So I was making a nice little decorative wooden doo-dad for my brother's birthday at the start of the year. Computer told me it would take 90 minutes so I decided to step out and check back every 10 minutes or so......hmmmm....not one of my best ideas!
The next time I go to the garage I am met by thick smoke which started to burn my eyes! Over to the machine I run fumbling for the estop.
Once the smoke cleared (35 minutes!) I took a look at what had happened.
Turns out the z axis coupling had come loose and the whole spindle had dropped into the work piece. The v bit I was using cut through the 15mm oak workpiece, a 10mm bit of sacrificial pine and the 25mm mdf bed But the thing that surprised me was that the spindle collet nut had also managed to "mill" through the above mentioned wood!
I tightened the grub screw on the z axis and tried to move the spindle up - this is where my new found respect for the power of the stepper motors coupled to ballscrews came from - The spindle was stuck fast. As I tried to raise the z the spindle stayed put and the whole machine flexed like a banana! Now I'm the first to admit that my machine is no heavy weight (x - 25mm unsupported | y - 20mm unsupported | z - 20mm unsupported) but I thought the steppers would have stalled before the frame tried to fold in half!
I do feel lucky though, I'm sure I was seconds from a fire starting and I am glad I at least had an estop button, can't imagine how long it would have taken to find the mouse and try and find the estop button in mach!
Thinking back I remember looking at the first cuts it was making thinking it didn't look 100%. I put it down to me not setting my z zero correctly (just started using a probe to set z) and thought I would let it run and investigate it after. Should have seen the signs!!!!
I have now placed a smoke alarm and fire extinguisher in the garage!!!!!
Last edited by cncJim; 24-01-2014 at 03:46 PM.
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Well, sorry to read the bad news Jim.
I'm in the process of getting everything together that I will need to build my new (first time) workshop at the bottom of the garden, materials mostly as I've got all the tools now. I cant help thinking how gutted I would be if it went up in smoke (timber frame, will basically be a shed). Cant help but think you've been lucky Jim, we should all start advising smoke alarms and extinguishers to new builds at least.
Take care guys, I'm glad your safe Jim.
Lucky escape ! do you think the spindle lower bearings are cooked ? I'm thinking about the grease in them for one thing.
Regarding the E/Stop, I got one of those ready assembled ones in yellow plastic box and I'm thinking about putting a length of CY cable to it, securing a strong magnet to the bottom, thus allowing it to be moved to various positions around the machine depending upon what I'm regarding as the current 'best position'.
One thing I've always had in the workshop is a fire extinguisher. You got away with this one.
It looks like from the picture that the spindle clamp is tightened right up till the faces meet. If this is so then the clamp isn't right, there should still be a bit if a gap between the faces. This allows the clamp to fully tighten on the spindle.
I'm not sure you could tell if the bearings were affected, even if you took it apart they might be sealed for life type, I don't know. If they are sealed type then the seal itself might have been affected. Of course you would find out if they started to fail.
Last edited by EddyCurrent; 24-01-2014 at 04:54 PM.
Yes get the faces of the clamp reduced a bit. As you say about 2mm would probably do the job but check it again after its done.
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I would be concerned for the spindle bearings. From your photo is looks like things got hot enough to discolor the collet? If so then I expect the bearings would have got very hot as there's not much distance between the collet and the bearings.
The bearings on my spindle do have seals, although due to being high speed bearings they rely more on the labyrinth seal. These pictures should give you an idea what to expect:
If this had happened to me I'd definitely dismantle the spindle and have a look at the bearings. It's not too difficult to disassemble the spindle - the only difficult bit is removing the nut on the collet end. You might be fine as it is, or you might find the oil/grease has burnt away and the bearings fail in a few months.
Not needed either yet but I like the "plan for the worst hope for the best" approach.
How about a smoke detector connected to a contactor to turn of power to router etc. ..Clive
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