I need to make a special measuring timer

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

 

[Jamie]

etpm@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

Sounds to me like a poor stamping fabrication setup. Can't they use a
base the parts can sit in that has an outer wall to prevent them from
moving off center?

Also, are these parts carbon steel? can you magnetize the table
between cycles?

If you really want to do probe sensing, wrap a coil form loosely coupled
around the chuck that holds punches. Excite the coil with a ac reference
you can monitor. when the punch touches the surface, assuming this is
metal we are talking about, it'll create the secondary side of a loosely
coupled transformer and change the reference current. This way, you don't
need to worry about hard impacts destroying sensors.

Or you can do a E-line reflection detector on the punch.


Jamie

 

[Jon Kirwan]

On Sun, 21 Apr 2013 13:34:33 -0700, etpm@whidbey.com wrote:

I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?

What a description.

But I'm getting the idea that there are two hammers that drop
by gravity, lifted by cams that have a sudden edge on the cam
allowing the hammers to drop, and that they get out of
alignment from each other with use and the cam rotations need
to be readjusted periodically. The punches are spring loaded
against the work material before the hammers are released to
impact them. The problem is that the hammers don't hit
simultaneously. You need to work out a method of periodically
adjusting _something_ to get the timing true, again.

Is that about it?

Are both cams are on the same drive rod and motor? How
exactly are things adjusted (what is adjusted and how?) What
are the masses of the hammers?

If you use a piezo and can wire something to them while they
are in motion, you might place them at the backside of each
hammer. You will get quite a spurt of voltage spikes on
impact and they won't wear out located there. A digitizing
scope would make it pretty easy to estimate the timing
difference, I suppose. Could autocorrelate a digitized sound
recording, too, I suppose (the impact sounds of each hammer
being similar enough to each other should make the
autocorrelation work.) But you wouldn't necessarily know
which was first and which second, though you may know that
for other reasons. You certainly would know if you got them
well matched, though.

Jon

 

[Tim Wescott]

On Sun, 21 Apr 2013 13:34:33 -0700, etpm wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking process
sometimes doesn't work because the punches that do the staking don't hit
the parts at the same time and they need to be adjusted. The punches
first contact the parst, holding them in place with spring pressure,
then the punches are struck by a spring loaded hammer that is actuated
by a cam. So, after this long description what needs to be done is the
timing of the punches being struck needs to be measured. I'm thinking of
maybe using a piezo disc under each punch and then cycling the machine
and looking for a voltage spike with both channels of a 'scope. I'm not
sure how much voltage the disc would generate though and if it would
damage the 'scope. I have a TEK 465B oscilloscope but I'm not sure it
would be best suited for this job. I can buy a cheap 4 channel DSO that
I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990 I think it
would measure the timing of the voltage spikes to a fine enough interval
for what the customer needs. I think the timing of the strikes can be
measured to within at least 1 millisecond which would be plenty fine
enough. Then the machines can be adjusted. Any thoughts anyone?

I can't comment on the piezo sensing idea (I think you may just end up
with mashed piezos).

But on the DSO side, as long as your DSO actually measures simultaneously
you should be fine. That's not a guarantee in a really truly dirt-cheap
scope, and I'm not sure how to tell without getting one and finding out.

You might want to stop and think about how much your time and your
customer's time costs, then go buy a Rigol or similar inexpensive scope,
as opposed to the least expensive dirt cheap thing you can find.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

 

[Bob Masta]

On Sun, 21 Apr 2013 13:34:33 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

Most piezos are brittle ceramic, which would be a problem
here. You will probably want the kind made with plastic
film. I don't know models numbers, just heard about this
stuff. It's output voltage is lower than the ceramics, so
no issues with scope inputs.

You can even use a Windows computer with sound card to do
this, since modern sound cards have simultaneous sampling on
the A/D converters. Even at the default 48000 Hz sample
rate you could resolve to 20.8 microseconds, and most cards
(even cheapie built-in laptop chipsets) can sample at 96000
(10.4 usec) or 192000 (5.2 usec) these days.

Sound cards can only handle about +/-2.5 V, so if you are
not sure about just how big your signal might get, make a
simple limiter: Use a couple of reverse-paralleled LEDs to
ground across the input, and feed them with a dropping
resistor. See "Sound Card Input Range and Limiter Circuits"
at <http://www.daqarta.com/dw_0all.htm>

Best regards,


Bob Masta

DAQARTA v7.21
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusic generator
Science with your sound card!

 

On Sun, 21 Apr 2013 17:45:03 -0400, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

etpm@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

Sounds to me like a poor stamping fabrication setup. Can't they use a
base the parts can sit in that has an outer wall to prevent them from
moving off center?

Also, are these parts carbon steel? can you magnetize the table
between cycles?

If you really want to do probe sensing, wrap a coil form loosely coupled
around the chuck that holds punches. Excite the coil with a ac reference
you can monitor. when the punch touches the surface, assuming this is
metal we are talking about, it'll create the secondary side of a loosely
coupled transformer and change the reference current. This way, you don't
need to worry about hard impacts destroying sensors.

Or you can do a E-line reflection detector on the punch.


Jamie
The punch first touches the part and holds it in place. Then it is

struck to put the stake in. I need to know when the hammer strikes,
not when the punch touches.
Eric

 

On Sun, 21 Apr 2013 15:31:52 -0700, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Sun, 21 Apr 2013 13:34:33 -0700, etpm@whidbey.com wrote:

I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?

What a description.

But I'm getting the idea that there are two hammers that drop
by gravity, lifted by cams that have a sudden edge on the cam
allowing the hammers to drop, and that they get out of
alignment from each other with use and the cam rotations need
to be readjusted periodically. The punches are spring loaded
against the work material before the hammers are released to
impact them. The problem is that the hammers don't hit
simultaneously. You need to work out a method of periodically
adjusting _something_ to get the timing true, again.

Is that about it?

Are both cams are on the same drive rod and motor? How
exactly are things adjusted (what is adjusted and how?) What
are the masses of the hammers?

If you use a piezo and can wire something to them while they
are in motion, you might place them at the backside of each
hammer. You will get quite a spurt of voltage spikes on
impact and they won't wear out located there. A digitizing
scope would make it pretty easy to estimate the timing
difference, I suppose. Could autocorrelate a digitized sound
recording, too, I suppose (the impact sounds of each hammer
being similar enough to each other should make the
autocorrelation work.) But you wouldn't necessarily know
which was first and which second, though you may know that
for other reasons. You certainly would know if you got them
well matched, though.

Jon
Greetings Jon,

Your description is pretty close. I haven't actually seen the complete
machine, I just make some parts for it. I'm thinking that the piezo
could mounted to the underside of a piece of aluminum, the aluminum
being struck by the punch. I do need to determine which punch hits
first and the time difference between the hits.
Eric

 

On Sun, 21 Apr 2013 20:49:23 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

On Sun, 21 Apr 2013 13:34:33 -0700, etpm wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking process
sometimes doesn't work because the punches that do the staking don't hit
the parts at the same time and they need to be adjusted. The punches
first contact the parst, holding them in place with spring pressure,
then the punches are struck by a spring loaded hammer that is actuated
by a cam. So, after this long description what needs to be done is the
timing of the punches being struck needs to be measured. I'm thinking of
maybe using a piezo disc under each punch and then cycling the machine
and looking for a voltage spike with both channels of a 'scope. I'm not
sure how much voltage the disc would generate though and if it would
damage the 'scope. I have a TEK 465B oscilloscope but I'm not sure it
would be best suited for this job. I can buy a cheap 4 channel DSO that
I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990 I think it
would measure the timing of the voltage spikes to a fine enough interval
for what the customer needs. I think the timing of the strikes can be
measured to within at least 1 millisecond which would be plenty fine
enough. Then the machines can be adjusted. Any thoughts anyone?

I can't comment on the piezo sensing idea (I think you may just end up
with mashed piezos).

But on the DSO side, as long as your DSO actually measures simultaneously
you should be fine. That's not a guarantee in a really truly dirt-cheap
scope, and I'm not sure how to tell without getting one and finding out.

You might want to stop and think about how much your time and your
customer's time costs, then go buy a Rigol or similar inexpensive scope,
as opposed to the least expensive dirt cheap thing you can find.
Thanks Tim, I'll look at a Rigol. I have never heard of the name. I'm

not a real electronics guy, I mostly just fiddle with stuff when I
need to make or fix something.
Eric

 

On Mon, 22 Apr 2013 12:48:22 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 21 Apr 2013 13:34:33 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

Most piezos are brittle ceramic, which would be a problem
here. You will probably want the kind made with plastic
film. I don't know models numbers, just heard about this
stuff. It's output voltage is lower than the ceramics, so
no issues with scope inputs.

You can even use a Windows computer with sound card to do
this, since modern sound cards have simultaneous sampling on
the A/D converters. Even at the default 48000 Hz sample
rate you could resolve to 20.8 microseconds, and most cards
(even cheapie built-in laptop chipsets) can sample at 96000
(10.4 usec) or 192000 (5.2 usec) these days.

Sound cards can only handle about +/-2.5 V, so if you are
not sure about just how big your signal might get, make a
simple limiter: Use a couple of reverse-paralleled LEDs to
ground across the input, and feed them with a dropping
resistor. See "Sound Card Input Range and Limiter Circuits"
at <http://www.daqarta.com/dw_0all.htm

Best regards,


Bob Masta

DAQARTA v7.21
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusic generator
Science with your sound card!
Thanks for advice Bob. I'll check out the plastic piezos.

Eric

 

On Mon, 22 Apr 2013 07:30:40 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Apr 21, 4:34 pm, e...@whidbey.com wrote:
Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first  part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

I don't know about the peizo as sensor. I wouldn't worry too much
about damaging the scope, but you coould start with some resistance in
series with the scope input... maybe start 100k ohm... it depends on
how long a cable (how much capacitance.) Or use a x10 scope probe.

Other ways to sense the punch... maybe sound? put some little mic's
near each punch? Or could you use a LED and photodiode... attach
something to the punch that will break a beam as it moves. Hmm maybe
a magnetic reed switch?

George H.
Greetings George,

Since I need to sense impact, not the punch touching the part, a mic
might work. If the piezo idea doesn't pan out I'll try the mic.
Eric

 

[George Herold]

On Apr 21, 4:34 pm, e...@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first  part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

I don't know about the peizo as sensor. I wouldn't worry too much
about damaging the scope, but you coould start with some resistance in
series with the scope input... maybe start 100k ohm... it depends on
how long a cable (how much capacitance.) Or use a x10 scope probe.

Other ways to sense the punch... maybe sound? put some little mic's
near each punch? Or could you use a LED and photodiode... attach
something to the punch that will break a beam as it moves. Hmm maybe
a magnetic reed switch?

George H.

 

[tuinkabouter]

On 22.04.2013 17:53, etpm@whidbey.com wrote:

On Mon, 22 Apr 2013 07:30:40 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Apr 21, 4:34 pm, e...@whidbey.com wrote:
Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

I don't know about the peizo as sensor. I wouldn't worry too much
about damaging the scope, but you coould start with some resistance in
series with the scope input... maybe start 100k ohm... it depends on
how long a cable (how much capacitance.) Or use a x10 scope probe.

Other ways to sense the punch... maybe sound? put some little mic's
near each punch? Or could you use a LED and photodiode... attach
something to the punch that will break a beam as it moves. Hmm maybe
a magnetic reed switch?

George H.
Greetings George,
Since I need to sense impact, not the punch touching the part, a mic
might work. If the piezo idea doesn't pan out I'll try the mic.

Perhaps a Strain gauge would solve the measurement problem.

If the signal form is not important you can use the open bench logic
sniffer. With this you can easily measure the time between pulses.

 

[John Fields]

On Sun, 21 Apr 2013 13:34:33 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope.

---
Good idea, but you might want to consider inserting elastomeric
barriers between the transducers and the actuators, in order to keep
from destroying the transducers.
---

I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

---
The 465 would work, in chopped mode, and you'd have to set the trigger
to fire on the first pulse and then tune the second pulse for
congruence.

--
JF

 

[Jasen Betts]

On 2013-04-21, etpm@whidbey.com <etpm@whidbey.com> wrote:

Greetings All,
So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.

Could you use a of microphones to listen to the hammers and a graphing
sound recorder software like audacity to analyse the results?



or a dedicated device could be built with a few dollars worth of parts
a centre-zero meter on a phase detector on a pair of envelope
detectors on a pair of microphones.



I think the real problem is the machine has one hammer too many.

--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Jamie]

etpm@whidbey.com wrote:

On Sun, 21 Apr 2013 17:45:03 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


etpm@whidbey.com wrote:


Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

Sounds to me like a poor stamping fabrication setup. Can't they use a
base the parts can sit in that has an outer wall to prevent them from
moving off center?

Also, are these parts carbon steel? can you magnetize the table
between cycles?

If you really want to do probe sensing, wrap a coil form loosely coupled
around the chuck that holds punches. Excite the coil with a ac reference
you can monitor. when the punch touches the surface, assuming this is
metal we are talking about, it'll create the secondary side of a loosely
coupled transformer and change the reference current. This way, you don't
need to worry about hard impacts destroying sensors.

Or you can do a E-line reflection detector on the punch.


Jamie

The punch first touches the part and holds it in place. Then it is
struck to put the stake in. I need to know when the hammer strikes,
not when the punch touches.
Eric

That is kind of relevant if the miss timed punch has already impacted
and moved the worked piece. I thought you wanted a way to align it
automatically, not probe if for your eyes only?

How are the punches driven? hydraulic, pneumatic, solenoid, rotary
cams, explosives, quantum singularity, zpm, splitting quarks, higgs boson?

It would be nice to know a little more? And I am sure casimir polder
has nothing to do with this.

Jamie

 

[Bob Masta]

On 22 Apr 2013 21:29:31 GMT, Jasen Betts <jasen@xnet.co.nz>
wrote:

On 2013-04-21, etpm@whidbey.com <etpm@whidbey.com> wrote:
Greetings All,
So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.

Could you use a of microphones to listen to the hammers and a graphing
sound recorder software like audacity to analyse the results?

or a dedicated device could be built with a few dollars worth of parts
a centre-zero meter on a phase detector on a pair of envelope
detectors on a pair of microphones.

I like Jasen's (and George's) microphone idea. You can
probably do it with Audacity, but I'm more confident
recommending Daqarta because I know its real-time trigger
capabilities can handle this. (Audacity has an "audio"
orientation, while Daqarta is more about measurement and
instrumentation.)

You *might* be able to learn everything you need from a
single mic. I'd start out with a single mic in any case,
moving it around to see what the signal looks like in
various positions. The idea is that when the machine is set
properly you will get one big "bang", but when one hammer is
later than the other you will get a "b-bang".

This will probably be visible with a single mic that is
placed equidistant from the two points of impact. You'd
adjust the hammer timing until you get one maximal peak...
as you change relative timing the peak will get lower and
then split into two separate peaks.

You *might* be able to use an ordinary mic, plugged into the
ordinary Mic In on the sound card. If you haven't used mics
with computers, here are a few caveats: The most common
mics these days are electrets, and they are also best for
this job because they are small and have fast response (low
mass). But they need a DC bias voltage to operate, which is
provided by the Mic In connector. The Mic In connection has
more gain than Line In, but the sound card limits the
frequency response on Mic In (typically 9 kHz instead of 20+
kHz on Line In). There can also be screwy sample rate
conversion issues, since Mic In is apparently often done
with a separate A/D.

The other issue about Mic In is that it is usually mono
only, at least on systems that have a separate Line In.
Some of the newer cheapie laptops dispense with Line In
connectors and have stereo Mic In, however.

With all that, I'd still recommend trying whatever mic you
have on Mic In. If it looks promising, but for whatever
reason you feel you really need two mics (and don't have a
laptop with stereo Mic In), you will need a separate preamp
with connectors for two mics. The preamp will provide the
bias for each, and convert to Line In levels. A lot of
extra expense and fooling around, however, and I'd bet that
you don't need anything more than a simple mic.

If you want to try this with Daqarta, feel free to contact
me with any questions using the Contact links on the site.
Daqarta has a 30-day / 30-session trial period, which should
be more than enough to do this job. If you run short, let
me know and I can provide an extension. I'm also glad to
provide advice on triggering strategies or anything else.
(Note that you can right-click anything in Daqarta and
instantly see its Help topic.)

Best regards,


Bob Masta

DAQARTA v7.21
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusic generator
Science with your sound card!

 

On Mon, 22 Apr 2013 18:58:38 -0400, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

etpm@whidbey.com wrote:
On Sun, 21 Apr 2013 17:45:03 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


etpm@whidbey.com wrote:


Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

Sounds to me like a poor stamping fabrication setup. Can't they use a
base the parts can sit in that has an outer wall to prevent them from
moving off center?

Also, are these parts carbon steel? can you magnetize the table
between cycles?

If you really want to do probe sensing, wrap a coil form loosely coupled
around the chuck that holds punches. Excite the coil with a ac reference
you can monitor. when the punch touches the surface, assuming this is
metal we are talking about, it'll create the secondary side of a loosely
coupled transformer and change the reference current. This way, you don't
need to worry about hard impacts destroying sensors.

Or you can do a E-line reflection detector on the punch.


Jamie

The punch first touches the part and holds it in place. Then it is
struck to put the stake in. I need to know when the hammer strikes,
not when the punch touches.
Eric

That is kind of relevant if the miss timed punch has already impacted
and moved the worked piece. I thought you wanted a way to align it
automatically, not probe if for your eyes only?

How are the punches driven? hydraulic, pneumatic, solenoid, rotary
cams, explosives, quantum singularity, zpm, splitting quarks, higgs boson?

It would be nice to know a little more? And I am sure casimir polder
has nothing to do with this.

Jamie
Greetings Jamie,

The punches both touch at the same time. The mechanism that hits the
punches is what gets out of time. I am not quite sure how the whole
thing works, my customer is in a different state. Since I have solved
other mechanical engineering problems for this customer he asked if I
could help on this one. Somehow the whole thing is adjustable. I make
the punches to an exact length and that solves the problem of them
making the initial spring loaded contact. The hammer strike is a
different mechanism and it gets out of time.
Eric

 

On Mon, 22 Apr 2013 21:42:34 +0200, tuinkabouter
<dachthetniet@net.invalid> wrote:

On 22.04.2013 17:53, etpm@whidbey.com wrote:
On Mon, 22 Apr 2013 07:30:40 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Apr 21, 4:34 pm, e...@whidbey.com wrote:
Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

I don't know about the peizo as sensor. I wouldn't worry too much
about damaging the scope, but you coould start with some resistance in
series with the scope input... maybe start 100k ohm... it depends on
how long a cable (how much capacitance.) Or use a x10 scope probe.

Other ways to sense the punch... maybe sound? put some little mic's
near each punch? Or could you use a LED and photodiode... attach
something to the punch that will break a beam as it moves. Hmm maybe
a magnetic reed switch?

George H.
Greetings George,
Since I need to sense impact, not the punch touching the part, a mic
might work. If the piezo idea doesn't pan out I'll try the mic.

Perhaps a Strain gauge would solve the measurement problem.

If the signal form is not important you can use the open bench logic
sniffer. With this you can easily measure the time between pulses.

What is an "open bench logic sniffer"? Can you point me to a web site

that describes it?
Eric

 

[tuinkabouter]

On 23.04.2013 18:28, etpm@whidbey.com wrote:

On Mon, 22 Apr 2013 21:42:34 +0200, tuinkabouter
dachthetniet@net.invalid> wrote:

On 22.04.2013 17:53, etpm@whidbey.com wrote:
On Mon, 22 Apr 2013 07:30:40 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Apr 21, 4:34 pm, e...@whidbey.com wrote:
Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope. I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

I don't know about the peizo as sensor. I wouldn't worry too much
about damaging the scope, but you coould start with some resistance in
series with the scope input... maybe start 100k ohm... it depends on
how long a cable (how much capacitance.) Or use a x10 scope probe.

Other ways to sense the punch... maybe sound? put some little mic's
near each punch? Or could you use a LED and photodiode... attach
something to the punch that will break a beam as it moves. Hmm maybe
a magnetic reed switch?

George H.
Greetings George,
Since I need to sense impact, not the punch touching the part, a mic
might work. If the piezo idea doesn't pan out I'll try the mic.

Perhaps a Strain gauge would solve the measurement problem.

If the signal form is not important you can use the open bench logic
sniffer. With this you can easily measure the time between pulses.

What is an "open bench logic sniffer"? Can you point me to a web site
that describes it?

Ever heard of google? Put your question "open bench logic sniffer" in
it. You will find:

http://dangerousprototypes.com/docs/Open_Bench_Logic_Sniffer

What it does is, after a start or after a trigger record digital
signals. The duration is dependent on the sample rate and buffer size.
It can do max 200 Mega samples per second.
After the sampling the buffer is read by the controlling program.
Then it can be analyzed. In your case setting two cursors on the start
of the signals of the strain gauges and read the time difference.

 

On Mon, 22 Apr 2013 16:12:05 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Sun, 21 Apr 2013 13:34:33 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a customer that I make an assembly for that he uses in another
assembly to stake parts. By staking parts I mean dents are put in the
first part to retain a second part that fits in a hole in the first
part. Anyway, two dents are put in the part and they need to be done
simultaneously to prevent shifting of the parts. The parts I make work
perfectly but when the customer assembles everything the staking
process sometimes doesn't work because the punches that do the staking
don't hit the parts at the same time and they need to be adjusted. The
punches first contact the parst, holding them in place with spring
pressure, then the punches are struck by a spring loaded hammer that
is actuated by a cam. So, after this long description what needs to be
done is the timing of the punches being struck needs to be measured.
I'm thinking of maybe using a piezo disc under each punch and then
cycling the machine and looking for a voltage spike with both channels
of a 'scope.

---
Good idea, but you might want to consider inserting elastomeric
barriers between the transducers and the actuators, in order to keep
from destroying the transducers.
---

I'm not sure how much voltage the disc would generate
though and if it would damage the 'scope. I have a TEK 465B
oscilloscope but I'm not sure it would be best suited for this job. I
can buy a cheap 4 channel DSO that I think would work, see this link:
http://dx.com/p/ds-203-3-0-lcd-pocket-mini-oscilloscope-65990
I think it would measure the timing of the voltage spikes to a fine
enough interval for what the customer needs. I think the timing of the
strikes can be measured to within at least 1 millisecond which would
be plenty fine enough. Then the machines can be adjusted.
Any thoughts anyone?
Thanks,
Eric

---
The 465 would work, in chopped mode, and you'd have to set the trigger
to fire on the first pulse and then tune the second pulse for
congruence.
Thanks for the advice John. I have ordered the piezo transducers and

will experiment with them when they arrive and let everyone know if I
achieve success.
Eric