So i have been working on an open source project lately , and to spare you the long talk . the problem is about fixing an metallic shaft of 4mm on it's rotational axis .
as you can see in the picture below , there are two parallel circular holes where the 4mm shaft goes in , and it there is an other gear , obviously without proper fixation the shaft would fall right off . the designer used plastic sleeves , or flanges that i've also joined in the picture below .
so basically through friction that sleeve is supposed to keep the shaft in place . i don't find that reliable and i don't trust it .
what i am thinking about is making the circles around the axe (blue) thicker there , then adding a hole for a srew , then fixing the axe with a M2 or M1.6 screw .
though the whole thing is 3D printed (PLA , 100% filling) i don't know if it will stand a screw .
what do you guys suggest ?
Hello Robin , thank you for your attention sir, i joined an image drawn with paint to illustrate how the sleeves are mounted , basically i just place the sleeves there and then insert the 4mm shaft . basically the internal diameter of the sleeves is 3mm so as they extend a bit by the insertion of the shaft , they are then held in place . and therefore the inhibit the shaft from moving out of it's position . no , i am indifferent to whether or not the shaft rotates around it's axis , as that rotation won't bother at all . what i fear is the shaft leaving it's position my translating on it's axis . the red arrow shown in the picture below shows the direction that i fear the shaft might move in therefore leaving it's necessary position .
i cannot use things like Epoxy or superglue , as possible safe disassembly is a key feature of this design .
(Also thank you for the Image tip)
Hello Paul , also thank you for your attention , i don't trust plastic sleeves , and i have no access to them here . they won't arrive if i order them , and an other option would be to 3d print them out of Semi-flex but i have no access to fancy materials like Semi-flex here .
the 2 solutions i thought of are : (they are not very efficient) :
instead of using a smooth 4mm shaft , using a 4M screw with a 4M nut . that would be relaiably fixed to the rotational axis . the problem here is that the screw is not at all smooth , it would cause friction and problems with the Gear that is supposed to rotate on it .
the second solution is to drill a hole for a M2 screw , and then fixing the shaft with two screws . i joined an image that indicates where the two screws are supposed to be inserted .
the problem here is that drilling a hole in 3D printed material is not very efficient ,it might compromise the whole design and i don't know if it can reliably hold a screw .
Glue a ring onto the outer end of the shaft (so it looks like the head of a bolt). That would stop the shaft moving in one direction.
Glue a flat plate across the end of the 3D printed hole (or 3D print a blind hole on one side) - would have the same effect as the "bolt head"
Solder a piece of wire across the end of the shaft - to make a T shape. I can think of various ways that the wire might be held in place, including bending the end around the plastic frame.
Cut or file a groove in the shaft and bore a fine hole in the 3D printed plastic so you can slide a wire through the hole and through the groove. That would stop the shaft sliding and rotating and would probably be a lot easier than using screws as in your diagram.
If you do choose to use grub-screws then you only need one of them. If the screw end is pointed it will sit in a groove in the shaft.
Make 3D printed collars from PLA (equivalent to the yellow collars, but non-stretch) that are a tight fit.
Since they appear to have set screws, they should work for you.
In the US and other places, they are called "collars" because they are not designed to slip on a shaft. A "sleeve" is designed to be a space holder and slip on a shaft.
Paul_KD7HB:
Since they appear to have set screws, they should work for you.
In the US and other places, they are called "collars" because they are not designed to slip on a shaft. A "sleeve" is designed to be a space holder and slip on a shaft.
