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View Full Version : How I almost set fire to my garage...



cncJim
24-01-2014, 04:45 PM
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!

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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!!!! :nightmare:

I have now placed a smoke alarm and fire extinguisher in the garage!!!!!

Lee Roberts
24-01-2014, 05:25 PM
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.

.Me

EddyCurrent
24-01-2014, 05:30 PM
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'.

Web Goblin
24-01-2014, 05:34 PM
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.

cncJim
24-01-2014, 05:48 PM
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.

.Me
Thanks - Even worse, my garage is part of the house! I wonder what the insurance vultures would have made of it if it all went up? :culpability:


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'.

Good thought, must admit I don't know. I did fire up the spindle (no pun intended!) after and it sounded fine, well, sounded as it did before at least (only tried one speed though). Would there be any tell tail sign to look out for?


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.

Good spot - Your right I don't think there is a gap at all on either clamp. I haden't really thought about that. I guess the easiest thing would be take 1 or 2mm off the clamp?

EddyCurrent
24-01-2014, 05:53 PM
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.

Web Goblin
24-01-2014, 05:57 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.

Jonathan
24-01-2014, 06:43 PM
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:

11359113601136111362

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.

FatFreddie
24-01-2014, 07:43 PM
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'.

I have a bathroom isolation switch pull cord running the length of the back wall which will shut off all power to the garage and an RCD box just for the garage by the door next to the fire extinguisher.

Not needed either yet but I like the "plan for the worst hope for the best" approach.

Clive S
24-01-2014, 07:56 PM
How about a smoke detector connected to a contactor to turn of power to router etc. ..Clive

GEOFFREY
24-01-2014, 07:57 PM
Not wanting to teach my grandmother to suck eggs, - but you should Never leave a router cutting wood unattended. If the spindle manages to pick up on a piece wood and rotates with that piece on the cutter, when making the next Z down move can cause a fire in no time due to the friction of the rotating wood rubbing on the job. Matters can be even worse with a vacuum bed as the vacuum can cause the sacrificial board to smoulder, and perhaps burst into flames hours later when the machine has been abandoned for the night. I think you have indeed had a lucky escape!!!G.

cncJim
24-01-2014, 09:47 PM
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:

11359113601136111362

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.

Thanks Jonathan, I am in two minds about opening it up. Part of me wants to open it up and check it out but then I think stuff it, keep running it until I have problems, and deal with the bearings then.?

Jonathan
24-01-2014, 10:41 PM
Thanks Jonathan, I am in two minds about opening it up. Part of me wants to open it up and check it out but then I think stuff it, keep running it until I have problems, and deal with the bearings then.?

If you leave the bearings and the grease/oil is no longer present they're not going to last very long, then you'll need new bearings - i.e 7005 matched pair for about 50-100. Compare that to a few 's on the right lubricant. However you might find that there's nothing wrong...

Just looked at the photos again, and it looks like the spindle itself has blackened? Is that just soot? I hope it's not got hot enough to anneal the collet taper, as that would clearly be a big problem.

cncJim
24-01-2014, 10:54 PM
If you leave the bearings and the grease/oil is no longer present they're not going to last very long, then you'll need new bearings - i.e 7005 matched pair for about 50-100. Compare that to a few 's on the right lubricant. However you might find that there's nothing wrong...

Just looked at the photos again, and it looks like the spindle itself has blackened? Is that just soot? I hope it's not got hot enough to anneal the collet taper, as that would clearly be a big problem.

I didn't realise you meant I could potentially grease/oil them up again, I thought I would be opening it up to see if the bearing needed replacing or not. I also didn't realise new bearings would cost so much!

On reflection I think your right and it's worth a look.

You mention it getting hot enough to anneal the collet taper, forgive my ignorance but why would this be an issue?

Thanks.

Jonathan
24-01-2014, 11:01 PM
You mention it getting hot enough to anneal the collet taper, forgive my ignorance but why would this be an issue?

The spindle shaft is machined from a grade of steel which can subsequently be hardened and ground. This is necessary to ensure that the wear caused by changing the tool/collet doesn't wear the taper out (much), which would lead to high run-out. If yours has been heated above a certain temperature (which depends on the grade of steel), it will be softened and will wear out much more quickly. The temperature range is quite wide though, and we've not really got much idea how hot it got, although the colour can be an indication of that. Either way it's hard to tell...

JAZZCNC
24-01-2014, 11:02 PM
Jim I'd strip it just to be safe better spending 60mins and 1 worth of grease than 2 weeks waiting and 150 for new spindle or even 80 on bearings.
Like Jon says there's nothing to it other than plucking up the balls to do it.!!

Wouldn't worry to much about the annealing has while it could have I doubt it did because it didn't fire up and the amount of heat required to anneal would have set the wood on fire.!!

Jonathan
24-01-2014, 11:13 PM
Wouldn't worry to much about the annealing has while it could have I doubt it did because it didn't fire up and the amount of heat required to anneal would have set the wood on fire.!!

Yeah, to be fair I think you're right. According to wikipedia(!) the annealing temperature for steel is between 260C and 760C, depending on the grade, so if you compare that to the autoignition temperature for oak, which is around 250C applied for 5 mins...it's probably fine.

JAZZCNC
24-01-2014, 11:16 PM
Yeah, to be fair I think you're right.

It has been known from time to time.!. .:stupid:

JAZZCNC
25-01-2014, 12:00 AM
Back to the Potential fire and E-stop then I've seen Larger machines use a Rope E-stop with rope that runs around the machine that can be pulled from anywhere on the machine and activate the E-stop.!!

Oh by the way I'd already seen these pics fews weeks ago and asked Jim if he'd please post because it's important to show just how powerful and potentially dangerous even small machines can be.
I see it often people saying " Not botherd about E-stop because the steppers will stall or spindle will stall " or " I'll just switch it off at the wall" but they don't realise the full power even medium torque steppers can have when attached to ballscrews or how like a startled rabbit your froze on the spot for what seems like minutes but is nano seconds and by the time your brains recovered from the shock and told your arm to do something it's all just too late.!!
It's not until you actualy have some thing like this happen or see stationery 12mm cutter punch a hole thru 30mm of bed like it was punching butter do you stand back and say "OH SHITE".!!

So thanks for sharing Jim and Boy's he deserves some Thank's so get clicking. . :thumsup:

cncJim
25-01-2014, 10:16 AM
I have a bathroom isolation switch pull cord running the length of the back wall which will shut off all power to the garage and an RCD box just for the garage by the door next to the fire extinguisher.

Not needed either yet but I like the "plan for the worst hope for the best" approach.

I am in the process of turning the garage into a "proper workshop" with a mill and lathe and top of my list is to sort the electrics out. I like the idea of an isolator by the door, piece of mind knowing all power is off when I shut up for the night.


How about a smoke detector connected to a contactor to turn of power to router etc. ..Clive

Well I have a stand alone smoke detector in there now. The house alarm box is close by so I thought I might hook the smoke detector into one of the alert inputs. That way if there is any fire issue in the garage, I would know about it all over the house. I already have a raspberry pi hanging of the house alarm ready to send me an email if the alarm goes off!

cncJim
26-01-2014, 09:16 PM
Back to the Potential fire and E-stop then I've seen Larger machines use a Rope E-stop with rope that runs around the machine that can be pulled from anywhere on the machine and activate the E-stop.!!

Oh by the way I'd already seen these pics fews weeks ago and asked Jim if he'd please post because it's important to show just how powerful and potentially dangerous even small machines can be.
I see it often people saying " Not botherd about E-stop because the steppers will stall or spindle will stall " or " I'll just switch it off at the wall" but they don't realise the full power even medium torque steppers can have when attached to ballscrews or how like a startled rabbit your froze on the spot for what seems like minutes but is nano seconds and by the time your brains recovered from the shock and told your arm to do something it's all just too late.!!
It's not until you actualy have some thing like this happen or see stationery 12mm cutter punch a hole thru 30mm of bed like it was punching butter do you stand back and say "OH SHITE".!!

So thanks for sharing Jim and Boy's he deserves some Thank's so get clicking. . :thumsup:

Thanks jazz, I was (am!) amazed how powerful my steppers/ballscrews are. I tried putting all my weight on my machine and couldn't see much movement at all so seeing the machine bend as much as it did was a big surprise!

EddyCurrent
26-01-2014, 09:58 PM
Back to the Potential fire and E-stop then I've seen Larger machines use a Rope E-stop with rope that runs around the machine that can be pulled from anywhere on the machine and activate the E-stop.!!

I've install many a mile of trip wire on conveyor belt systems, it used to make great washing lines for my Mother too.

cncJim
07-02-2014, 10:42 AM
So I have finally got round to taking my spindle apart to check the bearings and I am a bit stuck...

All has come apart fine except for the black part that connect to the main silver body. I have removed the screws but it will not budge :confusion:

Any ideas?
(I will try and post some pics tonight)

Jim

Jonathan
07-02-2014, 11:07 AM
All has come apart fine except for the black part that connect to the main silver body. I have removed the screws but it will not budge :confusion:

That's the bit the water hoses and connector go into? If so then it will come off after removing the screws, however they can just be tight. If there's any gap between the black part and the water jacket you may be able to carefully tap a flat screwdriver in and pry it off. If that doesn't work you'll have to try something more imaginative, possibly involving a hammer...
Watch out for the O-rings beneath the coolant hose barbs - you don't want to loose them.

cncJim
07-02-2014, 11:37 AM
That's the bit the water hoses and connector go into? If so then it will come off after removing the screws, however they can just be tight. If there's any gap between the black part and the water jacket you may be able to carefully tap a flat screwdriver in and pry it off. If that doesn't work you'll have to try something more imaginative, possibly involving a hammer...
Watch out for the O-rings beneath the coolant hose barbs - you don't want to loose them.

Sorry Jonathan, its the other end (tool end) - connector end came off fine (I lost the o rings.....twice!), and removed the large bolt with the reversed thread but the black part on the tool side wont move....:dispirited:

Jonathan
07-02-2014, 11:47 AM
That's OK - you only have to remove the black part nearest the tool. The other one can stay. If you undo the nut on the tool end, which is a normal right hand thread, then you should be able to see the bearings and pull the shaft out.

11536

cncJim
07-02-2014, 11:51 AM
ahh ok - I will give that a try tonight, cheers!