ROLLER HEAD

Roller die systems can combine a dump extruder with a two bowl calender to produce good quality sheet for application in such products as conveyor belting. Roller head extruders are more integrated with the calender bowls mounted at the front of the extruder cylinder. 

A schematic diagram of the automated FIA/DCP/OES system is shown in Fig. 7.6. The carrier liquid is transported using a peristaltic pump, at a rate predetermined to suit the particular analysis. Teflon tubing (internal diameter 0.8 mm) is used where appropriate however, silicone tubing is applied at the roller heads to accommodate both organic and inorganic solvents. Samples are introduced by the autosampler through a loop. The size of the loop is variable for most applications a 600 pi loop is sufficient. 

However, the SynchroMed pump is not suitable for the delivery of insulin. The pressure of the roller heads on the tubing in the peristaltic pump causes intensive shear stresses which lead to stability problems for labile peptides and proteins. 

Calendering processes and machinery are described, and types of rubber and PVC products manufactured by this technology are examined. Details are also given of the roller head process, a cross between calendering and extrusion coating. 

The pump, which can meter up to 15 separate volumes of fluid or gas, consists of a constant-speed gear motor connected to a hinged roller head. This is raised or lowered against a plate on which the manifolds are placed. The roller head compresses the manifold tubing, pushing fluids or gases forward, while at the rear fluids are drawn into the tubes. The fluid volume, on a per time basis, is proportional to the inside diameter of the tube. 

A torque rheometer is used to determine fusion characteristics of PVC compounds. Components of formulation are first mixed in a beaker in an intensive mixer or ribbon blender. The rheometer is equipped with roller head and the premixed sample is added to a chamber having preselected temperature (typical temperatures used are 140 for flexible compounds, 180 for semirigid compounds, and 197°C for rigid compounds). The amount of the sample added is selected such that it occupies 65% of mixer bowl. Mixing is continued until torque peak is reached. Mixing time and maximum torque are two important results of testing. 

The development of the Roller Die (roller head) equipment made possible the production of wide thick sheets in a single operation, free from air inclusions and blisters. The extruder feeds a slab of material 30-60 mm thick directly into the calender nip, across the full width. The calendering operation is thus a gauge reduction no rolling bank forms, and the action may be regarded as an extension of the extrusion. The two parts of the plant are very close, the lips of the extruder die reaching deep into the calender nip. A pressure sensor is located in the die-lip, and this controls the calender speed to keep the stock pressure in the die constant. This ensures the matched running of the two halves of the plant. 

Brabender PlastiCorder test conditions heat rise test, 2 C/min 5 roller head used with 50 g charge temperature range 40-200 C. TABLE 8.8 Additional Brabender PlastiCorder Fusion Curve Data ... 

First part Roller train, stainless steel roUs, diameter 50 mm, pneumatical pivoting to get acces to the extrusion head, length approximately 0.7 m... 

Many manufacturers supply extruders with interchangeable heads, which can act as strainers, roller die devices or pelletisers. 

Plate bearings for printers, cable guides for printer heads bearings and sockets for photocopiers sliding parts and guiding rollers for high-speed printers and photocopiers. .. 

The applications of polyoxymethylene include plumbing and hardware (ballcock valves, shower heads, fittings and valves, pump and filter housings), machinery (gears, bearings, rollers, conveyor chains, airflow valves), transportion (fuel pump housing, cooling-fan parts, fuel... 

In fiber placement, a moving head is mounted to a multidegree of fieedom carriage. The fiber placement head is designed to cut and place each tow individually. The head may also include a controlled heat source and compaction roller for in situ consolidation. Tow placement with in situ consolidation has made it possible to place preimpregnated tape along nongeodesic paths, manufacture parts with concave sections, and to locate ply dropoffs precisely. 

Figure 14.20 Intermediate cross-head locations and corresponding component shapes during forming of a component that has a constant bend radius larger than the forming rollers...

Numerous kinds of mechanical adaptations have been introduced into this department varying in simplicity from Hie old head-stone rollers, to very intricate ar-... 

One thing the guide fails to do is to unite all the standard ISO methods described below into a logical series. Hence, the dead load method is called Method of determination of hardness whilst the durometer methods are under a separate number and headed Determination of indentation hardness. Methods for hardness of rollers come under a third number. 

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