PLM - Part 3: One too Many Dilemma

Links to Part 1 and Part 2.

PLM - Part 1: One too Many Dilemma
PLM - Part 2: One too Many Dilemma

In Part 3 of this series we will look at a real world example of a 'many to many' relationship that exist within a PLM system.

MCNs are Material Control Numbers, also known as company part numbers. 

PLM systems use MCNs. The MCNs control which Mfr Part Numbers are approved for use on a specific BOM.

Mfr P/N with many MCNs

First case has the same Mfr P/N used with more than one MCN.

As shown below a Samtec connector P/N BCS-115-F-D-TE is appearing in two MCNs in the PLM system. 

click on image to view
 

Why two MCNs for the same Mfr Part Number ?  

Let's take a closer look in PLM at the two MCNs.







The reason is simple. 

The P/N BCS-115-F-D-TE has been qualified and approved for use on two different BOMs.  

P/N BCS-115-F-D-TE is the only approved Mfr Part Number for the BOM that calls for MCN 206-0028-00. This MCN was created to restrict the use of Mfr P/Ns used on a specific BOM. 

MCN with many Mfr P/Ns 

This case is easy to understand because we can all agree that having alternate Mfr Part Numbers is a good thing.  

The alternate Mfr Part Numbers give manufacturing the ability to choose and buy approved parts for a build based on price and availability.

Conclusion

Many to many relationships are normally found in PLM systems.  Without these 'many to many' relationships it would not be possible to support the production line.

Most companies throw the engineering BOM over the wall to the company configuration control department, which has proven to work very well.

Then component engineers working with design engineers create MCNs with approved Mfr Part Numbers. In small companies the design engineers are the component engineers.

After the MCNs have been created in PLM, the engineering BOM is annotated with the MCNs, then the BOM is imported to PLM. 

The BOM with MCNs can be used to back annotate the CAD Library and Project Schematics.

If your company is using a PLM then you need a well designed CAD Library to deal with the 'many to many' relationships that are normally found in PLM systems.

There is a movement in the industry to create integrated solutions for CAD libraries and PLM systems. However I have not found any truly practical or affordable solutions, so I created my own solution which I call Parts.

The Parts database uses an incremented unique ID to create a solution for using CAD Libraries with PLM Systems.

That's It !

PLM - Part 2: One too Many Dilemma

If you missed PLM - Part 1 'One too Many Dilemma'.

Instead of jumping right into the 'many to many relationship' we are going to build our way up to it, starting with 'one to one'. This helps to understand how and why the 'many to many relationships' exist in PLM systems.

Relationships:

'One to One'
'One to Many'
'Many to Many'

Most PLM users have no idea what a 'many to many' relationship is or how it effects their company's products. 

PCB designers with CAD library responsibilities need to understand PLM systems and how PLM impacts their CAD database library. 

If you are still reading, I assume you have a CAD database or you thinking about creating CAD database library solution.

Usually people will glaze over when you try explain the 'many to many' relationship.  Until they 'get it' they will fail to understand PLM integration problems with CAD libraries.  

After management spends multiple thousands of dollars on a PLM system they really don't want to hear or believe there are integration issues. They are more inclined to believe they just haven't got the right people involved to solve the integration problem.

Experienced database designers are very familiar with the relationships listed above and therefore they 'get it'.

MCNs are Material Control Numbers (Company Part Numbers in a PLM)

Let's go through some relationship examples:

'One to One'

In the 'One to One' example below one MCN has been created in the PLM system and only one Manufacturer Part Number has been assigned to the MCN.

MCN: 624-0016-00 (Company P/N in PLM)
MCN Part Description: CAP 0.047uF ±10% 10V X7R 0402

Manufacturer: Murata
Manufacturer Part Number:  GRM155R71A473KA01D
Mfr Part Description: CAP 0.047uF ±10% 10V X7R 0402 (1005 Metric)
MCN: 624-0016-00

Note that the MCN Part Description should include all critical specifications for the part.

'One to Many'

PLM systems by design have MCNs with alternate manufacturer part numbers. Obvious reasons include; second source, availability and price.

In the 'One to Many' example below a second Mfr P/N has been added to the same MCN.

Notice that the second mfr P/N added to the MCN has a 16V specification vice the 10V specification listed in the MCN Part Description.

The 16V part is actually a better than part, because it's specifications exceeded the requirements in the MCN Part Descrption.

Since we have one MCN and more than one Mfr P/N approved for the MCN we now have a 'one to many' relationship.

MCN: 624-0016-00 (Company P/N in PLM)
MCN Part Description: CAP 0.047uF ±10% 10V X7R 0402

Manufacturer:  Murata
Manufacturer Part Number: GRM155R71A473KA01D
Mfr Part Description: CAP 0.047uF ±10% 10V X7R 0402 (1005 Metric)
MCN: 624-0016-00

Manufacturer:  Yageo
Manufacturer Part Number: CC0402KRX7R7BB473
Mfr Part Description: CAP 0.047uF ±10% 16V X7R 0402 (1005 Metric)
MCN: 624-0016-00

'Many to Many'

Let's look at the 16V approved alternate part for MCN: 624-0016-00.

Manufacturer:  Yageo
Manufacturer Part Number: CC0402KRX7R7BB473
Mfr Part Description: CAP 0.047uF ±10% 16V X7R 0402 (1005 Metric)
MCN: 624-0016-00

This 16V part is a better than part  for the original 10V part.  As it turns out this part was already in the database and was assigned to another MCN which required 16V.

After the 16V part was added to the MCN for the 10V part the same Mfr part number will exist in the PLM system under two different MCNs. Hence the 'many to many' relationship.

PLM systems by design support 'many to many' relationships. It is through these 'many to many' relationships that PLM maintains products in production.

'The Quandary'

While the many to many relationships found in PLM systems are a perfect solution for sustaining products in production, this relationship has issues for PLM and CAD integration.  

CAD libraries use 'one to one' and 'one to many' relationships to associate schematic symbols, footprints and parametric data to a specific part number.

You have been asked to keep the CAD library up to date with MCNs associated with Mfr Part Numbers. You get a Excel report from the PLM system to back annotate the CAD library with MCNs where Mfr Part Number in CAD = Mfr Part Number in PLM.

As shown previously the Mfr P/N for the 16V part is now in the PLM system with two MCNs associated with the same Mfr P/N.  You now have a 50/50 chance of updating CAD library with the correct MCN, that is where the MCN part description will be an exact form, fit and function equivalent to the Mfr P/N.

Back annotating the CAD library with a parameter like Mfr P/N from a PLM system which has 'many to many' relationships could compromise the data integrity in the CAD library.

If the 10V MCN which is now associated with 16V Mfr P/N in PLM is assigned to the 16V Mfr P/N in CAD library then designs which require the 16V part would be compromised.

Conclusion

Careful attention to details are required when assigning MCNs to Mfr Part Numbers in a CAD Library to avoid compromising form, fit and function of the parts defined in PLM.

The specifications of Mfr Part Numbers assigned to a Company Part Number (MCN) must be be equivalent or better than the specifications called for in the MCN.

A surrogate key provides the flexibility needed to deal with scenarios, like:

1. MCNs with one or more Mfr P/Ns
2. Same Mfr P/Ns used in one or more MCNs

The scenarios described above are frequently found in PLM systems.

To support a product through out it's life cycle requires having alternate Mfr P/Ns which have been qualified and approved for use in the PLM system.

Within a PLM system it is possible to have a Mfr P/N listed under one or more MCNs. 

Using a surrogate key in your CAD Library Database can solve the PLM to CAD Library integration issues created by the many to many relationships that exist in PLM systems.

In Part 3 of this series we take a look at a real world example of the 'many to many' relationship that can exist in a PLM system.

PLM - Part 1: One too Many Dilemma

'One too Many Dilemma' is a pun on words for the Relationships' which exist in PLM systems.  

This article attempts to explain the primary integration problem for PLM systems and CAD tools. 

PLM systems support 'many to many' relationships. CAD tools typically have 'one to one' or 'one to many' relationships. 

In the digital computer age numerous PLM, MRP and ERP systems have been created to support the design and manufacturing process. Circuit board EDA and CAD design tools have also advanced considerably during the past decade.

Efforts are being made to integrate PLM systems with PCB design tools with most of the efforts being made in vain. This is due to the 'many to many' relationships which is corner stone feature of PLM systems.

To appreciate the PLM to CAD integration issues, it is necessary to understand the role of the PLM system. PLM systems are designed to support a product through it's life cycle.

In most companies the PLM life cycle for a product begins after the design has been released from engineering to manufacturing.

There is a lot of brainstorming work that occurs in the design phase, such as qualifying parts and optimizing the design for production that is not really useful to put into PLM.

PLM is about maintaining products that are in production and sustaining manufacturing. 

You can find PLM systems that are designed to track your project from conception to the grave. It is just not very efficient to force a design team to use configuration control while a product is in the design phase. 

However if you project is highly critical, say like getting to the moon and back, you may need a complete track record of your project including the design phase work.

PLM systems use Engineering Change Orders (ECOs) to facilitate configuration control during the product's life cycle.

Designs typically begin with a Bill of Materials (BOMs) which list manufacturer part numbers.

PLM systems use Material Control Numbers (MCNs), also known as company part numbers. 

Before a BOM can be released to PLM the MCNs (company part numbers) must be exist in the PLM system.

Manufacturer part numbers are associated with MCNs in PLM systems. 

The approved manufacturer part numbers in PLM are often referred to as the AVL (Approved Vendors List).

Next step is to back-annotate engineering BOM with the MCNs. With MCNs assigned to each line item the BOM is ready to be imported into the PLM system.

In Part 2 we will delve into relationships between the manufacturer part numbers and the MCNs.

PLM - Part 2:  One too Many Dilemma . . .