Zimmermann FZ-5

[Chris Hall]

The spindle is ISO 40, formerly called SK40. Apparently 'SK' is an abbreviation for a German term meaning 'steep taper'. Similarly, in German 'Morse Taper' is abbreviated as MK.

I don't know what sort of taper or mounting is used on the secondary high speed head.

The main spindle has 16 speeds, as follows:

56/90/112/140/180/224/280/450/560/900/1120/1400/1800/2240/2800/4500rpm

The main reason I was looking for a milling machine like this is the high speed capability, and now i'm pleased to find it has such a wide range that it could handle more tasks than i was imagining. With two milling heads it has a total speed range from 56rpm all the way up to 14,000rpm. And I'm wondering if a pulley change or VFD on the secondary head perhaps might allow for up to 20,000 rpm capability. Something worth investigating perhaps.

The vendor took a video for me showing the spindle runout, which is on the order of 0.015mm, about 0.0006". That seems pretty good to me - what do you think?

[Brian]

I would think it pretty good as well, but I'm not expert enough to know with certainty. When I chuck up the cutter I posted in the other thread I'll check the runout and see how it compares. The tolerance for the kind of work I'm doing on my mill is probably not even .001", its larger than that, maybe .002" commonly, so I wouldn't even notice .0006". It's also worth noting that there is some tolerance stacking in the assembly of collet and spindle.

When we got the mill home I went over a few checks based on advice given to me by the machinist I worked for at the time, Paul. I checked the quill to see if it maintained squareness as it increased in depth, then i checked the ways to make sure they werent out as I approached the ends of the travel. Both of these were in good shape. All of my checks were done to .001", I don't recall what the numbers I found were but I remember it being unconcerning to Paul.

[Chris Hall]

As far as I understand it, minor amounts of runout come most strongly into play when you are running very tiny tools, though any amount of runout will decrease tool life.

I'm going to assume that the machine could benefit from new spindle bearings and look into getting a set soon. You're right that there may be just a tiny issue with a tool taper as well, a little dust in the interface, etc..

If I need to get the spindle worked on, there is a company not too far away, in New Hampshire:

http://highspeedtechnologies.com/

Hope for the best, prepare for the worst, you know?

I also put in an inquiry with a company in Chicago which deals with european electric motors, sending them pictures of the 4 motors and their data plates in the hope that they might be able to produce replacements in the voltage and hertz I need. If not, or if the price is too high, then it looks like it will be $2000 for a transformer and load center.

The transformer would be supplied by this company:

http://www.temcotransformer.com/europea ... rmers.html

I should have the answer about the motors on Monday of the coming week.

Otherwise, nothing to do for me know but wait until the seller is back from vacation, August 11th I think.

[Brian]

After 40~ years of use I expect it's probably due to receive some new bearings. I'm just thinking out loud but it may be possible that the bearings look fine without a load, but not with a load.

I think that's an excellent approach to prepare for all foreseeable obstacles, at least then you can determine after the fact which wear is tolerable and which is not and what might be effecting results if you find inconsistencies in the results.

[Chris Hall]

After 40~ years of use I expect it's probably due to receive some new bearings. I'm just thinking out loud but it may be possible that the bearings look fine without a load, but not with a load.

That's exactly what I was thinking. They may have been replaced at some point in the past, but it makes sense to look at new bearings I think all the same.

[Chris Hall]

While waiting for Fritz Ernst Machinenhandel to return from vacation, i have been looking into options as far as the situation with the machine motors running on 380v. 50hz..

One option would be to swap motors, but alas, this is not so simple to do. I contacted a company in Chicago called Elektrim Motors, which specializes in metric frame motors. After sending them pictures of the machine's 4 motor data plates, they got back to me and could only supply two of the 4 motors in a suitable configuration.

So the swapping motors option was somewhat out, though I'm sure with a bunch of screwing around other motors could be adapted to work on the machine.

I then looked into transformers, and Variable Frequency Drives (VFD's). To cut a long story short, what I have found out is that there is a relatively simple solution. It turns out that voltage and frequency (in hertz) need to be in balance with one another. If the voltage is too high, or the hertz to low or high, and the balance is out of whack, then the motor can suffer from iron or copper loss. That will lead to premature failure of the motor. More on this here: http://www.lmphotonics.com/motor_50Hz_60Hz.htm

The ratio of voltage to frequency is what counts. If you take 380v. and divide it by 50 (hz), you get a ratio of 7.6:1

Now, let's say I obtained a transformer which gave me an output of 380v., and the frequency was 60 hz: 380/60 = 6.33:1 ratio is the result. Using a transformer like that would damage the machine's motors.

Here's the cool thing. If you boost up to 460 volts, at 60 hz you obtain the following: 460/60 = 7.66:1 ratio. This ratio is very very close to the 380/50 ratio of 7.6:1. This means that the machine can be without issue run on 460v. 60hz power.

What about the difference in the Hertz though? Well, 50 to 60 hz. is a ratio of 5:6, or 0.8333:1

In other words, a 60hz. motor, when run on 50hz power, would spin 17% slower.

Going the other way, 60:50 hz. is 1.2:1

In other words, supplying a motor rated for 50 hertz with a 60 hz. feed means the frequency coming into the motor is 20% higher than normal. That means the motor will spin 20% faster. This does mean that greater heat is generated in the motor windings, however since the motor has a fan blade on the non-business end, it also cools more, probably to no appreciable overall gain in temperature. This is also pretty much a non-issue since the machine is only run intermittently, for at most 20 minutes at a go, so motor heat build up is unlikely.

If the machine has some sort of clock built into it that controlled other functions, then the frequency difference would screw things up, but with this milling machine such is not the case, and given that the machine has a wide range of spindle speeds, an increase of 20% really is neither here nor there. The high speed spindle will move from 14,000 rpm to 16,800rpm- suits me fine as I will be using it on wood 99% of the time.

While I could also convert the frequency, the extra cost of doing so, or in obtaining VFD devices for multiple motors, is simply not very cost effective. The machine should run quite well on 460v/60hz power. To give a comparison, a purpose built step-up frequency changing transformer is over $6000.00

A transformer that will step up my shop's 208v service to 460v. looks to cost $750, with another $290 for shipping. That's pretty reasonable I think. Hopefully I can get a single circuit load center, but if not I'll need to cough up another $500 for a panel. I can wire it myself so that will save on the costs of hiring an electrician.

[Brian]

Interesting stuff, I appreciate your posting up all of this info for general consumption

I've had a lingering thought lately about doing some copper work or work in brass at some point, wondering if you are planning to dabble in that area as well as I know it's quite difficult to source interesting and high quality hinges and door pulls.

[Chris Hall]

I've had a lingering thought lately about doing some copper work or work in brass at some point, wondering if you are planning to dabble in that area as well as I know it's quite difficult to source interesting and high quality hinges and door pulls.

oh, that's totally one of the motivations for getting this machine! Sourcing just the right hardware is difficult, as you know.

Take that job last year building the two bubinga tables for my west coast client. The bronze leveler feet cost me $800 to get machined, and I totally could have tackled the job myself were it not for the lack of equipment. I would enjoy doing this sort of work. I definitely plan to exploit the capacities of this machine in terms of processing brass, bronze, and so forth, into hardware for both furniture and architectural purposes.

[Brian]

Those are gorgeous feet, I had a feeling they had some time into them, but I know exactly how you feel. I'd rather put the money toward tooling and put the time in myself if it's a possibility since it gives you a greater ability to control the result and of course repeat specialty projects start to become far more reasonable in price.

During my recent trip to the Met I spent a great deal of time admiring how awesome the hardware was on the Ming furniture, and that it was not impossible to make, but certainly seems impossible to acquire.

[Chris Hall]

Sold my Landcruiser today

It went to Tennessee and I will never see it again.

People at Fritz Ernst contacted me today. They are back from vacation, and we are moving forward!!

Got my customs broker involved today, and tomorrow I will order up a transformer. Moving along...