A quality manufacturing process relies on multiple inspection points to ensure proper results and metal heat treatment is no different. Every reputable company will have a series of inspections; however it is the number and sequence of inspections that set Zion Industries apart from the competition.
The intense inspection schedule begins as the products enter the warehouse. The first step verifies the number of parts and weight shipped. For example, a container might ship from its point of origin containing 2,000 parts on a skid with a total weight of 1500 lbs. Any discrepancies might indicate lost pieces and generates a non-conformance report that Zion follows up with the customer.
Once the weight and part count are verified, paperwork proceeds to the scheduler. Here the packing list is checked against the purchase order once again and are subject to a contract review to match the parts against specifications on file. Once approved, parts move through the scheduling process. Parts are scheduled for processing in the order in which they are received and per Zion and customer agreements. Again, any discrepancies trigger a non-conformance report.
Value of Non-Conformance Reporting
The issuance of a non-conformance report or the case of pieces not matching the shipping notice is very rare and often easily resolved. For example, 15,000 parts might have shipped instead of the intended 10,000, or if only part of the shipment arrived it might have been split into two separate trucks. Open and early communication however, avoids creating issues in the future.
Each shipment is assigned a unique lot number to help track the part load through its processing. The lot tag contains critical information related to control charts specifying processing parameters such as tempering temperature, time, etc. As the parts are processed this critical information is used to ensure the proper procedures are followed.
Prior to setting up the tooling, which is switched out manually, the set-up technician checks the “recipe” for factors such as product cycle time, heating temperature, cooling, etc. Once the recipe is verified and the machine tooling set up, the first product inspection begins.
First Product Inspection
A single part is run through the recipe and then inspected. A typical application might involve hardening for example. The part is checked against a control chart that details part specifications:
- Area of the part to be heat treated
- Hardness level
- Crack detection via mag particle inspection
At this point if the hardness level does not fall within required parameters and all aspects of the recipe have been entered and correctly conducted, a new inspection is triggered. Depending on the part’s history, Zion may test additional pieces. The green (non-heat treated) materials are more closely inspected. On occasion, parts may have been made out of a different material that may not meet the chemistry requirements for the hardness. If a cracking issue is identified at setup it may be from parts that have experienced stress or have small cracks due to turning, milling or forging. Zion would contact the customer at this point to determine a viable solution.
Once physical characteristics are verified and the part passes crack verification, production begins. But inspections are far from over.
Regularly Scheduled Production Inspections
- As-quenched surface hardness
- induction hardness pattern location
- magnetic particle evaluations
At the eight-hour mark in addition to the normal two-hour inspections, Zion adds in a cut. Cutting into a part allows Zion to check the depth and hardness of the depth, otherwise known as total or effective depth
This final inspection of a job is similar to the eight-hour procedures. The batch of parts is thoroughly reviewed for the right level of hardness, depth and patterns. Also, at this point an after-temper inspection would occur. A part might begin at 55 to 60 Rockwell as quenched and after tempering measure at 50 to 54. The goal is to reduce the hardness by the appropriate amount.
At the end of the heat treatment, parts are packed back into the original customer containers. At this point a visual inspection while packing helps identify any anomalies, such as parts that are different color, or look rusty or have visual defects. If all is well with the product, a yellow tag signifies the finished product is ready for shipping. There, the final weight and count is compared to weight and count logged at its entry. Parts then return to the customer.
Most products are inspected once every two hours, however when tempering a new product for the first time a safe launch might be recommended. This introduces additional inspections every hour for the first several hours or days of production. This allows Zion to detect any issues or problems and/or adjust the recipe in the initial phase of production.
Potential Causes of Non-Conformance
There can be a variety of reasons why a product doesn’t pass one of these routine inspection points. Zion would focus on possible changes to our parameters, temperature, quench contamination or concentration etc. Some issues can be caused by material changes from lot to lot, we would investigate and adjust for or report difference noted.
Beyond thorough is what sets Zion apart, following procedures that can exceed ISO and IATF standards that ensure clients receive parts that meet and exceed expectations. Ready to try Zion for Induction heat treating? Request a quote today.