Interesting omission, my friend @michaelt! The sink marks are indeed nasty.

John, I can only speak about one small molding factory I worked for - commercial products, no models. QC's job is to observe and report. I can guarantee that QC saw the sink problem either at the machine, on the cooling table, or upon inspecting storage boxes of shot X before it was packed with the other shots, decals, and instructions into the kit boxes. This kind of problem would usually happen either early in the run before the injection machine settings had been adequately adjusted, during the run when the Production Manager increased the machine speed as the operator became accustomed to any special considerations with the particular shot the machine was making, when the machine ran too hot or cold for whatever reason, or during a night shift when a less experienced floor manager was discouraged from making adjustments in the machine's settings. It's also possible, but much less likely, that a change in raw material (raw styrene pellets) could cause it, and more likely when too much regrind (mostly spoiled shots and cut off sprues - technically, we modelers almost never see the sprue, a conical channel where the hot liquid plastic is injected into the mold. What we call sprue is the frame less the parts (frame plus parts is a shot) or a runner (portion of a frame) was added to the raw material.

While the QC people will see most problems-eventually, they do not make the decisions to reset the injection machine or to start or stop packing out the shots. They can mark boxes of shots as suspect or even rejected, but they will be boxed if the PM decides to keep the machine running with its current settings. The PM and top-level manages/owners will decide what gets packed into the kit boxes - what they hope customers won't notice or will be willing to live with. Reacting to every problem plays havoc with production schedules and cuts into profits - perfect is the enemy of good enough. The QC manager just gets to add a note in the product file for inspectors to watch out for problems that are likely to reoccur when the mold is next run. Oh, and if an irate customer does come in to complain about a problem the QC Manager pointed out to the PM and upper managers and warned them not to pack out and ship, the QC Manager gets to stand there and take the roasting while the PM and UMs go out in the factory to "examine the problem." Yeah, I worked QC.

BTW, the Airfix P-40E is the old Arii/Otake kit unless they've changed their source molds. It has some simplifications - landing gear doors and retraction struts, no mass balance on rudder, engine, exhausts, and removable cowl panels fit - and the wings have a slight swept back angle, but ti's still a nice build and can look very good with some work.

@michaelt - good research on the small details - that's the stuff that leads to an outstanding result. Very nice work going on here.

This is really valuable info regarding quality aspects of molding technology, my friend @brummbaer!

Designing the mold and drafting (drawing) the plans for it is at best one skill set; cutting the mold is another very different skill set. These are almost always done by different people or departments. Mistakes and omissions happen in both processes. Ideally, the designer/drafter should check the mold against the plans with a micrometer and calipers before it's run, but once mounted in the injection machine, it would take a major flaw to halt production and dismount, clean, and rework the mold. Adding a raised detail to the plastic requires cutting into the mold and then polishing the new recess. While expensive enough and requiring great care and skill, it's a relatively quick, simple process that might even be possible without dismounting the mold. Adding a recessed detail requires welding new material into the mold, then cutting the excess material away to leave a raised metal shape to form a recess in the plastic, possibly adding one or more new KO pins depending on the size and depth of the new shape, and polishing the shape and weld area to match the surrounding finish. This is much more time-consuming and expensive, requires dismounting the mold, and is fraught with the possibility of inadvertently damaging the mold. It can be done, but if done it will be after the initial production run is completed and the mold dismounted in due course. Someone who ran the Arii/Otaki molds damaged several of them, most of the Japanese fighters, by letting the KO pins smash into the front of the mold, and you can see the attempts to repair the molds by sloppily welding in metal and recutting it. The Monogram Bf 110G mold was even worse damaged by closing it on a tool or dropping a heavy tool in it, but it was eventually much better repaired. For such a small error as Airfix made, it's rather unlikely that they will ever correct this tab, even less likely that a smaller company like Arma Hobby will add the missing panel lines on the wing and fuselage halves of their otherwise quite good 1/48 PZL P.11c (https://modellair.blogspot.com/2021/02/48-p11c-r.html), and it's why whoever now owns the Monogram mold for the F5F-5P Panther will never return it to the fighter version.

As for the sink in your first kit that was fixed in the second, look at the gates closest to that area, It's possible Airfix made one or two ever so slightly larger so more material would get to that area. This would be the simplest fix that would give the PM more latitude during the run to speed up the cycle time - at the risk of a little bit of flash if he overdid it. The faster the mold runs, the hotter it's likely to get, which can lead to more sink there or elsewhere. Setting the machine is both a science and an art, a balancing act!

BTW, QC seldom gets involved with any of this mold work. QC will compare molded parts with the mold plans and the customer's specifications when necessary and will report any mold shifts or damage, misshapen parts, flash and short shots, gassing and raw material problems (mostly too brittle or contaminated), &c during the mold run to the Production Manager and higher management if the PM wants to continue production despite out-of-spec product. QC will sometimes, with management permission, take the problem to the customer for final approval or rejection if a large count of parts is out-of-spec - 90% of the time QC and management knows what the answer will be based on previous occurrences, so this is more a matter of ritual than business. What also happens, which is against everything QC should be responsible for, is that QC personnel will be delegated to sort through the mess and pick out defective products rather than inspect current production, leading to more cruddy products in the long run.

Great work all around so far.

Superb progress, my friend @michaelt!

Great work on these P-40s, Michael @michaelt. I am looking forward to your various paint schemes. I'm not sure I would have ever noticed the missing trim tab on one side.