The angle pin core-pulling mechanism consists of an angle pin and a slide forming an angle gainst the mold opening direction, and is provided with a slide positioning device and locking device to ensure safe and reliable pulling movement. a typical example as indicated in Fig. 2-17 angle pin 3 is secured on fixed plate 2, slide 8 glides in the chute of plate 7, and side core 5 is fixed on slide 8 with pin 4. When opening, the mold opening force acts on the slide through the angle pin, forcing the slide to glide out from the guiding chute of the moving plate and thereby completes core-pulling. The plastic part is pulled out by ejector sleeve 6. The stop device composed by bracket 9, bolt ll and spring 10 is applied to ensure that the slide stops at the final position after core-pulling so that the angle pin can smoothly enter the angle hole during mold opening and that the slide can successfully restore to its former position. Wedge block I is used to lock the slide and prevent it from gliding out as caused by the forming pressure on the side core The following factors should be taken into account during designing 1)The core should be set preferably in the moving or fixed mold vertical against the parting line so that the side core can be pulled out through mold opening or the pulling action; Fig. 2-17: angle pin core-pulling mechanism I-wedge block, 2-fixed plate, 3-angle pin; 4-pin; 5-side core; 6-ejector sleeve: 7-moving plate;, &slide, 9-stop block; 10-spring: 11-bolt 2)Use preferably core-pulling mechanism wherein the angle pin is located in the fixed mold nd the slide in the moving mold 3)Wedge angle b of the wedge block should be larger than the obliquity a of angle pin, usually larger than 2-3, otherwise, the angle pin cannot drive the slide 4)Upon completion of core-pulling, the slide left in the chute should not be less than 2/3 of total length of slide 5)Try not to make the projection of the ejector pin coincide with that the of the active core on the parting line to prevent mutual interference of the slide and the ejector unit during restoration: 6)When the slide is set on the fixed mold, the side-direction core must be pulled out prior to mold opening to ensure that the plastic part remains on the moving mold. A limit straining device can be used for this purpose 2. Pulling force During its molding and cooling in the mold, the plastic part wraps around the side-direction active core owing to the contraction of its volume. Yet when stripping it must overcome the wrapping force and the friction force produced by the core-pulling mechanism so that the active
The angle pin core-pulling mechanism consists of an angle pin and a slide forming an angle against the mold opening direction, and is provided with a slide positioning device and locking device to ensure safe and reliable pulling movement. A typical example as indicated in Fig.2-17: angle pin 3 is secured on fixed plate 2, slide 8 glides in the chute of plate 7, and side core 5 is fixed on slide 8 with pin 4. When opening, the mold opening force acts on the slide through the angle pin, forcing the slide to glide out from the guiding chute of the moving plate and thereby completes core-pulling. The plastic part is pulled out by ejector sleeve 6. The stop device composed by bracket 9, bolt 11 and spring 10 is applied to ensure that the slide stops at the final position after core-pulling so that the angle pin can smoothly enter the angle hole during mold opening and that the slide can successfully restore to its former position. Wedge block 1 is used to lock the slide and prevent it from gliding out as caused by the forming pressure on the side core. The following factors should be taken into account during designing: 1) The core should be set preferably in the moving or fixed mold vertical against the parting line so that the side core can be pulled out through mold opening or the pulling action; Fig. 2-17: angle pin core-pulling mechanism 1- wedge block; 2- fixed plate; 3- angle pin; 4- pin; 5- side core; 6- ejector sleeve; 7- moving plate; 8- slide; 9- stop block; 10- spring; 11- bolt 2) Use preferably core-pulling mechanism wherein the angle pin is located in the fixed mold and the slide in the moving mold; 3) Wedge angleθ of the wedge block should be larger than the obliquity a of angle pin, usually larger than 2°~ 3°; otherwise, the angle pin cannot drive the slide; 4) Upon completion of core-pulling, the slide left in the chute should not be less than 2/3 of total length of slide; 5) Try not to make the projection of the ejector pin coincide with that the of the active core on the parting line to prevent mutual interference of the slide and the ejector unit during restoration; 6) When the slide is set on the fixed mold, the side-direction core must be pulled out prior to mold opening to ensure that the plastic part remains on the moving mold. A limit straining device can be used for this purpose. 2. Pulling Force During its molding and cooling in the mold, the plastic part wraps around the side-direction active core owing to the contraction of its volume. Yet when stripping it must overcome the wrapping force and the friction force produced by the core-pulling mechanism so that the active
core can be pulled out The pulling force can be calculated as per the following formula F=pAcos(f-tan a)/(1+fsin a, cos a,) (2-10) Wherein: p-Contraction stress of plastic parts, MPa, plastic parts cooled within the mold p=196MPa and those cooled outside the mold p=392Mpa; A-Side area of the core wrapped by the plastic parts, m f-friction coefficient, generally=0.15-1.0 Draft F— Pulling force,N Bending force of the angle pin is Fh=F/cosa (2-11) Wherein: a- Dip angle of the angle pin Fb-Bending force of the angle pin, M 3. Core-pulling Distance Pull the active core out from the molding position to a place not interfering ejection of the plastic parts, and the distance moved by the active core or slide is called core-pulling distance Generally, core-pulling distance equals to the depth of side hole plus a safety distance of mm- mI The formula is: S=H a+(2-3) (2-12) Wherein: H- The mold opening journey required by the an pleting the core-pulling distance, mm; A- Dip angle of the angle pin S--Core-pulling distance, mm 4. Dip Angle of the Angle Pin a The size of dip angle is not only related with the bending force of angle pin and the actually ealized pulling force but also connected with the working length of angle pin, the core-pulling distance as well as the journey for mold opening. To ensure a certain amount of pulling force and certain intensity of angle pin, a shall be taken as less than 25 and shall be generally selected ithin the range of l2°25° 5. Diameter of Angle pin The formula for diameter of angle pin can be inferred according to mechanics of materials d=(F,xL/0.1[ol, cos a)" (2-13) Wherein: a-Dip angle of the angle pin F L-Effective working length of angle pin, m lo-Bending allowable stress, take 140Mpa for carbon steel
core can be pulled out. The pulling force can be calculated as per the following formula: cos( tan )/(1 sin cos ) 1 1 F = pA f − a + f a a （2-10） Wherein: p —— Contraction stress of plastic parts, MPa, plastic parts cooled within the mold p＝19.6MPa and those cooled outside the mold p＝39.2Mpa; A —— Side area of the core wrapped by the plastic parts, m 2 ; f —— friction coefficient, generally f ＝0.15 ~ 1.0; a1 —— Draft; F —— Pulling force, N. Bending force of the angle pin is: Fb = F / cos a （2-11） Wherein: a —— Dip angle of the angle pin; Fb ——Bending force of the angle pin, N. 3. Core-pulling Distance Pull the active core out from the molding position to a place not interfering ejection of the plastic parts, and the distance moved by the active core or slide is called core-pulling distance. Generally, core-pulling distance equals to the depth of side hole plus a safety distance of 2mm~3mm. The formula is: S = H tan a + (2 ~ 3) （2-12） Wherein: H —— The mold opening journey required by the angle pin for completing the core-pulling distance, mm; A —— Dip angle of the angle pin; S —— Core-pulling distance, mm. 4. Dip Angle of the Angle Pin a The size of dip angle is not only related with the bending force of angle pin and the actually realized pulling force but also connected with the working length of angle pin, the core-pulling distance as well as the journey for mold opening. To ensure a certain amount of pulling force and certain intensity of angle pin, a shall be taken as less than 25° and shall be generally selected within the range of 12°~ 25°. 5. Diameter of Angle Pin The formula for diameter of angle pin can be inferred according to mechanics of materials: 1/ 3 d (F L / 0.1[ ] cos a) = b × σ b （2-13） Wherein: a ——Dip angle of the angle pin; F 弯—— Bending force of angle pin, N; L —— Effective working length of angle pin, m; b [σ ] —— Bending allowable stress, take 140Mpa for carbon steel