Thread: Deckel FP1 spindle motor problem

After having it for many years, I am finally getting a chance to actually use my 1988 FP1--yay! A few months back when I was initially powering it up and using it to mill some hex flats on a chunk of mild steel, I heard the sound begin to change and saw the spindle slow down to the point of stopping. I was startled and probably hit the stop button before it stopped completely. I noticed a hot smell coming from the spindle motor. I took the shroud off the back of the motor and found oily muck, probably an accumulation from years of use, but not likely enough to block air flow so I cleaned that up. It seemed like the smell was strongest in the back of the motor. After letting it cool down, I took it out of gear (speed dial set to 0) and started it up. It ran for a few minutes and did the same thing, but the next day it seemed to be behaving itself and would run for the time that I needed to get the flats milled. I have used it occasionally since then without seeing the problem again.

Yesterday I was squaring up a block of S7, and after maybe 30-40 minutes of use the spindle again began to slow and I noticed the hot smell from the motor. The motor's cooling fins were only warm to the touch. After letting it cool for maybe 10 minutes, I took it out of gear and started it again. After a few minutes on low speed, it started slowing down again. When it happens, it seems to slow down within maybe 10 seconds. When I hit the stop button, the spindle stops immediately (about a second).

My guess is that the spindle motor brake is getting hot and is the source of the hot smell. I would assume that the brake is normally engaged only after power is cut to the motor. Knowing that the motor brake is engaged when the power is off, I would assume that if the brake's coil were failing, the brake could engage while the motor was still powered--likely causing the symptoms I've observed. If I read the schematics correctly, it looks like the brake is controlled by the same contactors that control the motor, so maybe it could be one of the contactors?? My guess is I am seeing the motor brake failing, is this common or reasonable?

My other guess is that the motor is bogging down, but this doesn't make much sense to me as I do not believe that I have been putting it under much stress. My cuts in the S7 were 1mm with a .750 4-flute carbide EM at about 192rpm and a feed rate of 40 (is this mm/min?).

This is the 2 speed, 1.6/2.0KW AEG motor. I have not yet started to look, but I wonder if the brake is replaceable.

As for power, it is 3-phase 240 (via Phase-perfect) to Deckel 220-380 transformer. Actual voltage supplied to machine (using the -5% transformer taps) is 394 (avg of three legs); legs are within 1% of each other.

Am I on the right track with my diagnosis so far & any other hints? Thanks!

--Larry

There is a turn switch upper left of control panel to turn the motor brake off...what happens when you do that...can you turn the spindle freely by hand ? And even if you can, perhaps leave brake release switch on for an hour and come back to see if you can still turn it freely ?

Never had that particular problem but did have an Active Deckel once where the brake would not release quite as quickly as it should when the spindle motor was first turned on. Been so long ago can't remember now how I fixed it...maybe a timer adjust in the electrical cabinet...

Originally Posted by Milacron

There is a turn switch upper left of control panel to turn the motor brake off...what happens when you do that...can you turn the spindle freely by hand ? And even if you can, perhaps leave brake release switch on for an hour and come back to see if you can still turn it freely ?

Never had that particular problem but did have an Active Deckel once where the brake would not release quite as quickly as it should when the spindle motor was first turned on. Been so long ago can't remember now how I fixed it...maybe a timer adjust in the electrical cabinet...

As dumb as this sounds, after reading the manual and operating the machine, I am not completely clear on the purpose of the motor brake switch on the upper left of the pannel. That said, I leave the motor brake switch in the horizontal or right position, which seems to indicate that the brake is released. If I put the switch in the vertical or left position, the spindle motor will not start (seems like it is locked out), and if I briefly put the switch in the vertical position while the spindle is running, it does not seem to have any effect. With the brake switch in the released position I can turn the spindle freely by hand--easier in low speed ranges than high of course.

To be clear, this is happening after the spindle has been on for some time, does not seem to be any issue at start time.

On edit, after reading what I just wrote, I'll now assume that the purpose of the motor brake switch is to lock the spindle for tooling changes. Am open to a dope slap if this is still not correct.

--Larry

I was thinking with switch clockwise the brake power is off, which means the brake is braking (via springs) But it must be in that position to start the motor- when you press spindle on, it not only activates the spindle motor contactor but also activates the brake release contactor. That way, when you turn the motor off, brake contactor also goes off and motor automatically brakes.

To release brake when motor not running, turn switch counterclockwise...purpose is mostly to assist in engaging gears as you change spindle speeds.

Okay thanks Don, your explanation helps to clarify the function of that switch, and I observe the behavior you describe: with the spindle off, the motor brake switch in the vertical or counter-clockwise position, the brake is released. Doesn't seem to make much difference in gear selection though as this is smooth and easy with the switch in either position.

Will be interested to hear thoughts about my original question. After some initial searching, these AEG motors don't appear to be very common & I haven't opened it up yet to try to identify the brake they used. Motor nameplate ID is AEG Typ AMBX 90 LY 4/2.

--Larry

Perhaps the rectifier for the DC brake is not working properly
Or perhaps the airgap of the brake is too small
If you engage /disengage the brake with the motor off you should hear a loud click


Peter from holland

Are you running this machine on a phase converter? Sounds to me like the motor might be single phasing, or perhaps one or more legs are way off in voltage. My suggestion would be to check the voltage at the motor terminals with the machine running.

Alan

Some additional information. Did as Don suggested and with the spindle off, set the motor brake to the released position. After about 10 minutes I noticed a faint hot smell, which upon sticking my nose to the back of the motor seemed to be coming from the same location and smell similar to the hot smell I noticed when the spindle began to slow down yesterday. I pulled the shroud off and put a temperature probe on the body of the brake and after 30 minutes noted that the temperature was rising at the rate of about 1F per minute. So without the motor running the heat and smell at least is isolated to the motor brake and not the motor.

Peter, I do hear the click from the brake as I turn the motor brake switch, so I know that much is working. I do not know anything about adjusting the brake however. I can look for more information about that, thanks for the mention of the air gap.

Alan, it is running off a digital phase converter (10HP Phase perfect). From earlier measurements, the incoming legs are balanced within 1% of each other, and I just did a quick check with the spindle running, the legs at the motor also appear to be balanced. I think I can rule out the phase converter as the source of troubles.

Brake identification is: Lenze 14.448.10.1.0 190V So that is something additional for me to look up.

--Larry

Originally Posted by peterve

Perhaps the rectifier for the DC brake is not working properly

Just checked the rectifier: 234VAC in from control, 210VDC out to brake. After a 20 min test with the brake released the DC voltage had dropped to 208 and the AC was down proportionately. I think this is consistent with the coil drawing more current, and as before I notice the brake has heated up. I don't think the rectifier is the problem.

--Larry

Originally Posted by Larry Fahnoe

Brake identification is: Lenze 14.448.10.1.0 190V So that is something additional for me to look up.

I suspect you've figured this out already, but Lenze does have USA representation Lenze Americas Clutches & Brakes I had brake troubles on my Schaublin 135 lathe years ago (different type of trouble) and it turned out to be a Swiss motor but with a USA made brake...even on a 1970's brake I got parts, no problem.

Can't you somehow simply disable the brake for a test? Remove the springs or place a shim between the brake shoes so they can't clamp down for example. Just long enough to test the theory that the brake is the source of the problem.

Originally Posted by Larry Fahnoe

Some additional information. Did as Don suggested and with the spindle off, set the motor brake to the released position. After about 10 minutes I noticed a faint hot smell, which upon sticking my nose to the back of the motor seemed to be coming from the same location and smell similar to the hot smell I noticed when the spindle began to slow down yesterday. I pulled the shroud off and put a temperature probe on the body of the brake and after 30 minutes noted that the temperature was rising at the rate of about 1F per minute. So without the motor running the heat and smell at least is isolated to the motor brake and not the motor.


--Larry

Those brakes are they designed to operate without cooling from the fan for so long ??

I second the idea of running the machine with the brake springs loosend to determen if the problem is the motor or the brake


peter from Holland

I have been looking for any manual for the 14.448 brake assy, but have only been able to find manuals for the BFK458 series which replaced the 14.448 series. It would seem that Lenze is no longer making the spring operated brakes as references are now all for Intorq. Intorq's US e-mail address is not working, so have sent a note to Germany (home office). Have also sent a note off to Midwest Industrial Sales as their web site suggests they have Lenze 14.448 / BFK458 experience.

The AEG motor has a separate plate on it which reads BREMSE 220v / 13NM. The BFK458-10 is listed at 16NM with a rotor size of 95mm. Rotor on the 14.448 is about 90mm, so at least a close relative. The BFK manual calls for an air gap of .2mm while mine is showing a gap of about .41mm. There is also some swarf around & maybe in the air gap which I imagine may cause issues. Looks like the gap should be reduced. Manuals also talk about rotor thickness and other wear points.

I have not attempted to take anything apart or shim the brake because I'm being cautious, not knowing anything about these brakes. I'll see if my inquiries produce the proper manual, and in the meantime will study the BFK458 manuals.

Lenze PUB426 -- BFK458

Intorq BFK458

I may have some more time on it this afternoon, but if not, it is going to be another week before I can work on this.

--Larry

So I took the brake assy entirely off the motor and ran the spindle for about 30 minutes on several speeds, both high and low motor speed ranges. The spindle ran without issue. While running I carefully checked the balance of the voltage at the motor terminals and they were within 1% of each other.

The brake rotor diameter is 94.7 mm which matches the BFK458-10 as does its coil resistance of 1295, but the rotor thickness is 11.9 mm vs. the BFK458-10 which is 9.0 (new) through 7.5 (min), so clearly some differences between the 14.448 and BFK458. Would be nice to know what the allowable thickness range is as well as the air gap for the 14.448.

Next time I have a chance to work on it, I'll clean it up and put it back on and see how it behaves.

--Larry

So, to clarify, you are now 90 percent sure when motor previously bogged down during milling it was due to motor brake drag, yes ? And brake drag was most likely due to overheating brake coil that weakened the magnetic push or pull that keeps the spring from activating the brake, right ?

Originally Posted by Milacron

So, to clarify, you are now 90 percent sure when motor previously bogged down during milling it was due to motor brake drag, yes ? And brake drag was most likely due to overheating brake coil that weakened the magnetic push or pull that keeps the spring from activating the brake, right ?

Yes 90% sure that it was motor brake drag that caused the motor to slow to a stop, both when milling *and* with speed dial set to 0.

I think the brake coil issue is probably caused by the air gap being too big & maybe swarf. Peter called out the air gap earlier, but I did not know what to adjust it to. Overnight I got a reply from Intorq with the manual for the 14.448 series. The representative (and manual) said it should be adjusted to .2mm. The rotor thickness is still within spec--12mm (new) to 7.5mm (min). I will adjust the air gap, clean out any swarf, reassemble & keep my fingers crossed. Won't be able to do that until next week though...

--Larry

Following up on my issue with the spindle motor brake. I adjusted the air gap to the 0.2mm called for and then ran the spindle on low speed. The brake began dragging and heating within a couple of minutes, so clearly I made it worse by reducing the gap.

I took the brake apart again and carefully measured the flatness of the armature plate (which the coil attracts to disengage the brake). I found that the armature plate was dished (a shallow cone). The center portion was on average, about .010" (sorry to mix measuring systems!) lower than the outer portion; the low portion was toward the coil. Initially I had assumed that the armature plate was flat and had taken my air gap measurements at the outside only so they were off by .010". I also noticed that both the armature and friction plates (other side of the rotor) were scored by the rotor. The scoring looked to be at least .001", possibly .002" and the manual suggests replacement of the plates if there is heavy scoring.

I reassembled and carefully set the air gap to 0.2mm, this time measuring the gap on the inside next to the rotor. I ran the spindle motor on low speed for 30 minutes, taking a speed measurement every 30 seconds, then I ran the same test on high speed. After an hour of running the spindle did not slow down, the brake didn't heat up and it still engaged to rapidly stop the spindle. So, at least for now, I think I have it adjusted properly.

If it acts up again, I think replacement is probably in order. The current replacement brake (Intorq BFK458-10E) will cost about $240 and the rotor by itself is about $90. I did not ask for pricing on the armature and friction plates, but I suspect it would be best just to replace the entire brake.

As stated above, I had no previous experience with something like this, so it has been an interesting learning process.

--Larry

I am glad for you all worked out for the best
Remember the brake force mentioned being 16 and 13Nm is generated by the springs
So you can use the springs of the 13Nm and put them on the 16Nm brake
For most brakes you can buy different springs (with different colors sometimes) to set a lower brakeforce
Also that air gap is not that critical Only to small you have a chance of draging Too big, the magnet will not get the brake disengaged
But I have seen brakes with a airgap 100% more as discribed and working perfectly
Too small is the danger

Peter from Holland