SX3 CNC with CNC fusion kit #1

[adochoa]

Overall, this is a new machine build thread, but I am encountering a problem so I start off asking for help.

The Mill:

SX3 Grizzly G0619
CNC fusion kit #1 (no ball screw upgrades until I see I need them)
Motor driver: G540
Motors: X/Y 270 oz-in (Nema23), Z is 400 oz-in (Nema34)
power supply: The power supply is rated at 12amp and 24V (from camtronics-cnc.com)
Other: Gas spring kit
Software: CamBam Plus, Mach3, Solidworks 2009

I chose the smaller motors after being advised the 1000 oz-in were severe overkill. Dan (from Camtronics-cnc.com) put together his recomendation for motor/power supply/driver and I bought the kit from him. He seems to be a good guy and promptly returns emails with all of my questions.

The problem:
I've installed my Z axis stepper, but it seems underpowered and misses steps or barely moves at all. I've lowered the velocity/acceleration to ~100 mm/min, but still misses steps. When I took the assembly apart, I tried holding the motor with my hand to feel the torque. I was suprised, that with only slightly more than firm handshake grip, I could prevent the 400oz motor from turning. The video doesn't show very well the screen, but I was only trying to show that my motor tuning is a bare minimum speed/acceleration.

[can't get the file to attach, so I put it on youtube instead]: "http://www.youtube.com/watch?v=l7DVBJNO8l0"]YouTube - Z axis problem


Any help here is appreciated, is it a defective motor, or is the motor even too big for the G540? or is there another obvious setting I am neglecting?

Dave

[devers6]

I have the Grizzly SX3 as well, and I use the CNCFusion Deluxe kit with optimally 0 backlash. I use a KelingInc 640 oz-in Nema 34 on my Z, and it is OK with my motor settings of 80 IPM and acceleration of 5. I am running it somewhat derated at 3 Amps Bipolar Series, so I am not likely getting much more than 500 oz-in from it. However, it will only work this way with the assist of the gas spring - without it, the motor would frequently stall.

My initial thoughts are that using the stock leadscrews might need somewhat more torque. Although the mechanical advantage of the acme leadscrew is higher than a 5mm ball screw, the friction is undoubtedly much greater; especially on the Z with the heavy head (even with the gas spring assist). I would try loosening the taper gib on the head, back down your IPM and accelerations settings until you get reliable movement; then tighten the gib back up to normal. If you then stall out with the same motor settings, I would think 400 oz-in is just underpowered in this application. Perhaps backing speed/acc down more will help.

[2_many_hobbies]

I don't have an X3 but have been looking at one and have played around with a few setups that I own and I think for starters 24V for any stepper system is pretty much useless. I have tried it with transformers from work (Im an electrician) and currently run 48V. My table under 24V I could stop stop with a few fingers while at 48V I cant stop it at all.

I think thats why you have less than rated power and can stop the motor by hand. I remember the motor voltage equation is something like 32 *sqrt(inductance) so my motors are 2.2mH and I run them at 48V

If that's all good and you still lack power I say go to small drive products and change the belt ratio of the Z axis, the fusion kit is nice enough you should have enough room for a 2:1 reduction I would imagine. Other than that either get a bigger stepper you could rig up a pulley and blast as some have done on the forum. If done right they say you can one finger lift and lower the head!

Hopefully that helps!

[Crevice Reamer]

Hi Dave. Congrats (finally) for your first post.

You are severely underpowering this mill. The Z needs at least 640 oz, and the X,Y around 400 to operate well. Not only are your motors too small, but you are underVolting them as well with that tiny power supply.

Since Dan has given you this bad advice, maybe he will allow you to return some parts for refund so that you can buy the right stuff.

Here's what I would recommend that you use for an SX3 with the G540:

1. Keling KL-350-48 48V 7.3A PSU, $60.
2. Keling KL34H295-43-8A 906 oz N34 motor for Z, $99. This will detune to about 520 Oz @ 3.5A.
3. Keling KL23H284-35-4B 387 oz motor for X-Y, $49 each.

http://kelinginc.net/

You will also need some 3.48K current set resistors from Digikey.

There is not room in the CNCFusion kit for 2:1 reduction. However it IS possible to gear the Z down just a little to 1.2 to 1 by adding a smaller drive pulley. This would up Z torque from the 906 to 640 oz.

CR.