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