IH Mill Accuracy

[Cruiser]

turning down the end of the shaft is easy, best way is with a tight fiting collet and support the other end with tail stock and small live center, tool point will have to get in close to the center. just make sure that you measure well and do it right the first time or you'll be spending some money having someone else weld it and return it true. the motor comes apart real easy and reassembles just as easy

[Runner4404spd]

did you just mill the key way after turning it down?

[Randall]

cruiser is right on thats exactly how I mounted it . you take the armature out of the case and remove the cooling fan then its easy to chuck up. I didnt do the key on mine a machinist did. but he ground a new key way on the oposite side and it worked great.
Randy
PS sorry for the poor layout of this message I'm doing this at work and its cazy.

[CNCPlastic]

Originally Posted by bill south Bob; My lathemaster is killing a 3/4" ballscrew due the weight of the head. The initial very low backlash increaseing almost daily and is up to about .050". Bill

That sounds like the funky Z axis slide to screw assembly issue. Mine had .020 slop from the factory. The Z axis slide is not attached to the screw, thats the problem. There is a bushing bolted to the screw which sticks out and into a hole bored into the slide. This is kind of a clunk/clunk up/down fit, rather sloppy plus its cast iron on cast iron with no real way to lubricate it. Aaron's mod lets you bolt the slide directly to the screw with a rather large bolt. That eliminates 100% of the slop. Screw alignment becomes critical though because there is no longer any slop in the assembly. With the cnc conversion the ballscrew is only attached at the top which gives you a little bit of play at the bottom of the travel.

The head on this machine is quite heavy and hangs out over the table. That thing weighs like 250 pounds with the motor. I counter weighted mine with 180 pounds which made a big improvement and took a lot of stress of the axis.

[Cruiser]

Hey there CNCPLASTIC, I'd really be interested in hearing more about your counterbalance system and how it reacts with the drive for starting and stopping. I can't help but concider the laws of phisics applied in so far as added mass to the system which must increase the load to the axis drive even tho it is somewhat in a balance. anyway i'd like to hear some first hand account as to the benefits v/s any shortcommings. how about it, you can make it a tutorial of sorts, and if your convincing i may try it on my IH mill and Thanks !

[CNCPlastic]

Originally Posted by Cruiser Hey there CNCPLASTIC, I'd really be interested in hearing more about your counterbalance system and how it reacts with the drive for starting and stopping. I can't help but concider the laws of phisics applied in so far as added mass to the system which must increase the load to the axis drive even tho it is somewhat in a balance. anyway i'd like to hear some first hand account as to the benefits v/s any shortcommings. how about it, you can make it a tutorial of sorts, and if your convincing i may try it on my IH mill and Thanks !

I counter balanced the head using two steel cables attached to a bar which runs under the head, its positioned about half way between the column and the front of the head. The cables run straight up vertically to pulleys bolted near the ceiling, then horizontally to a second set of pulleys towards the rear of the mill, then straight down to the 180 pound weight behind the mill.

I can't speak to the physics of counter weighting. All I can say is that before counter weighting the head I had to leave the gib rather loose else the stepper motor would lose steps on up moves. After I counter weighted the head I was able to tighten up the gib quite a bit and retune the stepper because it wasn't working nearly as hard as before on up moves.

Many VMC's are counterweighted, some use weights, others gas cylinders, or more recently some are counterweighted with servo motors.

I think in general terms its best to have improved balance when it comes to the amount of force required to move the head up versus down. Perfect balance would be nice but I did not take it to that level. I felt 180 pounds was sufficient enough of an improvement.

Charles