monitoring drilling acceleration

Hello

i am working on a project, trying to monitor, the accelerating of a handdrill, while drilling ( and thus being able to register the slip when the drill go through the other edge of the wood panel ).

I was thinking about using an accelerometer or a linear potentiometer as a sensor to achieve that ? or a pressure sensor ? it could be nice to visualize the changing in force / resistance through the wood panel so you can the slip when going through the edge.

are those sensors precise enought to moniter that ? otherwise What is the best way to approach that ?

Any help will be appreciated. Thanks

you seem to want to monitor a lot of things.

if you look at the volts and watts, you can derive what the motor is doing. very hard computationallly.

we useslly just monitor the spindle for speed. but, we use one point. if you want to have better monitoring, then the more points the better.

not sure how how you could use a linear pot or an accelaramoter makes me think you are doing something but have not defined you whole project.

how could you use a linear pot to measure load on a motor ?

where would you mount your accelatamoter ?

I suspect the idea is to use the potentiometer to measure the movement of the drill through the wood.

If you are using a hand-held drill (as compared to a hand-drill in a drill stand) I find it hard to see the value of what you are thinking of doing when it would be so much easier to put a depth-stop on the drill.

I also suspect that, even if you were equipped to measure either the motor current or the RPM there would be so much normal variation in the values that it would be difficult to detect break-through reliably.

In any case, to prevent damage to the wood it is normal to have a piece of scrap wood protecting the exit side so that the drill does not break-through to empty space.

...R

if practical answers are optional, then use a drill bit designed for wood. they have a cutter on the perimeter and not the Vee shape of a twist drill.

using a twist drill in wood is like using a hammer to drive in screws. it can be done, but is completely the wrong application of tools.

but, alas, without details from the OP, we are just guessing.

Thanks guys for the answers ... monitoring the density of the material is somewhat optional .. what is most important is being able to register the edge of the material when a drill cut through.

my idea behind using a potientometer og an accelerometer, is it for registering that sudden "slip" when you get through the material. you know, when drilling you have somehow a constant pressure and somehow the resistance disappear .. registrering that slip could be an indicator for the material "edge".

but i dont know if it is the most optimal way to do it.

Wouldn't the quickest way be to put a sheet of metal under the wood and watch for contact between the drill and the metal?

Paul

Or know how thick the wood is and stop at a given point?

The OP has not said WHY he wants to detect the emergence of the drill and I suspect that may be very relevant.

In my experience of drilling holes in wood there are two major choices - do I care if the drill bursts through and causes cosmetic damage on the rear side OR do I want both sides in good cosmetic condition.

I can't see the need to worry about breakthrough if the damage does not matter.

However if you want two good sides then you cannot allow breakthrough at all. Either you cushion the board with a piece of scrap and drill right through into the scrap. Or you drill part way from either side. None of these lends itself to detecting the changing force on the drill.

...R

the speed of the drill is dependent on the load. the harder one pushes and the more dull the bit, the slower the motor. the sharper the bit and the softer the material and the weakness of the push will allow the drill to run at a higher speed.

the key is to determine if; the user pushes at a constant rate and the drill bit is breaking though the hole or, the user relaxes the grip and stops pushing as much or, the material has a soft zone

since the force of the hand on the drill that pushed it into the material is key, a sensor needs to be on the handle. a distance sensor from the machine to the work needs to be very precise. if the forward movement halts, a spin up of the motor would be expected. if the rate of movement is constant, and the motor speeds up, then it can be deduced that the load has decreased. of course a tachometer or even a watt meter is needed to monitor the speed of the motor. the speed of the drill, or rather the input that would turn the drill on and off needs to be monitored. probably much easier if it is just an on/off switch.

as i see it, the greatest obstacle is the forward motion sensor and eliminating any hand movements that would influence the readings.

@dave-in-nj, none of that will be relevant if the drill is driving through the board into a piece of scrap to protect the reverse side of the board. In that case the only effective indicator will be depth. And a physical depth stop is very cheap and effective.

...R

I can think of a few places where such a feature might be useful. Notably, and given that I'm rewiring my house right now, it'd be nice to have a drill that would shut off after you burst through that hole when you're drilling joists with an auger bit (overhead, offbalance). It's not difficult to blow out a gearbox when the bit rattles in the hole.

Granted, OP appears to be describing drilling through layers of a thing, but I'd still be happy to have that feature on my drill.

Replying to post#1.

Use the pot to get position samples - then:

(oldPosition - newPosition) / samplePeriod = estimatedVelocity

(oldEstimatedVelocity - newEstimatedVelocity) / samplePeriod = estimatedAcceleration

The more you go down this derivative chain the more and more noise in the original samples will be amplified - suggest using a Kalman Filter to help with that...

All can be done with one analog input and a pages worth or less of code - at least I've done as much in C++.

1:1: Use the pot to get position samples

How, exactly ?

...R

Choose your flavour of linear to rotary motion ?

Then get handy :grin:

Drill presses themselves do it - you turn the handle, the drill goes up and down - mind you, I'm not saying you should go off the handle, but you could...

In addition, there are linear pots as I'm sure you're aware

Anyway, I thought the OP had an idea for this already...

I was answering their post directly, just for some balance ;)

ha ha -

it's a hand drill !

didn't read that properly

hrrm - well, a linear pot and some kind sliding and sprung guide thingo that attaches to the drill but slides wrt to the work, the OP must realise that being a hand drill it's a bit of an odd project, I reckon it would suit a drill press better...

Anyways, all the degrees of freedom issues and redundant um, 'projection' of information to the linear axis they are sensing is for them to nut out, I can assist with the code logic though :D

Thanks for All the replies ... but guys SERIOUSLY !!! ... this is not a woodworking forum, this is an electronic forum, i am aware of the different mechanical ways of doing that, like a stop in drill bit and so on.

I am asking what would be the most realistic solution, if i want to do that ELECTRONICLY. and by the way, drilling through wood was only an example. the problem is not drilling through wood, but just monitoring "the slip" when the drill gets through the other side !.

So .. but thanks for answers, some interessting posts ! ... so of what i understand, the real / only way to do it is to monitor the rotation of the drill motor and then the resistance ? i cannot just measure the acceleration, when the slip accure

Lot’s of people here are workshop tinkerers, if not professional machinists etc. so the conversation will flow as it does. In that context the discussion with Robin, was discussion with Robin - somewhere in all that my specific reply to you was to ‘get handy’ - which I’m sure you will :wink:

But back to the topic: you could estimate the acceleration as I outlined (that is, if that is the metric you’re still interested in)

The other options look interesting too.

go where you interests take you !

stregoi: the problem is not drilling through wood,

It's beginning to sound like an XY problem

Tell us what you are actually trying to do and you might get some useful advice. And don't leave it so long before your next reply.

...R

Well basically, you have a material you want to drill through, let say, you have something hard, and just underneath it something soft, like brain surgery for instance. so you have drilling but you want to get noticed just when you get through the hard material, so you don't damage the softer one. So in brain surgery for eksemple, they are doing that mechanicly so the bit retracts automaticly when hetting the soft surface. I am just curious, if monitoring that slip can be done through sensors, like accelerometers and so on.

I hope this is not going to turn out to be a medical Thread - if so I am retiring.

…R