Dynamic Safety Stock

[Former Member]

I configured dynamic safety stock...I am doing this first time .First question I have ..Is dynamic safety stock visible in material master ? Where I can see it ?

Second question :I configured coverage profile with following parameter and I put the weekly requirement 100 for 5 weeks .Material didn't have any stock or any other requirement .So total requirement was 500..Once I run the MRP it created the planned order for 549..I can't figure out how this number came ?

Coverage profile     Z02  Weekly Coverage

Period indicator     W Week

  Number of periods    13
  Type of per.length   1                               No. of Days per Period   0

  Min.  0     Tgt   30    Max.  0                      Number of Periods        0

  Min.  0     Tgt   0     Max.  0                      Number of Periods        0

  Min.  0     Tgt   0     Max.  0

Please help me to understand .

[marianoc · Accepted solution]

Hello,

Dynamic safety stock is configured in t-code OMIA. It is called Coverage Profile.

Once the configuration is done, it is assigned in the material master, in MRP2.

The result of the coverage profile can be seen in MD04 in the projected stock after the MRP is executed.

Take a look of this thread, in which there is an explanation of the coverage profile:

Regarding the setup of your coverage profile, I think it is incorrect. Both: the No of Days per period and Number of periods should not be cero. The first field:  No. of Days per Period  will tell you how many weeks you are going to consider to calculate your daily demand. The second field: Number of periods is the number of periods for which the first range of coverage is valid.

Period indicator     W Week

  Number of periods    13
  Type of per.length   1                               No. of Days per Period   0

  Min.  0     Tgt   30    Max.  0                      Number of Periods        0

  Min.  0     Tgt   0     Max.  0                      Number of Periods        0

  Min.  0     Tgt   0     Max.  0

Now if the MRP generates a planned order for 549, maybe that is because a minimum lot size or rouinding value.

Please correct the coverage profile setup and rerun your MRP. If you still see something wrong, please share with us the views: MRP1 & MRP2 and also the MD04.

Thanks and Regards,

Mariano

[Former Member · Accepted solution]

Mariano,

I like to explain you our requirement .We like to calculate average daily requirement for 90 days..that's the reason we put 13 weeks. Our period is monthly but for dynamic calculation we like to use weekly.

We are using week indicator for calculation and work days for Type of Per. Length that is indicator 1.My understating is if you are using anything except standard days indicator 3 in the field type of per length the number of days per period should be 0.

I made changes as per recommendation and put 1 number of days per period.

MD04

We are using PD MRP type and monthly lot size. We don't have any rounding value.

[marianoc · Accepted solution]

Hello,

You are absolutely right. When the type of Period Length is 1, then you don´t need to enter the number of days per period. I will amend my previous comment.. sorry about my mistake I did not look at the type of per.length.

Now let me explain your numbers.

You have a total of 700 CS of PIRs for the following 90 days. The daily demand is calculated as: 700 CS / 90 Days = 7.77778 CS / day.

Based on your settings, your target safety stock is equal to 30days (appliable only during the first month). So it is: 30 days x 7,77778 CS / Day = 234 CS.

Now, as you can see, the sum of those planned orders is 234 CS.

This example is not clear, because you have PIR in the past and a monthly lot size (I suppose). Try to make the same example, but I recommend to start with the PIRs in the first week of Oct. Run the MRP and you will see a more clear example...

Kind Regards,

Mariano

[Former Member · Accepted solution]

Mariano ,

I made the changes as you requested...following results came.

[marianoc · Accepted solution]

Hi,

Please extend the Number of Periods to 2 months and try again.

Right now your settings say that the coverage should be considered from Sep 8th to Oct 7th. I am quite sure you will see the coverage if you increase the horizon (Number of Periods) from 1 to 2.

Kind Regards,

Mariano

[Former Member · Accepted solution]

Mariano here is the result..

MD63

MD02

[marianoc · Accepted solution]

Hi,

The problem is the No of Periods. I told you to put 2 (the problem is that I was thinking in months, when your period type is W: week). Put 8 in No of Periods.

The number of periods is the horizon that you want to cover with coverage. You had 2 weeks, this is why the MRP does not increase the quantity on your order..

This is what you will see if you put for example 8 weeks:

Kind Regards,

Mariano

[Former Member · Accepted solution]

Oh ok...I guess in  my case week defined as a period...so for coverage I should put at least 4 in number of periods...that way we are covering for 1 month.

[marianoc · Accepted solution]

Hi MK,

Yes. 4 will be covered almost 1 month, the problem is that today we are on Sep 9th, so you will need 8 weeks to cover still the end of Oct. If you want to generate coverage for the second months, then you will need to enter 12 weeks.. etc.. etc...

Try with 8 and you will see.

Hope this clarifies your doubt.

Kind Regards,

Mariano

[Former Member · Accepted solution]

Hi Mariano,

Here is the screen shots of what we discussed.

Can you help me to understand this calculation .I can't figure out this..

Thanks for all your help!

[marianoc · Accepted solution]

Hi MK,

Please check if you have assigned the coverage profile in MM02. It is weird what I see in your MD04 screenshot.

Also please run the MRP with the parameters:

NETCH
1
3
1
3

2

Kind Regards,

Mariano

[Former Member · Accepted solution]

You were right ..:)

Here are the results...and please explain me how target value is different from number of periods in coverage profile.

[marianoc · Accepted solution]

Hi MK,

I will try to explain your numbers. Note that the period type 1 is based on workdays and this depends on your factory calendar.

Note two things:

1- The first week Sep 8th is in the past, so the MRP will not generate coverage for this week.. will only generate a purchase requisition for 100CS, but not coverage.

2- You will need to consider the rescheduling messages and see where each order should be considered in your calculation.

The calculation is being explained in this excel:

Look at the week Sep 15th. The coverage calculated is 276 CS + 100 CS of the VSF, in my calculation you should buy 376 CS. Now for that week in your system you buy 385. The difference is because you have 2 holidays and instead dividing by 65 days (13 weeks x 5 days), you should divide by 63.

Hope this is clear enough !!

Kind Regards,

Mariano

[Former Member · Accepted solution]

Mariano,

Thank you so much for your explanation ! You are very helpful.

I started to follow the logic which you mentioned and I was able to figure out half of the calculation .

Week 8th:-Standard MRP as week is gone.

Week 15th:-(100*6)*30/63=285.71

This number match with screen shot.

Week 22nd:-(100*5)*30/63=238.09

This number match with screen shot.

Week 29th:-(100*4)*30/63=190.47

This number doesn't match. Screen shot has 193.56.

Another thing from where pur req 52.39 and 55.45 are coming. Please check the screen shot.

[marianoc · Accepted solution]

Hi MK,

I don't know what are your holidays, but looking at the numbers in MD04, I have estimated how many working days were considered by your MRP in the calculation...

Please check my 2 tables: one with the quantities and the another with the formulas:

Take a look and close this thread if you agree with the explanation.

Kind Regards,

Mariano

[Former Member · Accepted solution]

Thank you so much again !

[Former Member · Accepted solution]

You calculation make sense...I am trying to understand how system is calculating calendar days 62,61

[marianoc · Accepted solution]

Hi MK,

I can not see September, October, November and December in your screenshot.

Anyway.. The system will consider 61, 62, 63, 64, etc.. it is not going to consider 62.61 as working days... It could be another mathematical error in the calculation.. You maybe will never be able to reproduce the same exactly number including decimal places. I think you already got the concept.

Anyway.. 61 or 62 days sound probable to me. It seems you have an average of 1 holiday per month.

Kind Regards,

Mariano

[Caetano]

Hello

Please read carefully the explanation provides on the following thread:

Dynamic Safety Stock Calculation | SCN

Best regards

Caetano Almeida