Processing Issues solved with blending/dosing
Many product performance issues that can impact the acceptability and usability of plastic products may seem more likely to be caused by improper drying or final processing – but – if you don’t know exactly what proportions of which materials and additives are entering the process machine, solving your quality problems could be like chasing ghosts.
Like any recipe – the correct ingredients must be measured carefully – and mixed properly. If they are not, the end result will not be what’s expected – even if you “cook” it exactly right.
Here are some common issues that frequently stem directly from improper blending techniques.
Poor Product Quality
Substandard product performance can often be traced to an uncontrolled use of regrind in the process. Regrind, if used at a higher level than prescribed by the material or product engineer can result in premature product breakage and other performance issues. Often times, product testing can be the culprit as tested products are returned to the granulator at one time and inadvertently end up overloading the regrind content of the product. The controlled introduction of regrind into the process can not be left to chance or the inaccuracies of sub-standard ‘mixing” devices like proportioning valves or even volumetric dosing devices. Critical quality products require critical blending equipment.
Lack of color concentrate or poor mixing are typical culprits when colors are not consistent in plastic products. Inaccurate blending practices are usually to blame when colorant is not sufficiently introduced or blended. Many processors make up for this possibility by “overdosing” color into the mix to make sure that it is amply distributed during processing. But that leads to runaway colorant costs. The best solution is to use automated equipment that meters colorant by weight and then provides ample mixing prior to processing. Devices like these are designed to halt production if proper coloring is not possible (due to a blockage, lack of material, etc) and typically save thousands of dollars over time in colorant costs.
High Colorant Costs
Color concentrate and other additives, especially if custom compounded, can represent a significant expense to the processor if the use of them is not highly controlled. It is common practice to “overdose” to assure an adequate color or property when lower tech methods are used to introduce additives to the process. Overdosing is a very expensive waste of money and lacks the cost control essential to cost effective molding or extruding. The use of an automated blender that meters precious additives consistently and then checks and corrects each batch by weight is key to keeping costs under control.
High Labor Costs
Incorrect production of parts not only creates waste from rejected parts, but also the labor to deal with them. In addition, sub-standard mixing and blending equipment, that requires frequent calibration and checking to assure consistent operation also consumes too many labor hours as well as introducing the element of human error. Consistency and lack of human interaction are best achieved by automated blending equipment that does not require calibration by using weight readings for every dosing.