I have been looking at the nema 34's and I am confused about the specs..
They all seem to quote a recommended voltage of about 2v, whats that all about? Would one nema 23 just not be able to move the mass because the 34's are quite a bit larger and wont fit in the location I have put it, which means putting 2 nema 23's one on each ballscrew which then also means a controller which supports slaved drives and controllers with error detection which means £££ ! I am trying to sell this to the better half as a bit of additional income but when I mention a couple of hundred pounds extra on top of my ever increasing budget she doesnt seem very impressed, I don't know why
Charlie, what's the weight of your gantry complete with the spindle? If you put that weight into the motor calculator spreadsheet you'll be able to see if one Nema 23 will do it. On my gantry it was going to be only just ok (I've got more plate in mine than you have as I believe from the drawings you're using alu box sectio to mount your rails to?) so I went larger to be on the safe side. If you're borderline all it will mean is that you won't get the higher speeds of velocity and acceleration.Neil...
Well I have attempted to work it all out and this is what I came up with?
Aluminium on gantry 31kg
800mm rails+blocks 5.8kg
400mm rails+blocks 3.6kg
4 blocks on x axis 1.6kg
Z ballscrew+mounts 2.5kg
Y Ballscrew+mounts 3kg
x axis ballnuts 1kg
2 nema23 motors 3.6kg
Total weight 54.1Kg
Does that sound about right? have I missed anything. I suppose I need to look at the calculator now.
How about your spindle? You'll also need a bit extra for cable tray, cables water tubes etc....Neil...
Just had a look at spindle weight and it looks like 5.6kg, maybe another 1kg for cable and pipe so total weight comes in at 60.7kg
Quick answer to your question about "2 volt motors". Ignore motor voltage ratings. For all practical purposes, they are irrelevant. The control electronics are driving short pulses through the motor windings and include some clever controls on motor current, which is the important bit. The motors work using magnetic fields; the higher the current the stronger the field and the more torque you get out of the motor. However, the motor windings are coils of wire which have inductance. In this situation inductance is a bad thing because it slows down the rate of increase in current at the start of each pulse so you lose power. To get round this, you drive the coils with many times their rated voltage - maybe 60-70V for a nominal 2-3V motor - so the current builds more quickly. Then the current limiter in the driver reduces the applied voltage automatically during the pulse so the motor isn't over-driven. This all happens like magic and all you need to know about is the current limit setting in the driver module which should match the motor.
The Following User Says Thank You to Neale For This Useful Post:
Neale Very good explanation much better than I could have done it ..Clive
Last edited by Clive S; 28-08-2015 at 04:55 PM...Clive
Well, I've gone and done it, no turning back now....
Chester champion 20v milling machine ordered
steel for frame ordered
aluminium for gantry/frame ordered
Bit lighter in the plastic pocket now but feel like it's something I need to do otherwise I will never get started!
I will get the frame and gantry started before I order the ballscrews and rails, I wont be making any fixings for them until I have them in hand just in case and once they are done I will then decide on the motors,drives and controller at which point I will need a lot of help :-)
The Following User Says Thank You to CharlieRam For This Useful Post:
Here goes, my steel and aluminium have arrived. My mill is installed and I've had a play with my evolution saw... It's bloody loud when cutting steel but I'm really impressed with it. I feel like I need to make a new build log and close this thread off now? Just one question though, how do you lot measure your large beams (eg. 1350mm) after machining, do you just rely on your machines açcuracy, I've only got a tape measure!
I was thinking about getting a 3 axis dro for my machine but connecting the 3rd longest scale to some round rail to make a large height gauge. What do you think?
Anyway here's a couple of pics and I'll see you all in my build log when I post it :-)
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