referring to the drawings wherein like reference numerals designate corresponding parts throughout the several figures , reference is made first to fig1 . an extruder screw 1 is rotated in an extruder bore 2 into which polymer pellets , powder and other substances are fed into the extruder bore 2 through a hopper 3 . the extruder screw 1 is rotated to mix , crush , melt and otherwise process polymer material in various extruder machinery . processed polymer in liquid form of desired consistency is extruded through a gate 4 at a distal end of the extruder bore 2 . this process is referred to in the trade as &# 34 ; plastication &# 34 ;. referring to fig1 and 2 , the extruder screw 1 has a shank 5 at a proximal end and a discharge tip 6 at a distal end . a main flight 7 is a helical ridge extended radially outward from a screw core 8 in helical progression to form a screw channel 9 intermediate the shank 5 and the discharge tip 6 . depth of the screw channel 9 varies in different sections of the extruder screw 1 . maximum depth of the screw channel 9 is at a mixing section 10 which comprises approximately the first forty percent of a length of the extruder screw 1 . greatest depth of the screw channel 9 at the mixing section 10 is provided to accommodate a desired maximum of polymer pellets and other materials . depth of the screw channel 9 can be decreased as the polymer pellets are mixed with smaller particles and broken by shearing and compression . optionally , some of the decrease in depth of the screw channel 9 can commence in the mixing section 10 as shown . most of the decrease in depth of the screw channel 9 , however , is in a transition section 11 . the transition section 11 comprises approximately twenty percent of the length of the extruder screw 1 intermediate the mixing section 10 and a metering section 12 . in the transition section 11 , diameter of the screw core 8 is increased with a resulting decrease in depth of the screw channel 9 . also , screw - flight distance between helical rotations of the main flight 7 can be increased . shallowness of the screw channel 9 provides linear pressure for limited linear shearing action and thorough mixing prior to the metering section 12 . increase in distance between helical rotations of the main screw 7 provides a broader surface for high - pressure processing of the polymers in the metering section 12 . reference is made now to fig3 and 4 primarily and to fig1 and 2 secondarily . the metering section 12 has a plurality of at least three pressure channels juxtaposed helically between helical rotations of the screw flights 7 . three pressure channels are a proximal - side pressure channel 13 , a distal - side pressure channel 14 and a center pressure channel 15 . spaces in which the pressure channels 13 - 15 and other channel components are positioned between helical rotations of the main screw 7 are referred to as screw flights 16 . although the main flight 7 is a continuous helical ridge , the screw flights 16 are linear sections from a point of reference to a nonrotating extruder screw 1 . screw flights 16 correspond to pitch in regular screws . the pressure channels 13 - 15 are not continuous . they are interrupted by channel interruptions having side interruption tops 17 and center interruption tops 18 from which helical slopes 19 are extended inward radially on opposite helical sides of the side interruption tops 17 and on opposite sides of the center interruption tops 18 respectively . the helical slopes 19 can have different angles of incline on opposite sides of the interruption tops 17 and 18 and can be designed differently for different types of polymers . typically , the helical slopes 19 have less incline on pressure sides than on aft sides of the interruption tops 17 and 18 . pressure sides or leading sides of interruption tops 17 and 18 with less incline of helical slopes 19 are the helically distal sides . at positions where helical slopes 19 are ascending from pressure - channel bottoms 20 of side pressure channels 13 and 14 , channel bottoms 20 of pressure channel 15 are descending from center interruption tops 18 . at a point in their passing of ascent and descent , the depths of pressure channels 13 - 15 at slopes 19 can be equal as shown in fig4 . the interruption tops 17 and 18 have constancy of radii in relation to an axis of the extruder screw 1 as designed for plasticating desired polymer substances . constancy of radii of interruption tops 17 and 18 can be constant or near constant . constant radii results in circular interruption tops or circular portions of interruption tops 17 and 18 . near - constant radii results in near - circular portions of interruption tops 17 and 18 . the near - circular portions of interruption tops 17 and 18 are typically at leading or distal sides , although they can be at both sides of the interruption tops 17 and 18 . pressure - channel bottoms 20 of the side pressure channels 13 and 14 are offset helically as desired from pressure - channel bottoms 20 of the center pressure channel 15 . the pressure - channel bottoms 20 can have constant or varied radii from the axis of the extruder screw as desired for plastication of particular types of polymers . the pressure channels 13 - 15 provide rotational shearing pressure by directing particles to helical slopes 19 where the particles are then forced between the extruder bore 2 and a decreasing - clearance space in helical progression towards the interruption tops 17 and 18 . the pressure channels 13 - 15 have pressure - channel flights 21 which taper away to evenness with the interruption tops 17 and 18 . thus , the channels 13 - 15 are terminated or interrupted completely at the interruption tops 17 and 18 . this allows bidirectional escape of particles being pressurized and escape of &# 34 ; melt &# 34 ; resulting from pressurization and external heat added in the plastication process . crucially important , the absence of pressure - channel flights 21 on interruption tops 17 and 18 allows the interruption tops 17 and 18 to be positioned closer to the extruder bore 2 to achieve finer plastication . the pressure - channel flights 21 contain particle mix within the channels 13 - 15 as the particle mix is conveyed to and forced between a progressively narrowing space between channel bottoms 20 and the extruder bore 2 . finer or smaller particles remaining are restrained by tapering pressure - channel flights 21 in approach towards the pressure tops 17 and 18 . then as the pressure - channel flights 21 terminate , remaining particles are trapped in the narrow space between the extruder bore 2 and broad surfaces of the interruption tops 17 and 18 without the pressure - channel flights 21 . unrestricted bidirectional escape of more minute particles than possible with continuing secondary flights of the kruder technology then aids mix of pressure - induced melt with melt caused by external heat . heat from melt transfers to the finer particles in the narrow space to accomplish a more uniform consistency of the melt . absence of the pressure - channel flights 21 at the interruption tops 17 and 18 aids flow of melt and particles in combination to enhance the heat transfer from melt to particles for more effective , uniform and reliable plastication . together with narrower compression space and broad compression surfaces , the bidirectional travel of mix multiplies by several times the proportion of rotational in contrast to linear pressurization that is possible with known extruder screws . it avoids travel of particles to a distal end of an extruder screw for linear pressurization that jeopardizes melt quality as with meat - grinder screws , the iddon rubber - processing screw or the kruder technology . in contrast , continued channels of the kruder technology allow relatively large particles to travel to a distal end of the extruder screw and thus decrease plastication completeness that can occur fluidly upstream from an extruder gate 4 . travel of particles to a distal end of the extruder screw 1 causes a far greater portion of pressurization to be linear with less effective plastication than is possible with the much higher proportion of far more complete rotational compression provided by this invention . referring to fig5 in combination with fig1 - 4 , a small difference in constant - radii height of a center interruption channel 18 and diameter of the main flight 7 is provided . helical slopes 19 are represented by dotted lines ascending from a transition - section 11 depth of screw core 8 to a center interruption top 18 . also represented by dotted lines are helical slopes 19 descending from the interruption top 18 to a channel bottom 20 . represented by a dashed line is helical slope 19 ascending from the channel bottom 20 to the interruption top 18 . length of the interruption top 18 with constant radii is preferably ninety degrees of rotation of the extruder screw 1 . length of ascent from the diameter of the screw core 8 at the transition section 11 and length of descent to the pressure - channel bottom 20 also are preferably ninety degrees from respective proximal and distal ends of the interruption top 18 in helical progression that is represented circumferentially in this diagram . referring to fig6 a side interruption top 17 offset ninety degrees has the same relationships although preferably but not necessarily the same dimensions as for the center interruption top 18 shown in fig5 . referring to fig7 interruption tops 17 and 18 , represented by center interruption top 18 , can have a section of near - constant - radii top 22 on either or both helical sides . this can be little more than a slight rounding of dihedral angles of slopes 19 with interruption tops 17 and 18 . it can be most effective if employed at the distal side to provide a yet smaller distance progressively between the extruder bore 2 and the interruption tops 17 and 18 . alternatively , the helical slope 19 leading onto interruption tops 17 and 18 can be longer with less if any constant - radii pressure - channel bottom 20 and then flattened out in approaches to the interruption tops 17 and 18 . referring to fig8 the pressure channels 13 - 15 can have equal depth at a discharge tip 6 . this provides an even flow at the extruder gate 4 shown in fig1 . referring to fig9 linear representation of relationships of the interruption tops 17 and 18 , which are represented by extruder top 17 , to other portions of the metering section 12 are diagrammed in relation to a dashed line representing inside diameter of the extruder bore 2 across a top of the diagram . a top broken line represents diameter of the screw flights 7 in nearest proximity to the extruder bore 2 . a bottom broken line represents constant - radii surfaces of the interruption tops 17 and 18 . a horizontal centerline represents a diameter of the transition section 11 from which pressure channels 13 - 15 commence . leading from the transition section 11 , a helical slope 19 drops with relative abruptness to a pressure - channel bottom 20 . the pressure - channel bottom 20 can have constant radii as shown by a straight line before ascending with a helical slope 19 to a side interruption top 17 . the side interruption top 17 continues with constant radii to a termination of an interruption cycle before descending in new interruption cycle with a helical slope represented by a heavy dashed line 19 . preferably for many polymers for which this extruder screw 1 is designed , rotational duration of the first descent of helical slope 19 from a diameter of the transition section 11 is ninety degrees circumferentially . proportionately , a length of constant - radii pressure - channel bottom 20 is one hundred and eighty degrees circumferentially . an ascent of helical slope 19 is one hundred and eighty degrees and constant length of the interruption top 17 is ninety degrees . in total then , an interruption cycle is five hundred and forty degrees . the descent 19 for the next cycle also is ninety degrees . but the descent 19 must be slightly steeper to descend from a larger diameter at the interruption top 17 than from the transition section 11 to the same depth at the pressure - channel bottom 20 . there is no requirement for symmetry . relative uniformity is desirable , however , within requirements for optimizing design for plasticating polymers having different characteristics . circumferential duration of the constant - radii pressure - channel bottoms 20 is a guide to the amount of variation in design that is compatible for cycles less than five hundred and forty degrees . in other words , cycles can be one hundred and eighty degrees shorter or three hundred and sixty degrees of rotation with application of the same design criteria . shorter cycles are possible with proportionally shallower channels throughout the system . for some polymers , shorter cycles are possible with the same depth of pressure - channel bottoms 20 . shown in dotted lines at both ends of the interruption top 17 are near - constant - radii sections of the interruption top 17 . these are explained further in relation to fig7 . near - constant - radii sections 22 can have a down - gearing compression effect . but they can be replaced by appropriate flattening of helical slopes 19 . various modifications may be made of the invention without departing from the scope thereof and it is desired , therefore , that only such limitations shall be placed thereon as are imposed by the prior art and which are set forth in the appended claims .