Large CNC Router for Steel & Aluminium - BELT DRIVE SPINDLE and other questions

[denhen89]

Hello everyone,
before i start to ask my questions (many of them ), i want to tell something about me, because its my first thread here in this Forum. I will write pretty much (i hope not too much), just so you know my situation and know what i need. Also, im sorry for my english.

My name is Denis, i'm from Germany, but living in Poland since 2013. About an month ago i finished to build my workshop (67m2) and i quickly realised how helpful it would be to have an Milling machine and also a CNC milling router, so i started to use all of my free time to read about milling machines, cnc routers, etc.. In about an month i want to buy an Bridgeport series 1 mill, so i will be able to build a lot of stuff for the CNC router. I'm a car mechanic/electric, not an machinist, but i know that i will manage to build an large & rigid CNC router for milling steel and aluminium by my self, but due to the lack of experience i will still need your help. Many of my questions got answered through this forum, just by googling. This shows me what a nice and helpful community it is, also because experienced poeple take unexperienced poeple quiet serious and trying to answer all questions very informative. I'm unexperienced (no practical experience with milling at all), and for sure i will ask questions which are maybe not very smart, but i hope you can make some kind of explaination and not just saying yes or no, because i want to learn and understand.

To be honest, i'm not sure what kind of type of CNC Router i will exactly build and that depends a bit of your recommendations and help.
I want to build an very universal CNC router, so it should be large (about 2500mm x 1500mm), and be able to mill steel and aluminium without any problems, what means it has to be very rigid (screwed and welded steel frame). The reason for the size is that i want also to cut sheet metal and if needed also MDF wood plates. I know, if i want to cut sheet metal, i should go for a plasma cnc router, which does not need to be that rigid and precize and for sure its also cheaper and easier to build, but then again i have no CNC milling machine. I have enough space for an large CNC Router, but not for an large cnc router and large plasma cutter, thats why i want to build an universal cnc router which will be very rigid and precize to do all the work. This machine should be later also used for commercial purpose.

I know, i want much, maybe too much. Milling companys have many different machines, for aluminiun milling, steel milling, sheet metal cutting, wood, etc., but for the start, i need an cnc router which manage to do all the jobs and not because of the commercial reasons, but just because i need to build many different things for my self and i cant afford couple different machines, also i have no space for that right now (actually i have, but i want to use my car repair workshop pit for cars and not to put an large cnc router on it ).

First i thought to build an moving table cnc router, because of the better rigidity, but then i saw the DATRON M8 Cube, which has an moving gantry and mills even stainless steel with an good performance. I know, its an high end machine, but that shows me that an moving gantry is not even such a big problem. I tryed to find some kind of information how the Datron M8 cube is build, but unfortunately i could'nt find anything.

So, now its time to ask my questions:
- Linear guide rails: Are 4 x 30mm-Linear guide rails for the Y-Axis enough (2 on each site of the frame)? I was thinking to put one linear guide rail on the side of the frame and one on top, or do you have better ideas? The gantry will be very heavy. I think a about 100kg (about 220lbs)

- Ball screws: I was thinking to use one ball screw on each site for the Y axes, because i think that one ball screw in the middle should'nt be enough, but then my question is if i should use 2 closed loop stepper motors for each ball screw on the Y axis or just one which is connected to both ball screws with an belt? What size of closed loop stepper motors you recommend for that big machine and heavy gantry? Are you even recommend to use closed loop stepper motors like e.g. EasyServo motors from LEADSHINE?

- Spindle (im very stuck at this): I would like use an belt driven spindle (like this one:, with 2 different ratios, to use lower speeds for steel and higher for aluminium, so my question is, if its possible to have speeds from 3000-12000 rpm? I know that i need higher torque for steel, but the biggest problem i think is to find an electric motor which has an rpm of 6000. Also i want to control the speeds through Mach3 with an VFD. Is there any chance to realize this ? I think thats very difficult, because all electric motors i found had rpms to max 3600rpm. BUT, i found electric motors for vehicles like cars or motorcycles, etc.. , but they run on low voltage. Please check this website: http://www.into.pl/silniki/#silnik_24kW_indukcyjny . Its an polish website, but there are just tables with informations about the motor which is easy to understand. Just scroll down to the first induction motor. There reads that the electric motor has different RPMs depending on the voltage, but always same torque. So for example: 24v = 3000 rpm and 19nm torque , 48v = 6000 rpm and 19nm torque , 96v = 12000 rpm and 19nm torque. This are just examples and i pretty sure this is not going to work, because if it would work then someone would use this kind of motors for spindles, but what is the problem ? Is it not possible to use an variable transformer for the motor ?
Do you know any alternative for the spindle problem?

Okay, for now thats all and i even wrote too much. Maybe the whole idea is not that smart. Maybe its better to build something smaller and an moving table router to get better rigidity, but thats why i wrote so much so you can understand in what situation i am and maybe you could tell me good alternatives.

Thanks in advance!

Best regards,
Denis

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[hanermo]

It is perfectly doable.
Correct budget is about 10-25.000€ for parts, and 400-1000 hours work.
About 3000-4000 kg in mass, in steel.

2500 is easy, 1500 mm is not, unless and only when it is a portal mill=dual column.
Always, with moving table design aka dual column mill, in my examples.

I use 35 mm linear rails now.
100 kg is too light.
Forget it, for 1500 mm.

My up-down z axis is 700 kg.
For 1600 mm free space or work area.

[skubajon]

Awesome to see another person wanting to do more than wood with their router! I built one and finished up last year.

I've been machining lots of aluminum and brass parts. I run probably 4 hour a week.

Though my cost of materials was about 10000 dollars

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[skubajon]

I haven't attempted steel because I have all my steel sent out to machine shop and done on heavy duty lathe or vmc. This machine is for non ferrous prototyping in my home

http://www.cnczone.com/forums/diy-cn...ba-router.html



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[pirate323i]

Hi Denis,
I cant help with your questions, however have you seen the "Grünblau Platform" (on this site) the original design scope was to have a replaceable/convertible bed so that the machine could be used either as a plasma table or as a router/mill... I personally think it is a beautifully designed machine (if I was in the US I would buy his kit!)
Good luck with your design/build!

[skubajon]

Denis. Following the datron concept you will see they use high frequency spindles. For budget purposes you can get about 24000 rpm.

This is also very crucial in a router due to rigidity. Datron uses primarily HSM tool paths and high rpm. I'm not sure how well it will work on slower rpm.

When doing aluminum alone, I notice a major difference running slower rpm. I typically run my cut paths at about 150 to 200 ipm and 20000 rpm. I do a lot of trochoidal paths as well


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[denhen89]

Hi again!

First of all, thank you very much for your help.

@hanermo: To be honest, i thought already it could go easily over 10.000$ and if i want to build a very rigid and large cnc with good quality parts then it will be an long project. I'm sorry, but i do not understand what you are saying about the moving table design. I wanted to build an Moving gantry, so why you think 1500mm are not easy to build ? Do you mean i should go for an Fixed gantry/moving table design? Then of course the 1500mm in X axis will be not easy but if i would build an Fixed gantry design, then i would build an smaller CNC router. I have an nice room in my workshop where i just need to crush 2 walls (one is a support wall which is 38cm thick, but that shouldnt be a problem). This room is 330cm long and 300cm wide, so i could build an table with an Y axis size of 1250mm and 1250mm in X axis and could easily go around the cnc router. That build would be much cheaper and easier to build (rigidity) and the saved money i could spend to build an large plasma cutter for the sheet metal and if possible mount there an cheaper high speed spindle for wood cutting. Maybe, thats an good idea, i dont know really know what is the best plan.

@skubajon: Because of your build i got stuck (really nice build!). I havent read everything, because i wanted to answer here asap, but i added it to my favourites as VERY IMPORTANT ! Unfortunately i couldnt find any videos. All uploaded videos in your thread couldn't be watched and on youtube i couldn't find anything when searching for SKUBA ROUTER. You said you haven't tryed steel, because you sent your steel to an Machine shop, but are you not courious to try it out ? Do you fear to destroy the spindle bearings ? Could you tell me what Spindle you are using and which Servo Motors (closed loop or real servo?) you have used?

@pirate323i: Thats an AWESOME looking build. The idea is great and i also thought already about something like that and if i would build an large and rigid machine then building an bed for plasma cutting and mounting an Plasma cutter to it shouldnt be a problem. I think the only thing which then needs to be added to the system is an automatic z-axis adjuster (dont know the exact name of it anymore), because thin sheet metal could lie curved on the bed.But yeah, ITS AN OPTION!

@skubajon (again): Thanks for that. So, do understand it right (i just read very shortly about HSM on this website: High Speed Machining (HSM) for CNC Milling: The spindle speed just needs to be quick enough (HSM starts from 18.000rpm when i read correcly) to use HSM tool path?
I thought the biggest problem will be the Spindle, because of the different RPMs for Steel and Aluminium, but since i watched some videos on youtube i think i could just use that kind of spindle (the ALIEXPRESS link is extremly long so please just copy the title to aliexpress search): CNC Water cooled Spindle Motor ER25 4KW 269-380V 9000-18000rpm D=125mm 4.24Nm Permanent Power for CNC Router
Also i thought about it to use an BT30 ATC spindle, (not for the start, but then i don't need to buy an new one for the future), but they are very expensive. Is it possible to build some kind of ATC for an ER25 spindle like that one on Aliexpress (if i understand the system of the tool mount on an ER25 spindle right, then its not possible.., but maybe?). Again, i see a lot of videos on youtube where they do the whole milling process on CNC machines with only one finish end mill because of the high rpm.

Here an video of someone who has modified an Chinese router (2.2kw high rpm spindle and added extra rails for rigidity) and he's milling steel with 18.000 rpm: ( On the same video he wrote an comment that he's milling steel with that spindle for 2 years and the spindle can handle it.

Here an video of high speed machining of tool steel (10.000rpm) :
What is so special on that machine that its possible to cut with this feeds and speeds ? I mean, of course the whole machine is some kind of high end, but the RPM shows me that the spindle i posted here (aliexpress spindle: 4kw - 9000-18000rpm), could be an good decision, or am i wrong?

One last question: I want to learn some kind of CAD program to start to draw my CNC router and i have already Solidworks 2014 installed, but is it the right software for an beginner? What would you recommend? I want to learn an program which i can also later use for my CNC drawings.

Guys, thanks again and thanks in advance for your help.

When i will start the project (i will build an CNC router for sure), then i will for sure write about it here with a lot of pictures and videos, but that can take some time (at least couple of month).

Best regards,
Denis

[wizard]

Denis

Your post is very interesting but i wonder if you are biting off more than you can chew.

Here is the thing a CNC router type machine, capable of machining steel, is completrly doable. In industry they are often called bridge mills, you can also get something similar called a planer mill. The thing is these machines are massive, especially if you are interested in the tolerances associated with machining steel.

So the first thing you need to do is ask your self how are you going to handle the massive parts. Immediately after consider how you will machine those parts.

The issue of machining is huge because you likely will not be able to do the job well on a Bridgeport. Consider this for a 1500mm work area yot will likely need a gantry at least 2 meters long. For one you need to accomodate Y acis saddle length and ideally provide room for tool changing. So you need to machine (for linear rails & etc) this very long gantry beam to high tolerance usually associated with machining steel. I just don't see this being done to well under 1/1000 of an inch over a foot (pretty sloppy really) on a bridgeport with no experience behind you.

Honestly i think you woild be better off buying a CNC mill instead of a Bridgeport if you want to CNC steel. The controls on todays CNC mills can be very friendly and just as productive for one off as a manual mill. This would give you a CNC for steel and a machine to help you build a high quality router type machine.

Speaking of plasma machines, it isnt impossibke to design such a machine that can be built out doors. As you note the machines are usually fairly cheap. Building one for outroors would cost more but not dramatically so. IN my estimation an outdoor router woild be far more expensive to achieve. In any event putting a big machine outdoors solves your space problem.

I mention the outdoor plasma machine because you really haven't related why you want these machines. Your expectations are key. My thinking was that you expect to wotk with a lot of aluminum and steel sheets. With especially thin sheet goods you really want to avoid the use of a router.

[denhen89]

Hi!

Wizard, i'm very thankful for your very informative post.

You're for sure right when saying i'm biting off more then i can chew . Since yesterday evening i thought already to change the whole idea and build an smaller machine with an moving table/fixed gantry. Not because i think i will not manage to build that large and rigid machine, but maybe its totally nonsense. Im pretty sure that even if i would like to have an machine also for commercial purpose, then i rarly will need that size for aluminium or steel. I think that "clients" who will need to get milled that kind of big parts, then they have money and know where to go and will not look for an small company. Another reason is that it will be cheaper and easier to build an rigid cnc router with an fixed gantry. I thought about 1250mm x 750mm.

You're saying that its difficult to machine such a big parts on an Bridgeport for the rails etc. and its not the first time i hear that, but i have an idea which maybe could work!? Lets say i build the smaller machine with an x-axis travel distance of 750mm, so lets say the gantry needs to be about 1250mm. The bridgeport series one has an table size of 1250mm x 300 (when i remember right) and an travel distance of about 800mm x 300mm. So, to mill all surfaces of all square steel tubings i need for the machine, i would need to move the workpiece at least ones (for the y-axis (2500mm) even couple times). But i thought build that kind of square tunnels. I try to explain: I thinking to build 2 tunnels out of thick surface milled steel plates or aluminium. Each tunnel (2) will have 4 bearings rolls on top of the tunnel. This bearings will be connected to springs like the that kind of which are used for car cylinderhead valves. This springs can be adjusted through an screw. I put one tunnel on left and one of the right side of the milling are with an distane of only about 200mm. This tunnels will be fixed to the table. Then i put the square steel turbing which i want to surface mill, through both tunnels and start to mill. Of course the bearings rolls will be placed so that they will be almost unvisible when watching through the tunnel, but when the square steel tubing is inside of the both tunnels and the springs are tighten up, then the tubing gets pushed to the tunnel bottom plate. Throgh the bearing rolls the square tubing should be able to get pushed by hand without even moving the table and in same time mill the surface. I hope you understand what i mean. For me, without any experience its very difficult to say if that will work, but i think the idea is pretty good !? Of course the tunnel plate (4 plates for each tunnel) should also be very precised milled and the surface needs to be very falt, but with that kind of system i dont need to move the workpieces by taking it of and fix it again to the table, just push them by hand through the tunnels with switched on mill. Maybe the tunnels should have also 4 bearing rolls on one side plate, but even if not and the square tubing just fits good and will move just a bit to left or right inside the tunnel then this shouldnt be a problem at all.
Maybe my thinking is completly wrong, but i will try it out until you or someone else will not tell me that this will not work .

An CNC mill would be nice, but costs a lot more (about 3 times more for an old used one) and for me its important to learn manual milling before i even start with CNC. I could also buy an ready CNC router and just upgrade it a bit and make it more rigid, then slowly mill steel plates for an bigger cnc router, but for sure i will need also an conventional mill for some stuff, and an bridgeport is very universal and in future i can upgrade it to CNC if needed.

The outdoor plasma router is an nice idea, and after i'm finished to write this post i will google for it. But, for the plasma cutter cnc router i have already an very good idea which will solve the problem with the space inside my workshop. I will buy an used cheap 20ft container (available for about 1200$, or 1000€ or 4xxx polish "zloty"). It almost 6 meters long and over 2,3 meters wide, so enough space for an 2500x1500 plasma cutter. If i would use that plasma router outside, then i would get very quickly problems with my neigbor .

So, even if i'm switching all the time from large moving gantry to smaller fixed gantry cnc router, i'm pretty sure i will go for the smaller fixed gantry. I can save some money and quicker build an plasma cutter for sheet metal. And with the CNC router i can build many parts for the plasma cnc router.
I think thats the best what i can do.

Still, i'm very very very stuck with the Spindle. I hope you can help me out with that, when i explain what is important for me: Like i already described, i want to cut steel and aluminium with good performance, but also i would like to have an ATC in future, but when looking for spindles on aliexpress i see that its not easy to find that kind of flexible spindle with ATC. Please take a look at this spindle (aliexpress - url shortlink(5.5KW chłodzony wodą Silnik Wrzeciona 3000 ~ 18000 rpm 380 V 10.5A 150 ~ 900Hz 125*321mm GDS5500 ER25 dla CNC Grawerowanie Maszyny I w 5.5KW chłodzony wodą Silnik Wrzeciona 3000 ~ 18000 rpm 380 V 10.5A 150 ~ 900Hz 125*321mm GDS5500 ER25 dla CNC Grawer This spindle has 5.5 kw, 3000x18000 rpms and same torque from 3000-18000rpm, is water cooled, but is an ER collet spindle, so without ATC. I can't find an ATC spindle with similar performance.. WHY ? Could someone explain it to me? I'm not just asking here to go for the easy way, because since yesterday evening i spend at least 6hours to look for an alternative. I found the Tormach "TTS" system, but if i udnerstand write the chuck is different and will not fit into an ER collet spindle. I'm soooo stuck with that, that i haven't even start to learn solidworks and i wanted to start already 5 days ago... Hope so much you can help me out with that. I would even go for an Belt driven system, and buy an very good belt drive spindle (up to 15000rpm) with BT30 ATC, but then again i see a problem with the motor. I couldn't find any induction motors with more than 3600rpm, but mostly only 2900rpm. So, if i want to achieve 15000rpm, i need an 5/1 ration, but i dont know if there will be then enough torque ? For aluminium maybe, but for steel on high speed?! Then again 3000-6000rpm should be already very good for steel and i can just take an stronger induction motor, lets say 5-7kw?! I thought also about an high speed servo motor like that one on ebay: Infranor Mavilor BLS-143 High speed servomotor, Mavilor motor | eBay, but they are just too expensive. The total cost with belt drive spindle would be close to 5000$.
Guys, like you see, due to no experience i really need your help with that. I want to build an really good machine, not just one who can handle steel and aluminium. I don't want to go the cheap way and later buy new parts. It can take more (cause of money), but when its ready then it should be an beast .

Its not "asslicking", but i already have to say that i love this forum. Very kind help, and not just pushing someone down who has no experience and just want (maybe) too much . I hope that i can soon help other poeples.

Best regards,
Denis

[pirate323i]

Is there any reason you cant mount two spindles? On high speed and another low speed?

Also with your intention of milling in the tunnels - yes it will remove the variable of the Bridgeport table (and the 'rocking' of the canterlevered table) however you will need to be VERY careful... I think you will need to have some mechanical way of pushing the tube through (ie a screw) the risk of the mill either pulling it out of your hands (and shooting it across the room) or spitting it back at you (!) Is very high... Or the cutting force pushing it into the side of the tunnel may be too high to overcome by hand...
(I have no experience of this however the concept scares me!)

[denhen89]

The double spindle is a good idea, but do you mean next to each other ? So, for e.g. make the gantry a bit and use two mounts for the z-axis for both spindles ? Then i would 2 x VFD , 2 x cooling system, etc... . Even if i have no experience i think i can say that it shouldnt be such a problem to realise this, but it could be very costly. I thought about also about it to have two different spindles, but not to mount them both, but have some kind of quick change system and use an VFD which is compatible with both spindles. Then there will be still the problem with the water cooling system if i want to use water cooled spindles, i think i should them. I'm sure, that all is possible to realise, but it would be great to have some more comfortable system.

Nice that you are saying that i have to be very careful when using this tunnels and pushing the square tubing by hand. I have no experience about the power when milling and its difficult to image that there are such forces when doing small cuts, so its a very good info. But, im very happy to hear that its possible, so using a screw to push/pull the square or some other kind of system to solve the problem with the cutting force should be a small problem to solve. I have already some ideas.