I'm trying to make some Stop Motion animation but some of the parts on my Minifigures are very stiff, which reduces the control I have when making small adjustments during each frame.
Is there a safe way to loosen the joints that will still allow them to hold their position once set?
Both arms and legs are held in place through a fairly simple compression pin.
A small dab of washing up liquid applied to the joint should lubricate it quite well - avoid oils as they can cause discolouration of the plastic.
If that doesn't work for you, then you could try physically loosening the pins - gently pull the arms out of the sockets and the legs off the hips and replace them a couple of times - this is usually enough to compress the arms of the pin enough while still maintaining a grip on the part. Going further you can obviously compress the pins manually and fairly permanently - however this will likely make the joints too loose for your needs - I've certainly got some older minifigs with very wobbly hip joints that can no longer stand up on their own.
The simple solution is to just move the joins a lot, the plastic will wear down with use. This is why mini-figures that little kids have played with for years are just downright floppy.
Zhaph gives some good advice about oils, watch out for stuff that is hydrocarbon based as this might also be act as a solvent. I want to say that silicone based lubricants might be the thing that could work for you. I recall someone talking about using it for some technic axles awhile back. You might do some google research on this topic.
If you remove arms, be careful, as torsos can develop stress cracks along the bottom edge that will split up to the arms. These are not repairable, and ruin the torso.
Finally, if you want to FIX loose Lego figure arms, legs, heads, etc. I have a very solid and simple fix that I have used many times over the years. Take a VERY tiny drop of crazy glue and put it inside the joint, and let it dry overnight. This will cause the joint to be come ever so slightly smaller, and it will make the joint nice and tight. It is inside the joint, so it is completely invisible, and if needed it could be done repeatedly.
But be very careful, as crazy glue will mark Lego it drips on. Let it dry for a long time, so you don't accidentally glue the joint together. And finally, just to repeat, a VERY small amount of glue. It doesn't take much at all.
Happy filming!
