topic Re: Conveyor decision point stop and delay: can it use accel / decel? in FlexSim Forum

Conveyor decision point stop and delay: can it use accel / decel?

craig_dickson — Thu, 11 Feb 2021 00:23:44 GMT

[ FlexSim 20.2.3 ]

When a conveyor conveyor decision point has its arrival trigger set to "stop item and delay", it appears that the conveyor acceleration is not used: the item just goes immediately from full speed to stopped in zero, and then after the delay from stopped to full speed in zero time. Is there a way to make the item accelerate (and maybe decelerate) on the conveyor? I don't want to use a motor because there are other items elsewhere on the same conveyor that should not stop, and the conveyor has multiple places where the item could stop.

Re: Conveyor decision point stop and delay: can it use accel / decel?

jason_lightfoot_adsk — Thu, 11 Feb 2021 12:38:42 GMT

The legacy basic conveyor did this but it didn't have decision points. Can you not use multiple conveyor sections ?

Re: Conveyor decision point stop and delay: can it use accel / decel?

craig_dickson — Sat, 20 Feb 2021 01:10:41 GMT

I have (at a minimum) 84 places along the conveyor where an item might stop, with following items queueing up behind during the stop. The item then continues. So that would be (at best) impractical.

I'll probably just do some math and increase the stop time to reflect the accel/decel. Analytically correct, but doesn't look quite right in the animation.

I can understand the difficulty of using decel if you're counting on the arrival trigger of the dp to decide whether to stop the item. But it seems like it should be feasible if you actively route the item to that dp from a previous dp (or process flow)

Re: Conveyor decision point stop and delay: can it use accel / decel?

joerg_vogel_HsH — Sat, 20 Feb 2021 04:56:05 GMT

Hi @Craig DIckson, I want to learn which mechanical device let a flow item decelerate on a conveyor. Thank you for your support. Pleases don’t feel offended. I am just curious. Thank you very much.

Re: Conveyor decision point stop and delay: can it use accel / decel?

craig_dickson — Sat, 20 Feb 2021 17:48:29 GMT

@Jörg Vogel Mechanically what I am modeling not actually a conveyor, it's a set of shuttles on a loop track, carrying and sorting other items. In theory I could also have modeled it as a set of AGVs, but it's much more straightforward to build the actual logic in a FlexSim conveyor system, and also much more analogous to how the actual system operates.

But there are plenty of conveyor systems that actually accel and decel individual items. For example, conveyors that use powered rollers have independent zones and the zones don't stop or start immediately. Usually we model this accel/decel time using the conveyor restart delay. And as controls get cheaper and smarter there are more situations where it may become important. (Descramblers come to mind.)

Re: Conveyor decision point stop and delay: can it use accel / decel?

jason_lightfoot_adsk — Sat, 20 Feb 2021 17:54:19 GMT

Then I suggest if this behaviour becomes critical you should use the AGV logic or basic conveyors. I don't see why it's so much simpler to use conveyors.

Re: Conveyor decision point stop and delay: can it use accel / decel?

joerg_vogel_HsH — Sun, 21 Feb 2021 02:59:36 GMT

Thank you!

Re: Conveyor decision point stop and delay: can it use accel / decel?

joerg_vogel_HsH — Sun, 21 Feb 2021 05:07:40 GMT

Currently this is only a feature of a transfer wether exit or entry. And this means you have to insert a conveyor section in your system.

You can extend the location to a full stop by a repeating stop and go mechanism implemented by a delayed repeated message mechanism. Each message let the item stop longer and travel shorter in alternating occurrences until a full stop should happen.

Another bogus deceleration could you implement by delayed message initiating a stop. You set the conveyor item invisible from the time the event occurs until a drawsurrogate item has fulfilled a kinematic deceleration to the point on the conveyor where you have stopped the conveyor item. Then you set the conveyor item visible again and delete the drawsurrogate.

Re: Conveyor decision point stop and delay: can it use accel / decel?

joerg_vogel_HsH — Sun, 21 Feb 2021 05:22:26 GMT

The bogus deceleration mechanism works with an acceleration, too. And you can replace the kinematic by animations in the item. It is still a fake, but it will look quite realistic on straight sections for any leading item. Each following item will bump into the previous one and a static animation will mess up the visualization.

Re: Conveyor decision point stop and delay: can it use accel / decel?

jason_lightfoot_adsk — Thu, 25 Feb 2021 00:44:52 GMT

Hi @Craig DIckson, was Jörg Vogel's or jason.lightfoot's answer helpful? If so, please click the red "Accept" button at the bottom of one of their answers. Or if you still have questions, add a comment and we'll continue the conversation.

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