topic Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results in FlexSim Forum

Roller and Mass Flow Conveyor With Same Config Showing Different Results

arunTTT2P — Tue, 22 Aug 2023 10:22:03 GMT

[ FlexSim 23.2.0 ]

Hi,

I have created a roller and mass flow conveyor with the same parameters. The mass flow conveyor is having a width rule with the number of lanes 1.

The conveyors are having the same speed, length, and flow item size. Initially, for some period of time, the throughput remains the same. And after some time there is a difference in the throughput. I believe it should be the same since the mass flow is using a width rule here.

Attaching the model for reference.

MassFlowConveyor.fsm

Regards,

Arun KR

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

jason_lightfoot_adsk — Tue, 22 Aug 2023 11:35:46 GMT

Have you calculated which one is wrong?

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

jason_lightfoot_adsk — Tue, 22 Aug 2023 12:01:08 GMT

Yes - it looks like the regular conveyor has extra gaps between the items.

Change your decimal displayed precision to 6 digits and run this script with items on the conveyors:

applicationcommand("outputconsole");
Conveyor conv=Model.find("StraightConveyor1");
Array convItems=conv.itemData.toArray();
double lastpos=0;
double pos;
for (int n=convItems.length;n>0;n--){
    pos=convItems.as(Conveyor.Item).position.x;
    print(n, " Pitch is:  ", pos-lastpos);
    lastpos=pos;
}

You'll see the items on the regular conveyor are sometimes 0.2mm apart where there should be no gap. You can even see the gap visually compared to the mass flow conveyor.

I'll send it into the developers for them to consider.

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

arunTTT2P — Tue, 22 Aug 2023 12:42:52 GMT

The roller conveyor throughput is incorrect as per my calculation. The mass flow matches my calculation.

The model units are in meters and seconds.

Here's my calculation.

The item dia is 0.04 m. The assumed speed of the conveyor is 1 m/s.

Number of Items moved in 1 second = 1/0.04 = 25 units

Conveyor Input for a model run time = Model run time * No. pucks moved in 1 secondmassflowconveyor_1.fsm

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

jason_lightfoot_adsk — Tue, 22 Aug 2023 12:44:18 GMT

They were 0.05 diameter in the model you uploaded, but I agree - it looks like the regular/roller conveyor is incorrect.

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

arunTTT2P — Tue, 22 Aug 2023 16:01:44 GMT

Pls give this a priority

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

JordanLJohnson — Tue, 22 Aug 2023 19:34:11 GMT

As far as I can tell, this is the designed behavior. See this answer for an in-depth explanation:

https://answers.flexsim.com/questions/141949/accuracy-of-conveyor-speed.html

Re: Roller and Mass Flow Conveyor With Same Config Showing Different Results

jason_lightfoot_adsk — Tue, 22 Aug 2023 21:06:00 GMT

@Arun Kr , in a nutshell the tinyGap value used in the conveyor's background behavior is based on the ConveyorSystem's 'Snap Threshold' property which was set to 0.2m:

If you reduce that to 0.01m (which is the minimum) then the tinyGap will adjust to a lower number and the conveyor will become more accurate. It seems this is a direct relationship - the tiny gap value that influences the pitch of the items is 1000th of the Snap Threshold - so 0.01m snap gives you 0.01mm gap between items.