Conveyor Etc.
Originally Posted by J0J0!
Idle rollers (1" dia. x 1.25" length) on a small 20-year old conveyer system are made of nylon running on steel shoulder bolts turning < 100 rpm. The nylon rollers wear over a year or 2 such that the bearing clearance is no longer acceptable and the belts that run over these rollers start to wander.
Replacement rollers made from delrin don't last much longer.
So we've decided to try inserting sintered bronze bushings into the rollers. When drilled, the nylon bushings are not holding the bushings. They press in (-0.003 interference fit) but then loosen immediately. (The machinist says the nylon is cracking, but I can't see evidence; it looks to me like scoring, not cracking.)
Does delrin have better properties such that it will be better at maintaining the pressed bushings? A better, commonly-available plastic we should look at?
Any observations, suggestions that help toward the goal of getting these rollers rolling again would be greatly appreciated.
Thanks.
If this is a an un-powered roller skate conveyor-which I thnk it is the better course is to replace the entire unit with a new one or a roller ball conveyor bed (If they are made that small) as you will be money, time and aggravation, ahead
Sadly the skate conveyor in any use was not ment to last forever because it allows a lower cost method of material movement.
You might as well buy a replacement from Mcmaster Carr and be done with it as it will be less work.
lzaharis ■
Bronze Bushing In Nylon Support
The outer diameter of the bushing should have an profiled surface like shown in attached sketch. Such bushings I have seen in several non-outdoor + non-heavy-duty applications, so it remains to decide whether such solution is appropriate or not.
In order to get the thing done as it is you should base on professional know-how of a experienced supplier, as success truly depends on: correct tolerance of bushing to bore connection, correct choice of material (nylon is not everytime nylon, there're differences), correct definition of materials thickness around the bore.
Nylon is by far less stiff than metal (bronze), so the material gives way..anyway. IMO: If the press fit is too stiff (tolerances!) and/or the flange too thin, the nylon will crack at the contact. If the press fit is less stiff, the surface of the nylon will give way and will look like scored, even if not having turned.
So make the contact surface of the bushing profiled in a way that surplus material can find it's way... --> sketch
Regards
Roland ■
Pressed Bronze Bushings?
Delrin: ability to accept pressed bronze bushings?
Idle rollers (1" dia. x 1.25" length) on a small 20-year old conveyer system are made of nylon running on steel shoulder bolts turning < 100 rpm. The nylon rollers wear over a year or 2 such that the bearing clearance is no longer acceptable and the belts that run over these rollers start to wander.
Replacement rollers made from delrin don't last much longer.
So we've decided to try inserting sintered bronze bushings into the rollers. When drilled, the nylon bushings are not holding the bushings. They press in (-0.003 interference fit) but then loosen immediately. (The machinist says the nylon is cracking, but I can't see evidence; it looks to me like scoring, not cracking.)
Does delrin have better properties such that it will be better at maintaining the pressed bushings? A better, commonly-available plastic we should look at?
Any observations, suggestions that help toward the goal of getting these rollers rolling again would be greatly appreciated.
Thanks. ■