Moldmaking Resource Plastic Mold Makers, Mold Designers, Mold Repair Guide Plastic molding repair is one of those things, like death and taxes, you just have to accept that it is part of the plastic molding process. Too often, companies seem to ignore the fact that sooner or later, you are going to have to repair and replace components.
Injection moulding schedules never wait
The plastic molding repair depends largely on the quantities demanded of the mold. If it is a prototype or short-run tool, the effort and expense put into the repair will be considerably different than a 16 cavity hardened production tool for medical parts.
There are, of course, many short-cuts in mold repair. Shims, liquid steel, peening and fake textured surfaces are just a few examples. These are all actually more commonly used than management might realize, especially when there is no time left to meet a production schedule.
Short-cuts tend to be just that: they don’t last very long and sometimes cause more problems than they solve. They might get you out of the immediate bind, but, further down the road, trouble often lurks. Shims can work great for a quick fix, but when the day comes to do other work on the tool, it often happens that things don’t fit anymore, and it is because of the hidden shims that were never documented.
The best plastic molding repair is to totally replace the component, but sometimes this is just not practical or affordable. When it is an option, this certainly is the best choice. There are not subsequent problems that come as a result of replacing a core or cavity or some other part.
Gates and runners often need special attention
Very often, gates and runners must be adjusted to mold an acceptable plastic part. Sometimes it requires welding, or it may need to have inserts made to change the geometry. It is usually not as easy as it sounds to the molder though.
Inserting components is another good, permanent fix. This has the advantage of avoiding replacing an entire core block, for example. The wire EDM, or WEDM, is great for this. The damaged area can be isolated, designed as a replacement component, and wired out and inserted with a minimum of evidence.
Welding seems to fall into several categories of repair. Some parts simply are not weldable, perhaps because of the surface finish, or maybe the delicate nature of the detail. On the other hand, welding is fast, can be almost undetectable and can also mimic the parent metal quite well. A good micro-welder or laser welder is one of the most valuable craftsmen to be found. Everybody is nice to the welder!
Core pins, molding details or mold base features are all commonly welded, which very often saves a huge amount of time and money. Rather than replacing an entire plate, for example, the damaged area can be welded and be perfectly useful for production.
Plastic molding repair is underrated
Plastic molding repair is an essential, though generally ignored aspect of plastic processing. Adequate thought must be given to repair when quoting and scheduling production.
Some repair options include replacing components, quick fixes, welding, WEDMing of damaged areas and complete replacement of cores and cavities. The decision is often driven by cost, time and production quantities.