Routing Question (Marc Graff)

Hi Marc,
 
Attempting to make your Shop Order scheduled time match the "static" MRP lead 
time can be tricky. It's fairly straight-forward if your order quantities are 
constant. However in many environments, the quantities from one instance to the 
next (for the same item) can vary significantly. In your example, you didn't 
reference if there were quantity swings between the shop orders. Also, I'll 
assume you are not running these Shop Orders as part of a campaign in API.
 
The following information should prove helpful in your analysis. You correctly 
stated that BPCS schedules backward. On a shop order, regardless of quantity, 
the Queue, Setup and Move times will be constant. Therefore any variation in 
the operation Start/Complete times would come from multiplying the order 
quantity by the Run (or Machine) times. 
 
As a general rule for BPCS scheduling, Queue is time added before the 
Operation's Start Date. Move Time is added after the Operation's Complete Date. 
The calculated Operational Time (Setup + calculated Run/Machine time) is 
sandwiched in the middle. So the back-scheduling calculation for a one-step 
shop order is performed as follows:
 
Order Start Date  =  (Order Due Date) - (Move Time Days) - (Calculated 
Operation Time) - (Queue Days)
 
Note: Calculated Operation Time = (Setup Hrs) + (Run Hrs/Unit  x  Order 
Quantity).  
BPCS inserts the operation's Start and Complete dates at the beginning and end 
of this segment. 
 
Some additional thoughts that might help are:

1.      
        Check the  Run/Machine times and Time Basis Codes within the routing . 
Be sure the total Operation Times are being calculated consistent with your 
expected lead time.
2.      
        Consider utilizing a combination of "Lead Time Days" (static) and 
"Daily Lead Time Rate" (variable) in MRP140. In essence, this allows MRP to 
calculate a "dynamic" lead time for planned orders. This could help if there 
are wide swings in order quantities.

Marc, hopefully this information helps you solve the problem. Feel free to post 
a follow-up question if necessary.
 
Sincerely,
 
Michael J. Sarro II, CPIM, CSCP
PHOENIX Business Consulting, Inc.
Direct: 484-431-4260
msarro@xxxxxxxxxxxxxxxx

message: 1
date: Wed, 24 Jan 2007 08:16:27 -0800
from: "Marc Graff" <mgraff@xxxxxxxxxxxxx>
subject: [BPCS-L] Routing question

I'm hoping someone can offer some insight into how manipulating routing
Queue and Move times impacts capacity regarding how Bpcs plans orders at
workcenters.

We recently changed the lead time days for planned items to 4 days; we
are using Bpcs 405cd.  We discovered that some of our routings total
time (Set Up, Run, Q, Move) was more than the lead time days.  This
caused the 'release date' to be later than the start date of the first
operation; from a capacity standpoint the first operation start date was
a day prior to when the system told us to open the shop order.

In order to have the routing time be less than or equal to 4 days I
removed 1 day worth of Move from the routing (example below).  I was
expecting the result to be that the first operation start date would be
equal to the release date-the first operation start date would move to a
day later.  This did not happen.  Of the 6 planned items that had the 1
day of Move removed, 4 planned items actually had the first operation
start date move to a day earlier, and 2 didn't change.

Since, I believe, Bpcs backward propagates to get operation start times,
when removing Queue or Move times, should the operation start times move
to a later date/time and not an earlier date/time?

Any insight into how Bpcs manages this would be greatly appreciated.








Marc Graff

Production Control Manager

States Industries, Inc.

(541) 688-7871 ext. 283





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