I want to know impact of schedule margine key in production scheduling in following changes in mateial master 
1) if I have schedule key where all floats are zero but I enter in-house prodution time as e.g. 7 days . 
2) if I have key where floats before prodution is 5 days and same values in next floats and in house production time as 1 day. 
All above with MTO what is impact of above cases in scheduling. 

While "Basic Scheduling" in MRP... Scheduling margin key is not considered. It takes the "In house production" days for fixing up the start date. This is only exact to "days". 

Lead Time scheduling is carried out on request from the scope of MRP. Target dates are calculated from routing and Capacity requirement calculations are also done. The calculations are exact to the seconds (time). 

SCHEDULING MARGIN KEY takes effect only for Lead Time Scheduling. For this you have to configure for "scheduling horizon" to limit the period for which lead time scheduling and capacity planning should be carried out. scheduling horizon is the period in working days. If a planned order has its basic start date within this period in future, lead time scheduling is carried out using the selected routing. The production times are calculated from the float times of the scheduling margin key in the material master record and the time from the individual operations. If the planned order has its basic start date further in the future than this scheduling horizon, the basic dates are calculated from the in-house production times in the material master and are transferred to the production times.
 

Could you explain what's function of opening period in Sched Margin key. 

Opening period is like a "release window". The length of the opening period is the window of opportunity a planner has to convert the planned order to a purchase req. 

For example - Component A has a lead time of 14 days and opening period of 5 days. Requirement on 12-22-03 

Opening Date - 12-01-03 
Start Date - 12-08-03 
Finish Date - 12-22-03 

Now the planner can convert the order starting Dec. 1st, instead of Dec. 8. It basically is a buffer in the lead time to get things on order a little sooner than needed. 
 

What's the function for Plan order convert to production order? 

As your example, 
Requirement on 12-22-03 

Opening Date - 12-01-03 
Start Date - 12-08-03 
Finish Date - 12-22-03 

But I can convert plan order to production before 12-01-03 at random, so I wonder what is the opening period real function? it looks useless to restrict when to convert plan order to production order.
 

CO41 and MD15 are used for the conversion process. Here you enter the opening dates you wish to convert. Of course the opening period will not stop you from converting planned orders - hopefully your planner is not randomly converting orders or you have much bigger issues!!!! 

The opening period is basically just to get the planned order to show up on the CO41 or MD15 lists in case you wish to convert it sooner than the lead time suggests.
 

Your answer make me clear to understand the opening period. 
BTW,could you explain the release key ,float after production and float before production parameter in SchedMargin key? 
I know the parameter affection in production,but I am not sure why to define how many days in each parameter. 
for example, release key defined for 10 workdays,but you can release production order out of the release period randomly.any way to stop release out of the release period? 

For example - Component A has a lead time of 14 days and opening period of 5 days. Requirement on 12-22-03 
Opening Date - 12-01-03 ??? 
Start Date - 12-08-03 (from requirement date - lead time ?) 
Finish Date - 12-22-03 (from requirement date ?) 
Why Openning date = 12/01/2003 how system calculate , Could you please explain to me.. 

I know that when we run MRP system will check if the opening date is out of open period system will generate Plan order instead of PR . 
 

The times in the sch. margin key are in workdays. That's how it gets the dates. The component I was describing originally would have been a purchased part, where lead time is in calendar days. 

The order start date and the order finish date form the framework within which a production order is to be executed. Since malfunctions and disturbances in the production process can never be fully prevented, the system uses particular floats in a production order. The system takes into account so-called "before and after production floats" when scheduling an order. 

The float before production is a start float. It has two functions: 

It can compensate for delays in the staging of the material components. 
If there is a capacity bottleneck at the work centers involved, the production dates can be moved forward in the future. In this way it serves as a float for capacity leveling. 
The float after production is a finish float. It is used to compensate for unexpected disturbances in the production process, so that they do not delay the scheduled finish date. 

The floats before and after production are defined for each material using a scheduling margin key. This scheduling margin key is automatically transferred from the material master when an order is created. However, you can change the times in the order. 

The system calculates the scheduled start of the order by adding the float before production to the order start date. It calculates the scheduled finish of the order by subtracting the float after production from the order finish date. 

The system deducts the number of days defined in the release period from the scheduled start of the order and thus determines the scheduled release date of the order. This date can be used for collective release.

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