If you're reading this, I am probably modeling BattleMechas. www.3dpprofessor.com/2023/08/24/how-to-solve-loose-printablok-ball-joints-video/

Loosening ball joints has been the bane of my existence when printing articulated figures. Thanks for this video! Also subbed.

You were in the right direction, It's the problem with the PLA, it's not shrinkage, and it's not the "ball" part deforming under pressure that caused the problem. Instead, it's the "joint" part (the Y/U-shaped part that holds the ball joint) being stretched outward under pressure, that's why rotating the "ball" part doesn't fix the problem, as it is the joint that's getting too loose. PLA does have a tendency to deform under pressure over time, that's why when I am working with ball joints and other mechanical parts, I tend to use PETG, which holds way better than PLA while being fairly easy to print.

Petg for sure is a great material for the ball joints, it’s low friction and flexibility make it hold ball joints so much better, even better than ABS.

I've had problems with loose ball joints in the past, and these are some great solutions. Thank you!

this is fantastic thank you!!

Love everything about this video ❤

PLA is known for "mechanical creep" (for a lack of a better term)... It's not the ball that's the problem, it's the socket. The "ears" of the socket are being pushed outward by the ball. Eventually the PLA will just give in to the shape that it's being forced into. And PLA doesn't / won't return to it's original shape when the force being applied is removed like other plastics may do easier, ABS for example. You may be able to "fix" this a little if there is a way to reinforce the ears so they don't/can't flex as easily?

I found out the hard way after printing shelf supports to hold filament on my wall that PETG creeps over time. Originally I could hold my full body weight off of each individual support, then later after putting a laminate shelf on it and about 20 spools of filament, 2 months later it all crashed to the floor, which knocked over a table holding other things and made a big mess. Watched some KZfaq videos about 3d printed material creep and learned that there was a good reason why Vorons are made using ABS(ASA works too) instead of PLA, PETG, or Nylon(even CF Nylon creeps, see Stefan's example with cnckitchen and his Voron). I think PETG or ABS would be great for this application but I've had multiple examples of PLA creep in different functional applications and have used different materials, mainly ABS because with only a cardboard enclosure I've been more happy with printing it than the effort of drying PETG just to print something basic. ..plus vapor smoothing ABS is a fantastic thing

have you tried damping grease? it'll give a bit of stiction and provide a smooth articulation

Is that Super Robot Spirits for the Nintendo 64 on the screen at the start?

Have you tried using ABS for the ball joints? Jim

CREEP, and I don't mean the guy in the video. I mean "creep" the phenomenon plastics are subject to when they are under constant stress, they will undergo slow deformation, hence the loosened up joint. Some plastics are more prone to creep than others, look up for the creep curves in material datasheets. So, your 2nd theory is most likely the root cause. The ball itself will not deform much because of it's spherical shape, the hub is the one deforming, so it does not matter if you rotate the connector in any direction, the joint will still be loose. One way of solving this thru design is to maintain stress levels low, the lower the stress the lower the deformation caused by creep. It is challenging since you do want the hub to apply pressure around the spherical ball, try reducing stress concentrators, round-off sharp corners, etc. Trust me, I'm an engineer.