Definitions: Plant: meaning a facilities / operation where manufacturing is occurring. Cooling: 1) free of heat 2) capable of lowering temperature. System: an assemblage or combination of things or parts forming a complex or unitary whole: a cooling system. Documentation: data, recordings, records of process results.
As the fluid leaves the mold and then flows through the hoses to the manifolds and then back to the temperature control unit of which there may be many. The cooling circuit is completed and the entire of the process starts again. Knowing what is happening from a temperature, flow, and or pressure point helps to control the overall process.
In many plants fluid temperature and pressure is measured, thus a relationship can be established as to cooling or a better word is temperature control of fluid and mold / process. From the processors point of view a better way may be to measure the temperature of the parts upon ejection or if extruding measuring the temperature of the extrudant at a point within the line. This can also be done on the other processing systems too.
In measuring temperature of a product, one must also remember the time function, i.e. how long since manufacture do we wait to measure, or we do as is ejected, extruded or blown. The use of a non-contact system is ideal and the only caution is to use one that is calibrated for the plastic materials you may be running and also what is the spot or width of the measurement you are taking. As an example a unit that the author carries has the following 24mm spot @ 300mm distance, 30mm spot @ 900mm distance and 62mm spot @ 1500mm distance. The point here is to know what is the diameter of the spot you are measuring so as to be correct in your documentation and not to be measuring the surrounding area.
In many places a non-contact temperature unit is not available thus there may be a contact pyrometer. These too can be used on the part, and the key to understanding is the time function / measurement function in how long it takes to react. One may need to take multiple readings on multiple parts to get an accurate documentation of part temperature out of the press, or process. The other method is to do what is commonly named as mapping the tool. This is a process of measuring via a surface contact pyrometer the actual steel temperature in various places. This typically can take many shots as only 1 or 2 points can be taken each time the mold is open to get accurate actual temperatures of the surface prior to it cooling off.
In many cases with the use of the pyrometer, one can measure how the plant water is performing for your machine process. This is accomplished by measuring the temperature to and from a particular circuit. This can be done by contact to the fitting for that circuit on the manifold. As previously stated we would look for a range of not more than 4 degrees F. and if a very critical component it may be less or no change.
If the shop is well equipped than a flow meter may be available which than would allow one to document each circuit as to the flow rate, this than can be recorded and used as a check for any processing of this tool. This is especially important in new tool set up, as it establishes a base line to the flow through the system that was established to validate the tool. Along with temperature this may yield a point for further consideration as the mold is moved to another press or shop.
Other areas of measurement are pressure both to and from the mold. Though ideally each circuit should be tested the overall manifold may be the starting point and or reference point. This along with temperature at the fitting can help in troubleshooting at a further point down the road.
The documentation of what is going on is critical to the overall picture. This than includes the temperature, flow, pressure and photos or diagrams of the connections from manifold to mold back to manifold.
The use of non-contact temperature measurement of the tool is difficult as unless the tool has a dull non reflective coating the temperature reading may be of someplace else. This is even true for the newer and less expensive IR cameras now available. So if using non-contact to measure steel temperature be aware of this issue and double check by comparing to a pyrometer with a surface probe.
Other:
- If one wishes to regulate flow to a particular circuit this regulation should be done on the exit / return of fluid from that which is begin controlled.
- Fluid flow in the mold should be checked both on a system basis, all water lines to the mold open and also on an individual basis all lines closed expect one which is being tested.
- This than shows what is really going on and may indicate a line which needs extra pressure to maintain flow, or possibility of a plugged or restricted circuit.
- Return flow should be as unrestricted as possible, thus the shortest lines to manifold and or even larger lines if necessary as long as the rest of the flow in the series is equally increased.
Silveys Plastic Consulting
www.silveysplasticconsulting.com
360-882-3183
SL SILVEY
16102012.01
