Mandrel, adjusting

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).]...

Pipe and Tubing. A typical die for extmding tubular products is shown in Figure 4. It is an in-line design, ie, the center of the extmded pipe is concentric with the extmder barrel. The extmdate is formed into a tube by the male and female die parts. The male die part is supported in the center by a spider mandrel. Melt flows around legs of the mandrel and meets on the downstream side. The position of the female die part can be adjusted with bolts adjustment is requited to obtain a tube with a uniform wall thickness. 

A numerically controlled filament winder has been designed and constructed. The distance between the head-stock and tail-stock is six feet. Clearance between the centers emd the body of the winder is adjustable, but a specimen several feet in diameter could presently be fabricated. The mandrel and carriage are each driven by one horsepower, direct current motors with a maximum 2000 revolutions per minute. Three phase, 480 volt alternating current is transformed to a 90 volt, direct current power supply. A gear... 

Bend the ring around the ring mandrel and complete the form by gently tapping with a mallet. Adjust the ring to fit a finger. 

The fixturing and tooling requirements differ for both the fixed-pin and adjustable selfreacting (ASR) pin tools (Fig. 13.4). The fixed-pin configurations require an internal mandrel... 

After leaving the extruder, the melt flows through a circular die. The centre of the mandrel of the die is provided with an air inlet. The die is surrounded by an air-cooling ring, usually adjustable to provide for... 

Mandrel deflects with extrusion rate, necessitating die adjustment... 

In regard to parison control, a compromise is necessary between the desired net weight and the need to maintain a sufficient safety margin over a set of minimum specifications, which include minimum wall thickness, drop speed, drop strength, dimensional stability, and fluctuations in net weight. Most of these parameters can be directly affected by the molder s ability to control the parison wall thickness. The most common and practical way of doing this has been to adjust the gap between the die and mandrel (Table 4-2). 

To evaluate the braided materials properties three references have been investigated, Ref-55, Ref-45 and Ref-35. The structure was braided layer by layer upon a tubular mandrel with a 50-mm diameter. Four layers were braided on the same mandrel for each reference. The spools rotational velocity was held constant during braiding. As the braid was made of several layers, the thickness of each layer increases the apparent diameter on which the next layer will be braided. For this reason, the take-up speed was adjusted in order to keep the same braid angle from one layer to the next. According to the yam count, tubular mandrel geometry and braiding parameters, the cover factor [40] obtained is close to 100%. 

In Fig. 7.2 a thermoplastic filament winding process consisting of a material rack, a tension controller, a preheating zone, a main heater, a consolidation roller and a mandrel is shown schematically. Beside the material used, the most adjustable process parameters are winding velocity (which is defined by mandrel rotation and crosshead movement), roving tension, temperature, winding angle and mandrel/liner (material and temperature control). 

Clean the die Smooth and polish the die Increase mold temperature Increase air pressure Increase air blowing rate Increase purge time when changing materials Improve die streamlining Increase due to mandrel clearance Decrease material temperature Increase extrusion speed Decrease extrusion die temperature Increase stock temperature Decrease extrusion speed Increase die temperature Improve die streamlining Adjust material temperature Increase pinch blade land width Decrease rate of mold closing Adjust and center die-parison curls toward thin area... 

Tubular-Blown Film Dies (Circular Dies). Tubular coextrusion dies were the earliest dies used to make multilayer plastic film. Successfiil design requires formation of uniform concentric layers in the annular die land formed by the mandrel and adjustable or nonadjustable outer die ring. Early designs included center-fed dies that had the mandrel supported by a spider (4). Feedports arranged a concentric melt stream that was pierced by the mandrel as it flowed to the die exit, forming anniJar layers. Limitations of this early design were discontinuity and nommiformity cansed by spider-induced weld lines in the layers. 

---