SawStop Braking Mechanism

[Sideways]

What thickness is that wire, it has to be strong enough to resist the spring and so would need a fair pulse of current to guarantee to melt in a very short time frame.

0.25mm near enough
That translates to 30 AWG, but you can't use comparisons with fuse wire here. Someone has done the experiments and figured out how much current is needed to melt it very quickly and the capacitors are there to deliver that.
Assuming a stainless teel wire, tensile strength at the yield point could be as much as maybe 2000N per square mm so upto 9kg of force.
You'd want to be using the wire well below the yield point so it's clearly part of the trigger mechanism, but I guess it won't have the full force of that big spring bearing directly on that tiny strand.

 

[recipio]

I can't and don't speak for Sawstop. I'd never even seen one a week ago.
But the saw is being sold into the UK and continental europe so it has to conform to our regulations.
The MD said that something like 400 modifications were made to the USA version of the saw for europe.

The blade photo shows that the saw at the demo had a 30mm arbor. I'm pretty sure but could be wrong, that the arbor on the saw I watched wasn't long enough to take any sort of dado stack.

Thanks. I'm actually a fan of American style saws and have a DeWalt 746. I'd buy the 5/8" arbour saw if it were made available as it offers a mid range saw capable of ripping down 8 x4 sheets. I think the Yanks have a switch off facility in case they need to fit a dado stack but correct me if I'm wrong. I can see employers buying the Sawstop if they have a number of employees using it - the peace of mind may be worth the cost of replacement cartridges. ?

 

[sploo]

Great write up on the cartridge, and very interesting.

I'm slightly surprised at the use of that ST Micro chip though, as I would have thought the logic it would be running would be pretty simple (i.e. IF armed AND capacitance detected THEN fire); but maybe there's more to it.

 

[Inspector]

Thanks. I'm actually a fan of American style saws and have a DeWalt 746. I'd buy the 5/8" arbour saw if it were made available as it offers a mid range saw capable of ripping down 8 x4 sheets. I think the Yanks have a switch off facility in case they need to fit a dado stack but correct me if I'm wrong. I can see employers buying the Sawstop if they have a number of employees using it - the peace of mind may be worth the cost of replacement cartridges. ?

To use a dado blade (8") they have a different cartridge. It is wider to grab the entire stack of blades and a different size for the 8" rather than 10" blades.

Many commercial shops use them as it is one more layer of protection for their employees. Fewer hospital visits mean lower WCB (Workmans Compensation) and insurance premiums.

Out local high school got rid of all their table saws (Wadkin-Bursgreen, General and Rockwell Unisaws) and replaced them with SawStops. Even though all students have the first month of classes on safety it was deemed worth the extra safety.

Pete

 

[Eshmiel]

The question I always ask is why do the Americans have such a track record for saw injuries, what do they do differently or is it a behavioral thing, maybe it is just because of the vast number of Americans using saws and the percentage of incidents is not that much different to europe.

Hers's the most recent survey of US table saw injuries I can find:

https://www.cpsc.gov/s3fs-public/statsaws.pdf

The figures are rather damning.

Two main factors seem to be in play: a macho attitude that rejects safety devices as somehow a nanny thing not for real woodworkers; the unisaw design which has for decades eschewed riving knife, effective guards, a blade brake and many of the other safety features long built in to European table saws.

It does seem to be a behavioural/cultural issue. I can't find the report now but I recall reading one that looked at various kinds of "accidents" across different nations. On many fronts, with various potentially dangerous machinery, the USA was pro rata a highly dangerous place to work with such things compared to other first world nations and even some rather less developed nations. Their traffic "accident" rate was reported as poor compared to many other nations too.

Sawstop is, from one perspective, a highly necessary development for the US, since a lot of users refuse to adopt safe operating procedures recommended by the likes of HSE as "not convenient". Sawstop is the unavoidable nanny in their tablesaw that stops them self-harming.

I seem to recall that riving knives are now mandated by the US government on new table saws sold in the US (but not on the millions of old/extant ones). Another necessary nanny. Will some remove them on principle, to regain their freedom to enjoy a nice kickback from a plank?

 

[Sideways]

I've inserted the video clip of the demo into post #8 please scroll back and take a look.

 

[Spectric]

As you see, Michael was pushing the timber and the "finger" into the blade at a realistic rate. He wasn't holding back in any way.

Did anyone see that program where Guy Martin was in a factory that makes bullet proof vest, the guy was so confident in the product that with Guy wearing one of the vest he shot him, so why the sausage ?

 

[Jacob]

Neither of those examples stack up.
I wouldn't drive a car without a seat belt or airbag.
I wouldn't climb with or without a rope, I ain't 20 years old dude!

Plus you snipped my post so it makes no sense, tsk tsk



See how that works?

The way I see it, the SawStop tech/mech is an additional level of safety, in addition to the usual blahblahblah discussed already, it's designed for the home user/small workshop, NOT industrial use. IIRC @Inspector said he's had one for the last 20 years? and is happy with it, that will do nicely as a starting point.

Airbag comparisons don't really work.
Drivers have to have lessons and a fairly stringent test before being even allowed out unaccompanied. Some may fail, others may get banned. Also the consequences of collisions are potentially lethal, also to other drivers and their passengers if other vehicles involved
Saw stop devices are equivalent to air bags for people who don't even know how to drive, or are self taught but badly and only risking their own fingers, not their own or other peoples lives. The danger is vanishingly small if just a few sensible precautions taken.

 

[Sideways]

Did anyone see that program where Guy Martin was in a factory that makes bullet proof vest, the guy was so confident in the product that with Guy wearing one of the vest he shot him, so why the sausage ?

That wasn't in the UK.
Imagine trying to defend yourself in court if something had gone wrong !

And, we talk about crazy American youtube videos. Imagine what we'd be saying if the internet was full of video clips of SawStop reps, UK or USA, doing these demos with their own fingers.
It would also be an invitation to the idiots to post ever more extreme copycats. Who's going to be the first to stick their wiener in a sawstop guys ?

!!!

 

[Sideways]

The danger is vanishingly small if just a few sensible precautions taken.

Quite right.
But what about when we fail to take those precautions.
We're distracted because we go into the workshop after an argument with the wife / kid / partner / parent / neighbour.
After reading an unwelcome letter from the NHS, the bank, the solicitor.
We're hustling to finish because we've been called in for lunch, the kids need to be picked up from school or whatever, you need to get out and catch the shop or trade counter before it shuts, otherwise you lose hours rhe next day.
You're just lazy and couldn't be bothered to sweep the offcuts from underfoot, trip and fall forward. It's a site saw not a full industrial. The riving knife bends, the crown guard doesn't protect, fingers go in...

It's not a vanishingly small risk in the real world because we don't always take all those sensible precautions.

 

[Jacob]

Quite right.
But what about when we fail to take those precautions.

Spectric said it earlier https://www.ukworkshop.co.uk/threads/sawstop-braking-mechanism.151621/#post-1800011
PUWER
I'd add: to make HSE rules more up to date and stringent, and in the public interest to over-ride any patent or copyrights on the gadget, if better alternatives are not found.
The threat of these would soon sharpen peoples minds on the need for Saw stop

 

[Spectric]

Looking at the pictures it shows the actuator and control unit, the actuator side is fairly straightforward but the sensor side takes more thinking. So apart from that module with the brake is there another module, component or sensor for the detection aspect ?

The sensor needs to react to human flesh, the blade is spining and at ground potential like the table saw itself so we only have a few options here, resistive, capacitive or maybe some form of inductive modulation like an ABS sensor but how does it differentiate between slightly damp wood and flesh, that is the clever bit and going by the fact there is plenty of processing power I tend to think it is some algorithm that interprets the data from whatever the input is taken. How it actually senses is another question.

But what about when we fail to take those precautions.

That is where I struggle to comprehend behavior, yes accidents can happen but it is the mindset that gives me a roadblock. If your tablesaw was a lion in a cage you would not stick your hands in the cage, so why stick them into a sawblade. When I look at my tablesaw I see a nasty beast with a bad attitude that likes the taste of human flesh but I value my flesh more so it is not getting it, end of.

I suppose it all comes down to the human psyche otherwise we would not have the Darwin awards and the answer is that we are all different so see things differently and more importantly perceive danger and hazzards differently. This is clearly demonstrated when you see CCTV footage taken at level crossings where people ignore the barriers and walk across with there dog oblivious to the mess a train will cause.

 

[deema]

Of all the professional wood workers I’ve met, more have digits missing than those that can still count to ten! I’ve drunk tea with each and listened to how they can no longer counts to ten. Most have been time served with their C&G certificates. In every case, it was tiredness, end of day, just a two minute job, distracted that led to a bad day!

 

[Katomi woodsmith]

Having read the posts,
If this could be retro fitted to any saw, if would be brill maybe in time it could
Having read sideways post. Yes hell yes that is so true add to the list
Dad mum says…….as the nipper is tugging your are to get your attention cos you are using ear protection
I make it VERY clear Thais anyone waits until I have stopped the tool. I place my self so that I can see anyone approaching
Back to the theme, if that device could be retro fitted to any saw I would have one. Adding another layer of protection