stop a circular saw

[Fulvio Romano]

Ever seen something like that?http://www.youtube.com/watch?v=omd3agp5hv0

sawstop saws are equipped with a safety system to stop the blade within 5 milliseconds of detecting contact with skin. sawstop saws detect contact with skin. the blade carries a small electrical signal, which the safety system continually monitors.
when skin contacts the blade, the signal changes because the human body is conductive.
the change to the signal activates the safety system.
a heavy-duty aluminum brake stops the blade. the blade stops within milliseconds of detecting contact, quicker than a car airbag deploys.

during this time three things happen:

1.an aluminum brake springs into the spinning blade, to stop the blade.
2.the blades angular momentum drives the blade beneath the table, removing the risk of subsequent contact.
3.power to the motor is shut off.

resetting the saw is easy. it takes about five minutes to replace the $69 single-use brake cartridge and blade.
sawstop® table saws are the most advanced saws in the world, setting the standard for table saw safety.
sawstop saws are equipped with a safety system that detects when someone accidentally contacts the spinning saw blade, and then stops the blade in milliseconds. in most cases, such an accident would result in just a nick on a sawstop saw, instead of the devastating injury which would likely occur on an ordinary table saw.

the sawstop safety system includes an electronic detection system that detects when a person contacts the blade. the system induces an electrical signal onto the blade and then monitors that signal for changes. the human body has a relatively large inherent electrical capacitance and conductivity, which cause the signal to drop when a person contacts the blade. wood has a relatively small inherent capacitance and conductivity and does not cause the signal to drop.

this drawing shows the changes in the electrical signal when a finger touched the teeth of a spinning saw blade during an actual test.




the line represents the electrical signal, which dropped quickly when the blade touched the finger. the dips in the signal line illustrate the changes in the electrical signal that were detected as two successive teeth touched the finger. when the detection system sees dips like these, it knows a person has touched the blade.

in order to stop the saw, a fast-acting brake stops the blade when contact is detected. the brake includes a heavy-duty spring to push a block of aluminum, called a brake pawl, into the teeth of the blade to stop the blade from spinning. the spring is held in compression by a fuse wire until contact is detected. when contact is detected, the system sends a surge of electricity through the fuse wire to burn the wire and release the spring. the spring pushes the brake pawl into the teeth of the spinning blade, and the teeth cut into the aluminum and bind, thereby stopping the blade. all this happens in about 35 milliseconds, or 1/200th of a second. at the same time, the angular momentum of the blade causes the blade to retract below the table and the power to the motor is shut off.

the brake mechanism is shown in the drawing to the right. the arrow shows how the aluminum brake pawl pivots into the teeth of the blade. the brake pawl is part of a replaceable cartridge that includes the spring, fuse wire and electronics necessary to burn the fuse wire. an optional dado cartridge provides the same protection for dado cuts.




the standard and dado brake cartridges are single-use components that must be changed if the brake is ever activated. changing a brake cartridge is fast and easy, no more complicated than changing the blade.

 

[Mario SJPD]

Awesome! !

 

[Er Presidente]

Beautiful! I think you use a philosophy similar to capacitive touchpads, right?

 

[gerod]

it would be to understand the reliability of the security system but I would say it is a good story.
really impressive and I think the inventor will make the money.
I don't know how it works, but it looks effective.
The only doubt I have left is the possible break of the blade on the alllumination brake. If it breaks, maybe it throws pieces on you.
Thank you very much for reporting. Hi.

 

[sampom]

...the only doubt I have left is the possible break of the blade on the alllumine brake. If it breaks, maybe it throws pieces on you.

Meanwhile it looks like saw stick and locking system... Of course, always better than the finger..:biggrin:

 

[cacciatorino]

Very nice!
It remains to see how it behaves with false positives, such as a damp wood.

 

[Fulvio Romano]

as the president says, it should work as the touchpads of the cell phones and pcs, of those that do not work with the pen, therefore capacitive.
the reliability of the system should be good. in the sense that there should be few false negatives. less than rust or oil on the blade.
as though it says hunter the false positives could be there, and for everyone they go away 69 dollars and five minutes of maintenance. . Oh, my God. .
Besides the damp wood, which could be much less conductive than the finger, there are the mobile phones ringing.

You don't understand clearly, but I think the saw doesn't ruin the impact. the brake is aluminum, so the teeth enter with facilty. Also you see that the saw disappears below. because the moment of inertia of the same sucks under doing pin right on the brake.

 

[marcof]

the reliability of the system should be good. in the sense that there should be few false negatives. less than rust or oil on the blade.
as though it says hunter the false positives could be there, and for everyone they go away 69 dollars and five minutes of maintenance. . Oh, my God. .
Besides the damp wood, which could be much less conductive than the finger, there are the mobile phones ringing.

really impressive as ingenious, but I wonder how it works when the operator wears gloves like anti-slips that are covered with a thin layer of rubber...

You don't understand clearly, but I think the saw doesn't ruin the impact.
the brake is aluminum, so the teeth enter with facilty. Also you see that the saw disappears below. because the moment of inertia of the same sucks under doing pin right on the brake.

The blade after the safety device is to be thrown. the teeth break and the body takes permanent ripples cje make it unusable for precision work.
I think the blade tree doesn't like that kind of arrest too. I think it might be good for small machines like those of the video, I wouldn't be too quiet to stop in that way my that has a 7.5hp engine, 400 mm diameter blade and the blade lifting group that will weigh at least twenty kilos.
Unfortunately, in the field of woodworking machinery such as wire pialles, tape saws, toupes etc.) the moving masses of both tools and mechanics are always very large so I believe that the diffusion of similar devices will remain confined to small circular saws
ah,of course the destruction of the machine is worth a finger or a hand...

 

[Er Presidente]

really impressive as ingenious, but I wonder how it works when the operator wears gloves like anti-slips that are covered with a thin layer of rubber...



The blade after the safety device is to be thrown. the teeth break and the body takes permanent ripples cje make it unusable for precision work.
I think the blade tree doesn't like that kind of arrest too. I think it might be good for small machines like those of the video, I wouldn't be too quiet to stop in that way my that has a 7.5hp engine, 400 mm diameter blade and the blade lifting group that will weigh at least twenty kilos.
Unfortunately, in the field of woodworking machinery such as wire pialles, tape saws, toupes etc.) the moving masses of both tools and mechanics are always very large so I believe that the diffusion of similar devices will remain confined to small circular saws
ah,of course the destruction of the machine is worth a finger or a hand...

the vustel was definitely a "false positvio". and if I want to cut off the viustells with the circular saw I make?
:smile:

I think if the big houses start working on it, it might be a solution for the bigger machines.
They put some kind of air bag under the table, I know!
:biggrin:

 

[Er Presidente]

really impressive as ingenious, but I wonder how it works when the operator wears gloves like anti-slips that are covered with a thin layer of rubber...

fabio said, cut the glove and when it comes to the finger stops.

He said.
:smile:

 

[Mike1967]

a Swiss carpenter I know would have been happy to have a sawer with that security system, maybe instead of having four fingers... Three would have saved them.
I hope it's really reliable, I've always been terrified of those blades. with those speeds.

 

[sampom]

a Swiss carpenter I know would have been happy to have a sawer with that security system, maybe instead of having four fingers... Three would have saved them.
I hope it's really reliable, I've always been terrified of those blades. with those speeds.

I think it's worth all the moths. . Who knows why you identify them from that "characteristic" :biggrin:

 

[Fulvio Romano]

really impressive as ingenious, but I wonder how it works when the operator wears gloves like anti-slips that are covered with a thin layer of rubber...

I thought about it, too, but as the president says, he should stop when he passed the glove and touches the skin.

The blade after the safety device is to be thrown. the teeth break and the body takes permanent ripples cje make it unusable for precision work.
I think the blade tree doesn't like that kind of arrest too. I think it might be good for small machines like those of the video, I wouldn't be too quiet to stop in that way my that has a 7.5hp engine, 400 mm diameter blade and the blade lifting group that will weigh at least twenty kilos.

I don't know, but you're probably right. the blade is to be thrown, perhaps not so much for the teeth, as for the disc that will no longer be balanced.
for precision cutting speech, is it also valid for wood? I have always considered a little precise cut. Am I right?
But the tree should not suffer damage. at the bottom if you cut off the power and brake the blade, the shaft should not suffer any kind of stress. Moreover without the inertia of the blade, the tree should stop practically immediately. Perhaps it only undergoes the twist of the engine rotor inertia.
for the bigger cars instead... well, there the hands have to stay away, I don't think there is any other solution. The solution is good for the DIY machine.

the vustel was definitely a "false positvio". and if I want to cut off the viustells with the circular saw I make?
:smile:

use the slicer! :tongue:
However to avoid throwing away the brake block, you could touch the steady blade with the material to cut, so see if it intervenes or not. If it intervenes, feel the "click", and replace only the fuse hollow that keeps the spring down. No?

I think it's worth all the moths. . Who knows why you identify them from that "characteristic" :biggrin:

Why only the moths? I left mine between the chain and the lazy...:redface:

 

[marcof]

for precision cutting speech, is it also valid for wood? I have always considered a little precise cut. Am I right?

as in mechanics also in the wood sector there are machines that can or leave surfaces from the characteristics of an ocetylene cut or a rectification.
you would then be surprised to see the precision and repeatability that you can get by hand working. we say that the tenth millimeter is the standard

But the tree should not suffer damage. at the bottom if you cut off the power and brake the blade, the shaft should not suffer any kind of stress. Moreover without the inertia of the blade, the tree should stop practically immediately. Perhaps it only undergoes the twist of the engine rotor inertia.

I don't know, it should be that (you:smile I made two accounts to see how much the tree on the pulley side is called considering the mass of a rotor of an asynchronous mother we say from 1.5 cv to 2800 rpm as that of the video machine. Moreover the bouncing part from the high pulley should undergo a bending not recently.

for the bigger cars instead... well, there the hands have to stay away, I don't think there is any other solution. The solution is good for the DIY machine.

especially with regard to the immediate descent of the lifting group. are devices with lifting through endless screw, manual or electric, then such a quick descent of all the acrocco, even neglecting the weight, I see it quite problematic.
[mode temperacaxxi ON]I was reflecting on the examples of the video, where the speed of advancement is very modest, let's say at most 40 cm/sec. if you look at the wurstel you see a notch left by the deep blade about 1 mm (at minute 0:09 looks at the proportions with the width, typically 3.5 mm).
typically those who cut off with that type of circular saws do not hold the hand beautifully in line with the blade and cutting advancing strictly to 30/40 cm/sec; l0irstinto takes over and pulls you back before separating the whole hand from the pole.. .
accidents happen more frequently for sudden movements in proximity to the rotating blades for example to take a crop or because the hand that pushes the wood slides sharply against the blade and other similar amenities concerning the bad use of the machines themselves.
in these cases the speeds of movement of the limbs are much higher. reach the 3 m/sec by stretching a hand to collect an object is not at all extraordinary.
to that speed of translation with 5 milliseconds necessary for the arrest of the blade the hand runs 1,5 cm, enough to rub you a finger or 4 tendons of the back of the hand and however to create highly invalidating damage.[temperacaxxi mode OFF]I mean, imho must still be perfected.
I add that the psychological effect of having the machine error-proof could then play bad jokes.

 

[Fulvio Romano]

I add that the psychological effect of having the machine error-proof could then play bad jokes.

Here. The speech finally came out.
I am and rest of the notice that excess security is dangerous. People never get hurt with dangerous things, but with safe ones. There are hundreds of examples.
You die in suvs and not in pandas. who works eight hours near a steel fusery furnace, then is invested by the forklift in the pedestrian crossing to go to the canteen, etc. etc.
They are not opinions, they are facts.

 

[Tequila]

interesting this system... However, I agree with fulvio and marcof on the too much safety that can play bad jokes, but it is also true that I would rather throw in the path a circular saw that go quickly and fury to the emergency room to get me hung up a ram.
Perhaps you will reach the right compromise for these things, but at the moment the system used is really brilliant.

 

[marcof]

the vustel was definitely a "false positvio". and if I want to cut off the viustells with the circular saw I make?
:smile:

get you a circular saw that has the security devices of thishttp://www.youtube.com/watch?v=zdkmasxtmro&feature=related and you will have no difficulty cutting sausage. if you then use it as the video kamikaze, without knife dividing behind the blade while making a deep cut at least 60 mm it is easy that you can dress salad with phalanges of various sizes:tongue:

 

[Er Presidente]

get you a circular saw that has the security devices of thishttp://www.youtube.com/watch?v=zdkmasxtmro&feature=related and you will have no difficulty cutting sausage. if you then use it as the video kamikaze, without knife dividing behind the blade while making a deep cut at least 60 mm it is easy that you can dress salad with phalanges of various sizes:tongue:

What do you need in "division knife"?
to cut your fingers before they accidentally contact the blade?

p.s.: to me these machines have always put anxiety, but it is not possible to work wood in a less disturbing way?
:smile:

 

[gerod]

What if the ominous uses the glove?
first takes the glove that is dragged on the blade along with the finger. then the blade stops and falls back, carrying glove and finger.
and then, the speed of advance generally is that of the "paron" that tells you: "You must make production" or, go to the maximum.

 

[marcof]

What do you need in "division knife"?
to cut your fingers before they accidentally contact the blade?

to keep the two parts cut apart. and place after the blade to which it is exactly aligned and of the same thickness. in case the wood has internal tensions that deform it tending to close the cut, it avoids that the blade is tightened in the cut and the piece of wood is shot towards the operator at the peripheral speed of the blade, typically around 30 m/sec...
only one demented can work with a circular saw with manual feed without knife mounted divider.

p.s.: to me these machines have always put anxiety, but it is not possible to work wood in a less disturbing way?
:smile:

with automatic machines it is possible, with those where the advancement of the piece is done manually the protections serve up to a certain point because the tool is in part discovered; you have to stay awake and do not take confidence (as the kamikaze of the video I posted you).
I think it also helps to have seen some images of amputation wounds caused by machines that are used...