder
2. Use a cheap quality gasless Mig

Cheers
John

[smreish]

John,
The welding on the project has all been keenly designed to not be cosmetic or that critical. A good quality arc welder with 60 or 70 series rod (1/8, 3/32) will do fine.

Good luck.

Sean

[bradm]

Welcome, John.

Note that your G251s are sufficient to drive certain NEMA34s on a Mechmate, if combined with either gear or belt reduction. You can search the forum for various discussions on the G540 for more information.

[guerd87]

bradm, You say certain type of Nema34's? Are these the ones with internal gearing already?

I still have alot of reading to do, But does everyone use the internal gearing steppers + Another reduction, or is it usually a standard stepper with reduction?

[shaper]

Hi John

The oriental motor's with the 7.2 reduction drive (built in) are the standard around here and one of the motors that will fit with your G251 drives, unfortunately in Oz these are very expensive (though others have imported from canada I think at lower cost). The reduction drive is largely down to personal prefference and what motors you can get your hands on (afford), the rest of it you can probably argue the toss on.

Jed

[bradm]

John, the key is to carefully match the impedance and current specs to the G251s. That means a "single stack" NEMA34. The (expensive) Oriental Motors with gearboxes match perfectly (PK296A2A-SG7.2), but there are other cheaper motors out there with similar electrical specifications that you could match with a homemade belt drive to save $$.

As you'll see as you read, there are folks using both the geared steppers and the belt drives; the engineering of the belt drives has matured a lot over the last couple of years.

[guerd87]

Well Ive done ALOT of reading today. I really like the specs of the PK motors but I cant seen to justify spending that much after also spending that again on drivers. I do have a smaller budget then I would like, but I will make it work

Going over some electronics here just for reference. I have notes jotted down on paper and here is a good place to put them for when I need to check back.

Motors: Keiling KL34H280-45-8A
Controllers: Gecko's, Either 202 or 203's

I will sell the 251's as they just arnt right for this CNC I dont think.

I am also interested in the MotionKing 9801 Motors, I am waiting to see how they are priced. Which ever motor I go with I will be making a 3.2:1 reduction unit for the machine, one of the first projects on the new CNC.

Some maths:
Unipolar mH: 2.2
Amps: 4.5, Limit to 4 on Gecko
Voltage: 47V Max

So I need a 30V Transformer to produce (after rectified) 42.4 VDC - Just to be safe

Which needs a whopping 678VA - This seems high, but this is taking into consideration that every motor is running at 100%. I could probably get away with 600VA.

These Keiling motors are rated for 640oz. Does this mean after running in Unipolar I essentially half the output? if so I may need to move up to the next level of 906oz

The other option is to go for the KL34H280-45-4A - Handle 70-80V but would need around 1100VA - I dont know if more voltage is a good thing or not.

The MationKings would handle around 64V @ 1000VA

More reading is required before I purchase.

John

[KenC]

You can get away with 300VA transformer.

[bradm]

John, you have done a lot of reading and more important, comprehending!

Don't forget to factor in your belt reductions in considering torque - they act as speed reducers and torque multipliers!

As a reference point, consider the proven OM PK296A2A-SG7.2 rated at 704 Oz/In at 3amps. To match this, try 704 / 3.2 reduction = 220 Oz/In or better as the target for your motors.

Those 640 Oz/In motors at 320 Oz/In are more than enough.

Which brings us back to the G251s. As long as the motor you choose will output 220 Oz/In or better when driven at around 40 volts and 3.5A, you could still use the G251s. It won't get the max out of the motors, but that will make the motors run cool, and it will be sufficient.

Note that the OM PK motors with gearboxes are actually limited by the torque handling capabilities of the gearboxes, and the same motor without the gearbox has a higher amperage and torque rating close to the MK or Kelings.

I agree with Ken's assessment of 300VA as well.

[guerd87]

Thanks for all the replies guys. I have been up and down about keeping the G251's or to get something a bit beefier. I think I will end up getting a larger controller just to get the full potential out of my motors. I have posted in the MotionKing thread about some motors and controllers if you want to look.

I have also organised for a close friend to take ownership of JGRO router when my MM is done, So he will be getting the 251 setup with the current machine. All he needs to add is a router.

As for the 300VA, is there something I am missing here? Im not sure how I seem to be calculating it wrong?

John

[bradm]

John, you aren't miscalculating the 300VA, we are applying collective real world experience that you will never have a sustained peak draw - and the capacitance handles any momentary spikes.

Intuitively, maximum current draw would occur either during maximum acceleration or when experiencing a large cutting resistance. The former doesn't last long - because you reach peak speed of the motors and/or jogging speed quickly and then the current draw drops back down. The latter is unlikely to impact more than two motors at the same time, especially not in a sustained fashion.

So, If you plan to couple the motor shafts to each other, and run them in opposition until they explode, go for a 700VA supply. But if you're going to drive the MM, 300VA should be sufficient. Or bump to 400VA or so if you're skeptical, but certainly 600VA plus is overkill and just adds expense.

Sounds like the 251s are going to a good home.

[guerd87]

Ahh, Much experience to be learned from on this site

251's along with the whole machine will be going to a good home. I currently cut a fair amount of stuff for him so my natural thought was to offer the machine to him.

[domino11]

Welcome John!

[guerd87]

Motors and drivers arrived today. Paid for them on 28th July - They confirmed shipping on 31st July - Received 4th August

That was quick! From Driver-Motor (Deitech) in HK

I will post some pictures up tonight. Drivers are 2M982 and are built well. Motors are 86HS9801 - Didnt realise how heavy these things are compared to my nema23's

Picking up Laser parts in a few weeks from Rick and sorting out my steel order aswell

John

** Ive just noticed I cant edit my first post - I wanted to update the title to Motors and Drivers Received or similar, but theres no edit option?

[domino11]

You can only edit your posts for a few minutes after you post it then it is admin edit only. Thread titles will get changed as your build progresses, or just ask, Im sure someone will update it for you.

[guerd87]

Ahh ok, thats quite a nifty Idea. At least you know the Admins are keeping an eye on everything

Heres some pictures of what I received today

[Red_boards]

You're on your way, John.
Now to get the wire stripper out ...