Polybelt melting to pulley

Our current conveyor system is using poly belts to transport the power cells and is working reasonably well. We have belts on either side of the ball to prevent jamming. We are utilizing sensors to help provide spacing between balls so they hopefully don’t touch. We are currently utilizing one NEO to power the system, and using a polybelt twisted in a figure 8 to power both the top conveyor belt and the bottom belt. Occasionally we will have 2 balls touch and jam for a second or so. The belt driven directly by the NEO continues to turn and we can eject the balls/clear jam. The problem is that sometimes the belt is melting and sticking/adhering to the pulley which drivers the figure 8 belt. The pulley is currently printed with PETG. Wondering if anyone else has similar experiences, and what solutions you discovered?

We are thinking trying pulleys printed out of either PLA or Nylon and see what happens. Also considering trying to find aluminum pulleys we could broach if necessary. Ideally our sensors and programming will eliminate this issue, but we are trying to eliminate as many possible points of failure as possible.

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We have small pulleys made of PLA routing urethane round belt (link). For the prototypes the whole system was driven by the belts and we did see some residue left on the pulleys. Our final design has motors driving the shafts, and chains distributing power to other shafts. The pulleys and belts are driven that way, not on their own.

Your setup is putting a large stress on the belt if it is a direct drive NEO.

The belts are from McMaster.

Can you tell where the heat is being generated in that figure 8? It seems to me a lot of it might be caused where the two strands cross and are (presumably) in contact with each other. If so, putting a slick baffle between the two (teflon, coroplast, etc) may reduce the heating.

We used polycarbonate rollers + polycord in 2017 for our feeding system and the polycarbonate always held up to the friction. I don’t think we ever really had to replace the belts after we broke a couple initially from bad joints.

Comes from belt slipping on pulley when we had a jam. We are probably running the conveyor a little too fast when we get a jam. We are shooting all 5 power cells into top goal balls in under a second from the base of the target. If we don’t jam, we have no problems. Spacing via software and sensors should help. Just trying to find if other pulley material would be better.

i would defiantly recommend slowing your speed down. I am not sure any plastic material on the pulleys will help much. The polycord is TPU (thermoplastic Polyurethane) which is essentially a glue and typically melts above 375^F - which is very low. You can try to smooth, sand and polish the pulleys to reduce the friction and hopefully not melt the TPU. Using a wax to polish the pulleys could help with the friction as well.

What sort of reduction ratio do you have between the NEO and the rollers? What is the diameter of the rollers?

I would try increasing the belt tension, increasing the pulley friction, and decreasing the motor current limit to prevent the belt slipping. Decreasing friction between the pulley and belt is probably contrary to what you want to do

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1:1 ratio. 2 inch pulley.

Any suggestion on a material that can withstand higher temp, be made custom length, and run in a figure 8 pattern?

We’ve used PLA pulleys in the past with success. Last year, we had a similar issue with slipping, so we doubled the pulleys and polycord and it helped prevent the issue.

This isn’t your issue. You’re creating a lot of friction in the jam state with your neo running so fast. Have you considered running something slower? Our feed system is run off a bag motor on a 30:1 ratio with great speed and feed.
Last year we ran our intake with a figure 8 loop polybelt with rollers on a bag with 10:1 ratio and experienced no heat, even though our design was done to want jamming to keep the ball in our intake.
I would suggest slowing your system down, as well as look to see if you are rubbing the belt onto itself.
Otherwise, you could look at machining a pulley our of a plastic like Delrin. Great for machining, and we run poly on it all the time with great results.

i have not found any belt material that is easy to bond and higher temperature. monitoring motor current might also be an option for you.

Thanks for all of the input. We are going to slow down the drive belts and hope software can help out as well. Trying to find the balance between maximum speed and limiting mechanical problems is a challenge.

How fast do you want the belts to be moving?

You should work out what the surface speed is on the circumference of your pulley with the free speed of your motor. With the 1:1 drive to the pulley, the motor won’t really be turning at that speed but my gut feeling is that if the motor is running at 50% of it’s free speed, your surface speed would be much higher than your desired speed. Without going through the math, the 30:1 ratio at @Anthony4004 mentions sounds more reasonable.

We had a similar issue with polycord on PLA printed pulleys for an off season bot last year. If the rollers jammed, the belt slipped on the pulley and got hot, then they glued together when they stopped. Not really sure which was melting, the poly or the PLA, but I think it was the PLA mostly just from looking at it, but might have been both. Our solution, since it was an off season bot with one competition day to get through, was simply to ensure the intake was always moving, so if it jammed, we could run it backwards to clear the jam, and the system would then keep moving at a slow speed to keep the belts and pulleys from gluing together as they cooled, then back to high speed when we wanted to intake. It worked, but was not a great solution and not one I would plan to use in a real competition if at all possible, and not a solution that would work in your case anyway. All that to say PLA won’t likely help you at all.

Possibly remove the figure 8 belt and use two motors instead?