Feed Screw and Non Return Valve Terms Glossary

Feed Screw Terms

All figures referenced are located at the end of the list of terms. Download PDF

conventional-fligthed-screw

“A” Channel – Refers to one of the two flow channels through a DM2 section. The A channel is the melt side of the channel at the beginning of the section. Depending on the number of peaks, the “A” channel may end ahead of or behind the “B” channel. {Figure 5}

ASB – Advancing Spiral Barrier. A barrier section in which the secondary flight has a lead greater than that of the main flight. This causes the secondary flight to gain on the main flight from behind. The melt channel widens and the solid channel becomes narrower as this section develops along the screw. {Figure 4}

Auxiliary Flight – a.k.a. Barrier Flight, Secondary Flight, and Undercut Flight.

“B” Channel – Refers to one of the two flow channels through a DM2 section. The B channel is the solids side of the channel at the beginning of the section. Depending on the number of peaks, the “B” channel may end ahead of or behind the “A” channel. {Figure 5}

Barrel – The cylinder in which the screw turns, and possibly reciprocates, to melt, mix, and process materials.

Barrier Flight – The undercut flight through a barrier section. It serves as a barrier between the melt and solid channels. {Figure 3 & 4}

Barrier Section – A section of the Feed screw, usually in the area just after the feed section, which divides the melted material from the pellets that are still solid. {Figure 3 & 4}

Belt Polish – Material removal by means of a belt covered with a gritty material. The belts have various grit classifications relating to how coarse they are. A 320 grit belt is much smoother than an 80 grit.

Blister – A restriction in the flow of material typically placed at the output end of the screw. There isn’t usually a flight in this area and the root diameter is increased for a shallower gap between the screw and barrel. {Figure 6}

Board – To dull the outer surface of a screw and remove irregularities by running a board covered with a sanding belt over the part.

Buff – To put a high polish on a part using a buffing wheel and a rouge compound.

Butter Layer – A layer of softer material used when hardfacing to allow shifting between the harder outer layer and the base material of the screw. (a.k.a. Underlay) {Figure 2}

CNC – Computer Numeric Control

Carbide Coating – A very hard coating applied by a high velocity thermal spray.

Chamfer – A short taper between surfaces. Quite often used to break an edge or to help when installing parts with close clearances.

Channel – 1. An operation whereas a groove is cut into the part for the application of a hardfacing alloy. 2.The area of a screw cut away for material to flow in while it is processed. (a.k.a. Flow Channel.)

Chrome Plate – A surface treatment where chrome is electrodeposited onto the surface from a solution of chromic acid. Glycon’s triple chrome has three layers of chrome and the part is polished between each layer’s application.

Colmonoy – A manufacturer of hardfacing materials. Glycon uses Colomonoy 56, 57, and 83 to hardface many of the screw manufactured.

Compression Ratio – The ratio of feed depth to meter depth. (feed depth ÷ meter depth) {Figure 1}

Conventionally Flighted – A screw consisting of simple feed, transition, and metering sections without auxiliary flights. {Figure 1}

Diamond Mixer – A mixer made up of diamonds to break up the material flow through the section. {Figure 6}

DM2 Section – Distributive Mix/Melt. This section pumps the material back and forth across an undercut flight while the channels are changing depths between peaks and valleys. {Figure 5}

Drive End – The end of the screw, which is connected to the drive system with a key or keys, flats, pin, spline, or thread. {Figure 7}

Dy-Clad – An electrodeposited chrome that is very thin and adds lubricity to the surface.

Eagle Mixer – A special mixer, similar to a short ASB, with channels cut across the flights. {Figure 7}

Feed Depth – Depth of the flow channel in the feed section. {Figure 1}

Feed Pocket – The start of the flow channel where material is fed into the system to be processed. {Figure 1}

Feed Section – The first section of the flow channel. Typically, the deepest part of a conventionally flighted screw. {Figure 1}

Fillet Radius – A radius blending two surfaces.

Flame Harden – A surface treatment with a process of heating the part with a carburizing flame and quenching to achieve a case hardened surface.

Flank – Refers to the sides of a flow channel. The right flank is the right side of the channel or the trailing side of the flight. The left flank is the left side of the channel or the push side of the flight. {Figure 2}

Flash Chrome – A very thin layer of chrome. Typically between .0001” and .0005” thick.

Flight – The part of the Feed screw that pushes material as the screw is turned.

Flight Width – The width of the flight at its outer surface furthest from the screw’s central axis. {Figure 2}

Flight End – The beginning or ending of a flight. This area is usually tapered to the root either by a conical taper or simply by blending its tail.

Flight Micrometer (Flight Mic) – A measuring instrument that has been modified with a long bar on the anvil to span across flights on a screw while the spindle contacts the single flight on the opposite side. {Figure 9}

Flight Start – The beginning of a main or auxiliary flight.

Flighted Length – The distance from the pocket to the output end of the screw. Although the flight typically stops before the register or nose taper, the flighted length includes this area. {Figure 1}

Flute – The groove or flow channel through a mixer.

Gear Mixer – A two-piece mixer consisting of teeth cut into a flange or flanges on the screw and a ring with teeth cut on its internal diameter (looking a little like an internal gear). {Figure 6}

Hardfacing – Material added to a surface with a welding process to extend its wear life. (Examples: Colmonoy #56, Colmonoy #57, Colmonoy #83, Stellite #6, and Stellite #12) {Figure 2}

Heat Treat – A process including heating, quenching, and possibly aging, to increase a part’s strength, hardness, or toughness. Some heat treatments include cryogenics or sub-zero temperatures.

Hub – The area directly behind the feed pocket. {Figure 1}

Hub Grooves – Grooves cut into the hub. Typically, these grooves are cut on a spiral with a lead that is either in the same direction as that of the main flight or opposite to it.

Hurricane Mixer – A Glycon mixer consisting of multiple channels with changing depths and interruptions due to channels cut in the opposite direction. {Figure 6}

Induction Harden – A surface treatment with a process of heating the part with an induction coil and quenching to achieve a case hardened surface.

In-Process Inspection – A step in the procedure at every operation where the operator measures and records dimensions they have effected at their station.

Involute Spline – A drive type with teeth resembling gear teeth. {Figure 7}

L/D (L over D) – Flighted length divided by the nominal diameter of the screw.

Land – An area without depth or diameter change.

Lathe – A machine used to remove material with a stationary cutting tool while rotating the part.

Lead – The distance a flight is advanced with a single turn or revolution of the screw. Measured from leading edge to leading edge or trailing edge to trailing edge. The lead can be right hand or left hand. (a.k.a. Pitch for single flighted screws) {Figure 2}

Leading Edge – The edge of the flight nearest the output of the screw. This is the push side of the flight. {Figure 2}

Left Flank - The left flank is the left side of the channel or the push side of the flight. {Figure 2}

Long Peak – The first peak after the barrier section in the solids channel and the beginning of the B channel in the DM2 section. {Figure 5}

Maddock Mixer – A mixer with longitudinal flights, alternating inlet and outlet channels, and very shallow gaps (undercuts) between the inlet channels and outlet channels. {Figure 6}

Major Diameter – With reference to a spline, it is the outside diameter of the external spline. With reference to a thread, it is the outside diameter of the external thread. {Figure 7}

Melt Channel – The flow channel behind the barrier flight. Melted material flows over the barrier flight and into this channel. {Figures 3 & 4}

Meter Depth – Depth of the flow channel in the meter section. {Figure 1}

Meter Section – The last section of the flow channel. Typically the shallowest part of a conventionally flighted screw. {Figure 1}

MIG – Metal inert-gas welding. Also GMAW (Gas Metal-Arc Welding). An arc welding process in which the heat for welding is generated by an arc between a consumable electrode and the work metal. The electrode, a bare solid wire that is continuously fed into the work area, becomes the filler metal as it is consumed. The electrode, weld pool, arc, and adjacent areas of the base metal are protected from atmospheric contamination by a gaseous shield fed through the welding gun.

Mill – A machine and a process where material is removed by a rotating cutter against the part.

Milled Pocket – A style of feed pocket generated with a ball mill or end mill with a corner radius. {Figure 1}

Minor Diameter – With reference to a spline, it is the diameter of the area between teeth on an external spline. With reference to a thread, it is the diameter at the valley between threads of an external thread. {Figure 7}

Mixer – A section added specifically to mix material. {Figure 6}

Nose – The end opposite of the drive, usually the output end. It may have a conical taper or a register with threads. {Figure 1}

Nose Threads – Threads at the nose end of the screw.

O.D. (Outer Diameter) – Main O.D. refers to the outer diameter of the main flight of the screw. {Figure 2}

O.D. Grind – Grinding of the outer most surface of a part by means of a rotating wheel.

Output End – The end of the screw where the material exits the system. It is usually opposite the drive end, but not always.

PTA – Plasma Transfer Arc welding. Closely related to TIG welding with the plasma level increased by a constricting orifice (or nozzle) placed around the arc. The result is a higher arc temperature and a more concentrated heat pattern.

Parallel Barrier – A barrier section where the main and barrier flights have the same lead. The melt channel gets deeper as the solids channel gets shallower. {Figure 3}

Peak – A shallow point in the DM2 section. {Figure 5}

Pineapple Mixer – Another name for a diamond mixer. {Figure 6}

Pitch – The distance from a point on a flight or thread to the same point on the next flight or thread. For a screw or a thread with two equally spaced starts, the pitch is one half of the lead. If there are three starts equally spaced, the pitch is one third of the lead. A square pitch is one that equals the nominal diameter.

Pitch Diameter – With reference to a spline, it is the diameter at which the tooth thickness equals the gap. With reference to threads, it is the diameter at which the thread ridge and groove are of equal width.

Pocket Line – The line at which the pocket starts. With a tapered or shooting pocket, this is the pocket start, not the point of full depth. {Figure 1}

Pocket Start – The distance from the drive end to the pocket line.

Profile – The depth information for a flow channel. {Figure 1}

Register – An area of constant diameter at the end of a part used to mate with a similar diameter on the adjoining part. {Figure 6}

Right Flank - The right flank is the right side of the channel or the trailing side of the flight. {Figure 2}

Root – The bottom of the flow channel. {Figure 2}

Root Grind – Grinding of the root area of a screw on a lathe that has been modified to include a grinding attachment. Various leads are achieved by changing gears in the drive.

Root Radius – The fillet radius between the channel’s root and the flank. {Figure 2}

Secondary Flight – a.k.a. Auxiliary Flight, Barrier Flight, and Undercut Flight.

Shank – The drive portion of the screw. {Figure 1}

Shooting Pocket – A style of feed pocket where the channel is full width, but the depth tapers from the surface to full feed depth over a given distance. (a.k.a. Tapered Pocket) {Figure 1}

Side Grind – Grinding of the sides of the flight on a lathe that has been modified to include a grinding attachment. Various leads are achieved by changing gears in the drive.

Slotted Mixer – A restriction resembling a blister but with numerous longitudinal channels cut through it. {Figure 6}

Solids Channel – The flow channel ahead of the barrier flight. Melted material flows over the barrier flight leaving this channel. {Figures 3 & 4}

Spiral Mixer – A mixer consisting of multiple flights with alternating inlet and outlet channels.

Spline – A drive type with multiple teeth. Can be involute or straight sided.

Split Ring Groove – A groove cut between the drive and the feed pocket for a close fitting collar used to pull the screw back during part of the molding cycle.

Stellite – A manufacturer of hardfacing materials. Stellite 6 and Stellite 12 are materials Glycon uses regularly.

Stone Belt – A belt polishing technique where the belt has been dressed with a stone to remove grit from a portion of the belt’s surface to minimize the material removed where this area contacts the part.

Straight Sided Spline – A drive type with multiple teeth where the teeth have flat, parallel sides.

Surface Treatment – Plating, coating, or conditioning of a part’s surface. (Examples: chrome, carbide, induction harden, flame harden, and Dy-Clad)

Tapered Pocket – A style of feed pocket where the channel is full width, but the depth tapers from the surface to full feed depth over a given distance. (a.k.a. Shooting Pocket) {Figure 1}

Thread Relief – In an internal thread it is the area at the end of the thread that is larger than the major diameter and is used to stop or start the cutting tool. On an external thread this area is smaller than the minor diameter.

TIG Welding – Tungsten inert-gas welding. Also GTAW (Gas Tungsten-Arc Welding). An arc welding process in which the heat is produced between a nonconsumable electrode and the work metal. . The electrode, weld pool, arc, and adjacent areas of the base metal are protected from atmospheric contamination by a gaseous shield. TIG welding doesn’t necessarily include a filler metal, however Glycon uses various filler metals with this process often to repair and recondition damaged parts.

Tip Counterbore – An internal diameter used to align the tip (non-return valve) with the screw.

Tooth Width – With reference to a straight sided spline, gear mixer, or a slotted mixer, it is the width of a single tooth. {Figure 7}

Trailing Edge – The edge of the flight nearest the feed pocket. {Figure 2}

Transition Section – The section between the feed and meter sections or between the feed and a DM2™ section. {Figure 1} Any portion of a flow channel that changes depth is called a transition. With reference to the whirler and CNC belt, the barrier solids channel is called a transition as it is a continuation of the run from the feed section. Also, a transition doesn’t have to be from deeper to shallower** – a barrier melt channel transitions from shallow to deep and there are transitions from peaks to valleys in the DM2™ section. {Figure 5}

Undercut (U-Cut) – An area of smaller diameter or the distance between this surface and the main O.D. of the screw. {Figures 3, 4, & 6}

Undercut (U-Cut) Flight – A flight with an outer surface below the main O.D. of the screw. {Figures 3 & 4}

Underlay – A layer of softer material used when hardfacing to allow shifting between the harder outer layer and the base material of the screw. (a.k.a. Butter Layer) {Figure 2}

UniMix – A mixing section with a single flight and a central channel within the main flow channel where the depths vary.

Valley – Refers to the deepest part of a DM2 section. {Figure 5}

Wax Belt – A belt polishing technique where buffing compound (rouge) is applied to the belt to fill between the grit particles and used in preparation to buffing for chrome.

Whirled Pocket – The style of pocket developed by the whirling operation. It is about one third to one half of the main flow channel width and tapers to full depth in 60° to 75° of rotation. {Figure 1}

Whirler – A CNC machining center using a ring with cutting tools set to the inside to quickly machine bars such as Feed screws.

Wide Peak – The first peak in a DM2™ section when it follows a barrier. This peak is usually longer than the others. It is sometimes referred to as a land.

Wiper Flight – The flight in a Maddock mixer that is not undercut from the main O.D. {Figure 6}

Non-Return Valve Terms

Check Ring – A sliding ring which seats against the rear seat during the injection portion of a molding cycle to prevent material from flowing back along the flight of the screw. {Figure 8}

Front Seat – A piece for the Check Ring to seat against while the screw is turning and the valve is open. Found in four piece non-return valves.

Poppet – The sliding piece of a Q.S.O. Valve. {Figure 8}

Q.S.O. – Glycon’s Quick Shut-Off Valve {Figure 8}

Rear Seat – The piece for the Check Ring to seat against during injection and the valve is closed. It sets against the screw. {Figure 8}

Retainer – The part of a Q.S.O. Valve that holds the Poppet in. {Figure 8}

Tip Pilot – The area between the threads and a shoulder, which fits into a counterbore to align the tip with the screw. {Figure 8}

Valve Body – The main portion of a three-piece non-return valve, which includes the nose, flutes, and threads. Or, the housing of a Q.S.O. Valve. {Figure 8}

Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Figure 7

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Figure 8

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