1100MX Collet Closer Belleville Spring Washer Stack Problems

Is it common on the Belleville Spring Washer Stack on the Collet Closer to crack and explode when the spindle is turning? I’ve had my 1100MX for two years and have had the washer stack and the collet closer bolt adjusted just like the documentation describes so that a BT30 collet will fall freely into my free hand when the Collet Release is pressed. Last week, after a collet change and the spindle turned up to speed, several of the washers exploded from the stack. On inspection, 4 of the washers had split apart and the pieces were found in the spindle enclosure and another 6 of the washers were found to have radial cracks. Replacement of all of the washers was easy, but is this common?

Not from anything I’ve heard or seen posted. I’ve heard of them losing their spring force with time but that’s it.

Our first 770M ran for more than 2 years with the same washers. We got a second 770M and it ran for a year until the the washers cracked, so we got new washers from Tormach and replaced them on both machines and now they fail like clockwork every 90 days.

Mine hasn’t exploded yet. Maybe I won’t press the button with the motor shield up anymore though. The prospect of steel discs exploding at eye level is scary.

This is not normal! Sounds like a batch of bad steel was used to fabricate the washers.

@Jeffery_Babis I can confidently say that no one here has heard of this occurring before. Wearing down and cracking, sure. But ‘exploding’? Certainly not. This has been brought up to the appropriate departments, and we will absolutely look into this.

It’s also recommended to replace the spring stack every year or so.

I thought everyone might like to see the ‘Exploded’ washers, so I have attached a photo of the 4 broken washers and one of the 6 with radial cracks.

@Jeffery_Babis cracks like that is generally what we will see develop. My guess would be there were hairline fractures present for some time.

That being said, I certainly have not heard of them ‘exploding’ out or anything. Generally you start noticing a lack of tool holding force.

Ive seenbthis in high speed stamping dies. I think the “exploding” was them losing tention and being cracked enough that centripetal force flung them apart. Could have been a bad batch that didnt get heat treated properly. It also helps to take them out and lubricate them once a year at least. Ive had the same set for about 4yrs. You can source them from MSC.

Do you know the MSC item # for the correct size?

I replaced my stack of 16 with McMaster-Carr PN# 96445K339. They are slightly thicker (2.25 vs 2.00 mm) but the uncompressed height is the same as the original (3.15mm).

Thanks, but the washer for the 770 is different, smaller, and I can’t find it anywhere else.

11.4mm ID x 30mm OD

Just wondering if this is still exploding? Mines a year old soon and I havnt lost any springs yet. I’m still afraid to do the tool changer with the cover open though.

For reference, the spring washer for the MX machines can be found here: 39689 - Disc Spring, 40mm x 20.4mm x 3.1mm

I generally wouldn’t be doing tool changes with the spindle door open, at that same time, I wouldn’t be overly concerned or expect to see the springs ‘explode’.

Please everyone, as I noted in my original post, the ‘explosion’ of the washer stack occured after a ATC tool change and during the speed-up of the spindle ( probably to 3500 RPM on High Belt). I have not circumvented the spindle shield interlock, so the shield was down and the enclosure doors were also closed. The centrifugal force of the washer stack was sufficient to cause nicks in the powder coat on the inside of the shield.

Been thinking about this a lot. First I have to say, I wish I could have seen this on slow motion as I am sure it was wild. And glad no one was hurt.

Ok so I am wondering if you have your air pressure too high. If on a regulator you might want to test the pressure at the piston. If the pressure is to high it can compress the spring washers enough to partially invert them and that could pop them pretty quick. And how many tool changes are you doing a day? I’m assuming it’s not several hundred but just thought I would ask.

Also if I were you I would get some Kevlar sail tape or something like a Kevlar sock and put it over that stack to contain the parts. They use this stuff to keep exploding jet turbine blades from piercing aircraft fuselages.

Once you rebuild it post us a picture. That way we can all speculate further.