Which 4020 ?

[efidoug]

I'm in the market for a mid 90s 4020 to do prototype work on which years have the AC drives or DC drives. I understand I want the AC drives because they are the same as mid 2000 models. Anything else to watch for ?
Thanks Doug W

[Neal]

Doug--
The 1990 machine will have DC servo motor. The AC servo motors were not used until very late 1995 and early 1996 machines. The VMC 15 machines were all DC drives. There are a few VMC 15s with AC drives but they were the early 2016L machines that didn't have the name changed at that time.

Neal

[efidoug]

Is there any problem with the DC drives?
Doug W

[little bubba]

My take on the AC DC thing. I worked where we had an AC machine and now own 2 DC machines myself.

The DC driver boards seem to hold up much much better than the AC boards. It seemed like any little crash blew a driver board. At well over $1000 up towards $2000 a piece, that gets expensive, we ate threw I think 6 of them in 4 years. Not all due to crashes, had a few just die.

Now with my own machines, 5 years of machine time and no toasted boards (DC). Knock on wood. And if they go, they are about half the price of the AC boards. Then again, I don't crash MY machines.

Just my observations.

Anything else to watch for ?

Same things as with any other machine. Tool retention is easily and cheaply fixed on Fadals, and is really a maintenance item anyways. Lots of sloppy backlash is usually the thrust bearings, not the ballscrews and is easily and very cheaply fixed.

One thing I would highly suggest if you can find it, extended Z, 28". Those extra 8" are the best 8" in the world.

[DareBee]

yep
I wouldn't be without the extended Z, rigid tap and 10K spindle.
No issues with the DC system on my '94.
I feel that the boxway machines are better over the long run.
I also use my 4th axis a lot.
Lube system and cool power system needs to be checked/maintained carefully.
A lot of us "prototypers" disconnect the ball screw cooling to save maintenance or failure of the thrust washers.