What is a Two-Stage Blow Molding Process? Their blow sections also complete two to three cycles for every injection cycle.Ĭonsequently, this saves blow cavities while also reducing the tooling cost a reason that makes the single-stage method more suitable for companies that are out to produce bottles in low or medium volumes. They are those featuring multiple pairs or triple injection cavities in each blow cavity. The issue of inefficient blow station has been combated with the creation of another category of single-stage machines which can be considered as integrated two-stage machines. The result is a thicker design at the back of most bottles that employ this method, even though its manufacturer or brand may sometimes disguise it using labels. What happens here is, the movement of the melt material along the barrel and hot-runner channels which exerts some amount of heat on it.ĭespite this, the melt still retains some amount of thickness or viscosity and the warmer part tends to flow to the back of the new channel. Generally, PET material can level by itself, but there are cases where an uneven wall distribution will still be evident in the final product. Let’s take a look at some of these scenarios: – Wall Distribution May be Uneven: Inefficient blow station due to injection station having more precedent over cycle time.Great expertise is required in mastering both processes and PET drying.The disadvantages of employing this method include: Suitable for blowing rectangular and non-circular shapesĭisadvantages of Single-Stage Blow Molding Process.Less expensive in comparison to two-stage machines.Control over thread start to align with bottle’s shape.There are several advantages of a single-stage molding process and they include: Transfer of the hot preform mold to a bottle mold to begin the stretch moldingĪdvantages of Single-Stage Blow Molding Process.Cooling of the molten material in the preform mold to 120 ° Celsius.Melting and injecting of the raw materials into the preform mold through the injection nozzle.Dehumidifying and drying of PET materials.The transformation of the raw materials into a bottle using the single-stage follows the procedures outlined below: Processes Involved in the Single-Stage Method
The 4-station, on the other hand, comprises of these three stages and an additional reheating stage. It also uses latent heat which saves the cost of having to reheat, thereby reducing 25% of heat in tooling. Likewise, the machine can either be a 3-station or 4-station system.Ī 3-station single-stage machine has three stages which are injection, stretch blow, and ejection. This level of functionality can be attributed to the injection molding system and blow molding station being built into one machine. Therefore, single stage PET blow molding machines can also be said to employ a direct method. What is the Single-Stage Blow Molding Process?Ī single-stage process gains its name from the fact that it creates preforms, stretches, and blows them on the same machine before cooling. While each of these will lead to the production of a bottle, the injection stretch blow molding process is what is required to create PET or plastic bottles. In a bid to make this possible, there are three major processes: It takes advantage of several processes to form hollow parts in plastics before these parts are joined together to form a bottle. However, the significant differences between single-stage and two-stage molding processes require you to make a decision.īlow molding machines are an equipment that is used in manufacturing plastic and glass bottles. The ability to choose the right method comes with the perks of increasing productivity, reducing cost, and also minimizing the cycles required to produce these materials. In the world of manufacturing, especially bottle manufacturing, blow molding machines are essential - but which is better for you: a single-stage process or a two-stage process?īlow molding machines employed in PET (polyethylene terephthalate) bottle manufacturing are of various types, and that is why manufacturers need to ascertain the actual injection stretch blow molding process to use in producing plastic bottles.