Definition: Troubleshooting: the process of resolving issues and or causes to defects. Troubleshooter: an expert in discovering, and eliminating the cause of trouble in mechanical equipment. Defining: to explain the whys
Defining the issue is one of those processes that have many either stumped and or they don't even think about it. By stumped one means that they know what the problem (or at least think they do) but than they do not know the next step and or issues to be concerned about. In some cases they have no clue where to start and or what the problem is, though the result of the problem is known.
Typically in defining a problem we first have to see the results of the issues. By this the results are what someone looks at. For example a part with incomplete fill may be referred to as a short part, i.e. not enough material in the part thus it is short. The key word here was not enough material in the part. Yes commonly referred to as a short part but the issue being is that it is not full or the material did not go into the part. Once it has been defined it as not enough material in the cavity, than it is why there isn't, and further definition or searching must be done.
The why is still in the define stage
1- Is it a single cavity mold?
2- Is it a multiple cavity mold, or a family mold, hot runner tool, 3-plate ...etc.?
3- Is it only one cavity and or multiple cavities if a multiple cavity tool?
4- Is it on every shot or random every so often
5- What is the material is it virgin, regrind or a combination of the two.
6- What is the melt temperature, and mold temperature
7- Etc...
The list above though not complete starts to yield a picture of what has to be thought of, and or possibly reviewed to come to a conclusion and or next step. If the tool was a single cavity, sprue gated, with virgin material, and it was every shot, than one could possible look at the cushion, screw recovery time, shot size to evaluate if the shot was adequate. Again it is still defining the issue. Further looking at the part one may notice either that it is always the same or that it does vary with each shot. If the problem is the same each shot than it is constant, if varying with each shot than it is moving around as something is changing. If the screw bottoms out each shot than shot size, leaking nozzles, bad check ring, and back pressure may be things to look at. If it varies each shot, but still bottoms out, than in addition screw recovery time may want to be observed to determine if it is constant, and then back pressure to see if it is high or nonexistent.
In determining the cause, many questions need be answered, but it is not a long drawn out process, though some make it to be, this is where development of a checklist can help and or a mental check list.
A method and or process used with lean and or other learned quality/ Kazain type process as explained to the author is to , ask "WHY" 5 times to try and delve into the reason for the issue and come to a conclusion. In molding when in fact one is trying to define the issue, many times it is to jump to the first thing , try it and if it works walk away until something else calls one back to the press, usually the same issue. Sometimes this jump before observation causes more harm. In many cases if one waits the issue goes away, and that than becomes WHY.
Observation is critical and documentation is also as one may want to establish that the process is stable, constant and at the proper settings / results as per the process/setup sheet and or molding standard. This again is in the defining stage. Though this is listed last here in this discussion it should be the first thing to review in defining the process.
An example of short shots is one which occurred many years ago for the author. In a well-documented and controlled molding environment, (i.e. ISO/ military) an issued occurred with short shots. While reviewing the issue, a random problem it appeared, various factors came up, two of which proved to be capable of resolving the issue. The first was that melt temperature was below minimum recommendation per manufacture, and second was that the new lot of material was a larger pellet size. While increasing melt temperature resolved the issue, immediately, due to internal and external standards and protocol it was not acceptable, and using a smaller pellet size was to be used in the short run while they debated the requalification of process with a higher melt temperature.
To be continued>
Slsilvey
12082013.02
