Who recognizes what this is?

MVPCues

AzB Silver Member
Silver Member
I thought posting this pic might be a change of pace for the forum. I'm sure a few of you will recognize it pretty quickly. It lasted 19 years before the (obvious) catastrophic failure.

mystery.JPG
 
It looks a little like a collet for an electric motor. A small piece of metal covered plastic that is designed to break if the drive becomes taxed saving both the motor and the attachment.
 
It looks a little like a collet for an electric motor. A small piece of metal covered plastic that is designed to break if the drive becomes taxed saving both the motor and the attachment.

Very close but not quite.
 
The encoder in my Z servo decided to go bad. The pic is what is left of the coupler spider after the crash at (probably) the servos top speed. I have been told when the spiders fail, they FAIL. With such a small travel (compared to x/y), it crashed at one end of the travel, then reversed and crashed at the other end before I could hit the emergency stop.
 
The encoder in my Z servo decided to go bad. The pic is what is left of the coupler spider after the crash at (probably) the servos top speed. I have been told when the spiders fail, they FAIL. With such a small travel (compared to x/y), it crashed at one end of the travel, then reversed and crashed at the other end before I could hit the emergency stop.

I never liked rubber spiders in those Lovejoy-style couplers. When I've been forced to use them - for difficult-to-access assembly applications, or because someone else involved thought they were the "nuts" - I always machine a Delrin spider to a very tight tolerance. The snug fit between coupler halves cannot overcome the slippery nature of Delrin, so the coupler still does its job, and the spider will NEVER "age" the way rubber does.

Not saying your crash would have come out better - probably would have been worse. But for accuracy, the resolution with a solid spider beats the sponginess of rubber all day long.

TW
 


I never liked rubber spiders in those Lovejoy-style couplers. When I've been forced to use them - for difficult-to-access assembly applications, or because someone else involved thought they were the "nuts" - I always machine a Delrin spider to a very tight tolerance. The snug fit between coupler halves cannot overcome the slippery nature of Delrin, so the coupler still does its job, and the spider will NEVER "age" the way rubber does.

Not saying your crash would have come out better - probably would have been worse. But for accuracy, the resolution with a solid spider beats the sponginess of rubber all day long.

TW

Thank you kindly. My X axis has a different coupler that uses a harder red plastic spider. I asked the guy who helps support the old Techno-Isel (what I own) machines if it would be worth it for me to upgrade the other axes to the same. He said it would not make a difference in accuracy of the cut. I'm a CNC machinery noob, but it was hard for me to imagine that there is zero performance difference between a brand new spider and a well aged spider. I appreciate your input.
 
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