[shedbob]

This is probably the best stepper selection piece I have seen,in case you havent seen it.
What size stepper motor do I-need.
You need to have data on the rotary inertia of your screws and motor,from there datasheets if possible.Be careful not to mix metric and imperial units and that your using dimensions of the correct magnitude -mm/cm/m eg.

[Feist92]

That was more what I was looking for thanks. The funny thing is I worked all of it out long hand as I read it to find that when I got to the end that he didnt include any way to relate the calculated torque to the rated torque of the motor.
I thought Id challenge myself not to use the spreadsheet he provided but It turned out I had to anyway. Oh well at least my numbers matched up lol.

According to those calcs I can use a motor rated for 4.2Nm which surprise surprise is about the same size the tormach uses.
I think I might go to a 6.8Nm motor on the Xaxis tho due to the extra weight and loss when microstepping depending on cost.

Unless I can find some 3 phase steppers in Nz I might have to wait for quite some time before I buy as the exchange rate has absolutely tanked atm

[daniellyall]

going to a 6.8 Nm could do the reverse you need a motor that`s just above whats needed with the lowest inductance

this place has the same motor`s as every where else at a lower prices and will still be cheaper than here
NEMA 34 Archives - Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Printers For Sale Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Printers For Sale

[mactec54]

I just recieved a chunk of 32mm steel plate that will be used as the table. I didnt really think about this but it weighs aroud 23kg by its self.
Does anyone have any suggestions for which size steppers to go for and where to get them? Im leaning towards nema 34 size but thats just a guess based on the fact that there will be alot of weight on the x and y axis to throw around.

With regards to the spindle motor I think Ill be going with one of the Adlee 2,2kw motors shown here
Adlee AM2200-H BLDC Motor & Drive
Or one of these servo motors.
130ST cnc servo kit ac servo motor electric motor 220v 10N.M 2.6KW servo motor cnc 130ST M10025 B025D-in AC Motor from Industry & Business on Aliexpress.com | Alibaba Group

The servo motor ends up around $400 cheaper but im not sure how suitable it would be

The servo motor is most likely very good, the servo drive from this manufacture is junk

Building a machine like you have, you won't be happy with steppers, they are cheaper than servos, but don't compare to ac servos, 400w @ 2.1 would do your X & Y axes, may even be ok @ 1:1, for your Z axes 750w

Something for you to look at DMM Tec AC servos with 17 Bit Encoders (65,534 PPR ) are very good, price is good as well
DMM | AC SERVO DRIVE | AC SERVO MOTOR | ROTARY ENCODER

[RCaffin]

Hi Feist

Unless I can find some 3 phase steppers in Nz I might have to wait for quite some time before I buy as the exchange rate has absolutely tanked atm

Try Homann Designs here in Oz. Peter Homann is a good guy and FULLY supports what he sells.

I think I might go to a 6.8Nm motor on the Xaxis

More grunt, but often les speed.

I use DC servos with 512 line encoders and driven with Gecko 320X. The latter from Homann. They work very nicely.

Personally, I suspect people worry far too much about motor power and not enough about backlash and bearings. If your motor can't go quite as fast is you dreamt of - no worries, just tone it down a bit. If your bearings and ball screws have backlash and non-linearities, you are stuffed.

Cheers
Roger

[Feist92]

The reason I was looking as steppers over servos is that the travels are very small compared to a large machine. Even at 1200rpm which is well within required torque for a rapid, and 5mm pitch ball screws means that it will take around 3 seconds to go from one end of the table to the other. If it was a larger machine it would be a different story but this sounds reasonable for what it is. If you dont think this is fast enough please let me know what kind of numbers I should aim for. The other reason is that it will be much simpler to be able to direct drive the steppers vs belt reduction for servos. I did make provisions in the mill that I can do a reduction if I have to but its something Id like to avoid if I can

[mactec54]

Feist92

You will be spending some money on quality drives to get your steppers up to 1200rpm, most peak at around 700rpm, they can go as high as a servo, but you will be paying, the same as you would for a servo system, you won't have a true closed loop system, with your stepper system, which you really want for any serious machining

If you are worried about you small travels, lots of machining centers don't have anymore travel that what your machine has, they all use servos

[handlewanker]

Hi all........sick as a dog that I am.....some nasty bug got into my system and I'm pretty crook but after 3 weeks feeling a bit better now.

I've come to the conclusion that to get the machine to work like a big one but in a smaller package is going to be a monumental compromise all round.......Nature just can't be scaled to suit the needs and you have to still have the necessary spindle motor HP and steppers or servos of significant size just to perform reasonably well.

Well, to that end I looked at a hydraulic motor as a possible solution to the/my problem of spindle power.

Just as an exercise I looked at some hydro motors with the speed range from 3,000 to 5,000 and 2 to 3 hundred bar oil pressure.

First, they are quite small both in diam and length but pack huge torque output........price for one at 5,000 rpm was $220.

A pump will cost $220 as well......add to that a 1.5HP 3 phase motor for around $175, a flow control valve for $100, a couple of hydro hoses and you have the package.

The motor is always at full pump pressure for high to low speed , as the speed is controlled at the exhaust, so even turning slowly has tremendous torque.

The motor itself is approx. 65mm diam and a body 110mm long.......pump approx. the same.

This makes it very suitable to mount side by side with a spindle and belt drive it at 2:1 to give a top speed of 10,000 rpm with bags of torque......the pump and drive motor being off the machine and out of site.

However, as I don't need to do heavy milling and the motor has so much torque available, it could also be driving the spindle at 3:1 to give 15,000 rpm.

It's a line of thought I'm pursuing at the moment.
Ian.

[RCaffin]

some hydro motors with the speed range from 3,000 to 5,000 and 2 to 3 hundred bar oil pressure.

That's fine for the X axis, but you will need some very robust hoses for the Y axis - and the drag and resistance there will be bad.

I built a hydraulically-powered R-theta robot once with Moog servo valves, and saw it walk across the room when the servo system went into oscillation ... lotsa grunt there! And that was with a lot of concrete slabs 'holding it down'.

If you want to go into hydraulics, consider a straight ram (plus linear bearings) and a precision optical grating for feedback. But please, put lots of safety limit switches around it! And keep your arms out of the way.

Cheers

[handlewanker]

Wooooaa.....I think we're talking on two different applications.......The one I'm considering is purely as a spindle drive motor, which being quite small would suit the need for a compact drive motor in place of a huge 3 phase model I previously mentioned.

The pump and it's drive motor can be placed in a cabinet under the mill.....out of sight etc......and only have two relatively small hydraulic pipes going over the back of the X axis to the motor.....there being practically no resistance to movement in any direction.

It's only a thought, but as I worked on hydraulics many years ago it occurred to me how compact the end drive can be for immense power output.

What you would have would be a potential to mill steel with fairly large facing cutters, which with the electric drives available would be impossible.

There is no way that I would contemplate driving any linear slide by hydraulics as it's too complicated and almost impossible to accurately control to micro MM of movement in any direction and live to tell the tale.

As I said long ago, my motto is KISS.

If you consider the simplicity of a car's power steering from pump to steering actuator, that is how simple I'd like to keep it..........and in that application you have perfect finger tip control of a rack and pinion steering system with only a few hundred PSI of oil pressure..........in a spindle drive the pump pressure can be maintained very accurately to give constant motor speed accuracy against fluctuating cutter loading.

I think that Feisty could benefit from such an application for a spindle drive as he intends to mill steel in a big way and he could benefit from having an R8 or ISO 30 spindle with bags of grunt.
Ian.

[RCaffin]

Hi Ian

If you are going to use a hydraulic motor to drive the ball screw, you might need to up the ball screw diameter to take the forces!

driving any linear slide by hydraulics as it's too complicated and almost impossible to accurately control to micro MM of movement in any direction and live to tell the tale.

Oh, it's very possible, and you can get very good control, but you need to use something like MOOG servo valves, not simple on/off ones. That's what we were using, and the positioning was very good (when it wasn't oscillating!) However (there is always a 'however'), the price tag for a single valve ranges from $1k to >$3k, and that's on eBay. Um.

the simplicity of a car's power steering from pump to steering actuator,

Hum - from a modern power-steering system. Hum ...

he could benefit from having an R8 or ISO 30 spindle with bags of grunt.

I have R8 on my manual mill. It's solid, but the range of collets is very limited. I have ISO30 on the CNC. Also solid.

Cheers
Roger

[Stigoe]

Hi Ian

If you are going to use a hydraulic motor to drive the ball screw, you might need to up the ball screw diameter to take the forces!

He's not. He was talking about using a hydraulic motor as a spindle motor.

[handlewanker]

Hi Rog, it has to be kept simple as that is why it's being built to a small size as opposed to building a biggy to cover all prospective milling ops for future thoughts.

Building smaller, and a 300mm X 300mm work envelope is actually big if you consider the frame size of the machine that caters for that size work envelope.......that means you also need to take into consideration that going down in frame size for the machine also means you need to down size the drives, be they for the ball screws or the spindle as the frame size doesn't have the room to support bigger drive trains.

It's quite apparent that going down in frame size is not a satisfactory achievement if the metal removal rate also has to be down sized.

The ideal is to have the work envelope as small and compact as you need for the jobs anticipated, and a machine frame that is capable of being rigid enough to support a larger than scale metal removal rate.

That is the problem, as you can't get motors that put out the HP without also having weight, mass and physical size for the HP reqd.

That is also one reason why I'm exploring the world of Hydraulic motors....PRIMARILY....... for the spindle drive, mainly due to their small size and huge torque capacity as well as their speed range.........cost is also a factor in this equation and is at the moment very acceptable.

I wouldn't contemplate using any hydraulic motor for ball screw driving, as in this machine size steppers or servos are well catered for, although they could be employed if necessary but with encoders mandatory.

If an R8 spindle was considered, it would be with TTS in mind......no other reason........for any other solid shank tooling, ISO 30 is probably the cat's whiskers.

BTW, if a hydraulic motor was being employed to drive the spindle, it's also absolutely feasible to have a hydraulic PDB with a very small and compact cylinder.
Ian.

[daniellyall]

Ian slow down 1 step at a time if you wont to do meaty cut full the machine with epoxy granite the materials should be easy to come by over your way

[Feist92]

I do rather like the idea of using a hydraulic motor to transmit power to the spindle. I hadnt even considered the possibility as I thought they were very restricted in terms of rpm but Im glad to be wrong. If you end up testing the idea Id be very interested in the results to see if its viable

Just found this
Hydraulic Axial Drilling-Milling Head DA66-ER25
Its defiantly possible but probably not cost effective

[handlewanker]

Hi Feisty, it's all a matter of assuming from past experience what is possible for a problem that is all now.

We had a small power pack with a small hydro motor on a couple of hoses driving a portable drill for something or other and it occurred to me that it might be a solution.

I looked on EBAY and found a MARZOCCHI hydraulic motor.....$220 and $30 delivery, seller Hydraulicdistributors, with the rpm at 5,000 and an oil pressure of max 260 bar.....that's almost 4,000 PSI which translates to bags of torque.

The motor is approx. 65mm diam and 110mm long (body).

There is also a pump by the same maker going for $220 too, which would be capable of supplying this motor.

I made inquiries as to the ability to drive it with a 1-1/2 hp 3 phase motor, but they only quoted me the shipping cost to Melbourne from NSW, so some inquiries as to the size of the pump drive motor would be needed.

You'd need a flow control valve to regulate the speed of the motor and a small oil tank to mount the pump and drive motor on to make a power pack etc.

It's something I'm considering seriously as an electrical solution for this small machine frame design is becoming out of proportion to the end result.

I think the total price would come to approx. $700 or thereabouts, but it's liquid dynamite package for the problem in a nut shell.

It's quite possible to drive the spindle with that motor at 2:1 and get 10,000 rpm easily.
Ian.

[handlewanker]

Hi, just looked at the link you posted last..........now that is definitely interesting in the compactness.....6,000 rpm speed range too......BUT......being mounted on top of the spindle it does not have a PDB capability which for me is imperative above all else..........one reason why I looked at the separate hydraulic motor with a belt drive to a spindle with PDB.

The price for a set-up like that, which I costed for a complete package, would be under $700, whereas the linked one from USA would probably be over a grand, and that would give you just a single ER type collet chuck spindle and an attached hydraulic motor without any means to power it.
Ian.

[handlewanker]

Hi Feisty, just been doing some posting on the Tormach thread where Simpson36 has built a dedicated 4th axis to do a CNC lathe operation by fitting it to the Tormach;s mill table and using a tool fixed to a bracket on the head.......he's posted a series on UTUBE too of the build and of it running.

As I am doing a steel fixed gantry build like you, it occurred to me that a gantry model would lend itself very well to a CNC lathe function without too much drama.

I propose to have the turning tools on either a 6 station turret on the Z axis face where the spindle and housing would normally fit, or have a gang set up also on the Z axis face with the X axis doing the tool selection for each tool..........probably a bit of redesign to make the Z axis slide heavier.

Alternatively, a QCT block mounted on the Z axis face would allow multi lathe tools in QCT holders to be used, but with a manual change over for each tool.

I think this might interest you as the machine you're building is a heavy construction, and so ideally suited to turning as well as milling.
Ian.

[Feist92]

Hi Ian
Im not really wanting to add any unnecessary complexity before its working. It might be something I look at in the future but id be more likely to build a dedicated machine for turning.

I have a minor update as Ive just received three sets of 750w ac servo motors from Adtech. Ive already had these wired up and tested in jog mode and the seem to perform very well so far.

[handlewanker]

Hi, yeah the turning part does get complicated too if you deviate from the standard pattern of a stand alone lathe etc...

At the moment I'm waiting to get a mill I ordered from China.......two years ago.......long story, but it's happening at last.

The build I'm on has gone on the back burner for a while as I need to concentrate now on Fusion 360 for the Cad/Cam and also getting to know you with G code etc......I'll also need to invest in Mach3 before the mill arrives so lots of learning curve to work on.
Ian.