RE: Buffer day in MRP Start Date calculations

[Mark Dunn <mark.dunn@xxxxxxxxx>]

In MRP Lead time adjustment manufacturing only pushes your dates.
Try using the BOM Component lead time adjust.
This is the number of days BEFORE THE DUE DATE that the parts are required.
This allows you to create an item and have components recommended to be
ready part way through the assembly process.

e.g. Building a plane. You need the wings to be started and ready by day 20
of the process. You don't need them ready at the beginning because you have
to build the fuselage and won't be able to attach them until that date.
Lead time of plane = 50 days
Lead time to build wings 7 days
Component lead time adj of Wings = 30 days

Normally MRP will recommend to build the wings before the parent. This can
stop or improve that recommendation.

The Mnumbers would be raised like the following:
Mnumber to build the fuselage Start date: day 1. Due Date: day 50
Mnumber to build the Wings Start Date: day 13. Due date day 20

To calculate the start time of the wings MRP counts back from the due date
30 days (the component lead time adj) and sets that date as the required
(Due) date for that component.

You can also use this to prevent high value or short lifespan components
being held on stock for long periods during assembly.

You can also create (your actual question) a buffer zone by making the
component lead time adj 1 day (or 2 days) GREATER than the lead time of the
parent.
This way your subassemblies are ready or due to be completed a day or two
BEFORE the start date of the parent allowing you to have all of your stock
ready for the morning shift.

Component lead time adjustment is found in the BOM and not in the item
balance like other lead times factors.

Regards,
Mark Dunn
Business Analyst
PDL Electronics
New Zealand

-----Original Message-----
From: paul.connolly@selkirk.co.uk [mailto:paul.connolly@selkirk.co.uk]
Sent: Friday, 8 March 2002 7:24
To: MAPICS-L@midrange.com
Subject: Buffer day in MRP Start Date calculations


Hello

For an item is there a way to set a buffer day which allows MRP to
incorporate a one day gap between the Start Date calculated for a Parent
Item and the corresponding Due Date of the component? We currently do not
utilise operation scheduling in PCC (due to a lack of detailed routings) and
a typical leadtime will be 2 or 3 days per BOM level. Relying on a component
to be available first thing in the morning on a start date, when the
leadtimes are relatively short, causes us problems for the management of the
subsequent material issuing to the parent item.

We have looked at the Leadtime Adjustment Factor but this seems a bit messy.

Is this a common problem or is our thinking misguided as to the
interpretation of the due date to start date relationship?

Best regards

Paul

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