topic Re: Extremely confusing Rack and Astar Behavior in FlexSim Forum

Extremely confusing Rack and Astar Behavior

NC32 — Tue, 05 May 2026 16:10:52 GMT

I have two racks sitting on roughly the same plane in the astar navigator. One rack setup is the default size shape etc. the other setup is the same as the first, but two racks at half the y size facing back to back. The astar grid is showing inconsistent blocking patterns for the single rack vs the two back to back shown below.

I am building a large facility with racking that needs to be accessed back to back and the inconsistent astar spacings are driving me crazy. How should I set things up so that I can send objects to either side of a rack aisle and still keep expected star spacings? each aisle is a one way access so I must be able to send objects to a specific side of the racking.

Re: Extremely confusing Rack and Astar Behavior

joerg_vogel_HsH — Wed, 06 May 2026 11:17:39 GMT

One is a member of the A*Star system and the other is not. Please verify it in toolbox A*Navigator properties window.

Re: Extremely confusing Rack and Astar Behavior

moehlmann_fe — Wed, 06 May 2026 13:42:18 GMT

As far as I can tell, an object that is an A* member always blocks at least grid cell. Which one, is, as you say, weird sometimes.

As a workaround I would suggest to just not have the racks be A* members and instead use barriers to block the cells where needed. If the aisle spacing is not a whole multiple of 1m it might also make sense to change the grid spacing to better fit the layout.

Re: Extremely confusing Rack and Astar Behavior

NC32 — Wed, 06 May 2026 21:51:06 GMT

I found more details into what is going on when looking at the allocations.

When a rack was set in-between two grids, it blocked the node to the front of the rack, even though the object itself is closer to the back grid than the front. When spanning across 3 grids, it behaves closer to expected. It makes sense that the object needs to block atleast one grid, however which grid it chooses to block isn't always the closest as I'm finding out.

Re: Extremely confusing Rack and Astar Behavior

NC32 — Wed, 06 May 2026 21:52:52 GMT

I was able to nudge racking in different directions to get close to what I was looking for but removing them and adding barriers likely would have worked just as well.