Conveyor S Curve

[FONT=&quot]Advice request.[/FONT]
[FONT=&quot]I need to program a conveyor (200’(L) x 4’(w) with a S-curve motion so as not to shake a liquid in a 1L beaker. The liquid has a viscosity similar to molten parrafin. Are there any precautions or advice that I should know about to head off issues. I am planning to use an Automation Direct VFD to a 5hp motor to a gearbox that steps down the motor speed. The gearbox will not be new and has been on this same conveyor line for a long time, but the motor and drive will be new. The VFD manual shows that S-curve accel. and decel. are independently programmable over 7 pre-selected increments. [/FONT]
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[FONT=&quot]The way this works is that I choose the accel and decel times between 0.1 & 600 sec, but then I select a S-curve between 1 & 7 and turn over the actual speed to the VFD. AFAICT, 1 is the least S and 7 is the most S. If the motor speed does an S over a fixed time width (say 15 sec), then the belt will have to go faster in the middle of the S than it would be going with linear accel.[/FONT]
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[FONT=&quot]Really important that this liquid doesn’t shake. Miniscus must remain flat.[/FONT]

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[FONT=&quot]narlin
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Narlin,

several questions for you.

is this a new conveyor?
what type of belt?
do you mean there is an "S" curve in the belt or do you mean ramp up/down?
when you say 200 ft, is this one conveyor?
regards,
james

There is 1 conveyor with 8 linked belts to make 1 long belt. 200' one way and 200' back. 4'+ wide.
The conveyor frame and belt is not new and i will put some new glides on it to reduce friction and i will level it and figure out how to adjust tension.
The belt is some kind of chain link. I have seen it but not really started trying to assemble it. Each of the 8 sections is attached to the next with a 4+ foot long rod. by "S curve" i am referring to slow acceleration followed by speedier movement follow by slow deceleration. These curves are built into most VFDs.

Narlin,

its called a chained belt or chained link belt conveyor.

you should assemble the conveyor the way you take it apart.
its wear patterns will be the same and will not cause a big issue.

BEWARE of the sharp edges caused by wear! they will tear you up!

since you are reassembling the conveyor, you will need to retension the belt by stretching it a bit. by that I mean start it at a slow speed and then stop after 2 or 3 minutes.
check for slack. repeat only a little faster.

even though its used. you still need to wear it in.
finally fun it for 30 minutes at 125% speed ( speed your choice) 125% is what we used.

be careful, to much slack will cause the belt to fold over and lock up.
did you mean 4"+ or 4'+

regards,
james

Thanks for the info. I meant 4 feet wide. Probably closer to 4ft 6 in. It holds ~12 liter beakers across the width and each one gets filled up. When I get a little more info on the total number, i will calc the weight. Going to heavy! Meanwhile i am just depending on the fact that it used to work to replace the motor with close to like for like. I will warn the assembly guys to look for signs to reassemble the belt sections like they came off but . . . it came disassembled on the back of a semi and was unloaded unceremoniously. Might take some sleuthing. Have you ever used anything similar?

You need to consider what S-curve acceleration does for you and why it might help.

With constant acceleration the force resulting from acceleration appears in the system "instantaneously". The trouble is no physical system can change the force it is applying instantaneously. All sorts of things have to bend and twist and conform in order to transfer this force. In the process of accommodating these forces the various items can overshoot and oscillate, including the drive velocity loop. This is where you might get a little extra movement of the liquid.

This is different than the effect of force felt due to acceleration. Whether I use s-curve acceleration or not, if something is accelerating, force is being applied. You can't get around F=ma. So how far the miniscus climbs up the upstream side of the container is related to acceleration. The harder you accelerate the farther up the side it will climb.

Keith