SoliForum - 3D Printing Community — Pin shear

Re: Pin shear

null@example.com (elmoret) — Mon, 06 Jan 2014 02:17:09 +0000

Google "measuring stall current"

fourth link:

If you are applying DC then the stall current is simply V/R. Where V is applied voltage and R is the static resistance of the motor.

Re: Pin shear

null@example.com (Ralphxyz) — Mon, 06 Jan 2014 02:07:24 +0000

elmoret wrote:

It doesn't need to be adjustable, it just needs to be less than the stall current of the motor. You can measure stall current with an ohmmeter and ohm's law.
Google is your friend.

But only if you know what you are doing.

I know how to get the run current with a ohmmeter and ohm's law but not the stall current.

How would ohm's law know the load?

Ralph

Re: Pin shear

null@example.com (elmoret) — Mon, 06 Jan 2014 01:49:36 +0000

It doesn't need to be adjustable, it just needs to be less than the stall current of the motor. You can measure stall current with an ohmmeter and ohm's law.

Google is your friend.

Re: Pin shear

null@example.com (Ralphxyz) — Mon, 06 Jan 2014 01:42:30 +0000

But where does one get a adjustable circuit breaker?

Tim said:

"Push to reset circuit breaker set at the stall current so that if it ever stalls, the motor is disabled."

I know how to make a current sense circuit but what would the stall current be?

Ralph

Re: Pin shear

null@example.com (npeshman) — Sat, 04 Jan 2014 14:44:43 +0000

a circuit breaker does seem like the best solution. allows a solid mechanical connection without worry of burning up the motor. As long as the additional cost remains reasonable certainly a worthwhile feature

Re: Pin shear

null@example.com (laird) — Sat, 04 Jan 2014 01:46:05 +0000

MixFit wrote:

elmoret wrote:
9mm x 9mm square drive shaft (3/8" socket is 9.5mm x 9.5mm). Push to reset circuit breaker set at the stall current so that if it ever stalls, the motor is disabled.
It's been on my "to-do" for a while now, but I've been playing catchup ever since the KS ended.
That sounds ideal. i do worry about destroying my motor should it ever have a hard stall.

Indeed. I'm not too worried about the motor dying, but a circuit breaker certainly sounds better than a physical component "breaking" to protect the motor. If nothing else, resetting a breaker is less work than replacing the washer.

Re: Pin shear

null@example.com (MixFit) — Sat, 04 Jan 2014 00:17:12 +0000

elmoret wrote:

9mm x 9mm square drive shaft (3/8" socket is 9.5mm x 9.5mm). Push to reset circuit breaker set at the stall current so that if it ever stalls, the motor is disabled.
It's been on my "to-do" for a while now, but I've been playing catchup ever since the KS ended.

That sounds ideal. i do worry about destroying my motor should it ever have a hard stall.

Re: Pin shear

null@example.com (elmoret) — Sat, 04 Jan 2014 00:09:31 +0000

9mm x 9mm square drive shaft (3/8" socket is 9.5mm x 9.5mm). Push to reset circuit breaker set at the stall current so that if it ever stalls, the motor is disabled.

It's been on my "to-do" for a while now, but I've been playing catchup ever since the KS ended.

Re: Pin shear

null@example.com (laird) — Fri, 03 Jan 2014 23:00:38 +0000

The pin never worked for me - there's a little too much 'play' between the parts, so the pin just got squished and slid around. But with some hammering and tape, I managed to jam washers in that do the trick. And I have _lots_ of washers. :-)

The "square drive shaft and a circuit breaker" sounds interesting. How will that work?

Re: Pin shear

null@example.com (elmoret) — Fri, 03 Jan 2014 17:30:26 +0000

The pin is intentional by design. It was meant to crush if the motor was overloaded. As it turns out, there was a non-negligible degree of variation in the way it was installed and the tolerance of the shaft, pin, and socket which made this method less reliable than I'd hoped. I'm transitioning to a square drive shaft and a circuit breaker instead.

The trouble with filling it with JB weld is you lose both overload protection and the ability to cope with misalignment. Not the worst thing ever, but just be aware.

Re: Pin shear

null@example.com (npeshman) — Fri, 03 Jan 2014 14:13:12 +0000

Not a bad idea was thinking of doing something similar. For now i managed to push the pin in a little forther giving more surface area overall. So far its working. If when it fails i might try to use a propr set screw.

Re: Pin shear

null@example.com (MixFit) — Fri, 03 Jan 2014 13:07:59 +0000

I didn't really like the pin solution myself. I put my kit together and run it for a couple hours to see if the pin was getting damaged. It was becoming noticeably deformed. I pulled the motor off and filled the socket with JB weld. I then let it cure for a few minutes before greasing the motor's post and pushing it into the socket (and putting the pin back in). After letting it cure for a couple days I fired it up and have had no problems since. The motor is easily removable and the fit is tight.

Pin shear

null@example.com (npeshman) — Thu, 02 Jan 2014 04:50:45 +0000

Purging my filastruder with some osp 4043D pla at 3mm. And twice now the pin connecting the motor to the shaft coupler has sheared (edit by shear I mean that the side of the pin as squished allownig free rotation of the motor while not turning the auge). The first time I was soaked at 160 with a heat soak of 30 min after reaching the temp and the second was 170 soaked for 1 hour after reaching the temp. I am a bit confused by the second occurrence. Anyone have an idea of why this has happened and what can be done for a remedy?