Where to get cheep servos in Oz

[deancnc]

I grabbed some cheep a cheerful steppers and controller from Oceancontrols, but under load the max speed is just on 400mm/s. With the next step up in motor is not a nema23 frame, the next step is to go servo.

Ocean has some servos but the seem a bit expensive for what you get

I’m looking at Geckodrive G320sx drives but finding a supplier for good dc servos is not going well … anyone go a line on where one goes ?

I need to get 2000rpm 2 - 3nm …

[Stewey]

Hi, where in Oz are you, and how much do or don't you wish to spend- i.e. what's your budget?

[phomann]

Hi,

Have a look at http://www.kelinginc.net/ServoMotors.html

Cheers,

Peter.

[Stewey]

I just had a thought about what he typed- 2 to 3 newton metres torque- ?

about 300 oz.inch- feasible.

And his max speed is already 400 mm/sec- I'd love ours to fly like that.

Here, there's a limit of 150 mm/sec X & Y speed on this dinasaur of a router, & 25 mm/sec in Z, for routing speeds- and you'll only achieve that in straight lines, not anthing curvey or 3D. It's still fine though, but I'd be happy with twice the speed, which still isn't 400mm/s.


There's also a limit to the actual speed you can do in the material- depending on chip load, router rpm, material thickness & cutter size.

I wonder if those figures aren'ty a misprint?

There's a fellow on ebay, near the Gold Coast, also selling retrofits & parts- Countmonk. Looks like a very good product & prices. I think I'll dive into that when I can afford to retrofit our machine- it needs to pay for itself a bit more, first, though!

[deancnc]

Thanks folks - grabbed a handful of different motors and controllers from ketling - shipping was a bit over the top.

Based in Melbourne...

I have built a gantry mill - the table size is 1.5m 1.1m with z 600mm. I've hacked a old wood router (2400w) into 8:1 set of belts... not pretty but seems to get the basics underway.

Most of the "stuff" I'm working is AL, so with a spindle speed of 500-15000rpm - so for fast cutting is normally ~400mm with fine cuts. For deep controlled cuts I drop down to 25mm.

But as you can guess big tables take time to get from one end and back…I’m thinking of a auto tool changer (ATC) as a rack down one end, but if it takes 2 seconds to get to the end then say 5-10 to change the tool then another 2 to get back, you kind of limit the tool changes.

I found with Steppers to get them to rev you need to go nuts on voltage, I'm running 90v - I started out with 32v which seem to have most of the motors stalling at lowish revs.

The other thing that seemed to make a big difference was dropping the ball screws, for racks and pinion.

When I’ve coved the gantry speed, then I’ll address the ugly spindle.

My design is been evolving over the last year, this stated out as a simple project to address a long project that wouldn’t fit in a standard mill. It’s been a challenge to get the machine to make parts for it’s self. But that’s the fun part right.

[Benonymous]

This eBay seller may have you covered.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=280454723888

They ship free to Australia and I have bought three items off them. Very quick freight and good communication.

I bought the 400W kit for my proposed router X-900,Y-600, Z-200 all on ballscrews. The parts arrived very well packed and while they are used, you'd be hard pressed to find any wear or damage.

If you deal with them direct, they will ship individual parts rather than buy a whole kit off auction. I got four SR-20 trucks this way. Just ask them for the items you want.

[RayGardiner]

Hi Benonymous,

Thanks for that link, I see that the 400W controller is single phase 230V input, but the one I was looking at is the 750W appears to require 3 phase 230V input

What sort of router are you using your 400W motors on? Any ideas on what sort of torque?

Regards
Ray

Edit..ok I got the torque.. I can see the motor nameplate in the photo. 1.27 nm

[deancnc]

hey for anyone that falls over this page, and is weighing up Stepper v Servo...GO servo!!!

I’ve just finished play with a new set of servos, i get good holding like a stepper, and it knows if it has been pushed off the mark, and can get back to the mark by it's self if it's less than say 0.1mm, or trip the slow down, or if things go really fubar, hit the eStop...unless your really clever with the setup of you stepper, this normally is not the go

Basically it's the toy v the real thing.

I had to work hard at getting any speed out of a stepper, it as great for slowly shuffling around, and I had to build stepper drives for 90v, you can by them to this spec off the shelf.. but now you in the same cost as a servo drive…and after 500 rpm the power let in the motor was pretty sad. With servos getting more power full the faster the turn…you get the point.

I had sat down with a pen and paper (ok excel sheet and a keyboard) and worked out stepper was cheaper, but not by much…

I could rave on about servo’ s all day … basically if your starting up, save your self the drama and go servo. They are about the same effort to setup, and you wont be putting them in the bin next to the bit of work they screwed up..

[festy]

Any hints on reasonably cheap DC servo drives?
I've been gathering parts for a small 3 axis table for a while, and although I was originally planning on using steppers, I came across a couple of 30v DC servo motors at the right price.
This table will be purely a toy for learning, so the budget is tight/non-existent.
So far the best (ie cheapest) option I can find is to use a pluto-p fpga card with some L298 driver boards - my plan is to use EMC2 so the hardware should all play well together from what I have read.
My concern is that the L298s are only good for about 4 amps each and have no current limiting, and I'm pretty sure the stall current of my motors (Globe Motors 357A354s) would exceed that.
I've also thought about selling the servos and buying some steppers, but the fact that it's a big step backwards makes me want to stick with the servos.
There seems to be heaps of cheapish stepper drives available, but not much for servos?

Oh, and hi all, I think this is my first post
I've been intermittently lurking around these forums for a couple of years now reading up on this stuff, this is already a very slow build...

[Stewey]

I picked up a few from ebay in USA, but postage is often about $50.
There are some ebay sellers in Hong Kong who offer freepost to Australia.
You need to check the spec's of the servos first though- most are tiny- but some geared ones have a bit of power.

Of course you WILL need encoders with them. The ones I've picked up from ebay USA cost me barely any more than the cost of an encoder alone, here in Oz, especially if you combine postage & get two similar ones from the same supplier. NO warranty though...

It depends on how you define 'cheap'.

There's a fellow at the Gold Coast selling systems on ebay too- they look very good- but his servos are closer to 60Vdc, not 24-30 Vdc.

I don't think there is any short cut to getting a good powerful 24-30 Vdc servo for a no-frills price, though...

[festy]

Thanks for the input.
I never mentioned good or powerful as being requirements
The table is only about 600mm on the X axis, and 1200mm Y.

I check ebay every now and then, but even second hand Gecko 320s would be too pricey - my wife tolerates all my little projects, but spending hundreds of dollars on drives at this stage wouldn't go down well

The encoders are sorted, the x and y motors have HP HEDL-5500s and the z has a HEDS-5500 (encoder only, no line driver).
The motors are relatively small, rough specs from what I can tell are:
3000rpm no load
35oz.in load/300 oz.in stall
current 250mA no load, 3.5a max, 23a stall.
There's a pic of one the same here.

If I ever get this thing built it'll be used with a small plasma, so I don't need heaps of speed or torque.
I think I can build the controller/drives/power supply for about $100 all up if I go the pluto-p/L298 route.
I'm just a little cautious about the pluto-p as it's not that widely used, and FPGA programming isn't something I've played with before.
If it doesn't work out, I can always bypass the FPGA and drive some L298 boards directly from the parallel port, and let EMC2 do the PID.
That would limit me to 2 axis, but maybe adding a second parallel port would let me drive a third, I haven't looked into that yet.

I've spent more time hunting for an alternative than it would have taken me to build the damn thing, maybe I haven't found a better option because there isn't one

[CrazyIvan]

Originally Posted by festy Thanks for the input. I never mentioned good or powerful as being requirements

Make your own! http://ivan.blogs.chimerical.com.au/...le-minute.aspx