Thanks to all the people who have reported that the black lid cable is prone to failing after the lid is opened and closed many times. I had begun to not open the lid all the way, but now I raise it only an inch or two. Just enough to open the front cover. I slide my material in and out without fully opening the lid. Hopefully the black cable will last almost indefinately. I can still open the lid for stuff that requires it of course.
Good deal. Fully upright is stressing on the cable…anything less is not too bad. I rarely open mine all the way upright and it’s going on a couple of years now.
On our Pro at the shop we went with the no more than 35-45 degree lift method since it was new and we still had to replace it. I did notice that the newer cable is 1/2 longer to prevent from rubbing on the metal frame in back but I am not sure that it addressed the bending back and forth issue that may have caused our failure as we had no rub/rash marks on the one that failed.
We do use the shop machine 5 days a week so it was bound to happen.
Unfortunately, the most stress on the cable is when the lid is closed. When manufactured (or removed for replacement) it is completely flat. The very first time the lid is closed, the copper traces “printed” onto the surface of the plastic carrier are stressed in tension. Copper work hardens - it quickly becomes brittle with repeated bending.
The original cable was a little shorter at the “base” of the T, so it could contact an edge when the lid was fully open, which may have led to some failures, but in reality, it’s a poor choice of cable and will fail whether you open the lid a couple of inches or close to vertical.
Look at the one connected to the head to see an example of what would have been an appropriate choice for repeated flexing.
Limiting the amount of flex should surely help, but it’s not going to prevent failure. Thankfully, it’s a cheap part to replace, albeit very fiddly for the average owner.
I would like to say that stress on a part is not what causes failure. Fatigue cracking - that’s what causes the cable to break - is a function of stress reversal and number of cycles. In fact, when a part is stressed below its fatigue limit it will last indefinately. Just Google “Metal Fatigue”
The cable in my unit is definately preformed to promote the way it is shaped in use.
I posted mainly to thank the Glowforge community for drawing attention to the black cable breakage issue & share a technique which drastically reduces cable flex - very likely below the fatigue threshold.
Cheers & Happy New Year
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