Author Topic: CNC Crash Compilation  (Read 12758 times)

Offline philf

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CNC Crash Compilation
« on: March 15, 2013, 07:59:28 AM »
An interesting compilation of CNC blunders.

<a href="http://www.youtube.com/watch?v=xXmzT4bc7jY" target="_blank">http://www.youtube.com/watch?v=xXmzT4bc7jY</a>

Of course, I've never set feed rates in meters/sec instead of mm/min or set the safe Z height too low so that the tool cuts right through a clamp!  :(

Phil.
Phil Fern
Location: Marple, Cheshire

Offline JonIndigoman

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Re: CNC Crash Compilation
« Reply #1 on: March 15, 2013, 01:53:42 PM »
To err is human but to completely **** up you need a computer  :lol:

Offline AdeV

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Re: CNC Crash Compilation
« Reply #2 on: March 15, 2013, 01:57:44 PM »
Why is it, when things start going wrong in CNC-land, the emergency stop buttons are suddenly miles away & totally inoperative before the tool has destroyed itself & send the workpiece flying?

Fingers crossed, I've only bashed one tool with the CNC mill so far, and it was sufficiently robust (and fortunately hit a metal plate & not the table) that the machine realised something was wrong & halted before it did major damage to anything.
Cheers!
Ade.
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Offline sparky961

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Re: CNC Crash Compilation
« Reply #3 on: March 15, 2013, 02:50:48 PM »
Fingers crossed, I've only bashed one tool with the CNC mill so far, and it was sufficiently robust (and fortunately hit a metal plate & not the table) that the machine realised something was wrong & halted before it did major damage to anything.

If you aren't breaking tools, how will you ever know what you can get away with? :)

If you see something glowing red hot despite the flood coolant, hit the e-stop.  Don't ask me how I know...

Offline Swarfing

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Re: CNC Crash Compilation
« Reply #4 on: March 15, 2013, 04:30:02 PM »
What were you doing recording in my shed  :bang:
Once in hole stop digging.

Offline Stilldrillin

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Re: CNC Crash Compilation
« Reply #5 on: March 15, 2013, 06:24:22 PM »
Thanks Phil!  :thumbup:

 I still remember the slow motion action, of my hand heading towards the big red button........  :bang:


And....... Everyone cheering!

Then...... They'd all assemble on my duckboard, to have a look.........

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline fcheslop

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Re: CNC Crash Compilation
« Reply #6 on: March 16, 2013, 07:35:58 PM »
Don't worry David it used to keep me in a job :D :D and the excuses :D :D :D :D :D
History is scarcely capable of preserving the memory of anything except myths

Offline raynerd

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Re: CNC Crash Compilation
« Reply #7 on: March 16, 2013, 07:42:03 PM »
Funny, I've not been on here in weeks due to family commitments and bereavement, this is the first thread I read. This all being after coming up from my workshop (first day in weeks) after destroying 4 hours of work and 1/4" plate cz120 brass all due to CNC!! Grrrrrr  :doh: :doh:
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Offline dsquire

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Re: CNC Crash Compilation
« Reply #8 on: March 16, 2013, 11:08:31 PM »
Chris

My condolances.

Welcome back and sorry to hear that things have not been going well in the shop either. I'm wondering if maybe at times CNC stands for Crash N Crunch.  :doh: :doh:

Hopefully now that you have the practice piece the final piece will turn out flawless.  :D :D

Cheers  :beer:

Don
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'til your good is better,
and your better best

Offline raynerd

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Re: CNC Crash Compilation
« Reply #9 on: March 17, 2013, 03:59:11 AM »
Morning Don, thanks for your message. To keep on topic, here is my CNC disaster. Morning has come and I feel no less angry and upset than I did last night!!

Youtube: craynerd
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Offline philf

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Re: CNC Crash Compilation
« Reply #10 on: March 17, 2013, 04:23:46 AM »
Hi Chris,

I thought you'd been quiet! Please accept my condolences.

What went wrong?

Phil.
Phil Fern
Location: Marple, Cheshire

Rob.Wilson

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Re: CNC Crash Compilation
« Reply #11 on: March 17, 2013, 04:46:21 AM »
Hi Chris ,my condolences ,sad times .

Here is my ooooooops moment ,machine just went mental  :lol: :lol:



Rob


Offline AdeV

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Re: CNC Crash Compilation
« Reply #12 on: March 17, 2013, 10:10:11 AM »
Well, I can add my own tale of woe now.... after a happy 10+ hours of machining away, I am sufficiently confident I am not standing over the machine, so I'm the other side of the room when "Bang!" - no problem, just bust a cutter. So I go over, and sure enough the cutter's failed (not sure why, it was cutting as sweetly as you like). So I stop the machine, make a note of the program step, so i can restart in a civilised place instead of having to repeat hours of work, and for some reason I can't reset the controller to raise the spindle, it won't come out of "e-stop".

Reset machine. "DC 24v not present". Ubuggre. Machine = kauput.

I can turn everything on, the controller gets to sampling the 24v DC line & finds it dead, I can even turn the spindle brake on & off, and activate all the motor drives, but the controller of course won't send any signals. Ar­se.

The manual suggests testing the 24v regulator circuit, what it doesn't leave any hints about is what to do if it isn't being fed any juice....
Cheers!
Ade.
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Offline awemawson

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Re: CNC Crash Compilation
« Reply #13 on: March 17, 2013, 10:51:27 AM »
It's a long time since I was in an Interact cabinet, but I seem to remember that one of the two 24v supplies is just a little regulator board. Top left hand side if I remember correctly.
Andrew Mawson
East Sussex

Offline John Stevenson

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Re: CNC Crash Compilation
« Reply #14 on: March 17, 2013, 11:44:09 AM »
I had a couple of 24v RS 'brick' type supplies go down in quick succession for no apparent reason, both were S/H so that may had had something to do with it.
Swapped to a DIN rail mounted one, again S/H [ got shed loads of crap goodies ] and been good to go for a couple of years now.
John Stevenson

Offline AdeV

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Re: CNC Crash Compilation
« Reply #15 on: March 17, 2013, 11:46:18 AM »
It's a long time since I was in an Interact cabinet, but I seem to remember that one of the two 24v supplies is just a little regulator board. Top left hand side if I remember correctly.

Aye, I've found the board, I haven't had chance to probe it yet, due to limited access. If I'm lucky, it'll be the regulator board at fault, it doesn't look too difficult to repair, although getting the right regulator might be an interesting task, I can't see any writing on mine.
Cheers!
Ade.
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Offline awemawson

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Re: CNC Crash Compilation
« Reply #16 on: March 17, 2013, 12:47:56 PM »
7824 is the generic number for the 24v 1 amp three terminal regulators - widely available on ebay:

http://www.ebay.co.uk/itm/L78xx-Series-Positive-Voltage-Regulator-5V-6V-9V-10V-12V-15V-18V-24V-/130836774030?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item1e767abc8e

Cost all of £1.90 for a pack of five ! IIRC it is a very simple circuit. AC feed from the transformer to a rectifier, followed by a reservoir capacitor across the + and - of the regulator, going to the input leg of the three legged regulator.

Andrew Mawson
East Sussex

Offline DMIOM

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Re: CNC Crash Compilation
« Reply #17 on: March 17, 2013, 01:00:04 PM »
Ade,

Probably not relevant, but DC won't latch in on my TNC155 if the E-stop is active (either manual or a hard limit is tripped).

Dave

Offline PekkaNF

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Re: CNC Crash Compilation
« Reply #18 on: March 17, 2013, 02:02:54 PM »
Probably not relevant at all, but we used to shed a crapload of those 78-series regulators when we were students (like stone age....), but they had a grave drawback (least back then)...they were pretty sensitive for about 400 V voltage spikes emitted from relays or any contact within meters or even on same vehicle. LM317 used to be somewhat more robust....but we generally put a freewheeling diode over every contact and RC-pair as well + some ferrites or small toroids on every incoming supply line and "dirty" outputlines as well. Oh, and 78xx really needs those small "unnecessary" capacitors on both sides that are shown on every application sheet. Funny thing what you learn after you redo the same PC-board third time....It was a relay on auxiliary line and worked like a charm long time, but the 78xx would fail once every blue moon.

Pekka

Offline awemawson

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Re: CNC Crash Compilation
« Reply #19 on: March 17, 2013, 04:27:10 PM »
Those 'unnecessary' capacitors stop parasitic oscillations.

Andrew Mawson
East Sussex

Offline Meldonmech

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Re: CNC Crash Compilation
« Reply #20 on: March 18, 2013, 03:12:52 AM »
Hi Guys,
                  I have been thinking of buying a cnc mill/ router, but looking at these disasters, which appear to happen faster than the operators reactions, has put me right off. It seems to be quite a common occurrence, is this normally caused by a faulty program?

                                                                 Cheers David

Offline philf

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Re: CNC Crash Compilation
« Reply #21 on: March 18, 2013, 04:08:02 AM »
Hi Guys,
                  I have been thinking of buying a cnc mill/ router, but looking at these disasters, which appear to happen faster than the operators reactions, has put me right off. It seems to be quite a common occurrence, is this normally caused by a faulty program?

                                                                 Cheers David

Hi David,

Most, if not all, of my tool breakages have been down to carelessness on my part.

Not noticing feed speeds are in mm/sec rather than mm/min; setting the safe Z height too low so that it makes a fast move straight through my clamping fixture are the two that I had most problems with.

When I first set my machine up I set the Z home position so that the table moved towards the cutter. Most of the parts I was making were out of sheet and I was clamping the material to a piece of 18mm MDF which was fastened to the mill table. When I did a RefAllHome (which sets the axes to their home positions and is the first hing I do when I switch on) it would first drive the table up (so that the tool embedded itself in the MDF) before the table moved rapidly in the Y direction taking the end of the tool with it.  :doh:

After about 4 broken carbide cutters I added an intermediate Z axis (hall effect) switch so now the table drives down away from the cutter before X & Y are set.  :D

Commercial CNCs are often capable of unbelievable feed speeds and I guess no-one has reactions quick ehough to hit the E stop button.

Fingers crossed, I haven't broken a tool for quite a while!

CNC is fun - go for it!

 :beer:

Phil.
« Last Edit: March 18, 2013, 08:54:06 AM by philf »
Phil Fern
Location: Marple, Cheshire

Offline sparky961

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Re: CNC Crash Compilation
« Reply #22 on: March 18, 2013, 12:46:46 PM »
Hi Guys,
                  I have been thinking of buying a cnc mill/ router, but looking at these disasters, which appear to happen faster than the operators reactions, has put me right off. It seems to be quite a common occurrence, is this normally caused by a faulty program?

                                                                 Cheers David

Being fairly new to running an industrial CNC VMC (vertical machining centre), I can attest to the fact that when you first start you will break things.  I have run hobby CNC stuff for years now, but the commercial ones are a bit MUCH less forgiving. 

ALWAYS assume that when powered the machine can move anywhere at any time and at any speed, as far as your body parts are concerned.

In my experience with smaller machines, you will more likely scrap the part not the cutter if it's big enough to handle the force, rather than always breaking the tool.  Axes will often stall before too much damage is done.  Smaller tools, well they just snap off and the CNC continues on it's merry way. :)

I wouldn't be put off by any of this.  Some of the stuff you see in the video is due to very poor setup, others look like the program wasn't proven (run slowly without a part) before they hit start.  Most of it can be prevented by a careful operator, which as a hobbyist who doesn't have a boss saying "FASTER, FASTER" you shouldn't have a problem with.

I don't remember where I saw the quote, but my own slightly modified version has become something of a mantra...

"First you get good, then you get fast" .... and my own addition ... ", then you really mess up and are very humbled by the experience, only to start the cycle all over again"


Offline Stilldrillin

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Re: CNC Crash Compilation
« Reply #23 on: March 18, 2013, 02:14:25 PM »
During my 20yrs, as programmer/ operator of a Takisawa  machining center. No programme was ever trusted, until I had single blocked all the way through.

This included the progs, I had used many times previously.......

Probably had 8 or 10 of such mishaps, over the years. I can still remember them, in fine detail.  :palm:

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline philf

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Re: CNC Crash Compilation
« Reply #24 on: March 18, 2013, 02:39:37 PM »

Probably had 8 or 10 of such mishaps, over the years. I can still remember them, in fine detail.  :palm:


David,

Didn't you think to video any of them for us?

Phil.
Phil Fern
Location: Marple, Cheshire