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prolem with WO and leadtime of purchased components
04-28-2012, 08:16 AM
Post: #1
prolem with WO and leadtime of purchased components
I think this worked a few versions ago?

I have BOMS with a few purchased items.and have entered purchsing date, preferred supplier and leadtime. BOM set to autoissue.

After MRP calculation, suggested PO has for all purchased items the end date of the PO as MRP date and due date (?).

Shouldn't this be issueing date of WO minus lead time?

Again my question: is anybody using MRP, in which weberp version, and which features?
Is this supposed to work, or not? Any insight is appreciated.

Klaus
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04-28-2012, 11:52 PM
Post: #2
RE: prolem with WO and leadtime of purchased components
Hi, Klaus:

Thank you for your report.

There is a bug in MRPCalendar which leads to the working days cannot be calculated correctly. I've fixed it in attached file.

Did your WO converted from Sales Orders or created according to master plan?

The estimated delivery date of SO or the MRP demand date are used to minus lead time, that's the logic to get the required date. (The date was calibrated by MRP calendar which ensuring that it's a working date).

Does this make sense?

Best regards!

Exson



(04-28-2012 08:16 AM)opto Wrote:  I think this worked a few versions ago?

I have BOMS with a few purchased items.and have entered purchsing date, preferred supplier and leadtime. BOM set to autoissue.

After MRP calculation, suggested PO has for all purchased items the end date of the PO as MRP date and due date (?).

Shouldn't this be issueing date of WO minus lead time?

Again my question: is anybody using MRP, in which weberp version, and which features?
Is this supposed to work, or not? Any insight is appreciated.

Klaus


Attached File(s)
.php  MRPCalendar.php (Size: 10.64 KB / Downloads: 3)
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04-29-2012, 08:14 AM (This post was last modified: 04-29-2012 09:10 AM by opto.)
Post: #3
RE: prolem with WO and leadtime of purchased components
Hi Exson,

thanks for your help.

Unfortunately, that does not solve it, the due date is still the required date of the WO.

One WO was created manually, ther other is a child (converted) from the first.

Klaus

I think there is an error in the logic in mrp.php.

From the WO, the required date for purchased items is currently the required date of WO if autoissue - that is ok.

these dates are entered into mrprequirements table.

after all tables are created, the lode loops through all levels to compare requirement and supply (from top level to lowest level).

At each level, levelnetting is called for all parts of that level. Levelnetting enters the demand into the mrpplannedPO tabel WITHOUT taking leadtime into account.
In this function, createlowerlevel requirements is called, and takes leadtime into account for those components.

So it seems that depending on where a component is in the bom, it's lead time may or may not be considered.

Klaus
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04-29-2012, 09:20 AM (This post was last modified: 04-29-2012 09:21 AM by opto.)
Post: #4
RE: prolem with WO and leadtime of purchased components
which actually can be confirmed by the following:

create a BOM:

A: has AB, B

AB: has B, C.

create workorder for A.
Now there is demand for B from A and also from child AB.

Run Mrp calculation: for one demand of B, lead time is used, for the other, it is not.

If the planned WO for AB is converted, not lead time is used for B, because the component B which was on a lower level (or higher - I don't remember the definition) in A now moved its level after the WO for AB was created.

Maybe a specialist knows where to enter the leadtime for the toplevel components in levelnetting.

Klaus
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04-29-2012, 10:13 AM
Post: #5
RE: prolem with WO and leadtime of purchased components
Hi, Klaus:

I think the normal procedure for MRP operation is:
For those factory which run in mode Build to orders, they have to receive SO before they can issue a WO.
For those factory which run in mode of Build to plan, they have to prepare the master schedule first, then they can issue a WO.
For those factory run in mode of mixing of above, they also have to have both of above.
That means you cannot manually issue a WO without SO or FOR, otherwise, the Top part will have no required date available. So you have to prepare the master schedule first. You can do it via main menu->manufacture->master schedule. Then create the schedule for A. Then run MRP, then you can convert your WO from MRP Planned Work orders etc.

Hope it's helpful.

Best regards!

Exson


(04-29-2012 09:20 AM)opto Wrote:  which actually can be confirmed by the following:

create a BOM:

A: has AB, B

AB: has B, C.

create workorder for A.
Now there is demand for B from A and also from child AB.

Run Mrp calculation: for one demand of B, lead time is used, for the other, it is not.

If the planned WO for AB is converted, not lead time is used for B, because the component B which was on a lower level (or higher - I don't remember the definition) in A now moved its level after the WO for AB was created.

Maybe a specialist knows where to enter the leadtime for the toplevel components in levelnetting.

Klaus
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05-18-2012, 07:03 AM (This post was last modified: 05-18-2012 07:06 AM by opto.)
Post: #6
RE: prolem with WO and leadtime of purchased components
(04-29-2012 10:13 AM)Exsonqu_Qu Wrote:  That means you cannot manually issue a WO without SO or FOR, otherwise, the Top part will have no required date available.

I think this is a bug. If I make to stock, I create WO's to do that, but I want to manufacture only those and not create forecasts. Looking at the code and the wiki, master plan and autocreate masterplan are only used to create forecasts based on existing SO (autocreate) or on my own forecasted requirements.

What happens at the moment is:

create levels table.
higher levels: all items that are BOMs etc and have lower level parts
level 0: items that do not consist of other items

loop from high level to low level:
call levelnetting: does NOT use leadtime for part of this level and proposes PO without leadtime
levelnetting calls CreateLowerLevelReqirement and uses leadtime. This only creates a new requirement, not yet a planned PO.
On the next iteration of levels in levelnetting, this demand will be converted to a palnned PO.

Because createlowerlevelreq uses leadtime, all constitutnt parts will have leadtime considered
Because levelnetting does not consider leadtime, all requirements on that level do not use leadtime..

So, if A consists of

B and AB

and AB consists of
B and C,

then, after MRP, I will have one planned order for B with correct leadtime (originating from subBOM AB of part A), and I will have one planned order for B without lead time (from BOM for A)
Even worse: if I convert the proposed WO for AB to a WO, then both planned PO's will loose their lead timefor part B, as now the level of AB->B has changed due to the newly created WO.

FIX: move code for regarding leadtime from createlowerlevelreq into levelnetting.
Doing this, the leadtimes are used correctly for all levels. (have tested this)


I am not sure if this has an impact in other places (planned WO's, rescheduling etc.).
Another option of solving this problem would be to leave createlower .. as it is and use the leadtime in the place where the code for the first time fills the mrprequirements table.

Klaus
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05-18-2012, 09:04 AM
Post: #7
RE: prolem with WO and leadtime of purchased components
Hi, Klaus:

Thank you for your report!

Did you study the logic for assign level for each items in MRP?

Best regards!

Exson
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05-18-2012, 06:11 PM
Post: #8
RE: prolem with WO and leadtime of purchased components
Hi Exson,

I spent quite some time to try to understand it.

Independent from understanding, it is not correct that some levels where a part occurs have no leadtime, other levels have leadtime.

If I add my code change, all levels have leadtime.

best regards,

Klaus
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05-19-2012, 12:10 AM
Post: #9
RE: prolem with WO and leadtime of purchased components
Hi, Klaus:

Thank you for your report.

It sounds like a bug. The situation maybe ignored during coding this part. I'll check it tomorrow.

Best regards!

Exson
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05-19-2012, 03:55 AM
Post: #10
RE: prolem with WO and leadtime of purchased components
I attach the solution for this bug.

Problem:
main code adds top level items of WO into mrprequirements without leadtime

CreateLowerLevelRequirements adds those items into mrprequirements with leadtime.

The attachment solves this. It still has the commented old code and some explanations for easier understanding.

Klaus


Attached File(s)
.php  MRP.php (Size: 32.33 KB / Downloads: 5)
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