Sliding core mould (with angle pin) 1

Transcription

1 Sliding core mould (with angle pin) Tampere University of Technology Juho Taipale, Tuula Höök CAD tools in the exercise Sliding core Theoretical background mould (with angle Mould basic structure pin) Mould standard parts Ejection Modeling steps In this exercise you will prepare a mechanical sliding core system to an existing mould assembly. The slide movement is actuated with an angle pin. The mould has one single cavity. It is designed for a part, which has undercuts on two sides. 1. Get the zip file start_sliding_core.zip. Save and extract it to your computer. 2. Open CATIA assembly file start_slide.catpart and open Mold Tooling Design work bench ( Start Mechanical Design Mold Tooling Design ). 3. Bring ready designed moving cores ( Keerna3.CATPart and Keerna1&2.CATPart ) to the mould assembly under the Mold sub assembly. Use function Insert Existing Component. 4. Open Assembly Design work bench. ( Start Mechanical Design Assembly Design ) Place the cores with the Manipulate and Snap functions. Tie the core to its place with the Coincidence function. Mold Tooling Design Insert Existing Component New Slider Angle Pin Assembly design Manipulation Snap Coincidence Offset When ever you face difficulties in using CATIA tools, open Help files and try to find the solution there. Figure 1. Moving core set in its place. Sliding core mould (with angle pin) 1

2 5. Add slider with the New Slider function. Select slider from CATIA libraries and dimension it in the Parameters window. The following list presents some reference values and advice 1 : You can use some of the common straight guiding bar models as the angle pin, but there are specially designed angle pins as well. The angle pin has a rounded and tapered head. The angle pin diameter is calculated basically according to slide moving forces. In practice the diameter is selected empirically, based on designers experience. Wide slide requires more than one moving element. Set the angle pin to an angle (In the image below the angle is marked with α). Large angle extends the slide movement, but over 25 angles are not practicable, because large angle produces high stresses and may break the slide mechanism. Usually the slide is secured with a wedge. The contact surface is angled. The angle should be 2 3 larger than the angle pin angle. (In the image below the wedge angle is marked with β) The angle pin length is selected according to the required core movement (See image below). The head of the angle pin should be in contact with the guiding hole before the locking wedge comes in contact with the slide. This structure assures that the slide closes with the angle pin, not with the wedge. Slide opening is stopped mechanically at the instance when the angle pin has moved out of the guiding hole. If designed otherwise, the angle pin (or the locking wedge) does not fit back during the mould closing movement. In order to prevent the slide to move backwards while mould is kept open, it is locked with a spring loaded pin. Figure 2. Left: Slide closed. Right: Slide open. The length of the slide opening movement (L) is L = h sin α. Figure 3. Slide open and closed. Slide moves on rails. It is locked with a wedge. 1 Menges G, Michaeli W, Mohren P, How to Make Injection Molds, 2001, Hanser Publishers Sliding core mould (with angle pin) 2

3 6. Select the plane on to which you wish to tie the slider mechanism. Set the slider near the right place by changing the values of positioning parameters. Select Standard Drillings parameter. 7. When the slide is positioned as well as possible, tie it to the core. Open Assembly Design work bench and tie the slider with suitable constraints with the moving core. Check that the core has not moved, only slider should move during constraining. Place another slider following the same steps. 8. Model axles to both sliders. The axles should follow the centerline of the angle pin guiding hole. 9. Edit the fixed side cavity plate in Part Design work bench. Sketch centerlines for angle pins. The centerlines should take the same direction as the centerlines of guiding holes in the slider. You can estimate the slide opening stroke length and the required length of the angle pin from these lines. Dimension the top end of the centerline. The line end should be below the cavity plate top surface. (See image below.) 10. Add angle pin to the assembly ( Insert Ejection Components AnglePin ). Select angle pin from CATIA libraries. Set the dimensioned end of the previously modeled sketch as the base element. Select the direction of the slider guiding hole as the direction of the component. Change length of the angle pin if required. Select OK. 11. Add another angle pin with similar steps. 12. Model a pocket for the angle pin to the top of the fixed cavity plate. Dimension reasonably. 13. Add slide guiding rails. ( Insert Mold Base Components New Retainers ) Figure 4. Left: A slider and a moving core. Right: Angle pin should fit exactly to the slider guiding hole while core is in its exact position. Figure 5. Slide guiding rails (slide retainers). Sliding core mould (with angle pin) 3

4 14. Finally add slide locking elements. Premodeled locking components can be found indside the zip file Lukituskomponentit on start_sliding_core.zip. Bring the locking elements with Insert Existing Component function and tie them to their proper places in Assembly Design work bench. Change the locking wedge contact surface angle if required. The angle should be 2 3 degrees larger than the angle pin angle. Learning objectives Slide components Slider dimensioning Making and handling assemblies within CATIA CAD tools to learn Mold Tooling Design: Insert Existing Component, New Slider, Angle Pin Assembly Design: Manipulation, Snap, Coincidence, Offset Evaluation Accepted Single cavity mould with all listed slider components Excellent Single cavity mould with all listed slider components Correct dimensioning Sliding core mould (with angle pin) 4

5 CAD tools quick guide Manipulate/Snap Assembly Design Edit Move Manipulate/Snap Manipulation and Snap tools are targeted for moving components inside an assembly. These tools do not tie the component. Manipulation moves the component in x, y, z axles direction. Snap moves the component to some selected position. Coincidence/Angle/Offset Assembly Design Insert Coincidence/ Angle/ Offset Coincidence, Angle and Offset tools tie components or sub assemblies within an assembly. If you wish to tie components within a sub assembly select the sub assembly as active component. Sliding core mould (with angle pin) 5