Building a Mini CNC Milling Machine from Scratch
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- čas přidán 27. 05. 2024
- DIY/ Homemade Servo driven CNC Milling Machine with Automatic Tool Changer. It’s capable of machining various metals like aluminium, steel, titanium.
The overall build took about 2 year to this point - along work and university.
Every part of this build (development/design and manufacturing) was done by myself with the help of basic tools (angle grinder, Drill press ...) and a bench top lathe.
Besides the servo drive and spindle motor, it was a build on a budget. Most of the components are from industry sales. The spindle motor was sponsored by one of the companies I was working for during my bachelor studies (innospiring).
The overall plan of building a CNC Mill evolved during the process. The further I got and the more I learned, the more I wanted to achieve with this. Now it is usable and capable for building small complex prototypes of “high“ precision.
The Automatic Tool Changer was build with a friend of mine, as part of a semester project in university. A 4th and 5th Axis were also developed in the following semester (unfortunately not build yet..).
Some Specs of the Machine:
- X Travel: 240 mm
- Y Travel: 170 mm
- Z Travel: 210 mm
- max. G0 (X,Y): 14 m/min
- max. G0 (Z): 7 m/min
- Servo Power: 170 W (max.)
- Spindle Power: 2,2 kW (i = 2.5)
- Tool Holders: SK20 (max. D12 mm)
- total weight: about 80 kg
- outer dimensions: 500x500x700 mm
If you have any questions: leave a comment or feel free to contact me:
E-Mail: info@EngineeringSpareTime.de
Insta: @engineeringsparetime - Věda a technologie
you're a mad man that's insanely good quality.
Thanks 😄
He means the YT video - the cnc is okey'ish for dyi.. 😜
@@TheStuartstardust Yes, I actually just built it to have content for the video .. 😄👍🏼
@@EngineeringSpareTime hahaha 😄,
Learn us to how to make it again. Where is the tutorisk?
BURN THE WITCH!!! People say you need several tonnes of rotting American cast iron to cut steel, much less titanium. Despite what we just watched, it's impossible to cut steel on a desktop machine, everyone knows this.
Seriously great work! You've done a lot that isn't shown or discussed much around here, and produced great results. Parts within a few microns of nominal, or at least better than you can measure.
I would love to see more details on the pneumatic draw-in spindle mechanism. Also definitely would not be bored to hear about the design choices you made mounting the ballscrews and other motion components.
Awesome comment :D thank you - I appreciate it!
Yes, there was quite a bit of research and testing going into the design that’s not discussed in this video. Iterations I had to make, because I wasn’t pleased with the result…
At the moment it will be difficult for me to find the time to do an additional video about this machine, since I‘m working on different things I am going to share in a few weeks. Until I finished those I plan to do a more detailed video about the design and especially the ATC, since your not the only one that seems to be interested in this :)
For how small the machine is, it's capabilities are VERY impressive. Great work!
Add one vote for your evolved thoughts on spindle design and construction. That's genuinely some green field territory on CZcams, especially a pneumatic design.
I'm planning to do something about it, since several people have already asked for it. You‘re right, not on CZcams.. :)
i'm actually impressed how the machine is rigid, he doesn't vibrate at all !
great work !
Thank you!
WOW... just WOW... what an amazing job you did here. When I saw you machining the spindle I was like: "Wait... he made his own spindle, air cilinder and automatic tool changer!?!?... amazing"
Keep up the excelent work.... and upload some more vids, please! :D
Thanks a lot! I still have some older projects I could share (mostly slide shows.. I mainly took pictures) and I‘m currently working on a 6 DOF robot arm, this will take some time to finish though :) I could release some “early stages“ of the build, if this is of interest..
@@EngineeringSpareTime you really should! I believe there are a lot of people who enjoy watching the process!
Waow! One of the smartest little cnc I have ever seen, love it. You've done a terrific study and your skills are impressive. You need to show us a detailled serie of vids about your cnc, from birth to achievement, please🙏🙏🙏
👌👍🖖
Thanks! At the beginning I didn‘t know how it‘s going to look like at the end, because intentionally I just planed to upgrade my former CNC ... this plan changed a bit. That‘s why I haven’t token any further videos, just pictures of the building process and a slide show is probably not this exciting...
@@EngineeringSpareTime bro can you share the cad file of this little monster?
please aka.vandalo@gmail.com (or well, just the spindle would help me a lot)
As a mechanical engineer i can attest that you are very talented. Amazing job!
Thank you :)
That first test cut was extremely impressive. Well done!
Thank you! This was probably close to the limit of the NEMA 17 steppers that I used back then :)
This is an exceptionally engineered mill all round. Few would even consider building their own spindles.
Seems extremely rigid for an 80kg machine too; that concrete must be ultra-high performance indeed.
Thank you 🙏🏼
This blew my mind. Incredible work. Thank you for posting this.
Thank you!
Thank you for sharing this beautiful CNC machine.
Absolutely beautiful, stunning work! It is a maddening journey to build something like this at it warms the heart to see a finished one like this. I have been working about the same amount of time on my own build and the scope has creeped so far. A 300 pound Z axis is sitting on my workbench in the garage. It's happening...
Thanks a lot! Yes, I totally agree. It‘s way more work then you‘d expect before - so many small things to solve and to decide. But this is what makes it‘s so rewarding at the “end“. Just keep doing it!
I‘m also building a „“big“ one together with a friend of mine, for the last four years. We‘re getting there.. 😄
Absolutely amazing! Well done. I have been considering something similar. I love how you executed everything. They turn into such big projects, don't they? Fantastic work.
Thank you! Yes, it‘s definitely a huge amount of work - totally worth it though:)
This is superb work! Thanks for sharing.
Very Impressive! Love it, especially the ATC
Thank you!
Congratulations on your work. I admire your work a lot because I have been building a similar project for 6 years. I have also built the atc spindle with many hours on the lathe and dedication. I do not have engineering studies, but for many years I have built small machines that have given me a lot of personal satisfaction. Socially I notice that there is a lot of misunderstanding of people with our concerns, they think it is stupid to make a spindle and spend a lot of hours on something that you can get for 550 dollars.
Congratulations on your talent.
Greetings from Barcelona
This is nice. Thanks for sharing
Very nice. Reminds me of the old days on CNCzone where people pushed the limits without relying on cheap modules from asia. Very nice.
Thanks - I appreciate it! CNCZone was great. It was actually part of the motivation to do this
Just found your channel and subscribed. Very nice work. Nice mill
Nice machine! It's nice to look at this! The machine is a mirror reflecting the soul of its owner 😉
Thank you :)
That is just beautiful! And you made your own spindle! Any more info about making the individual parts or any new projects would be great if you can find the time. I've been trying to refurbish an older machine on weekends and after work for a couple of years now and know that it can take hours upon hours to do. And you can't really put a price on something like this that you clearly have lovingly designed and built with your own hands (and lathe). Any thing that you would like to share about this journey would be eagerly watched and rewatched.
Thank you, I appreciate it. I still have some older projects to show, which might be interesting as well as a current one. I‘m in the process of building a 6 axis robot arm from scratch (aluminium construction) including the driving system (servo driven) and programming. The mechanics of the first four axis are basically done. When I find the time, I‘ll make some videos in the next weeks.
I checked out your channel, looks like a really nice machine! Yes, such projects involve a big effort, but totally pay of in terms of learning and fun - in my opinion.
Awesome build!
Looks great. Brilliant work.
Impressive precision! Very good work, i am impressed.
Thank you!
Awesome video. Nice machine. Well done
This has been a huge inspiration
Looks legit. Great work!
Wow! You are perfectionist!
It was great pleasure for me, to watch this video clip. I have read almost the whole discussions with your answers. It was very nice, to read your professional opinions, written with a lot of patience sometimes. I wish you many health primarily, many successes in your professional career, and private life also.
I’m glad to hear that you enjoyed it and appreciate your words :)
When I choose what I’m doing, being patience is natural - in my opinion.
Thank you, wish you the best too!
Unbelievably great job! When you made your own spindle i almost spill my coffee ;)
Thank you :)
As most people have said that is incredible work! Thanks for sharing :)
Thanks! :)
This is otherworldly quality! 😮
Wow! Very impressive. Much respect and admiration for this piece engineering feat!
Thank you 🙏🏼
Wow I hope you're on our side
What a beautiful piece of machinery - I'll need another 2 lifetimes before I can build something like that :)
Thank you!
A lot can be done - one way to find out is just trying :)
Dam dude, ben watching a few of your vids and I love your builds. Would love to see an explanation of the auto tool changer, excellent work!
awesome project!! this is my dream.. Building cnc machine
the best mini cnc i have ever seen!!!
Thanks :)
The machine sounds great.
I assume you now have your degree by now. I am a CNC / Manual machinist for 45 yrs, worked in 17 shops, operated over 50 different cnc mills. From my experience with the engineers, the best ones have machining experience. You are off to a very successful career. That mill is sweet and you learned a lot. Try to incorporate manufacturing into your designs and make sure your boss knows how much $$ you saved them. Don't be bashful, toot your horn some.
I really appreciate your words and can totally relate! Making components yourself first gives you an understanding of what is important during development. Of course I need longer or even more attempts for the components I make, but in a professional context a much more productive level arises on which you can exchange ideas with the experts in the field - like you - and find a solution together. We can all learn from each other and that is, in my opinion, the fun of it all.
Thank you!
@@EngineeringSpareTime I agree, working together to solve problems is fun and the experience gained and shared keeps our world moving forward. I am Happy for you and your workmates, knowing your future will be rewarding.
looks great!
Impressive work
Thanks 🙏🏼
Hands down the best DIY CNC mill I have seen, only Piotr's build is comparable in sexiness. Sounds super smooth cutting steel/titanium, leaves a pretty good surface finish, large work envelope for such a compact machine, well thought out way covers and even has proper closed loop control with servos. That spindle blew my mind. Awesome.
The video description answers most of my questions, but how much does it weigh? What controls are you running, LinuxCNC?
Thank you, I appreciate it! Yes, Piotr‘s machine is a nice one. There are some other really nice ones too.
It weighs about 80 to 90 kg - I haven’t weighed it in a while. I run an old version of Mach 3, cause I was used to it from a older project.
For the upcoming portal machine, I‘ll use LinuxCNC.
Nice little unit. 👍🏻
If it is worth doing, it is worth overdoing.... Tolles Projekt! CNC-Grüße aus Remagen :-)
Overdoing - I don’t know what you‘re talking about :) Danke! Begeisterung übersteigt manchmal den Nutzen und da beginnt der Spaß! Ebenso, schöne Maschine und schicke Spindel ;)
This is good quality stuff...hope it's done in 6 months
Ich bin begeistert von Deiner Arbeit!!! Drei 👍👍👍 hoch. Ist natürlich kein Vergleich zu meiner DIY-Holzfräse. LG, Claus
Danke! Meine erste Fräsmaschine war auch aus Holz - es geht ja um die Begeisterung :)
@@EngineeringSpareTime Ja, so ist es....😄👍
Mind blown! Wow.
That is an awesome machine! Do want
This is such a nice machine ;D !!
Awesome feat!
Damn what did you even study to make something as amazing as this?
Thank you, I appreciate it!
When I started the machine I was doing an apprenticeship as industrial mechanic. I “finished” it mid of my mechanical engineering bachelors :)
@@EngineeringSpareTime thanks, I'm currently doing mechatronics in HS and wanted to do a mechatronics and automation systems specialization instead of a degree
Its the best build ive ever seen
GREAT MACHINE !!!!!!!
Thanks!
You need to market something like this, or a machine company needs to pay you a ridiculous amount of money to design machines for them. Well done!
Wow. That's an incredible project. I'm wondering - how much it weighs? The steel milling capability looks very impresive for this size of machine. Love the design.
Thanks! It weights about 80 kg.
I would love to learn more about this machines design.
Love the machine.
Could you please tell me what the depth of the machine is? Basically the length of the bottom on the side stiffening plate. I want to get a feel for the size of the machine.
Impressive...
I subscribe this channel. Love it
Thanks :)
u my friend are a GOD
your work is beautifuullll
Impressive 😀
This is awesome work, we have been trying to find an ATC spindle for a long while. Please share the BOM for the build. Thank you.
Thank you! The bom is kinda short:
- disc springs
- 7007 and 7006 from NSK -> spindle bearings
- 3.5mm ball bearings
The rest is custom and made from stock material :)
Thats cool, but what about collects? The spindle interface for the collects is what makes ATC spindles difficult to build.
Looks great, have you anything you can share in the spindle design?
i just came across your channel amazing work 👏 i love to see plans our more in depth on how you made everything the atc was poor class 😁👌
Kool project All I need now is to buy a proper mill and lathe to make and I’m laughing...
Thanks! I “just“ had the lathe available, no milling machine was used. The lathe is the only actual tool I‘ve used. You could check if someone close to you lets you use their lathe ;)
At some point you need some turned parts. Building a machine like this without a lathe is nearly impossible - except you buy all the components finished...
very cool!! from MIE's video
even gave you a sub to see some future vids
Thanks! :)
Nice machine! can you give more information on the spindle cartridge build?
Thanks! Someone else already asked about this. I plan to do a video about this.
I would also be interested
Do you have the design for the spindle available for download anywhere? Impressive build!
Just wondering, do you have any drawings of the ATC spindle? i got all the tooling to make one of my own, been trying to design one myself but i keep getting stuck and confused. even more pics of the spindle would help!
I saw your comment on NYC CNC's Tormach Tech video and, thankfully, clicked. What a beautiful "DIY" build. (I quote DIY because I suspect there aren't many people - myself included - who would have the skill and patience to execute such a build.) Can I ask a few questions? 1) Now that you've had this machine up and running for a few months, is there anything major that you would have done differently in retrospect? 2) Is there a reason that the machine rapids for the ATC are that slow, or was this just filmed in the early days when you weren't totally confident in its operation? 3) You mention the Clearpath servos; I'm curious what you think about them?
Thank you! 1) For what its is I am quite happy how it turned out. I would have done a few things differently, would have designed things differently but for the time I was building the machine this is what I was able to do with my resources - knowledge, tools and budged.. For example: I would have liked to nitride the spindle shaft, use even more high quality bearings and linear rails (the spindle once and the ball screws are top quality..) and so on. 2) Yes, this was in the early stage and actually the first test of the ATC - so I started slowly (this was at about 300 mm/min, now it’s capable of 14m/min - I should make a video about it) :) 3) So far the clear path servos doing great. The implementation was straight forward, the performance is way more than enough (they actually run at 40% torque limit, otherwise they could rip everything apart). The tracking error and disturbance rejection is also good. They are more expensive (double the price compared to e.g. JMC), this is still cheap in comparison to a “actual“/ industrial grade servo drive (not the same “quality“ obviously).. For the next CNC I would order the free programmable version to be able to implement my own control algorithms to enable model based temperature compensations and stuff like this, its not really necessary though.
This is awsome! I'm building something similar. Would you like to make a little cash and make another one of those spindles? Trying to find one capable of 24k rpm and have neumatic atc is a pain. You seem to have it down.
Thank you! Unfortunately, at the moment I can’t build you another one, because I couldn’t offer it to a reasonable price.. With my small lathe it takes a lot of time to machine and to get it working perfectly. Thanks for you interest though! Maybe I’m able to produce them more efficient in the future - we will see :)
Hello, I am curious to know which controller card you have used for mach3, I would also like to know if you consider the operation of macros in mach3 to control tool change reliable.
Greetings
Thanks for your comment. I am using an ESS SmoothStepper and additional break out boards for GPIO. The version I am using is most likely obsolete, since I have ordered back in 2015. Yes, I'm planningto use macros and a ModBus conntection to operate the ATC. Unfortunately, I couldn't find the time to fully utilize it yet..
Awesome
nice job... are you going to be offering plans and or cad models for anyone interested in building something like this?
Thanks! The build evolved over the time, so it‘s probably not the most efficient way to build it like this (e.g. more than 300 screws :D). That’s why I‘m not sure if someone would like to build it like this or should.. I‘d have to refine the plans and CAD for that to quite an extant. Due to my current projects and studies, I have to delay this.. But nice to hear that you would be interested in something like this, I’ll try to figure something out.
@@EngineeringSpareTime Many of us interesting in taking inspiration from your amazing build :)
That was one hell of an impressive desk CNC mill, very well thought out, compact, and yet still super accurate from the looks of those measurements you took of your test cuts! If I may ask, about how many € did you spend on it without that toolchanger? Was the frame made out of steel, or aluminium? And what material were those black side panels made from?
Thank you! :) the overall build excluding the ATC the spindle motor and the servo system (those are exchangeable..) was about 1.2k - building it like this decreases the price, increases the involved work though.
Could have a optical sensor just above the tool sensor. That way it could go faster down and slow when optical sensor is triggered. The optical sensor could be a part of the whole height sensor.
That’s a good idea 👍🏼 I could also move faster, hit the trigger ones, retract and repeat it with less speed - not that save though :)
Love this!! Im inspired to do something similar.
What linear rails are you using on the x, y and z? Looks like the Z is 20mm?
Also, how did you decide to do a separate spindle / motor?
Appreciate your work 👍🏾
Can you help me about servo motors and drivers ?
Amazing work! Maybe you can explain a bit more about base. There is metal (I think aluminum) plates cast in concrete? Or by UHPC you mean something else? How did you machined these parts at home wit such great precision? I'm just hawing problems with smaller parts...
Question. What signals do you run through the safety relay?
It’s triggered by the Emergency Stop Button with cross-circuit detection and a optional switch for e.g. an enclosure door. There is a 24V signal for e-stop that’s connected to the sps, a contractor for the spindle motor, a signal to the inverter and Servo drives. The servo encoders and the mcu are always powered. I hope this answers your question
Do you have the plans for the spindle?
Thank you for your knowledge.
Did you use SKF 7201 in both ends or only one end?
In one end two of 7201 in O-arrangement. On the other end you want to use a “floating“ bearing that allows lateral movement to compensate for temperature elongation - e.g. a needle roller or a regular 6000, 6200..
You can also get of the shelf bearing blocks - easier to use if the implementation is possible.
Nice!
So tiny... But so silent, powerful and accurate!
Top quality work. Subscribed!
Thank you, appreciate it!
Thank you for sharing. What kind of Lathe is that?
Thanks! It’s a nice one: Wabeco D6000 :)
Engineering Spare Time ah. Yes indeed a nice one!
That is awesome mate ! Do you think there is a way to grab the tool without pneumatics ? As If you intend to use the mill without a compressor.
Thank you! Yes, this would be possible for example with a electric motor and a short lead screw or some sort of mechanism that gives mechanical advantage. Downside of this would be the size and cost, since such a mechanism would be larger and more expensive then a single pneumatic cylinder - sure you need a compressor, that doesn’t need to be huge though and most of the time one is already used for cooling
As you meantion it there are these small type of car tire inflators that could get a pressure up to 10 bars(100psi?) and you already have them at home. They are small but maybe they are just enough to suck the cylinder If used as a compressor.
Really cool!! I intende to build one like this, that I can use to automatically mill blades from old files (keeping the original heat treatment, no annealing), just a bit more X travel but the rest is great. Could you help me or send me links to papers or videos that might help?
The head is stationary and the table moves, interesting...did this reduce the complexity? great job overall!
Thanks! This layout has some advantages in terms of stability and stiffness, the effective working area is smaller compared to e.g. a portal though. It’s like a Industrial VMC
More typical for a 3 axis machine to be configured this way, great job man, I wish I had the resources and I'd make one too
Hi, amazing machine! I was very surprised by the rigidity of the components. Was the spindle head made up of aluminum pieces, or was it a steel construction?
Hi, thank you!
The spindle head is made of 6mm steel plates, all dimensions were cut with an angle grinder and than hand filed to precision :)
@@EngineeringSpareTime makes sense, thank you!
Could u help me please building atc system for my cnc?
What are the side stiffeners made from? Why did you cut slots in them? Seems weight saving isn’t useful here?
They are made from S355 construction steel - laser plates.. The idea of the cut outs is to reduce surface deformation in X direction due to vibrations close to the eigenfrequencies (changing the vibration modes...), this shape is still stiff in Y and Z direction though. And it looks way cooler like this ;)
@@EngineeringSpareTime how did you go about evaluating eigen frequencies and whether they would be significant?
@@ewildgoose I just roughly calculated the nominal frequencies of the spindle motor, spindle shaft and according cutting frequencies. Some of the spectrum equals the vibration mode of the plate without the cut outs, so I decided to add them. If this was necessary is questionable, the plates are not vibrating or ringing though..
Nice machine!
Wonder what ratio the spindle has from the motor?
Maybe it is like 3:1 or 4:1. So max 24000 rpm from motor will give about max 6000 rpm on spindle? Was this the idea to get lower rpm? Could be that you wanted a tool changer and those can only run max 8000 rpm or something.
You said you used a 12 mm ball screw (the good one) and a SKF 7201 bearing. The bearing is 12 mm inside. Does that mean that you put the threads in the bearing directly? Maybe the ball screw was machined in the end but that would make me think that it would be more like 8 or 10 mm and different bearing was to be used?
What is the stiffeners made of?
Thank you!
The ratio is about 2.3:1 -> Max. 11 000 rpm. I did this to increase the torque at lower speed. Otherwise the torque would have been to small for milling high strength materials (e.g. carbon steel..) and the bearing lubrication of the main spindle is critical at higher speed with this diameter.. for the tool changer it’s not a problem, especially not if you build it yourself :-)
For the bearings: Good point! I machined an adapter and shrink fitted it on the machined end of the ball screw (it was 8mm OD) to achieve a proper shoulder for the bearing
What spindle are you using? I’m in the process of building a machine as well and can’t find a spindle with a low enough rpm and high enough torque to machine anything harder than aluminum.
The motor is a water cooled China 2,2 kW spindle, reduced by a belt drive -> max. spindle rpm is around 12000 rpm. The spindle cartridge with the tool changer is diy. For even higher torque I’ll upgrade the inverter to a vector driven one
@@EngineeringSpareTime Can you see how much power is actually being drawn by the spindle? i am currently upgrading a machine and have a 1.2kW DC motor to fit its max rpm is only 4200 so i was thinking of gearing for at least 8000.
Luc Davenport It’s possible to see check the power in the inverter ui, I didn’t check it though. How much power is actual needed, always depends on the cut you take. Lighter cut -> less power.. 1,2 kW should be enough for most operations up to a diameter of 6 mm.
What kind of benchtop lathe do you have? The machining looks really good!
It’s a Wabeco D6000
Awesome build! Do you have any info on the linear rails & ballscrews used? Sizes, preload etc. Thanks!
Thanks! I kinda used the “best“ stuff which I was able to get and not 100% what I would have liked to use (due to cost). But anyway: The Linear rails X and Y: HIWIN MGWR09 + carriage WGW09HZ1HM (sounds small, C_0 is 5.9 kN though..). For the Z axis: HIWIN MGN15HZ1HM. Both types with light preload (Z1). For the ball screws - I was lucky - I could get my hands on some ground 12mm P5 ball screws from STAR (Rexroth) check the video 10:43 .. normally those would have cost more then the rest of the machine (without the servos and spindle motor). For the ball screw bearing arrangement, I used precision spindle bearings from SKF 7201 (good bearing are important! Everything else is not worth the time..)
@@EngineeringSpareTime Thanks for the quick reply! Yes very impressive. It's amazing how much performance you can get from relatively "light weight" linear motion components. I see a lot of over-built machines that don't perform that well.
Any chance you have more info on that home built spindle cartridge? Even a video with some pictures and dimensions. I know a lot of us would be very grateful, as it's a bit of a stumbling block (for me anyways). Cheers!
Devin Moodley At the moment I‘m building a big CNC Machine, that is not light weight anymore - I could built this machine with the new one so much more efficient :) This small bench top machine is very practical in a sense of space, weight, speed and capability (it’s quite precise..) though. The working area in X, Y, Z is enough for most of the stuff you do.
I didn’t take to many pictures of the spindle, cause it took for ever to machine it with this small lathe and I forgot about it. I have to think about this, it was definitely no straight forward to build the spindle cartridge completely from scratch (incl. the pneum. cylinder), I learned a lot by doing this, and would do it a bit differently next time - I might not be happy with releasing/ showing this “80% spindle design“
@@EngineeringSpareTime I'd love to see a video discussing what you would have done differently with the spindle. There are so many "My First Cnc Router!" videos out there and not nearly enough about precise and rigid machines like this!
BuySomeApplez If there is interest in this, I‘ll think about making a video about the thought process and construction of such a spindle cartridge.
“My first CNC router“ is a nice way to say it - “Machining metals“ has sometimes different meanings :)
Yeah, there are really just a view - mostly bigger machines. This was actually part of the motivation of making a a video about my machine..
Amazing
Which CNC controller have you used?
Thanks! I used a SmoothStepper with expansion cards. I’m running it via Mach3
brother is it possible that you can share your project (info and cad files?)
How much NM(newton force) / Kw of a spindle power as minimum required for steel milling process ?
This mainly depends on the tools being used. To estimate/calculate the cutting forces you might want to check out the formula from Viktor/Kienzle