Purple-haze
Western Thunderer
Simon, Can I make a contribution please?
regards Rog
regards Rog
simond
Western Thunderer
simond
Western Thunderer
very curious.
Brian at work is a bit of a whizzkid with the silicon devices. I'd given him the previous Woodpecker CNC controller to look at when I purchased its replacement a few weeks back. this morning I asked if I should just buy the relevant MosFETs to repair the boards, and he remarked that it might se worth improving the back emf diode too - "something quicker" (yeah, I'd never thought about that either) and then started poking around with his meter. At this point, he says, "leave it with me" and five minutes later says "it's not broken".
"eh? but... what?"
he's right too. It works perfectly. We have no idea why it should have appeared to fail and suddenly work again. I shall now try the second one again. Very odd. But at least I have a spare and can do some more milling
That'll cheer madame up no end!
Brian at work is a bit of a whizzkid with the silicon devices. I'd given him the previous Woodpecker CNC controller to look at when I purchased its replacement a few weeks back. this morning I asked if I should just buy the relevant MosFETs to repair the boards, and he remarked that it might se worth improving the back emf diode too - "something quicker" (yeah, I'd never thought about that either) and then started poking around with his meter. At this point, he says, "leave it with me" and five minutes later says "it's not broken".
"eh? but... what?"
he's right too. It works perfectly. We have no idea why it should have appeared to fail and suddenly work again. I shall now try the second one again. Very odd. But at least I have a spare and can do some more milling
That'll cheer madame up no end!
simond
Western Thunderer
so I re-installed it, and it didn’t work. 
then I found out that I am actually a muppet.
Assumption being the root of all ***k-ups, I had reset the machine after the slight oops. I knew a reset turned the motor off (M5), but had failed to note the “S0” hidden in the command line. indeed, repeated, every time I reset it…
So turning the motor on at zero speed, it obediently did precisely that.
there are days I shouldn’t be allowed anything sharp!
then I found out that I am actually a muppet.
Assumption being the root of all ***k-ups, I had reset the machine after the slight oops. I knew a reset turned the motor off (M5), but had failed to note the “S0” hidden in the command line. indeed, repeated, every time I reset it…
So turning the motor on at zero speed, it obediently did precisely that.
there are days I shouldn’t be allowed anything sharp!
John57sharp
Western Thunderer
You've no idea how relieved some (many?) of us are to hear that “it's not just me….”
Good outcome though!
John
Good outcome though!
John
Dog Star
Western Thunderer
Welcome to the back row of the class, Jordan is in charge of seating and might bribed with tiffin.
mickoo
Western Thunderer
Everyone makes $£*( ups, it's how you deal with them that countsso I re-installed it, and it didn’t work.
then I found out that I am actually a muppet.
Assumption being the root of all ***k-ups, I had reset the machine after the slight oops. I knew a reset turned the motor off (M5), but had failed to note the “S0” hidden in the command line. indeed, repeated, every time I reset it…
So turning the motor on at zero speed, it obediently did precisely that.
there are days I shouldn’t be allowed anything sharp!
Way back in the 1970s I was working as an electrical design draftsman in an engineering company. My senior manager told me once when I had got something wrong. "The man who never makes a mistake is not working, sack him. The man who make many mistakes is not trying, sack him"Everyone makes $£*( ups, it's how you deal with them that counts
I did not get the sack but personal circumstances meant I left some time after.
Regards
Allen
magmouse
Western Thunderer
And that is the problem, right there - why would the reset both turn the motor off and set its speed to zero? It's not an operator problem, it's a design problem - as Donald Norman points out (in The Design of Everyday Things and other books), bad design makes us look stupid. He cites the example of the door that we pull when it needs a push to open it. It can have a sign saying 'push' but if the handle is designed (usually for aesthetic reasons) so that it says 'pull!' then we will pull. And we will feel stupid, but actually it's the design that is stupid.
Nick (who gets very grumpy with bad design)
mickoo
Western Thunderer
In fairness, it's not as daft as one might think, it's a two step/stop safety feature.
If it left the motor speed enabled, then there is a chance that when you reset the motor it could spin up to the previous speed setting autonomously.
On the Port all our cranes and two, sometimes three stops for a fault, power off, motor control to zero, brake tripped (physical mechanical reset required), it's quite a common set up for rotating machinery.
My Sieg lathe has something similar, if you hit the crash stop then it kills the motor and speed controller, even if you reset the emergency stop you need to turn the direction switch to off, then back to the direction you want before it'll start; some more complex machines will also make you set the speed controller to zero as well and then turn it back up to the speed you want.
Regarding the door, well there's a little yarn about why push doors have pull grips and it's for safety (yes I've been on lots of safety courses, more so to do with ingress/egress from cabins and cubicles etc, yawn) when people approach a push door with a flat plate they have no idea how much friction is in the door (or the push plate is slippery), consequently they push too hard/slip, door flies open (possibly smacks someone on the other side) and they end up on their face. The grab handle is there as an assist and something to hold onto in case of such instances.
You can argue common sense should prevail, but almost all safety features are there to mitigate the lack of common sense. That's not to say bad design doesn't exist, it does in spadefuls, just that some bad design is not overly obvious a clever design.
simond
Western Thunderer
I recall a safety briefing at my previous employer, who insisted that the biggest issue was falls, trips and slips on stairs (I think they assumed we were all office desk jockeys) and that holding the handrail whilst using the stairs was essential.
Until Covid, when you weren’t allowed to hold the handrails!
On the handrail topic, at London City Airport, there are stairs down from the lounge to the departure gates. Each beats the stern warning ”Pedestrians must use the handrail”. I always wondered if anyone else used the stairs.
Until Covid, when you weren’t allowed to hold the handrails!
On the handrail topic, at London City Airport, there are stairs down from the lounge to the departure gates. Each beats the stern warning ”Pedestrians must use the handrail”. I always wondered if anyone else used the stairs.
mickoo
Western Thunderer
They're not wrong, it was the same on the Port, 90% of accidents (resulting in lost man days off work) were slips, trips and falls under 0.5 m, it's where humans feel most comfortable and least on their guard.
It also happens to be where most humans work, so the figures are perhaps more of a reflection of where the majority of a workforce are employed rather than an indication of where the most danger exists; as with all safety, you have to be a bit pragmatic sometimes.
Risk assessment is a minefield, if someone can do something stupid, then there's a high chance they will; one of the first lessons we were ever taught (when risk assessing a process or environment) was to ignore common sense, because that's exactly what most victims do. I actually enjoyed it to be fair and sadly during my time we had three deaths (none in engineering), all utterly avoidable sadly. All of them were due to what we called a three link failure, I.E three things had to fail or go wrong to accomplish the final outcome, none were first link where the victim died through his own actions.
magmouse
Western Thunderer
All of which is fair enough, but your crane has physical controls which (if well designed) indicate their state to the user. If the crane doesn’t work, the user can presumably readily check which control is preventing it doing so. From Simon’s description, his CNC unit has no such user feedback - if it did, he wouldn’t have been caught out. If turning the motor off and the speed to zero on reset was a deliberate decision in the interest of safety, then there needs to be a way to indicate to the user this non-obvious behaviour - it’s still a design issue, it seems to me.
Nick.
mickoo
Western Thunderer
Not quite, the crane indication for the driver is all healthy, it does not indicate to the driver where the fault is or how to reset, that requires an engineer (if it's a critical safety fault) who is in another part of the crane. Even non critical faults that the driver can reset still require a two step authentication restart, in our case, turn everything off, set all controls to zero, reset and restart (power on). Reset and restart are two separate buttons and on two separate panels, thereby reducing the chance of accidental restart. The latest cranes with the highest safety rating required you to physically get out of the seat or if tall enough, just reach over at arms length to reset. There is no indication to the driver other than a singular fault lamp, he just has to follow set procedure to clear and reset.
Reset will set all drives to zero, if they haven't already be tripped to zero (usually the drive will also be monitoring the critical safety loop and trip it's self to zero), it'll reset the safety chain (if the fault has cleared) and enable the crane to be powered on. Restart will then bring in the main power, the really dangerous stuff and enable all controls.
In Simons case the non-obvious behaviour is only non obvious to those who do not understand (through no fault of their own) how the system works, I'll wager in the instructions some where it'll be written that in the event of a fault the motor speed may also be set to zero. If people are not normally exposed to this type of system then it's unfair for them to know (intuitively) how to reset.
This moves it from a design issue to an education/training and information issue. I'll readily concede that if the motor speed is set to zero in a fault condition then it really should have some sort of visual indication, it doesn't have to be obvious (but it helps) but whatever it is, it should at least be documented.
Most design issues I've come across are usually due to lack of training, education, instruction or documentation. It's hard to blame designers if operators simply don't RTFM
What is interesting is how people perceive what is good or bad, difficult or easy, intuitive or stupid, that's what makes writing manuals or designing hardware/software so bloody difficult, you have to try and cater for everyone; I don't think I ever accomplished that
What ever I figured was common sense and others would find intuitive never seemed to happen, the majority got it, but a small handful didn't, not their fault, they just view things differently. I just tried to make sure everything anyone might ever need to know was in the documentation.
Anyway, I'll let Simon have his thread back now
, control systems and operation design were something I enjoyed the most, wasn't so keen on running the training course though.
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magmouse
Western Thunderer
Well, I've learned about crane safety systems this evening - who woulda thunk it. My last tuppennyworth:
Yes indeed - been there, like you.
But my central point is that good design can reduce or eliminate the need for training and information.
And now back to the scheduled programming....
Nick.
Yes indeed - been there, like you.
But my central point is that good design can reduce or eliminate the need for training and information.
And now back to the scheduled programming....
Nick.
mickoo
Western Thunderer
That I would never dispute, very hard to achieve, very satisfying when it is
simond
Western Thunderer
Look, I’m a bloke, why would anyone expect me to RTFM…
Joking aside, all power tools are supposed to reset to a safe state, so that reconnecting them to the power supply doesn’t have somebody’s hand off, and this one is no different.
That said, setting speeds and feeds to zero as well as turning them off is almost certainly sensible, even if belt and braces. The machine has no way of knowing that I did a reset and immediately tried to run the motor at the speed Id previously set, or that it was simply powered down, put away, and perhaps plugged into a different computer on a different day (perhaps by a different student?) so what might be a sensible default for me might not be a very safe way of doing things in other circumstances, even for me next week, by when I might well have forgotten what I had set up.
There is, of course, no printed manual, though there are lots of online references to UGS (the freeware interface system) and GRBL (the firmware in the machine controller), and I have no doubt it was documented in some fashion somewhere. It’s all a little bit flaky anyway, mainly written by hobbyists, for hobbyists, but of course, one tends to RTBM to find out how to do something, rather than to troubleshoot what you were certain you'd done correctly.
it would have been nice if the UGS display had an indication of the speed and feed, but the version I was using didn’t (or it was far from obvious). I have just downloaded and installed v2.1.4 and Lo!, just under the XYZ positions is Feed Rate and Spindle, along with various other G code defaults including mm units and absolute position. This version also lists the source gcode file in an editable text file format in the same window. One of those hobbyists has been busy.
As I said, a mildly frustrating, relatively inexpensive and utterly harmless way todiscover reaffirm that I’m a muppet 
Joking aside, all power tools are supposed to reset to a safe state, so that reconnecting them to the power supply doesn’t have somebody’s hand off, and this one is no different.
That said, setting speeds and feeds to zero as well as turning them off is almost certainly sensible, even if belt and braces. The machine has no way of knowing that I did a reset and immediately tried to run the motor at the speed Id previously set, or that it was simply powered down, put away, and perhaps plugged into a different computer on a different day (perhaps by a different student?) so what might be a sensible default for me might not be a very safe way of doing things in other circumstances, even for me next week, by when I might well have forgotten what I had set up.
There is, of course, no printed manual, though there are lots of online references to UGS (the freeware interface system) and GRBL (the firmware in the machine controller), and I have no doubt it was documented in some fashion somewhere. It’s all a little bit flaky anyway, mainly written by hobbyists, for hobbyists, but of course, one tends to RTBM to find out how to do something, rather than to troubleshoot what you were certain you'd done correctly.
it would have been nice if the UGS display had an indication of the speed and feed, but the version I was using didn’t (or it was far from obvious). I have just downloaded and installed v2.1.4 and Lo!, just under the XYZ positions is Feed Rate and Spindle, along with various other G code defaults including mm units and absolute position. This version also lists the source gcode file in an editable text file format in the same window. One of those hobbyists has been busy.
As I said, a mildly frustrating, relatively inexpensive and utterly harmless way to
Osgood
Western Thunderer
A Muppet Advisory:
I was out one day riding shotgun in a friend's low loader (we were no doubt up to some kind of military Scammell mischief).
He was ex REME - always had highly polished boots, and always made some derogatory comment about the state of my scuffed rigger boots (patina I called it).
We were joking about something and I called him a muppet - at which point he turned an apoplectic colour , due I guess to a massive rise in blood pressure.
"What do you just call me?"
"A muppet"
"Do you have any idea what a muppet is?"
"Er well yes, a fury puppet character"
"No it %^%^*(*&^)^ isn't - it's the oily rag you shove down a gun barrel to clean it - and don't you call me that again!"
I think we were back on speaking terms only a few miles down the road......
Design? Also runs to the finish - I spotted this in the Vitra Design Museum at the German home of the Eames chair (hello @Simon ):
(No idea if that philosophy runs to crane operators seats)
I was out one day riding shotgun in a friend's low loader (we were no doubt up to some kind of military Scammell mischief).
He was ex REME - always had highly polished boots, and always made some derogatory comment about the state of my scuffed rigger boots (patina I called it).
We were joking about something and I called him a muppet - at which point he turned an apoplectic colour , due I guess to a massive rise in blood pressure.
"What do you just call me?"
"A muppet"
"Do you have any idea what a muppet is?"
"Er well yes, a fury puppet character"
"No it %^%^*(*&^)^ isn't - it's the oily rag you shove down a gun barrel to clean it - and don't you call me that again!"
I think we were back on speaking terms only a few miles down the road......
Design? Also runs to the finish - I spotted this in the Vitra Design Museum at the German home of the Eames chair (hello @Simon ):
(No idea if that philosophy runs to crane operators seats)
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