Lesson 22: Data and Decisions | Slides | Material Handling Academy

MATERIAL HANDLING ACADEMY

Part V. Lesson 22. Data and Decisions.

DRIVING QUESTION What has to move between systems, how fast, and what happens when it doesn't arrive?

PART V | LESSON 22: DATA AND DECISIONS

The Email That Changes the Design

You logged Ray's half-second WMS response as an open item and kept building on the placeholder. Then this lands in your inbox.

EMAIL | RAY, IT SYSTEMS ADMINISTRATOR

"Hey. Checked with our IT manager on the WMS response time question. The half second I mentioned in the meeting was best case on a normal day. Under peak load conditions the guaranteed response time is one second. That is what you should design to. Sorry I did not have the right number in the room. Let me know if you have other questions."

PART V | LESSON 22: DATA AND DECISIONS

The Three Data Questions

What information is needed here to make the correct decision? A barcode, a weight, a destination code, an order status.
Where does that information come from? Embedded in the barcode and readable right at the machine, or a lookup from a higher-level system through middleware.
Who makes the decision? The PLC on its own local logic, or a request up to the WCS or WMS and a wait for the answer.

PART V | LESSON 22: DATA AND DECISIONS

Information Flow Is Not Product Flow

Information flow is a separate thing from product flow. The carton moves down the belt, and that's product flow. The barcode read, the routing query, and the routing answer move across the network, and that's information flow. The whole trick of a smart decision point is getting the information flow to finish before the product flow arrives at the divert. Two races run at once, and the data has to win.

PART V | LESSON 22: DATA AND DECISIONS

FIELD INSIGHT | MICHAEL COLLINS

The controls conversation with the customer does not focus around machine level controls. It focuses around data acquisition at each smart point in the system. What information needs to be exchanged between the system controlling the automation and the systems of the house. That is fundamentally where a solutions engineer wants to live: what information needs to be ascertained from who, at what location, so we can make the decisions in our automation.

PART V | LESSON 22: DATA AND DECISIONS

The three-part data handshake, and where each part fails

Part	Direction	What happens	Where it fails
1. Request	Machine to upper system	The PLC reads the identification and sends it up through middleware with a request for routing.	No-read: the barcode's unreadable. Timeout: no answer comes back inside the window.
2. Response	Upper system to machine	The WCS or WMS looks up the item, picks the destination, and returns the routing instruction.	Wrong destination returned: the item's diverted to the wrong place. Delayed response: the item's already past the point, sort missed.
3. Confirmation	Machine to upper system	The PLC executes the divert and reports back that the item reached its assigned destination.	No confirmation sent: the upper system doesn't know it landed, inventory accuracy slips. False confirmation: the item jammed but the record says success.

Part

Direction

What happens

Where it fails

1. Request

Machine to upper system

The PLC reads the identification and sends it up through middleware with a request for routing.

No-read: the barcode's unreadable. Timeout: no answer comes back inside the window.

2. Response

Upper system to machine

The WCS or WMS looks up the item, picks the destination, and returns the routing instruction.

Wrong destination returned: the item's diverted to the wrong place. Delayed response: the item's already past the point, sort missed.

3. Confirmation

Machine to upper system

The PLC executes the divert and reports back that the item reached its assigned destination.

No confirmation sent: the upper system doesn't know it landed, inventory accuracy slips. False confirmation: the item jammed but the record says success.

PART V | LESSON 22: DATA AND DECISIONS

Two panels. The top panel shows the three-part handshake: a PLC machine-controls box and a WCS/WMS upper-system box with three arrows between them, request going up, response coming down, confirmation going up, each tagged with its job. The bottom panel shows the latency budget as a timeline along a belt: a carton at the scan trigger, a transmit point 24 inches downstream, the distance the carton travels during the 1-second response, a gold marker where the routing instruction must arrive, and the divert, with an illustrative figure at 120 feet per minute. — One sort point, two views. What moves between the systems, and the race the answer has to win before the carton reaches the divert.

PART V | LESSON 22: DATA AND DECISIONS

Latency Is Physical, Not Software

WHYThe item's moving from the moment it's read. If the answer arrives after it's past the divert, the sort's missed, no matter how good the software is. It's a distance-and-speed problem wearing a software costume.

WHENDuring the flow diagram phase, while belt speeds and gaps are being set, and re-checked the instant the number changes.

WHEREAt every sort point that depends on a lookup, and in the interface contract with whoever owns the upper system.

NOT WHENDon't file the response time under software and assume they'll handle it. It sets the distance between your scan point and your divert and it can set your belt speed. It's a physical requirement you own jointly with the controls team, not a setting someone tunes later.

FAILURE IF IGNOREDYou design the scan-to-divert distance around a number nobody confirmed, the real response time comes in slower under peak, and the instruction shows up after the carton's already past the divert. The sort misses on exactly the shifts that matter most, and now the fix is moving hardware instead of changing a line in a spec.

PART V | LESSON 22: DATA AND DECISIONS

Deliverable A: Latency budget worksheet reusable template

Line	Value	How you get it
Belt speed (V)	______ FPM	Your specified speed at the sort point.
Response window	1.0 s	Ray's confirmed number, guaranteed under peak load.
Response distance	V x 1.0 s	How far the carton travels while the upper system answers.
Actuation time	0.25 s	The divert mechanism, from the project data.
Actuation distance	V x 0.25 s	How far the carton travels while the divert fires.
Required transmit-to-divert	response + actuation distance	The minimum distance the layout has to give you.
Actual transmit-to-divert	______ in	Measured on your layout, from the 24 in transmit point to the divert.
Fits?	actual is at least required	If it doesn't, pull one of the levers below.
Levers if it fails	distance / speed / gap	More scan-to-divert distance, a slower belt, or a bigger gap. All three are physical.

Line

Value

How you get it

Belt speed (V)

______ FPM

Your specified speed at the sort point.

Response window

1.0 s

Ray's confirmed number, guaranteed under peak load.

Response distance

V x 1.0 s

How far the carton travels while the upper system answers.

Actuation time

0.25 s

The divert mechanism, from the project data.

Actuation distance

V x 0.25 s

How far the carton travels while the divert fires.

Required transmit-to-divert

response + actuation distance

The minimum distance the layout has to give you.

Actual transmit-to-divert

______ in

Measured on your layout, from the 24 in transmit point to the divert.

Fits?

actual is at least required

If it doesn't, pull one of the levers below.

Levers if it fails

distance / speed / gap

More scan-to-divert distance, a slower belt, or a bigger gap. All three are physical.

Illustrative check at 120 FPM, which is 24 inches per second: response distance 24 in, actuation distance 6 in, so you'd need about 30 in from the transmit point to the divert. That figure shows the method. It isn't Riverside's confirmed belt speed.

PART V | LESSON 22: DATA AND DECISIONS

Deliverable B: Interface map reusable template

Link	Payload up	Payload down	Timeout	Retry	Failure behavior
PLC to WCS	The barcode read.	The door assignment.	1 s	Your rule.	No answer in the window routes the carton to the hospital lane, the staffed exception spot where a person sorts what the system couldn't.
WCS to WMS	The routing query, keyed to the barcode.	The carrier-to-door instruction.	Inside the 1 s budget.	Your rule.	No destination returned is treated the same as a no-read.

Link

Payload up

Payload down

Timeout

Retry

Failure behavior

PLC to WCS

The barcode read.

The door assignment.

1 s

Your rule.

No answer in the window routes the carton to the hospital lane, the staffed exception spot where a person sorts what the system couldn't.

WCS to WMS

The routing query, keyed to the barcode.

The carrier-to-door instruction.

Inside the 1 s budget.

Your rule.

No destination returned is treated the same as a no-read.

How each failure actually gets handled, the timeout out to the hospital lane, the degraded mode when the WMS is down entirely, is the exception routing, and that's Lesson 23.

PART V | LESSON 22: DATA AND DECISIONS

COMMON MISTAKE

Treating the response time as a software problem only. The window between scan and divert is set by belt speed and distance, and both are physical. If the upper system can't answer in that window, no amount of code speeds up a carton that's already moving. The mechanical layout has to change, and both teams own that number.

Next: When it jams, stalls, or goes dark, how does the system recover?