Traceability Practices for Precision Machining Parts Production
Traceability means the ability to follow the chain of custody for a product forwards and backwards through some or all of its manufacturing journey. In precision machining, traceability extends from information about the materials to inspection records and where the part was shipped and used.
In a CNC precision machining shop traceability can be implemented in many ways. Here’s a look at the options and practices often used.
Internal and Chain Traceability
Internal traceability refers to tracking a job through a shop. It often involves recording which machines processed the batch and when. There may also be a note of who was running each machine, and in the case of CNC machining, the version number of the part program used. Dimensional and visual inspections are also recorded.
This information is purely internal. It might be logged in the ERP system and analyzed for OEE or productivity data. It often forms a basis for quoting future work.
Chain traceability refers to creating a history of the batch or part that is maintained across multiple businesses to the customer or end user.
For example, a precision machine shop will keep records of the material used for an order, including actual mill certificates, inspection records. When the parts are forgings they will keep the forge shop records, such as when the batch was forged and the material source. Machining and inspection records will be kept as part of internal traceability.
If the parts require heat treatment or surface treatment, these records will form part of the chain. Likewise, if the parts are assembled into a bigger product, like a camshaft going into an engine, these records will also be maintained.
Benefits of Chain Traceability
Businesses like traceability because it reduces recall costs while improving safety and addressing liability concerns. Consider the situation where a camshaft fails due to incorrect machining. With chain traceability it’s possible to trace back to when that batch of parts was machined, and forward to find out which engines and vehicles they went into.
Batch or Unit Level?
Most traceability happens at the batch level. For a machined part this links the mill certificate to a specific batch of parts, their heat treatment and their surface treatment. In the event of a recall it reduces the number of parts to be identified or replaced. However, depending on the type of defect, it might still mean replacing many good parts along with a few bad ones.
Customers of precision machined components, such as those used in the aerospace industry, are asking for traceability down to the individual item. This means giving every part a unique identifier when it’s first created and logging every machine and process it goes through, ideally with the specific process parameters employed at that time.
This requires a way of actually adding that unique number or code to each part in a way that will still be readable after it has been installed and used. There also needs to be a way of reading it and linking it to all the process information.
Parts are often identified by a date or batch code for lot traceability. While inexpensive it doesn’t provide the granularity of adding unique numbers or codes. Neither is it easy to capture the identification as it moves through the machine shop.
Machined parts are often identified by laser marking or pin stamping codes. Ink jet printing is less common as this wears off. An alternative to human-readable characters, which can quickly take up too much of the surface, is the Datamatrix code. Similar to a QR code, this packs a lot of information into a small space.
In addition, Datamatrix codes are easily read by cameras. These can feed the information into a database that logs every operation, the time, relevant process parameters and more.
Traceability is Another Precision Machining Technology
Traceability is of growing importance in many industries. Precision machine shops can implement internal traceability using any of a number of techniques and technologies. These can be further linked to records from businesses upstream and downstream in the manufacturing process.
When traceability solutions are in place, end customers can have complete confidence in the history of every part and their ability to track down any parts suspected of being nonconforming.
As precision machining specialists, Impro can provide the records and documentation customers expect. To discuss your specific needs, contact us today.