rung fu clone RF-45 ZX45 cnc conversion

[jumps4]

Re: zx45 milling machine cnc conversion

tony
thank you
that is exactly what i was avoiding is counter balancing, when you counter balance you loose the mass of the head working to reduce vibration.
the inertia will only be there on rapid moves. under cutting conditions the feed rate is reduced before contact and the feed rate of z is very slow when cutting because it's a plunge cut with an endmill, so my thinking is inertia will not be a problem. and because my motor figures at about 1.5hp (hard to figure because hp is figured with rpm. but this is a 3/4 shaft not 5/8 and most nema motors with 3/4 shafts are over 1hp) my ways will be set very snug to reduce chatter and bounce. this is all just my therory and i'm not really that smart
steve

 

[Tony Wells]

Re: zx45 milling machine cnc conversion

Actually it doesn't change the mass of the head. It reduces the weight hung on the lead screw. For plunge cutting and drilling, the weight without any counterbalance give you more downward pressure with less load on the axis drive motor. With the counterbalance, if you rapid out in a peck cycle you will be lifting less weight, and therefore loading the axis drive motor less, drawing less current and lowering any shock loads on the ball nut.

But given sufficient hp, the only disadvantage I can think if is wear and tear on the ball screw and nut. But there must be some reason the major manufacturers do it. Could be simply that the spindle and housing on some of them weighs several hundred to well over a thousand lbs.

 

[jumps4]

Re: zx45 milling machine cnc conversion

thats very true
i already located lift cylinders just in case in my original plans. and my ballscrew could be bigger not to mention my dislike of the bearing mount from china, these are all good thoughts an extra $100.00 for lift cylinders might be advised
thanks tony
steve

 

[jumps4]

Re: zx45 milling machine cnc conversion

this is a learn as i go project and any help or thoughts are welcome
going from a little sherline to this is quite a leap and there is a lot to be concidered
steve

 

[Tony Wells]

Re: zx45 milling machine cnc conversion

The simplest way I've seen it done is with a pair of sprockets mounted on top of the mast that were free-wheeling on bearings and a #50 chain connected to the head, and over the top to a roughly equal weight cast iron that hung down behind the mast.

 

[jumps4]

Re: zx45 milling machine cnc conversion

the head weight is about 300lbs the air lifter cylinders for 150lbs each are $20.72 from mcmastercarr.com
http://www.mcmaster.com/#lift-cylinders/=j91e0v
i'm ordering tomorrow after i weigh the head ( I have to wait untill the wife is gone to use her bathroom scale :lmao::lmao::lmao: )
mounted from the bottom of the column to the sides of the saddle will work well.
steve

 

[jumps4]

Re: zx45 milling machine cnc conversion

I got a nice surprise this afternoon, I assembled the z axis on the column and everything fit perfect even the lower screw support from the original screw fit the ballscrew so no further mods are needed. when i put it together it was out of parallel by .010 and that was a simple adjustment. I ran it with a cordless drill at the lowest speed and the sound of the drill motor never changes. If i let the stops loose on the saddle it spins down on it's own. after turning my attention to the y axis I noticed my idea for installing the motor on the back will not work out because there is a web in the way I dont want to weaken. so that motor is going in the front. the nice thing is i got everything inside the column without losing travel.
steve

 

[Tony Wells]

Re: zx45 milling machine cnc conversion

So your thinking is that you will apply up to 150 lbs per cylinder, effectively neutralizing the weight of the head altogether? I'll have to meditate on that a bit.

 

[jumps4]

Re: zx45 milling machine cnc conversion

i'm trying it without them first. the bearing is rated at 1100 lbs and the ball screw about the same so i want to see how it sounds. but i may as well have them here to try 1 at a time maybe. if they are here i will try them if it works without them i wont order them to try. that probably dont make sense but i know me once something works i move on.
steve

 

[jumps4]

Re: zx45 milling machine cnc conversion

I finally got all the controller wiring done high and low voltage and tested, It is all green lights so far. next i need to cutout the the enclosure for the front and rear panels and install everything then wire the motors and connect to a pc for a final wiring test. my replacement 4200 z motor has not arrived from china yet so i'll just wire one motor for testing right now. the mill will have another enclosure for all of its wiring and relays with plugs to go to the main controller box.