Special Release Systems

Previous Page safeguards for returning the ejector assembly with mold closing is not needed if doubleacting cylinders are employed For proper functioning of all systems, an ample stroke of the ejector plates is required The plates have to advance the ejector pins (or other means of ejection) sufficiently far towards the parting line that gravity can act on the molding Only then is a fully automatic operation possible In very deep molds (buckets) the ejector stroke may not be sufficient to completely release the molding Then a combined release method is often employed The part is first partially released by mechanical operation of the ejector assembly and then blown off the core by compressed air If no compressed air is available, the part has to be removed manually after breaking A combined, stepwise release method is also used if especially high breaking forces are needed The step-up ejector in Figure 12.43 increases the ejection force two to three times [12.25] After loosening the molding, it is advanced in a second step or taken off by hand 12.5 Special Release Systems 12.5.1 D o u b l e - S t a g e E j e c t i o n Large but thin-walled parts often have to be demolded in several stages This is especially the case if ejector pins cannot act at places where the moldings cannot withstand the forces without damage An example is presented with Figure 12.44 At first the molding is broken loose by the stripper ring To prevent formation of a vacuum under the bottom, the ejectors are moved likewise and support the bottom The element that is used for double ejection is introduced in the literature as ball notch [12.1] During, demolding the ejector bolt a moves against a fixed stop and so actuates the ejector system f At the same time the ejector system g is taken along by means of the engaged balls e Thus, stripper plate and ejector pins simultaneously remove the part from the core By now both ejector plates have advanced so far towards the parting line that the fixed bolt c has become too short to keep the balls apart They drop out of the recess and only the ejector plate f is actuated further Its ejector pins finally release the part Because of high wear, the balls (ball bearings), the bushing, and the bolt c have to be hardened To ensure proper function of the mold, attention has to be paid to the dimensions and the arrangement of the individual elements so that the balls are forced into a rolling motion The diameter of the balls has to be larger than the diameter of the bolt [12.1] Figure 12.45 presents a typical two-stage ejector for separating tunnel gates from the molding 12.5.2 C o m b i n e d E j e c t i o n Another version of double-stage ejection is the possibility shown with Figure 12.46 During mold opening the part is first stripped off the core mechanically Final ejection is done with compressed air This system has the advantage of lower mold costs compared Section x Section y Figure 12.44 Two-stage ejection actuated by ball catch [12.1] a Ejector bolt, b Bushing, c Fixed bolt, d Mounting plate, e Balls, f and g Ejector and ejector retainer plates Figure 12.45 Demolding of tunnel gates [12.23] Air Figure 12.46 Combined ejection [12.24] Figure 12.47 Disk or "mushroom" ejector pneumatically actuated (air ejector) [12.1] with a fully mechanical system and gentler ejection because the release pressure (air) acts upon the entire surface area It is primarily utilized where the length of the ejection stroke is insufficient for complete demolding (deep parts) The position of the air inlet is arbitrary A similar design is presented with a pneumatically operating "mushroom" or "disk" ejector The compressed air first lifts the disk and the part breaks loose; then it flows past the disk and ejects the molding completely (Figure 12.47) 12.5.3 T h r e e - P l a t e M o l d s If multi-cavity molds or molds for multiple gating of one part are employed, the runner system has to be separated from the molding inside the mold during mold opening and ejected to achieve a fully automatic operation Therefore, the mold has to have several parting lines at which the mold is opened successively The ejection movement can be actuated in different ways Most common is the stripper bolt or the latch bar 12.5.3.1 Ejector Movement by Stripper Bolt Figure 12.48 shows a three-plate mold in open (left) and closed position (right) [12.29] The mold is first opened in the plane of parting line One has to ensure that the part remains still on the core Thus it is separated from the gate or gates After a certain opening stroke the floating plate is taken along by the bolt B and the mold opens in the plane of parting line The runner system is still kept by undercuts until it is ejected by an ejector bar which is actuated by bolt B Parting line Parting line B2 B, Figure 12.48 Three-plate mold actuated by Stripper bolts [12.29] B , B Stripper bolts, left side: Open, right side: Closed 12.5.3.2 Ejector Movement by Latch This device first locks the floating plate with a latch After the opening stroke has advanced a certain distance, the release bar unlocks and the mold opens at the parting line Figure 12.49 shows the opening procedure of a mold with a latch Figure A is the closed position The latch a locks the floating plate g The latch can pivot around the bolt A Section X Section Y B C D Figure 12.49 Latch assembly [12.1], Explanation of A to D in text 1, Parting lines, a Latch bar, b Release bar, c Guide pin, d Pivot pin, e Spring, f Stop pin, g Floating plate d It is kept in a horizontal position by the spring e and the stopper f as long as the mold is closed During mold opening the release bar b lifts the bolt c (Figure B) and releases the latch a (Figure C) With the continuing movement the mold can, therefore, open at the parting line Thus, molding and runner are ejected separately Because of the occurring high wear, latch and release bar, as well as the stop at the floating plate, have to be made of hardened steel Such molds can be employed for part weights up to kg For larger sizes, pneumatic locking and hydraulic opening are preferable [12.1] In all molds which open in several planes the floating plates have to be precisely guided and aligned so that the cavity surfaces are properly engaged and not damaged The latch assembly has to be mounted in such a way that it does not interfere with the molding dropping out of the mold by gravity after demolding 12.5.3.3 Reversed Ejection from the Stationary Side Some molds are designed in such a way that the molding remains in the stationary mold half These molds have to have a different demolding action Demolding takes place by stripping the part off the core The stripper plate can be actuated by a stripper bolt (Figure 12.50), which is attached to the movable mold half by a pin-link chain, or by Figure 12.50 Demolding from stationary half with stripper bolts Figure 12.51 Demolding from stationary half with pin-link chain hydraulic or pneumatic action Thus the ejection occurs by traction in the direction of demolding (Figure 12.51) There are disadvantages, though The accessibility of the mold is poor Two other options are shown with Figure 12.52 The ejector is actuated by a lever or a crank a) View W b) Alternative cam Figure 12.52 Ejector actuation by lever or crank for flat moldings which stick to the stationary side a) Lever: Ejector, Return spring, Lever, Cam plate, b) Crank: Ejector, Return spring, Cam disk, Crank [12.23] 12.6 Ejector Return When the mold is being closed, the advanced ejector pins, stripper plates, etc have to be returned on time into their position for a closed mold Otherwise the ejection assembly or the opposite mold half may be damaged The return can be achieved by various means, either by return pins, by springs, or special return devices The most reliable solution for returning the ejector assembly is provided by return pins Ejector pins with cylindrical head and shaft can be used as return pins They are either nitrided or annealed, and are kept in the ejector plates like ejector pins During mold closing they are pushed back by the opposite mold half (Figure 12.53) or by pins mounted in that mold half (Figure 12.54) and return the entire ejector assembly Return pin Figure 12.54 Return pin with counter pin [12.27] Figure 12.53 Return pin [12.27] top: Mold open, bottom: Mold closed Such counter pins are recommended because of the ease of their replacement as parts subject to wear In other molds the ejector assembly is returned during closing by springs (Figure 12.37) The springs have to be sufficiently strong to reliably overcome the sometimes considerable friction on ejector and guide pins If the spring force is insufficient, the mold is damaged during closing The service life of a spring is limited and depends on the kind of loading and the stress, and also on the number of loading cycles With such molds it is advisable to provide for a return safeguard Therefore, a combination of return spring and return pin is frequently used Since return pins are often Figure 12.55 Pawl pin [12.30] 1) Mold is closed Slides are returned Ejector system A is in returned position 2) Mold is open Slide travel is complete Return bolt R has been inserted in catch F, has actuated ejector system A and ejected moldings Fingers of catch have locked behind bolt head 3) Closing mold has positively returned ejector system after having moved the distance B (ejector travel + mm) Slides can be moved now without restriction obstructive, electric limit switches are also employed as safeguards They shut the machine down if the ejector assembly is not completely returned Besides this, mechanically operating return devices have been developed, which are presented in Figures 12.55 and 12.56 Figure 12.56 Return System with ball catch [12.1] a Bushing, b Balls, c Sleeve, d Spring, e Set screw, f Locking sleeve, g Spring In the slide mold in Figure 12.55 a pawl pin b is screwed into the ejector plates a instead of an ejector bolt [12.30] This pin is surrounded by a clamping sleeve c, which is connected to the ejector housing by a fine thread and secured by a slotted nut d When the mold opens, the pawl pin hits the profiled tip of the knockout bolt e in the machine, which spreads the catches of the pawl pin As soon as the machine bolt has dipped into the hollow pawl pin, the catches snap back behind its collar This creates a positive connection between pin and machine bolt The machine bolt can now return the ejector assembly while the mold is being closed At the end of the return stroke the catches free the machine bolt The length of the stroke can be accurately determined by adjusting the bushing This system works very reliably The return system in Figure 12.56 operates with a ball notch [12.1] The machine does not carry a knockout bolt but the bushing a, which accommodates the balls b The small bolt c with a profiled surface can slide in this bushing A spring d keeps the bolt under tension and the set screw e stops it at the foremost position In this position the balls catch a recess in the bolt During mold opening the bushing a enters the sleeve f, which is attached to the movable plate The bolt c hits an ejector bolt The engaged balls provide for a solid connection and the ejector plates are moved towards the parting line An additional stroke frees the balls and the ejector assembly returns under the effect of the spring g provided that spring g is stronger than spring d During closing of the mold the bushing is retracted and the spring d pushes the bolt into its initial position, The disadvantage of this system is its limited ejection stroke; its advantage the possibility of returning the ejector assembly in a mold still open 12.7 Ejection of Parts with Undercuts The question of how to demold parts with undercuts depends above all on the shape and the depth of the undercut They determine whether the undercut can be directly demolded or special arrangements have to be made to free the undercut with slides, a split cavity, or by screwing it off Parts that cannot be demolded directly call, therefore, for expensive tooling and possibly additional equipment to the molding machine Consequently, one should first investigate whether or not undercuts can be avoided by a minor design change of the part such as clever use of a taper or an opening in a side wall Examples are presented in Figure 12.57 In the following, such moldings with undercuts, which still can be demolded directly, are discussed first Snap fits and threads belong to these relatively rare cases A B C A Box with opening in side wall results in undercut, B Converting opening to slit eliminates undercut, C-E With an inclined wall the slit can be closed again without creating an undercut and simple ejection from the core is made possible D E Figure 12.57 A change in part design results in a less expensive mold [12.31] 12.7.1 D e m o l d i n g o f P a r t s w i t h U n d e r c u t s b y P u s h i n g T h e m off Demolding of parts with undercuts by pushing them off without eliminating the undercut of the mold (Figures 12.58 to 12.60) is only possible by deforming the part sufficiently to overcome the undercut This must not cause a plastic deformation Top view of Figures 12.58 to 12.60 refer to Figure 12.63 Table 12.1 lists some data of permissible elongations, which can be equated to the maximal permissible undercuts in thin-walled parts Other references [12.32, 12.34] state larger permissible elongations but then demolding is not reliable under all possible conditions 12.8.3 D e m o l d i n g of Parts w i t h External T h r e a d s External threads can basically be produced in unscrewing molds in the same manner as internal threads Examples are provided with Figures 12.76 and 12.77 With the design of Figure 12.76 two threads with different pitch, and with that of Figure 12.77 an internal and an external thread are both demolded simultaneously In each case the sleeve forming the external thread is rotated by a lead screw It frees the molding, which is kept in the mold, with an axial motion Figure 12.76 Molding with two external threads with different pitch [12.1] a, b Threaded sleeves, c, d Nuts, e Ejector, f, g Gears Figure 12.77 Molding with internal and external thread [12.1] a Pinion, b Sleeve, c Threaded core, d Key, e, f Nuts for axial motion, g Ejector Unscrewing molds are structures of highest precision Therefore they are expensive They should only be employed for molding external threads in high quality parts, for which marks from a parting line cannot be tolerated and large quantities justify the expenses In many cases external threads can also be formed by slides especially if the unavoidable marks from a parting line are acceptable 12.9 U n d e r c u t s in N o n c y l i n d r i c a l Parts 12.9.1 I n t e r n a l U n d e r c u t s Figure 12.78 shows such a part as an example, a cover with undercuts in two opposite walls In simple cases it can be demolded with a collapsible core The core is composed of several oblique segments, which are stressed or relieved by a wedge There are no undercuts in the range of the wedge The employment of such a design assumes a certain minimum size of the mold Figure 12.78 Mold with split core [12.27] 12.9.2 E x t e r n a l U n d e r c u t s Ribs, cams, flanges, openings, blind holes, as well as threads can form external undercuts Parts with such undercuts are produced in molds in which that part of the forming contour, which creates the undercut, is laterally moved for demolding This frees the undercut Such so-called slide or split-cavity molds are discussed in the following section Slides actuate a core that forms a locally limited undercut (e.g., a blind hole) Split cavities form whole sides of parts with undercuts (e.g., ribs) Both design features have one thing in common; they have to be built very rigid and leaders and interlocks have to be fitted with special care Yielding molds expand under the cavity pressure during injection and melt can enter into the parting line The same happens with inadequately fitted slides Undesirable flash at the part is the least serious consequence, although it calls for a postmolding operation It is also possible that such high bending and shear stresses are generated in these components or the actuating elements and, of course, in the mold base, that they are severely damaged and made useless Slides can be guided with T-grooves, dovetail grooves, or leader pins Particular significance should be attached to their operating properties in emergencies Lubricating movable components with molybdenum disulfide can result in staining of moldings or discoloring of the melt Thus, its use is limited By properly pairing suitable materials, easy sliding has to be ensured and wear inhibited Aluminum bronze has been successfully used in molds of medium size In large molds, slide properties have been improved by build-up welding of bronze on the sliding surfaces [12.46] Hardened and adjustable rails can counteract wear of wedges for proper clamping During use, the molds are subjected to the effects of heat from the hot melt, the hot manifold in hot-runner molds, and the heat exchange system Thermal expansion can cause jamming of sliding components if not taken into account during design Either the whole mold has to be kept at the same temperature by connecting the movable parts to the heat exchange system or such fits have to be chosen that no inadmissible gaps are generated at parting lines or guide surfaces during operation Special design features of such molds, are presented in the following sections 12.9.2.1 Slide Molds During demolding, slides are positively actuated either by leader pins or lifters, or less frequently by direct hydraulic action In addition, there are special design features which are discussed below Figures 12.79 and 12.80 present the design and installation of leader pins and lifters and characteristic dimensional data for the assembly The function of these two mold types is demonstrated in Figures 12.81 and 12.82 While a leader pin moves the slide simultaneously with mold opening, a lifter allows a delayed onset of the lateral movement Commonly available leader pins can be used Their dimensions are determined by their loading from release forces (Section 12.2), the weight of the slides and the resistance from friction Figure 12.83 depicts a leader pin and the forces acting upon it during an upward movement of the slide The force that acts upon the leader pin can be computed from the motion of a body on an oblique plane (Figure 12.84) Figure 12.79 Schematic presentation of a cam pin assembly [12.2] Heel block, Mold plate, Clamping plate, Cam pin, Slide, Mold plate, Support plate Figure 12.80 Design with lifter [12.2] Heel block, Mold plate, Lifter, Slide, Mold plate Figure 12.81 Operation of a slide mold with cam pins [12.27] a Molding, b Cam pin, c Slide, d Clamping surface Figure 12.82 Operation of a mold with lifters [12.27] a Slide, b Clamping surface, c Stationary mold half, d Core, e Lifter Figure 12.83 Forces acting on a cam pin Figure 12.84 Motion on an inclined plane for calculating cam pins [12.47] The resultant from the individual forces PR follows from (12.30) Substituting for P (12.31) results in (12.32) or (12.33) Where (12.34) tan P should generally not exceed the value of 0.5 [12.49] From the diagram of forces with R = f • N (12.35) The coefficient of friction f is 0.1 for steel moving against steel This allows the angle for the inclination of the pins to be computed The resulting force perpendicular to the pin determines the cross section of the pin and is computed with (12.36) or in this case (12.37) In Figure 12.85 the opening force acting upon the pin is plotted against time The full force acts upon the pin only at the moment of breaking the part loose [12.48] P Tm i et Figure 12.85 time [12.48] Load upon a cam pin plotted against In order to evade overloading the cam pins, one has found out that the most favorable range for the inclination of cam pins is between 15 and 25 C Larger angles facilitate mold opening while smaller ones provide higher clamping forces One has to make a compromise, which is determined by the mold size and the clamping and opening forces The method of securing the slide with an inserted heel block against shifting under injection pressure is sufficient in most cases (Figure 12.79) The advantage of this design is its simplicity compared with machining a solid plate (Figure 12.81) and faster interchangeability after it is worn out The angle of the face should be kept to 3° steeper than the corresponding angle of the cam pin to compensate for a possible play between pin and hole [12.1, 12.2, 12.46] and to cause clamping in the closed state and with this a firm seat of the slide During mold closing the slides have to be returned to their original position This is accomplished either by the cam pin (Figure 12.86) or with the face of the mold The last method is used if only very short cam pins are acceptable for design reasons This design calls for means to keep the slide in place (with a ball notch in Figure 12.87) so that the pin accurately enters the hole in the slide when the mold is closed Clamping surface Cam pin Slide Figure 12.86 Return of slides with cam pins [12.1] a and Ot1 Inclination of cam pin and clamping surface, H Undercut, H Opening stroke of slide Figure 12.87 Return of slides with clamping surface [12.1] a and Ot1 Inclination of cam pin and clamping surface, H Undercut, H Opening stroke of slide The length of the cam pin depends on the required opening stroke Figure 12.87 shows a short pin A long stroke requires an appropriately long pin Then, as Figure 12.86 demonstrates, the pin has to enter deep into the movable mold half and an opening has to be provided accordingly To obtain longer slide travel with a shorter lead, the angle of inclination has to be increased Since an angle of 25° should not be exceeded (increased wear, poor force transmission), another design has to be found Figure 12.88 presents a slide mold in which rollers c are attached to the slide a They are guided in oblique grooves b It is the advantage of this design that the angle of the oblique grooves can be increased to more than 45° This results in the desired longer slide travel with shorter guide ways Because of the rolling motion, there is considerably less friction and wear than with sliding cam pins Another interesting variation is shown in Figure 12.89 The mechanism for actuating the slides is mounted outside the mold This provides more space for the cavity The device operates with two racks with helical gearing perpendicular to one another They are engaged within a leader block This equipment and its variations are commercially available as standards In contrast to pins, lifters can delay the onset of the slide motion The mold can open for a certain distance, which depends on the contour of the lifter, before the slides are laterally moved and the undercuts are freed for demolding This makes it possible to achieve a partial ejection of the molding from the core while the slides are still closed; e.g for deep sleeves or tumblers After the slides have released the part, it can be ejected pneumatically The angle of the slope of the lifters should be between 25 and 30° The angle of the clamping faces may be more acute This increases the clamping force Experience Section B-B Figure 12.88 Six-cavity mold for hooks with severe undercut made of polystyrene [12.49] This design is characterized by rollers C of slide a running in inclined grooves b This permits larger angles a (more than 45°) and with this longer slide travel with shorter leader distances Wear is reduced due to rolling motion if compared with the use of cam pins Section C-C View A-A Figure 12.89 Slide mold operated by two beveled racks and guide block [12.50] indicates an angle of about 15° Figures 12.90 and 12.91 show two examples of applications and the appropriate lifters [12.1, 12.2] Stripper plate Figure 12.90 Mold with lifter [12.1] H Undercut, H1 Opening stroke of slide, aj Inclination of clamping surface, a Inclination of lifter, x Height of molding, X1 Opening stroke; after this stroke the lifter initiates the motion of the slide Figure 12.91 Mold with lifter [12.1] X1 Initial opening stroke (see explanation to Figure 12.90) 12.9.2.2 Split-Cavity Molds If entire side faces have to be moved away to allow a stripping of the part from the main core, a split cavity is used Typical examples are boxes with outside ribbing and openings in the side wall Even in cases where the clamping force of the machine is insufficient, the base of a split cavity mold can provide part of the needed clamping force Figure 12.92 demonstrates the mode of operation of a split-cavity mold The wedge shaped sliding components are guided in a frame, which is adequately dimensioned so that it cannot expand under the cavity pressure during injection Otherwise flashing is inevitable The slides are guided in a dove-tail or T groove The possibilities of compensating for wear or keeping it small have already been discussed in connection with the guides for cam pins The slides should have a taper of 10 to 15° This range has been successfully used in practice Smaller angles may lead to jamming in the frame under the effect of the clamping force, while larger angles react against the clamping force These molds are locked by the opposite mold half, which also can accommodate protruding slides in a tapered recess (Figure 12.93) The same effect can be obtained with a design according to Figure 12.94 Here the expansion of the frame during injection is prevented with a tapered fit between movable and stationary mold half [12.1] The opening motion of a split-cavity mold can be positively initiated by the opening movement of the molding machine or by a separate actuator The machine movement acts upon the slides with toggles or latches (Figure 12.92), ejector pins (Figures 12.93 Split cavity Ribs Strap joint Strap joint Figure 12.92 Operation of a split-cavity mold actuated with strap joints [12.51] Figure 12.93 Countertaper to improve mold sealing [12.1] Figure 12.94 Tapered seat in the stationary half prevents excessive breathing of mold [12.1] and 12.94), links (Figure 12.95), springs (Figure 12.96) or lifters (Figure 12.97) Hydraulic cylinders can be employed as separate actuators (Figures 12.98 to 12.100) If ejector pins, links or springs are used as actuators, an additional demolding mechanism is usually needed With toggles, latches or cams the lateral opening motion can be delayed until the molding is stripped off the core Thus, additional ejection is generally not required It should be mentioned, finally, that spring operated split-cavity molds allow only a short opening stroke, which is limited by stops (Figure 12.96) Figure 12.95 Split cavity actuated by links [12.51] Figure 12.96 Split cavity actuated by springs, stroke limited by stop pins [12.1] Figure 12.97 Split cavity operated by cam [12.1] top: Mold closed, bottom: Mold opened Figure 12.98 Split cavity operated by hydraulic cylinder [12.1] Figure 12.99 Split cavity operated by hydraulic cylinder [12.1] Figures 12.98, 12.99, and 12.100 illustrate split-cavity molds, which are actuated by hydraulic cylinders They should be controlled in the framework of a fully automatic or a programmed control of the machine to increase reliability of operation The hydraulic cylinder has to be mounted in such a way that no lateral forces act upon the piston They would impede its function For this reason the piston cannot accept any guiding functions while moving the slides Adequate cooling of the slides has to keep the temperature of the hydraulic system low and provides for fast cooling of the injected material [12.1] Each slide has to be sufficiently cooled and should have a separate cooling circuit with temperature control 12.9.3 M o l d s w i t h Core-Pulling D e v i c e s When producing large pipe fittings the cores have to be pulled before the part is demolded Figure 12.101 pictures a sectional view of such a mold At first the core is pulled followed by core Because pulling of the core poses the hazard of tearing the socket off the pipe, the forming component is pushed from the core by the piston until the core is loosened from the fitting The component is taken along by the screw after a short free travel Figure 12.100 Operation of split cavity by hydraulic cylinder [12.23] Split cavity half, Hydraulic cylinder, Frame, Guide bar, Clamp bar, Core, 7, Air valves, Stripper ledge Figure 12.101 Mold with core pullers for the production of pipe fittings [12.23] Pull rod hydraulically operated, Tie-in of pull rod to core, Core for main pipe, Core for socket, Extended core guide, Socket release, Piston for socket release, Holding pin for socket release References [12.1] [12.2] [12.3] [12.4] [12.5] [12.6] Mohrwald, K.: Einblick in die Konstruktion von SpritzgieBwerkzeugen Garrels, Hamburg, 1965 Mink, W.: Grundzuge der Spritzgiefitechnik Kunststoffbucherei Vol Zechner & Hiithig, Speyer, Wien, Zurich, 1966 Entformungseinrichtungen Technical Information, 4.4, BASF, Ludwigshafen/Rh., 1969 Bangert, H.: Systematische Konstruktion von SpritzgieBwerkzeugen und Rechnereinsatz Dissertation, Techn Univ., Aachen, 1981 Kaminski, A.: Messungen und Berechnungen von Entformungskraften an geometrisch einfachen Formteilen In: Berechenbarkeit von SpritzgieBwerkzeugen VDI-Verlag, Diisseldorf, 1974 Karakiiciik, B.: Ermittlung von Entformungskraften bei hulsenformigen Formteilen Unpublished report, IKV, Aachen, 1979 [12.7] [12.8] [12.9] [12.10] [12.11] [12.12] [12.13] [12.14] [12.15] [12.16] [12.17] [12.18] [12.19] [12.20] [12.21] [ 12.22] [12.23] [12.24] [12.25] [12.26] [12.27] [12.28] [12.29] [12.30] [12.31] [12.32] [12.33] [12.34] [12.35] [12.36] [12.37] [12.38] [12.39] Schlattmann, M.: Messung von Entformungskraften Unpublished report, IKV, Aachen, 1978 SpritzgieBtechnik Publication, Chemische Werke HuIs AG, Marl, 1979 Yorgancioglu, Y Z.: Ermittlung von Entformungsbeiwerten beim SpritzgieBen von Thermoplasten (PS, ABS, PC) Unpublished report, IKV, Aachen, 1979 Ribbert, E J.: Ermittlung von Entformungsbeiwerten beim SpritzgieBen von Thermoplasten (PP, PE) Unpublished report, IKV, Aachen, 1979 Schrender, S.: Ermittlung von Entformungskraften beim SpritzgieBen von Thermoplasten Unpublished report, IKV, Aachen, 1979 Bangert, H.; Doring, E.; Lichius, U.; Kemper, W; Schumann, E.: Bessere Wirtschaftlichkeit beim SpritzgieBen durch optimale Werkzeugauslegung Paper block VII at the 10th Tech Conference on Plastics, IKV, Aachen, March 12-14, 1980 Cordes, H.: Theoretische Ermittlung von Entformungskraften Unpublished report, IKV, Aachen, 1975 Aengenheyster, G.: Gestaltung und Dimensionierung von Verbundkonstruktionen mit 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Officiel des Activites des Plastiques et du Caoutchoucs, 14 (1967), pp 269-276 and pp 620-628 Gastrow, H.: Der SpritzgieBwerkzeugbau in 100 Beispielen 3rd Ed., Carl Hanser Verlag, Munich, 1966 Lohmann, A.: Auswerfereinrichtungen an SpritzgieBmaschinen Kunststoffe, 59 (1969), 3, pp 137-139 Pye, R G E.: Injection Mould Design (for Thermoplastics) Iliffe Books, London, 1968 Actuation Methods for Part Ejection Prospectus, Husky GmbH, Hilchenbach/Dahlbruch, 1973 SpritzguB-Hostalen PP Handbook, Farbwerke Hoechst AG, Frankfurt Automatische Auswerfer-Ruckzug-Einrichtung Prospectus, Zimmermann, Lahr/Schwarzwald Kuroda, J.: Mold Designing and Construction for Automation and High Cycle Molding (1) Jpn Plast Age, 11 (1973), pp 39-44 Schnappverbindungen Material sheet 3101.1, BASF, Ludwigshafen, 1973 Halbzeugverarbeitung Information for Tech Application, Farbwerke Hoechst AG, Frankfurt, 1975 Erhard, G.: Schnappverbindungen bei Kunststoffteilen Kunststoffe, 58 (1968), 2, pp 131-133 Berechnen von 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