Blow-molding clamping

This calculation will indicate if your blow molding clamp tonnage is sufficient to blow the product with a specific air pressure and not have the clamp blow open during the process. 

Mold Platen and Blow Mold Clamping Unit... 

Vacuum forming has limitations due to the non-uniform wall thicknesses of its products. As the sheet is drawn into the mold, its thickness decreases, especially in the corners. For this reason, just as in blow molding, we design vacuum formed products to have rounded corners. If the depth of the cavity is excessive, walls can become locally so thin that they are unacceptably weak. One strategy that we use to alleviate this problem is to pump air into the cavity after the sheet has been clamped. This inflates the sheet, pushing it upwards and expanding its area approximately uniformly. When we subsequently apply a vacuum the expanded sheet is drawn back down into the mold. The finished product has a more uniform wall thickness than if we had applied the vacuum directly. 

In continuous extrusion blow molding, the preform is continuously produced at the same rate as the article is molded, cooled, and released. To avoid interference with the preform formation, the mold-clamping step must be rapid to capture the preform and move it to the blow mold station. There are various modifications of this that allow essentially continuous operation. 

Finally, another equibiaxial deformation test is carried out by blowing a bubble and measuring the pressure required to blow the bubble and the size of the bubble during the test, as schematically depicted in Fig. 2.52. This test has been successfully used to measure extensional properties of polymer membranes for blow molding and thermoforming applications. Here, a sheet is clamped between two plates with circular holes and a pressure differential is introduced to deform it. The pressure applied and deformation of the sheet are monitored over time and related to extensional properties of the material. 

Fig. 14.23 Typical blow molding die A, choke adjusting nut B, mandrel adjustment C, feed throat D, choke screw E, die head F, plastic melt G, die barrel H, heater band /, choke ring J, centering screw K, clamp ring L, die heater M, die N, mandrel. [Reprinted by permission from J. D. Frankland, A High Speed Blow Molding Process, Trans. Soc. Rheol., 19, 371 (1975).]...

FIGURE 21.2 Outline of the machinery used for blow molding, (a) A tube of molten polymer (the parison) is clamped into the mold. Then a puff of air expands the parison to the shape of the mold, the mold is briefly chilled, and (b) the blow-molded article is ejected. 

Another approach to increase production is to use one parison extra long to cover two or more cavities located vertically in the mold. In fact, one parison can extend the multiparison with two or more vertical cavities. AH that is required is a machine with the capacity to handle the output from the extruder to the clamping capability. See blow molding, extruder horizontal rotary-wheel blow molding, extruder vertical rotary-wheel clamping platen, rotary clamping platen, shuttle mold cavity. 

In blow molding, the clamping pressure is the pressure exerted on the two mold halves by the locking mechanism of the blowing table. This pressure keeps the mold closed during formation of the container. 

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