Conveyor indexing question

[450x]

Hello gentlemen,

I have an application that involves two short (10 feet) parallel (2 feet apart) indexing conveyors that are mechanically linked through shafts and at either end. Each conveyor is made from matching timing belts and timing pulleys. The conveyor is used to transport sections of stainless steel tube that sit in profiles that are attached to the timing belts. The conveyor is driven by a servo drive and servo motor with a gearbox (ratio to be determined). I need to index the conveyor a distance that matches the profile pitch, then stop and wait for another index trigger from another piece of machinery. The indexing is always in the same direction so the profiles on the belt will “recirculate”. Lets assume that I have ten indexes in one full rotation of the conveyor, will I get accumulating positional errors if I perform my index solely on encoder count from the servo motor, or should I use a registration sensor? When I spec a gearbox, is the ratio an exact ratio? ie could a nominal 3:1 gearbox be in reality a 3.0000001:1?

Thanks
Martin

 

[itsmoked]

Martin,
Nice description.. But I am not personally clear, probably just terminology.

Are these stainless tubes always the same size and shape? (profiles in my business would always refer to different things)


Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[450x]

Hi Keith
Yes, the tubes are always the same size. Same OD, ID and length. The "profiles" that are on the conveyor are the mechanical devices that secure the tube to the timing belt. Timing belt manufacturers always refer to these things as profiles


Thanks

 

[waross]

A fixed ratio gear box is just that, the ratio of the number of teeth on the respective gears. If it is not a rato of simple numbers then its reciprocal will be. Eg; A 3:4 or 4:3 ratio may be expressed as .75 or 1.333.
A ratio of 3:1 will be 3:1.
Consider detecting the position of the profiles or the tubes. You can do it optically, by contact or by proximity.
It will be much easier to maintain adjusty, and troubleshoot.
yours

 

[itsmoked]

Okay thanks, that was kinda what I was guessing.

My first question would be: Why not use optical or prox detection for exact positioning of the actual tubing and then just use a shaft speed sensor to control to any speed profile required? This would essentially avoid any cumulative position errors. Your gearbox could be 3.13131313- and it wouldn't matter. Belts can stretch, things can wear, and ultimately your part will stop where you want it.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[450x]

What you say makes sense.I have verified that as long as the tube is within the profile the upstream machine should be able to process the tube. This means that I will locate the profile with an appropraite sensor. I will connect the sensor directly to the drive to reduce the latency since I am not sure of the scan time of the main PLC. I appreciate your advice.

Thanks
Martin

 

[450x]

"what you say makes sense"

Wow, excuse my english if I can call it that.

 

[itsmoked]

Ahhh shucks don't yall be mentionating it no nevermind.


Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

eP.S. waross; I guess we think a like.