[rajhlinux]

Hello,

You think a Shapeoko 5 Pro or PM-25mv will be good to make 0.6mm sitting saw cuts to make PC water cooling blocks?
I want to get the 5 pro because it's easy to assemble and have great tolerances but I think it's not rigid enough.
The PM-25mv will require a lot of work and hassle to convert to CNC and modifying it to accept a high RPM spindle.

Basically need to make microfins such as the photo I attached to make CPU/GPU water blocks.

Here is a video of what I am trying to achieve:
https://www.youtube.com/watch?v=613qkiIrXFM&t=1s

He is using a BF-20 Vario with a Chinese spindle, he also made the CPU water block of the picture I attached.
Here is a complete thread forum of him making a high precision water block with many microfins about 10 years ago:
Build a high end waterblock on a cnc machine

I am not sure what kind of spindle I should use. Have any recommendation for a hobbyist level spindle?
Here is the spindle I need (used by the person who was using 0.2mm saw blade) but not sure what kind it is:
https://www.youtube.com/watch?v=A6z9y_QJO8E

Thanks for any advice.

[rajhlinux]

Hello Craig,

Thanks for the helpful information. Things are making more sense now on how to go about with the project practically witht he .
Many people was telling me to spin it at 60K RPM lol. Now that you have said 9K RPM is good enough it makes finding the spindle easier.

I was told to look for expensive spindles like NSK/Jaeger, however these are too expensive for me right now and need something more like an entry level before making that type of investment.
I know some Chinese spindles are good enough for the task with runout around <= 5um.

I see that you have a cylindrical spindle. Not sure if I should get that or a square type.
If you have any recommendation for a spindle that isn't over $400, I would look into it.

I'm also not too sure if the Shapeoko 5 Pro which uses HiWin rails and precision ball screws will be somewhat a cheaper option to start getting into the project as compared to the PM-25.
The 5 Pro costs $3,500 with tax and shipping, with the presumed $300 spindle, which totals around $3,800.

Now for the PM-25 seems to be $2,677 with shipping + tax. Complete CNC kit with steppers will be $1,500, so a total of $4,177 which is about $400 more than the 5 Pro.
Not sure which steppers motors + control board are decent enough that will work with CNCLinux.

I am more leaning towards the PM-25 because I believe it will provide better tolerance for machining small intricate designs.
Also it might be better at face milling, squaring stock and making threads which is also important.
However I am not sure in that conjecture because the 5 Pro also have good tolerance around 0.04mm (40 microns).

I will do all of my projects slow with great care to complete everything so fast cutting is not needed.
With this said not sure if I will truly benefit with the PM-25 of its small work area with high rigidity compared to the 5 Pro.

I will be machining a lot of aluminum and copper blocks to make intricate GPU/CPU water blocks such as shown in the attached pictures.

However I am unware of extra things that might be needed to practically get this project done.
If I get the 5 Pro, I will need a large 2x2 feet aluminum stock plate to make that into a machine bed and will also need clamps of some sort to hold down work pieces, if I get the PM-25 not sure if I need a vise.

How much more cash I need to spend to practically get things rolling?
What other important necessary things do I need to buy?

For example I was completely unaware about the coolant, not sure which would be the cheapest system to setup for.
On the YT video link I posted previously which shows the saw milling, "teledoof" seems to be using a compressed air system.
Yesterday "teledoof" recommended me on getting the PM-25. He designs and machines custom made state-of-the-art water blocks.

If I get the PM-25, do I need to do extra scraping on the ways to dial everything correctly? It seems the spindle that comes with the PM-25 are being switched out with better ones such as $300 AC servos.

Thanks.

[joeavaerage]

Hi,

Many people was telling me to spin it at 60K RPM lol. Now that you have said 9K RPM is good enough it makes finding the spindle easier.

If you spun a 27mm diameter slitting saw at 60,000rpm the peripheral speed would be 5089m/min or 84m/s....I reckon it would fly apart. If you have a larger diameter
saw blade the situation gets worse.

I run mine at 9000rpm which means its peripheral speed is 736m/min, and I think that is still way too fast! My 800W spindle is air cooled and its very bad practice to run them at less than half
speed as they tend to overheat. Water cooled spindles are better but the same recommendation applies, run at half speed or more. You can certainly run it at less speed but you are risking the
spindle. 9000 is as slow as I dare run mine.

I've had this little spindle for years and have had countless thousands of hours use from it. I now use for making PCBs and other small parts for my business, I'd go broke without it, so
I'm very careful with it. I paid quite dearly for it, its German made (Mechatron Gmbh), but it has proven its worth over and over again.

I do not have any experience with Chinese made spindles, but many thousands of people use them to great effect and sing their praises just as loudly as I do about mine. The upshot is that
many of the cheap spindles are in fact very good, and exceptional value for money. If there is a trap that many have fallen into is that they use a cheap Chinese VFD, and then not understanding the
critical role that programming the VFD plays proceed to blow either the VFD or the spindle or both. The VFD MUST, repeat MUST be correctly programmed to suit the spindle PRIOR to switching it on....
even breifly....even once.

Yesterday I just pulled the trigger on a new spindle. 10,000rpm (rated), 40,000rpm (max), 3.5kW (rated), 400V with an HSK32 ATC tool interface. Its Chinese made so I'm dipping my toe in the water so to speak.
I'd dearly love to but another spindle from Mechatron (42000rpm, 2.5kW, 230V and HSK25 ATC tool interface) but the last time I priced it just the spindle cost 5700Euro......holy s*****t!!!!

I personally think the drill-mill style PM-25 is a better bet. Its more rigid. Rigidity = Potential Accuracy, always has done, even with manual machines and CNC machines are no different.
Another way of expressing it is Flexible/Wobbly Machine= In-accurate machine, no matter how good anything else is machine flexure will defeat you every time

The PM-25 is a mill, a small one no doubt, but it is a mill whereas the Shapeoko is a CNC router. Undoubtedly there is some overlap, but if you want to cut metals a small uber rigid machine is what
you need. Reduction in machining volume/extents is just the cost for having a rigid machine.

On the YT video link I posted previously which shows the saw milling, "teledoof" seems to be using a compressed air system.
Yesterday "teledoof" recommended me on getting the PM-25. He designs and machines custom made state-of-the-art water blocks.

I get into ding-dong arguments with other forum posters on this all the time. They all reckon air blast with or without a little bit of lube is OK....and I say BS. I have used air blast, and it does work, but when
I bought a coolant pump it was a 'night and day' improvement in all and every material. I say go with flood coolant, and as much flow as you can. I use it on just about everything. Believe it or not
plastics are hard to machine as the chips tend to weld themselves back together and/ or stick to the tool. Flood coolant fixes that. If milling steel, you MUST keep the tool cool, even a few seconds without cooling
and the tip of your $30 carbide tool glows red hot....and its done. Flood coolant is the way to deal with that. Aluminum and copper chips are very prone to welding themselves to the tool, especially cheap tools with
a poor polish. Flood coolant is a good way to deal with that.

If I get the PM-25, do I need to do extra scraping on the ways to dial everything correctly?

No, I would not have thought so. Surely PM would have a bad reputation amongst buyers if it were not decently made?. I rather suspect that unless you are an expert at scraping and have some really top-notch
measuring gear and the experience to use it you're more likely to make it worse than better.

How much more cash I need to spend to practically get things rolling?
What other important necessary things do I need to buy?

There is no simple answer to that. What might satisfy me might be crap for you or vice-versa. Pick a big number, the add a zreo.......and try to stay within that budget!!!
I personally use a Vertex angle-lock vice, a Taiwanese made copy of Kurt...and am happy with it. I'd love a Kurt but I could get three Vertex's for one Kurt......as good as Kurt is
I can't quite see myself doing that.

Craig

[rajhlinux]

Thanks for the reply.

So I'm not sure which mill to get now under $3K. I also need to account for another $1,500 for CNC kit (ballscrews + steppers/servos).
I live in the US and it seems only PM mills are reputable for the price.
There are also Grizzly, but from my research, PM mills are somewhat better. There might be newer models which I am unaware of.

I have never done a CNC conversion on a mill and will need some help on choosing the correct ballscrew and stepper/servo.

I did some homework, I want to make sure that the ballscrews are from HiWin and the steppers/servos are from leadshine/OMC/clearpath.
However getting them will not be easy since it seems everyone are getting them from the manufacturer directly or locally.
I rather get from a local US authorized distributor to protect me from any issues with the items.

I also have no idea how to properly know which dimension and specifications for the CNC kit.
However I have seen two companies selling the CNC kit for some PM mill models, they do not mention about the brand/source of the ballscrews and do not sell stepper motors:
https://www.arizonacnckits.com/pm-940-cnc-kit.html
https://cnc4xr7.com/pm727m-cnc-conversion-kit.php

So below are the PM mill machines I plan to get. Not sure which one will be ideal and easiest to install for CNC kit and will be great quality upon opening the box with no faulty signs of craftmanship.
I want to get a PM model that is 100% Taiwanese made, I haven't heard any machinists being disappointed with the Taiwanese made mills.
If I remember correctly few years ago PM used to mention which mills are 100% Taiwanese but now it seems they do not mention any of that.

PM-25MV Milling Machine
From $2,399.00

PM-727M Milling Machine
From $2,699.00

PM-727V Milling Machine
From $2,899.00

PM-932M Milling Machine
From $2,799.00

[joeavaerage]

Hi,
both of those conversion kits look OK.

Lets face it all cheap ballscrews are made in China, it does not matter whether the supplier is in the US or Timbuktu, the products all come from China.

I did some homework, I want to make sure that the ballscrews are from HiWin and the steppers/servos are from leadshine/OMC/clearpath.

Ok, they are decent brands, so get them direct....and pay the premium. Not sure about OMC, but Hiwin are probably made in China despite being a Taiwanese brand.
I think Clearpath are made in the US, and priced accordingly. I use and buy 750W Delta B2 servo kits for $438USD plus shipping. I've bought four at that price in the last year.
So I pay about $100 less for a 1hp servo kit than Clearpath sell their 1/2 hp servo. Clearpath are good quality and have excellent support, especially for US customers, but they are not cheap,
in fact they are a rip-off in my opinion.

Precision Mathews is not well known in New Zealand, with most of the drill-mill style machines coming direct from China or Taiwan.

Of the models you have listed the 727 and the 932 have the most 'cast iron' about them. You don't list either the 940 or the Taiwanese made (according to the web site) 833.
Both look to have more 'cast iron' in them.

If you have not done a conversion then I would probably stick to a model for which there is a complete kit with which to do the conversion, and a supplier that can answer your questions.
That is the 'low risk' approach. You might end up with a better machine were you to select both the machine and all the parts that go into the conversion, but that is the riskiest option.
What's the bet for instance you get ballscrew model XYZ in from Taiwan or wherever only to find that's it's just a bit too long, or too short, or too something or rather. It's sort of too late
then. Whereas if buying a conversion kit then someone has already gone through that learning curve and you are buying that expertise.

I have built my machine from scratch, but it is a long and fraught process. All the details of building and integrating the electronics are yours to sort out. It is very satisfying but inevitably you make
mistakes and end up with some compromises....that is just part of the DIY build process. I made a mini-mill 13 years ago, and then used it for nine years. For all its little compromises and
outright faults I did a lot of work wit it. Even more importantly it fueled my desire to build another and better machine, and that new machine is what I have pictured above.

Were I to build yet another machine I would take what I've learned with me and would hope and imagine that I would create and build an even better machine.
I suggest you do the same. It would be nice to think that you could build the 'perfect' machine right from the outset, but that is just not what actually happens. You learn things
on the way, things like 'this machine has a step resolution of 0.1um......that's really good....isn't it?', but after a year or twos use you find the resolution is wasted, and in fact 5um
is still way good enough, and that 'next time I'll make sure the machine is way more rigid rather than ludicrously fine resolution. In short: you do not know what you do not know.
There is no shame in that, nor is there anyway to do anything about it but 'roll up your sleeves' and build that first machine.

My advice then is: don't try to build the 'perfect' machine, its just a too long and expensive process, but rather build a decent machine with parts that are readily available, reasonably priced,
with techniques that you can do yourself, or can at need, be done for you. The object is to build a usable machine that starts you on that learning curve. It may well be that in five years' time you'll build
a second machine and that will benefit from everything about this machine.

Craig

[rajhlinux]

Thanks for the reply.

So there is a new CNC breed in the game which got my attention beginning of this year seems promising for $4,500, the Langmuir MR-1, which is a gantry based design and weighs almost 1,000 LBs after setup.
I have seen many third party YouTube reviews and it coincides holding tolerances down to 1-3 thou.
Here is Langmuir's own tolerance tests and seems to hold much < 1 thou:
https://www.youtube.com/watch?v=0IswzwzdhEQ

Now the PM-25 and G0704 bench mills with proven history of decent tolerances around 1-3 thou as well, when converted to CNC.
There are big community of knowledge about them.
They weigh about ~ 300 LBs. The price on these will also be the same around $4K after CNC conversion.

So my question is which is better for the investment, more rigid and accurate?
I think the MR-1 should be more rigid. Want to hear thoughts on this. Thanks.

[joeavaerage]

Hi,
probably not a lot to pick and choose between them. My understanding is that the Langmuir gets a substantial fraction of its weight from concrete poured into the steel sections,
and if I'm not mistaken you do this yourself.

Ultimately, they are trying to achieve the same result but with two different design philosophies, one is a conventional mill whereas the other is a gantry style mill.
If the rigidity of both machines is the same, then you might imagine the machining results will be the same also.

As you have seen my own design is in the manner of a conventional column mill, and that is what I favor and is my recommendation......but it is a personal preference,
not based on any particular advantage that one has over the other.

Let's imagine that both machines are of the same rigidity and therefore capable of the same result. The only criterion that might influence your choice is 'what is the
upgrade path?'. For instance, you might want to swap the steppers for servos. Which of the two machines is most amenable to this upgrade? What about the spindle. Your
project suggest that a low torque high rpm spindle is the most widely applicable type. But what if you want to do some steel? Then you'll want to swap the highspeed spindle out
for a high torque one. Which machine is best for that kind of swap? Another possibility is 'what if I want to add a fourth axis?' Typically, the Z axis travel of gantry mills is very modest
and it is difficult when it's not impossible to fit a fourth axis 'under' the gantry.

To my mind a conventional column mill is most amenable to these sorts of upgrades. The design and construction of my machine means for instance when I install my trunnion fifth axis
and therefore lose its height from the Z axis travel that I can unbolt the Z axis cast iron bed and 'shift it upwards by the height of the trunnion and thereby regain the lost Z axis travel.
It was always my intention to do this and that in turn leaned towards a column mill rather than other styles.

Craig

[rajhlinux]

Also I have reached out to David Clements to buy a CNC kit for the PM-25.
He recommended to told buy the following closed-loop steppers for it, they seem to be affordable for entry level CNC usage, not sure if they are made from leadshine which I believe are also similar priced:

For the X & Y-Axis:
TS Series 4.0Nm(566.56oz.in) 1 Axis Closed Loop Stepper CNC Kit Nema 24 Motor & Driver w/ 2m Cable
https://www.omc-stepperonline.com/us...us-1-cl57t-s40

For the Z-Axis:
TS Series 9Nm(1274.5oz.in) 1 Axis Closed Loop Stepper CNC Kit Nema 34 Motor & Driver w/ 2m Cable
https://www.omc-stepperonline.com/us...us-1-cl86t-s90

What kind of the controller board do you recommend that would work with LinuxCNC?

Also not sure if you know about the Trinamic TMC5160 driver chips, know any controllers that have them that might work the steppers above?
I find it really strange how Trinamic drivers are not used in the open source milling CNC community.
I know that Trinamic drivers does not work with LinuxCNC, however I read it could be possible on some forums using which I haven't digged too deep into yet.
I want to use the TMC5160 because it has the silent feature which makes the steppers completely inaudible, I use the TMC2225 chips on my 3D printer and it makes the stepper motion 100% inaudible, amazing stuff.

[joeavaerage]

Hi,
to be honest I'm not a fan of closed loop steppers.

Steppers lose torque the faster they go, that is just plain physics, and open loop/closed loop makes no difference, they all lose torque.

If you listen to the close loop stepper manufacturers whom say 'go faster, more power, never lose steps'....all pure BS. Closing a position loop alters not the speed or the power of stepper one bit.
If a closed loop stepper is marginally overloaded and misses a step the drive will insert an extra one to keep up....but guess what....the extra step is just as likely missed and an ordinary step.
It is true that a closed loop stepper will 'try' to keep up, but if is overloaded it will perform no better than the same stepper but without being closed loop.

There are two genuine advantages that closed loop steppers have over the same stepper sans closed loop, one is resolution. An open loop stepper has a resolution of 1/2 step, no matter what microstepping regime is in place
whereas a closed loop stepper can actually resolve down to the resolution of the encoder, quite an improvement. If a closed loop stepper is overloaded and can't keep up despite the extra steps it will fault out
and signal the controller that a fault has occurred whereas an open loop stepper would carry on, but the part would be misshaped.

You are paying quite a premium for these two advantages. I personally think that if you want closed loop accuracy and certainty then get servos....don't mess around with mister 'in between'.
If you chose low inductance open loop steppers and decent high voltage (80VDC or better) drivers and use them within their performance envelope open loop steppers are every bit as good as closed loop steppers.
Having said that closed loop steppers are very popular and have come down in price, so it's far from a bad choice. The manufacturers of closed loop steppers ALWAYS choose the best low inductance steppers with which to make their
closed loop models, and in truth that same stepper would be a perfect candidate for open loop use as well.

Of the two steppers you have linked to the 24 size one has 2.6mH inductance, not bad, but not great either. In 23/24 size look for 1mH -2mH, 1mH preferred and reject anything over 2mH.
The second one, the 34 size as an inductance of 6.3mH....avoid like the plague!!! In 34 size look for 2mH-4mH , 2mH preferred and reject anything over 4mH. 6.3mH is poor in my opinion.

What kind of the controller board do you recommend that would work with LinuxCNC?

Don't know. I use Mach4 and an Ethernet SmoothSteeper and have done for 8.5 years. Check with Linux CNC aficionados but they almost certainly recommend one of the many Mesa motion control boards.
You could spend a lot of time designing and building your own drivers, but quite frankly they are dime a dozen on Ebay, and many of them kick arse over anything you could make yourself.
There are many areas where you can invest time and effort to get a better result, making your own stepper drivers is not one of them.

Who f*****ing cares what the steppers sound like? The spindle will be screaming so what matter if the steppers make a noise?. If you're really concerned about noise then use AC servos,
they'll eat ANY stepper ever made.

Craig

[rajhlinux]

Hello Craig.

Thanks for the reply.

Nice info about the inductance on the stepper motor anything over 2mH for the NEMA 23 and 4mH for the NEMA 34.
I didn't know about this until you have mentioned about it. I will do some research and understand why it's important and find better steppers in better mH specifications.

Right now I'm having issues in determining the proper power supply for the stepper motor.
From the same stepper links to the previous post, it seems omc-stepperonline.com wants everyone to use power supply that is basically half the voltage that is rated for the driver box.

Example the 9 N.m 6 Amp NEMA 32 stepper kit comes with the CL86T-V41 driver box. This driver box accepts 18 to 80 V AC and 24 to 110 V DC. Some have told me to use the highest DC voltage (110 V) power supply and limit the current. Is this the ideal way to determine the power supply?

The supplier "omc-stepperonline.com", wants us to do the opposite, wants to use half the voltage like 60 V DC. I saw they have another kit with the same stepper motor and it uses a 60V DC 350 power supply:
https://www.omc-stepperonline.com/ts...y-1-clts90-v41

I don't know whos right or wrong on this and not much info on it either.

Thanks.

[joeavaerage]

Hi,
all steppers lose torque the faster they go. Inductance is a parameter that describes how bad the torque degradation will be. The lower the inductance the better.
This is in fact a mild simplification of the true picture. In particular the rate of current rise is related to the inductive time constant which is the product of the resistance and the
inductance of the coil. Generally low inductance also means low resistance, so the simplification is broadly applicable.

Steppers are a category of motor called 'Variable Reluctance' motors. Such a motor achieves its maximum torque when the current is maximum. When a motor coil is energised
the current does not flow instantly but builds up over a short period of time due to the inductance. Referring to the diagram below I have simplified the circuit a little, and
made the coils resistance 1 Ohm, and the coil inductance 1 milli Henry.The inductive time const is therefore 1ms (=1 x 1mH) It is excited by a 1V source that turns on at t=0.
You can see that eventually the current will build up to 1A, and after 5ms its very close already. At one inductive time constant, ie 1ms the current has built up to about two thirds of its final
value. You might reasonably expect then the motor torque to increase from zero to about 2/3's of it maximum in 1ms.

If you want to run this motor fast, and who doesn't, then you need the current to build up very quickly. The faster it does so the sooner you can switch it again to take another step.
There are several ways to accomplish that:
1)Reduce the inductance. The inductance is determined by the number of turns of the coil. A large number of turns results in a strong magnetic field with minimal current, which is highly
desirable, but is also high inductance which is not. There is a balance to be struck

2) Reduce the resistance, ie increase the diameter of the wire. The bigger the wire the fewer the turns you can fit in the winding space, there again there is a balance to be struck.

3) Increase the applied voltage. The second diagram shows the same coil circuit but now with a 10V pulse applied. Note how the current build up that much sooner, and that if 0.65A is our target current,
then its taken only 1/10th of the inductive time constant or 0.1ms.

As you can see increasing the applied voltage drastically reduces the time required for the current to build up....which is a good thing.....BUT then the eventual current will be SO HIGH that
the stepper will blow up! This is the job of the driver to limit the current to the safe and rated current of the motor using pulse width modulation. This means that while the applied voltage
at the moment of switching is very high to cause the current to build up quickly the PWM throttles the voltage after that build up of current to a safe level....the best of both worlds.

Most newcomers to steppers buy on the basis of maximum torque, the higher the torque the better....right?? So they make steppers with lots of turns of small wire and that produces the most torque for a given
size and cost.....but also results in high inductive time constant so the motor goes slow. Manufactures know that newcomers do not understand inductance so they make high inductance/high torque
motors cheap to get the sales. Its only when the newcomer gets the stepper and it starts missing steps at 250rpm that he will realise that he has been duped. If you get a low inductance motor,
ie fewer turns of bigger wire, they cost more, and may even 'seem' to have less torque, but they will keep on keeping on and still have usable torque at 1000rpm when the high inductance stepper
stalled a long time ago!

Is this the ideal way to determine the power supply?

Basically the recommendation is to use the highest possible voltage you can. When a motor is decelerating it will generate power and push it back into the driver. Good drivers accommodate that voltage surge
whereas poor ones might blow up. Most people reduce the voltage to get away from the upper safe limit with a view to improving reliabilty, and its a worthy consideration.
My first mini-mill used high quality Vexta 5 phase steppers and Vexta 5 phase driver. Te driver had it own power supply built in, and got its supply direct from 230VAC mains.
Its DC supply (inside the driver) was about 150VDC, and that's what is applied to the steppers.....and man did they sing......3000rpm max, but I ran them at 2400rpm for the nine
years I used that machine....simply brilliant!

To be honest if a driver says 80VDC, then that's what I'd use. Yes, you might blow it up, but they are cheap so does it matter that much?. Once you get a good one, most probably Leadshine
or similar, then it won't blow up at 80VDC if that what it say and it will last for years.

At higher voltages and currents most people get switchmode supplies because they are cheapest, but linear supplies (transformer, rectifier and smoothing capacitors) are much more reliable
and forgiving of short term overloads. This is an example:

https://www.antekinc.com/ps-10n80-10...-power-supply/

Ideally you'd have a 15A supply if you had three 5A steppers, but that would be huge and expensive. Steppers, for the vast majority of the time, draw very little current and even less
often to they all draw max current at the same time so 1/2 to 2/3 of the total max current draw should be more than enough. Certainly if you use a linear supply then they will
tolerate (brief) overloads of double rated current anyway. It is for this reason that they are favored.

Craig

[rajhlinux]

Hello Craig, Thanks for the informative reply.

Finding low inductance stepper motor got tricky. So far from stepperonline.com I have found the following:
"P" Series is their professional line of Stepper Motors.
"S" Series is their standard line of Stepper Motors
"E" Series is their economy line of Stepper Motors.

For NEMA 23 to 24 [They all have an inductance of 1.8mH, these are the lowest I could find.]:

Nema 23 Bipolar 1.8deg 2.83Nm(400oz.in) 4A 57x57x84mm 8 Wires
https://www.omc-stepperonline.com/ne...s-23hs33-4008s

Dual Shaft Nema 23 Uni/Bipolar 1.8deg 2.83Nm(400oz.in) 4A 57x84mm 8 Wires
https://www.omc-stepperonline.com/du...s-23hs33-4008d

P Series Nema 24 Bipolar 1.8deg 3.5Nm(495.74oz.in) 5.0A 60x60x97.8mm 4 Wires
https://www.omc-stepperonline.com/p-...s-24hp39-5004s

P Series Nema 24 Closed Loop Stepper Motor 3Nm(424.83oz.in) with Encoder 1000PPR(4000CPR)
https://www.omc-stepperonline.com/p-...00cpr-24e1k-30

S Series Nema 24 Closed Loop Stepper Motor 3.0Nm(424.83oz.in) Encoder 1000PPR(4000CPR)
https://www.omc-stepperonline.com/s-...34-5004d-e1000


For NEMA 32:

P Series Nema 34 Bipolar 1.8deg 7.2Nm(1019.81oz.in) 6.0A 86x86x95.3mm 4 Wires - Inductance: 4mH:
https://www.omc-stepperonline.com/p-...s-34hp38-6004s

S Series Nema 34 Stepper Motor 8.0Nm(1132.89oz.in) 6.0A 86x86x98mm 4 Wires - Inductance: 4.6mH:
https://www.omc-stepperonline.com/s-...s-34hs39-6004s

P Series Nema 34 Closed Loop Stepper Motor 8.5Nm(1203.7oz.in) with Encoder 1000PPR(4000CPR) - Inductance: 5mH:
https://www.omc-stepperonline.com/p-...00cpr-34e1k-85

S Series Nema 34 Closed Loop Stepper Motor 9.0Nm(1274.5oz.in) Encoder 1000PPR(4000CPR) - Inductance: 3.6mH:
https://www.omc-stepperonline.com/s-...46-6004d-e1000

S Series Nema 34 Closed Loop Stepper Motor 12.0Nm(1699.34oz.in) Encoder 1000PPR(4000CPR) - Inductance: 4.8mH:
https://www.omc-stepperonline.com/s-...59-6004d-e1000


For the X/Y-Axis I should get the "P Series Nema 24 Closed Loop Stepper Motor", it has an inductance of 1.8mH with 3N.m of torque, this should be suffice for the PM-25mv bench mil X/Y-Axis?
For the Z-Axis I should get the "S Series Nema 34 Closed Loop Stepper Motor", it has an inductance of 3.6mH with 9N.m of torque, this should be suffice for the PM-25mv bench mil Z-Axis?

I find it strange that their "P" line for the NEMA 34 inductance have 5mH while "S" is much better of 3.6mH.

I plan on doing a lot of micro machining and high tolerance milling, so I don't need high speed motion, I guess less torque is fine when doing things slower?
I now need to find drivers for these. Have any recommendations from stepper online or any websites where you can find stepper motors with low inductance with good pricing with drivers?

These are the drivers omc-stepperonline have:

CLRS Series
DMAI Series
DMRS Series
ISC Series
ISD Series
T Series
Y Series
Y2S Series

Thanks.

Edit:

I found a kit that comes with the driver for the "S Series Nema 34 Closed Loop Stepper Motor" for the Z-axis.
It has the same serial number but different inductance. Even on the datasheet. Shows 6.3mH:
https://www.omc-stepperonline.com/ts...y-1-clts90-v41

Here is the same stepper motor without kit, shows 3.6 mH, even on the datasheet.
https://www.omc-stepperonline.com/s-...46-6004d-e1000

Same stepper but different inductances, even on the datasheet...?

[joeavaerage]

Hi,
well you certainly have been doing some research, and you have found a whole bunch of very useful motors. While some might be better than others, all of them are
pretty damned good.

For the X/Y-Axis I should get the "P Series Nema 24 Closed Loop Stepper Motor", it has an inductance of 1.8mH with 3N.m of torque, this should be suffice for the PM-25mv bench mil X/Y-Axis?
For the Z-Axis I should get the "S Series Nema 34 Closed Loop Stepper Motor", it has an inductance of 3.6mH with 9N.m of torque, this should be suffice for the PM-25mv bench mil Z-Axis?

Yes, these look like very fair choice.

Same stepper but different inductances, even on the datasheet...?

That is a mystery. Possibly worth an email to the supplier to find te truth of the matter. There is quite a difference between the two and it would be worthwhile
to know why.

I plan on doing a lot of micro machining and high tolerance milling, so I don't need high speed motion, I guess less torque is fine when doing things slower?

Do not delude yourself. The toolpaths you want to do consist of a huge number of small moves all of which requires the highest possible acceleration. Steppers are essentially
bolt-on and could reasonably be swapped out at a later date, but do you feel like wasting your money? The choice between a so-so stepper and a good one, one that you'll have for the life of the machine,
say twenty years, is a $10 difference.

I've had a quick scan through the drivers, some are fine but there are quite a few that just do not have the voltage capability. This is one that caught my eye, its high voltage, open loop and at a
big discount. I would use it not just for 34 size steppers but 24 size as well. It is a one size fits all solution. If you want closed loop then there are oher choices, but personally would not be bothered with closed loop.
Too much extra to pay for so little gain. Your money, your choice.

https://www.omc-stepperonline.com/y-...4-motor-dm860y

Craig

[joeavaerage]

Hi,
this would be my selection for open loop steppers;

https://www.omc-stepperonline.com/p-...s-24hp39-5004s

I have deliberately selected a 24 size or 60mm x 60mm because should you ever decide to swap to servos then its highly probable that you'll get Chinese manufactured units
on the basis of cost, and the majority of those are 60mm x 60mm. The 23size steppers are just a little bit smaller. You'd then be looking for US made servos at a real price hike.

In 34 size I'd go with one of these:

https://www.omc-stepperonline.com/e-...s-34he31-6004s
https://www.omc-stepperonline.com/p-...s-34hp29-6004s
https://www.omc-stepperonline.com/p-...s-34hp38-6004s

Note that they are all somewhat lower torque than others, but all the other more 'torquey' motors just have too high an inductance. My guess is that one of the units I've linked to will have MORE
torque than some of the bigger ones at 1000rpm.

I have just found a speed/torque diagram for the second one listed (4.5Nm, 2.5mH). Just look, its still got 60% of its torque at 700rpm....that's impressive, and note
also that is with only a 60VDC drive, imagine how much better it would be with 80VDC or 90VDC up its chuff!. If you can afford them, get one for all axes (X,Y and Z) and be done with it.
I personally think these are hands down the best.

Just as a comparison I found the same speed/torque curve for the first of the 34 size steppers (4.8Nm, 3.8mH) and see that at 700rpm with the same 60V it retains a little under half of its low speed
torque. Don't get me wrong, this is a good stepper too, but see how much difference to the 2.5mH one. Very illustrative.

If the manufacturers used the 2.5mH one as the basis for a closed loop version...then that would be great. If you can get a 34 size stepper with 2.5mH ....grab it....you'll never regret it.

I suspect if you use fine pitch ballscrews, I'd recommend 5mm, then you'll be able to direct connect these steppers and still have plenty of thrust. The high rotational speed of which these low inductance steppers
are capable of will ensure, if not blazing fast rapids, certainly very useable rapids, but more importantly good reserve thrust and acceleration.

Craig

[joeavaerage]

Hi,
the more I think on it the 4.5Nm, 2.5mH stepper above (34HP29-6004S) with 80VDC or 90VDC driving it will handily do 1000rpm and STILL retain half its torque, say 2.25Nm,
and may even do better, say 1250rpm or 1500rpm with still useful torque, approaching 2Nm.

If they were direct connected to 5mm pitch screws that would equate to rapids of 5000mm/min (1000rpm) to 7500mm/min (1500rpm), both of which are very respectable
in a smallish hobby machine and yet still have something like 5kN of thrust at low speed with a 5mm pitch screw of 16mm diameter.

I really do think this model motor is the hands down winner. Don't mess around with a small motor for the X and Y. If the larger 34 size motor will fit then bung them in there and let the fun begin!

Craig

[joeavaerage]

Hi,

take a look at this stepper, 34HS59-5004S. It has 13Nm and 11mH. With 13Nm its got to be good......right? But buried in the download section is this:

It starts with a hiss and a roar at 900N.cm at low speed but by ONLY 450rpm its down to 200N.cm I doubt this slug of a thing would even get to 1000rpm let alone
have any useful torque left to do any real work.

This is s classic example of a manufacturer making and marketing a high torque stepper that looks very appealing to newcomers but then disguise that fact that it can hardly get out of its own way
at 500rpm. What a joke.

Do not fall for this sort of s****t.

Craig