[daniellyall]

there's a place in nelson that sales bldc motor`s the prices looks ok Engineering and Machine Tool Supplies New Zealand

[handlewanker]

Hi Feisty, I don't think the stepper motors are the problem as you can get the most powerful off the shelf to fit if you make the mounting bracket to accept it.

What we're trying to do is take a Morris Minor and fit it with a 5 litre Vee 8 to do some track work.

While the car will work on the track, getting the engine into the frame is another matter........I saw a VW with a 7 litre vee 8.........it's been done with a Mini Minor, and shock horror some speed maniac fitted a V8 into a Harley frame for a hill climb.

So if the machine build was built around the motor package it would look a lot different to the current design...........but that means the machine is going to be as big as a Bridgeport eventually.

Do we really want to mill a large piece of steel with a large cutter......even a Bridgeport with it's relatively light quill drive head has limitations in the cutter size and power available, but I've milled with a Bridge, I used to own one, and used discretion in all cases, preferring the accuracy of the machine as opposed to brute force metal removal capability.

My opinion would be that a 1 HP motor 3,000 rpm, in whatever format is going to be the max for this build.......under CNC conditions the job will still get done successfully.

The work envelope of 300 X 300 X 200 does not mean that a slab of steel that size is expected to be handled......for years my Bridgeport only had work that fitted in the 8" wide vice jaws.
Ian.

[RCaffin]

Hi Feist

I think you are ignoring the Brushed DC motors, to your loss. I am running one on my slightly larger mill, and I am quite sure it can handle anything I throw at it 6 mm and smaller, and most things up to 10 mm, in Al alloy or steel. It's a whole different ball game from VFDs and 3-phase motors.

Have a look at UpgradeBrowser - Baldor, at
AP7402 .25HP, 3450RPM, 90 V DC, TENV, US$484
AP7422 .25HP, 3450RPM, 180 VDC, TENV, US$484 shipping wt for either 12 lb
I am using
VP3428D .37/.50KW, 3000RPM, DC, D71D, TEFC, ~US$870, actual wt 14 kg
The air spring takes ALL the weight, so it goes up easier than down.

But I have seen all of these at lower prices from dealers, and units on ebay go for very good prices.

Cheers
Roger

[Feist92]

Haha ive seen plenty of people trying to put engines where they dont fit, its a rather appropriate analogy. I realized pretty early on that its rather foolish to run big cutters on a small cnc so will limit myself to 10mm carbide cutters most of the time. But in saying that I want to be able to push those cutters really really hard. Im trying to work out if i should make the stretch to servo motors but I have a feeling that the higher torque of steppers would be best to overcome the.

Thanks for the link Daniel I hadnt heard of them before. The motors they sell seem to be the same as the ones I got a quote from the suppliers. Im going to have a good think about these to see if i can tempt myself enough to get one

[Feist92]

Hi Rodger the problem I have with them is that they seem to be very hard to find over here and when they do pop up they cost rather a lot. I keep meaning to call a few treadmill repair shops to see if they can help tho

[handlewanker]

Hi, I think we need to have a definite power factor requirement before the motor is sourced.

For example, if a 13mm 18 volt 2 speed cordless drill can push a 12.7mm HSS drill bit through a piece of steel plate at 600 rpm.....that's a benchmark.........go to carbide and the figure is double at 1200 rpm......how many NM's are being provided to do the drilling and maintaining a constant speed is anyone's guess as no indicator is ever provided.

I don't think an end mill consumes the same power as a drill bit being pushed directly into a block of steel, so I doubt anyone would want to have the mill as designed to work like a drill press.......starting small and progressively going bigger will allow the motor size to be more reasonable.

I think Feisty would like to design a motor/gearbox package around the outrunner motor he previously showed.

The motor in my 2 speed 13.7mm 18 volt Ryobi drill is quite small in diam and geared down tremendously from probably 30K down to 2 K.............although we're talking about a brushed DC motor running on NiCad batteries, so the comparison is on another plane......DC brushed and DC brushless.......if the NM at the shaft are the same then a possible solution in a small package could power the mill.

The motor capacity would need to start at 50,000 rpm to allow gearing down to a top speed of 10,000 rpm, but the torque would be enormous.

So if we know how much torque in NM is required to drive a 10mm carbide end mill in steel, 2mm deep and full width......speed and feed accordingly...... then that would be a starter.

What is a reasonable expectation of performance for this size mill is entirely up to the builder, but I'd be happy driving a 10mm carbide end mill at 2mm DOC with a reasonable feed rate full width in steel for my work needs.

I seem to remember someone advocating a 10mm carbide cutter 7mm DOC and a 1.2mm step over per pass as being an ideal run rate......you will need some HP, that's for sure, and therein lies the problem.....great expectations.

If you're going to clear some steel real estate with this small mill, then you won't be displeased with a 2mm DOC and a full width cutter engagement......10mm carbide end mill.....whatever........feed rate proportional to the motor HP.
Ian.

[daniellyall]

you need plenty of HP when driving endmills in steel its cnc so it will be moving in more than one direction sometimes 3 so a little BLDC motor will last 5 mins even if its geared down if you wont to do steel you need to start at .5 hp that will work but the depth of cut and cutting speed will be slow as a wet week aluminum wont be so bad but you will have to go slow you really need more than 1 hp,

look up this CNC Milling Spindle 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

[Feist92]

I dont necessarily want to use that motor as it requires a lot of electronics work on the control side which im not familiar with but it seems like an option that no one has really tried to make work. Maybe for good reason.

Im not sure the comparison to a drill is that relevant due to the difference in rps between a drill and an endmill but I could be wrong.

What im aiming for is to run a 10mm cutter at full doc but around 0.5mm step over. Ive been told that trochoidal tool paths reduce the required hp and maximise tool life.

Does anyone have Gwizard they could plug these numbers into to get an estimate in spindle hp required

[LeeWay]

I had very little problem with my old treadmill motor on my 80/20 mill. It claimed to be 2 HP running under 220 VAC. I could not find the proper brushes for it, so I bought the 1HP Iron Horse motor. It is not setup optimally, but is three times the weight of the old motor. It preforms about that much better too. Even at half the HP. Sooo, which motor is closer to the real value as far as HP is concerned? That is what you will always run into with treadmill stuff. Buy name brand stuff and overlook the rest. Better value for the dollar, euro, peso, etc. I understand that Iron Horse is made over yonder, but it is sold by Automation Direct. I have come to rely on them for quality products and service. I do not know if they ship down under though.

[RCaffin]

Ian has a point you know:

if a 13mm 18 volt 2 speed cordless drill can push a 12.7mm HSS drill bit through a piece of steel plate at 600 rpm.....that's a benchmark.........go to carbide and the figure is double at 1200 rpm.

The other thing is, I find my actual machining time is usually just a fraction of my designing and programming time. Are we blowing the spindle power requirements just a shade too high here?

I did take my spindle motor up to about 400 W at one stage. I was poking a 6mm drill bit through titanium 6Al4V alloy at far too high a speed - program error, but the Baldor DC brushed motor kept its revs. I dropped the feed to a reasonable value and the power dropped to about 100 W. Yes, I KNOW the power, because the motor voltage is given by the RPM, and the spindle current meter does its thing.

a 10mm carbide cutter 7mm DOC and a 1.2mm step over per pass

In your dreams!

Cheers
Roger

[handlewanker]

Hi Feist......the comparison to a drill was to indicate the torque reqd to push the bit through the job........it still requires rpm and feed rate to get there........too much of either and you won't get there.........blasting in with carbide to overcome the "softness" of the HSS is just using a bigger sledgehammer........and providing you have the muscle power, a sledgehammer is often the solution of choice for those that need to get there today.

I'm accepting the fact that the smaller the machine the smaller the machining capability, but in only one respect.....the motor capacity, as it has to fit on the machine and the smaller you go the less HP you'll get.

Designing from and around the motor package to get the power required to do the job and you'll end up with a 6040 machine as you can't scale the superstructure down to the smaller work envelope without also scaling down the motor and that means less HP.

I've wondered if an air motor (die grinder) or hydraulic motor would be the answer......you can supply air at a couple of hundred PSI and put the air motor into orbit.....LOL.......but they're designed to work at shop pressure or 100 PSI.....but it's still an unexplored field I think.

Most, if not all, die grinders are relatively slow moving vane type, that means they use the full pressure of the air to do the work and use tons of it too........a true turbine uses the velocity of the air not the volume to produce the output, and you can store lots of energy in even a small 50mm diam turbine wheel when it gets up to speed.

This would probably be safer than over driving an electric motor at 500 volts and 10 amps just to get more steroids into a smaller package.

It would be interesting to see how an air turbine would perform as a spindle driver..........100,000 rpm at 1:5 reduction to get 20,000 rpm at the spindle in a package as small as 50mm diam......and with a governor you could then drive a load at 7,000 rpm for milling without resorting to a further gearbox reduction.

I think the electrical path is simpler, and with NDM magnets a home brew motor could be achieved but with some effort.
Ian.
Ian.

[handlewanker]

Ian has a point you know:


The other thing is, I find my actual machining time is usually just a fraction of my designing and programming time. Are we blowing the spindle power requirements just a shade too high here?

I did take my spindle motor up to about 400 W at one stage. I was poking a 6mm drill bit through titanium 6Al4V alloy at far too high a speed - program error, but the Baldor DC brushed motor kept its revs. I dropped the feed to a reasonable value and the power dropped to about 100 W. Yes, I KNOW the power, because the motor voltage is given by the RPM, and the spindle current meter does its thing.


In your dreams!

Cheers
Roger

Hey Roger......not my dreams.......a poster Khoac3 post #125 a couple of posts back on this thread clearly stated it is what he achieves or does........that is, it's his preference to go with a 10mm diam carbide cutter in steel at 7mm deep and with a small 1.2mm step over at 5,000 rpm, as opposed to my 10mm end mill with a shallow full diam cut of 2mm.......not quite my cup of tea.
Ian.

[daniellyall]

the dream is at 50% depth of cut 50% width of cut and a 1 Hp machine could do more depth of cut but max at 50% is where it needs to be using the new types of tool path`s even in steel.

I have done a 25mm DOC with 75% step over using a 3Hp spindle with those fancy tool path`s it was with a 2 flute 1/2 inch blunt end mill it was cutting hardwood (from over your way Roger)and it was fine only using 1.5 amp at 1250mm/min.

that's with those fancy tool paths I would not try that with a normal tool path. trochoidal tool path`s make that much of a differences it`s not funny so if you have a program that use`s trochoidal tool paths you can get away with a smaller motor

[handlewanker]

Hi, first time I saw a trochoidal tool path being cut was on UTUBE where a 25mm wide slot was being cut with a 12mm end mill......looked a pretty neat way to keep the slot clean..

I expect it would also be a way to do a broad cut on a flat face without having to do multiple narrow up and down passes with a small cutter and leave all those narrow track marks......who needs a big diam facing mill.

A question.....if you had to face off a 100mm wide piece of steel bar ......100mm long... whatever, using a 10mm end mill.....would it be advantageous to do a trochoidal type sweep under CNC control, back and forth across the bar instead of a straight up and down one or is this only an advantage when you're cutting a slot.

To do a trochoidal path you need hundreds of screw reversals as opposed to a straight line run where the G code is just get to the end and go in reverse etc, so where is the advantage?
Ian.

[daniellyall]

I would just use 100 mm face mill I got one.

the trochoidal tool path are the **** when it comes to cutting slots or removing large amounts of material you can do bigger cuts as well, it is hard to put into words what it does but it`s just the shape of the cut you have to see it to under stand it, all it is, is the cutter has constant contact with the cut it goes into the cut in a scoop sort of way so it goes from 0 contact to full contact in a radius and when it gets to the end of the cut it comes out the same. the first time I did it, it had a big pucker factor 25mm deep with a 1/2 inch end mill with 50% step over at 21000 rpm 1250 mm/min. the spindle handled it very well pulling 1.5 amp is not a lot, when its just running at 21000 rpm it draws .4 amp, no screaming, no chatter just eating wood like butter and you know what your hard wood is like.

with the spoil board cutter it pulls 2.6 amp at 50% 1 - 2 mm depth its around 100 mm wide with a normal type of cut I am going to try a trochoidal cut on it in spring.

the advantage of it is there is less load on the machine and the cutter you can go both ways with it but you don't it is a bigger file it may take a couple of minutes longer but it saves money in the long run the big cut I did would of snapped a 1/2 end mill or had a **** load of chatter in a normal tool path. it was fine

[Feist92]

As I understand it trochoidal tool paths have no benefit with facing but have a huge impact on pocketing and profiling in the x/y plane

[shedbob]

Hallo Feist92 and all.FSwizard that I linked to in an earlier post does the same as Gwizard as far as I can tell. On line version free in case link doesn't work here it is again.In my play with it quite difficult to get it over .3kw .But power is at the spindle not motor.Look at the mrr-low.
FSWizard - Free Advanced CNC Speed and Feed Calculator


Have to say very interesting thread,great build,now with a good discussion on motor options.Its the classic engineering dilemma of balancing performance pros and cons with budget.We have all been there if not with a mill with lots of other stuff.I brought a new camera a year ago,an upgrade to a better type.I brought a lower end model and regretted it pretty soon after.I should have paid the extra and got a better model with improved performance,now I either live with its deficiencies or sell and upgrade-at considerable loss.

To put in my 10 cents on this.

I cant see you Feist92 as a pro machinist being satisfied with anything less than the maximum available power-metal removal rate is proportional to hp after all.But having said that its all about utilizing the available power.As daniellyall points out that is also heavily dependent on the tool paths the machine uses,as well as the machine and tooling.Or as Roger says essentially how much are you really going to use and how effective will the motor really be?As in most things there is no doubt a bit of specmanship going on with motors and do they mean consumed power or generated power,its difficult to tell from specs.Each type has its pros and cons.Maybe it comes down to your product-does it require lots of metal to be removed?(max power)Or is it a precision trim job?(less power?)Both?

You could just ignore the motor option for the moment I suppose,sort out the spindle then with the machine running lash up some temporary motor options to see what you actually need.

Anyone know the starting price of spindles with integral motors? I assume you need to be a lotto winner.

It will be interesting to see what you decide,good luck Feist92.

[handlewanker]

Hi, thanks for the info...... I wondered about the facing......when I get to that stage I'll have to experiment to see how it works.
Ian.

[handlewanker]

Hi, al lot will depend on the amount of real estate on the Z axis saddle to mount a spindle and a motor.....side by side belt drive would be the way so's you can get a PDB in.....it also gives flexibility to source various motors from scrap places and bargain bins etc.....not all motors come with foot mounting tapped holes.

Shock horror on the integral motor and spindle package........they are pretty big in diam apart from the weight, and being specific in their applications would be in the realms of crown jewels users and owners.

The big problem is that the motor has a spindle and that is press fitted in the rotor.....straight away that is a 3 phase set up and it only gets bigger when you think of 1 HP or more.....you'd be lucky to get to 7,000 rpm with that set-up...........tying to a motor and spindle is like running without a spare wheel, as the replacement cost is a complete rewind or change over motor stator part......I think that would mean a lot of money in the end.

Feist built the Z axis pretty ruggedly and with a fair amount of area, so I think he can still mount the motor and spindle without too much drama........better a 3,000 rpm spindle that mills than one on a wish list......on that score it can only get better.

So, if the spindle magically appeared, no doubt a motor.....whatever...... would very soon follow.

The spindle tooling taper is the question, and on that score you need to be very precise......run out is only as good as you make it, and send out for hardening and grinding does cost a few bob.

I would be inclined to spend the max on the spindle build and the least on the motor for a given spindle/motor package budget..........that means best quality bearings and accurate taper grinding......you can spoil the ship for want of a hapoth of tar.

The design of a PDB is also a factor that has to be considered when the spindle shaft is being designed.......a petal type PDB is to be preferred to the ball bearing ones as they have more retainer grip on the pull studs.

I think a buy in spindle with PDB would cost about $500 +.....depending on the tool shank taper.

One other thing on the design, if the body of the spindle is fairly long and parallel, and 80mm diam, mounted in a split housing bolted to the Z axis slide.....this will enable the spindle body to be lowered for close to the table work where the slide would be all the way down, or raised up to give maximum clearance under the tooling when the slide is all the way up........the body itself would add rigidity to the Z axis slide without undue hang down of the slide.

Now it's tool shank taper decision time........let the drums roll.
Ian.

[daniellyall]

yer facing is facing not to much fancy stuff can be done with that, area removal is where trochoidal comes in.

one of the big problems faced here is that the cost of a good brand motor is really high in NZ we have to import good stuff to save money sounds silly but it how it is something in Au or USA is cheaper than here by quite a bit unless customs decide to check the package a good $500 motor any where but here is around $1000 so the range of motor to get is limited he may be able to use a belt drive set up but it will have to be a very fancy set up a BLDC from where I posted is about the cheapest there is for something that`s about right