p l a s t i c i n j e c t i o n m o l d i n g p a r t 2 d e s i g n o f p l a s t i c p a r t s a n d p r o d u c t s e r i k d e l a n g e

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1 p l a s t i c i n j e c t i o n m o l d i n g p a r t 2 d e s i g n o f p l a s t i c p a r t s a n d p r o d u c t s e r i k d e l a n g e H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 1

2 lecture outline product tool (=mold) design design of injectionmolded products mold engineering manufacture injection molding process mold manufacturing H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 2

3 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 3

4 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 4

5 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 5

6 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 6

7 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 7

8 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 8

9 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 9

10 idealized workflow concept assembly level decomposition into set of parts part level detailed part design no undercuts or at least a feasible slide arrangement $ all parts fitting and reachable cost-effective! H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 10

11 decomposition in a set of parts Reachable: a possible assembly order must exist H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 11

12 decomposition in a set of parts Cost-effectiveness of the assembly Three golden rules: try to decompose you concept design in the smallest number of parts you can think of try to use the same part more than once try to eliminate separate hinges and fasteners hinge function living hinge fastening snap rims, snap hooks H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 12

13 decomposition in a set of parts Example: This part has three conflicting lines of draw. You cannot make this part in a mold, not even with slides H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 13

14 decomposition in a set of parts Solution #1: You might reorient the holes. This solves the drawing problem, but it s probably not what you had in mind. 2 3 H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 14

15 decomposition in a set of parts Solution #2: Decomposition along lines of draw. There might be a problem in the fitting or the fastening H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 15

16 decomposition in a set of parts Solution #4: Changing your viewpoint might give new ideas for decomposing yor concept. H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 16

17 decomposition in a set of parts Assembly design and parts design have conflicting design guidelines. Assembly design guidelines small number of parts integrating functions (hinges, fastening means) Part design guidelines injection-moldable shape single draw no slides Conflict! Try to find a good balance. H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 17

decomposition in a set of parts Advice Discuss

them involved in the early stages of the

18 decomposition in a set of parts Advice Discuss the parts decomposition with your mold manufacturer Treat your subcontractors as co-makers, rather than only subcontractors Have them involved in the early stages of the project H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 18

19 integration of functions Function integration reduces the number of parts. Examples: Hinge function Fastening function Closure fastening Spring function H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 19

opened end closed once to arrange (orient) the molecules.

20 design of living hinges PP-hinges can survive many thousands of open/close movements Right after the molding (when it is still hot) the hinge should be opened end closed once to arrange (orient) the molecules. Sources for instance: herring clip H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 20

21 design of snappers Snap hooks that are too short will overstrain or break. H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 21

22 design of snappers H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 22

23 end of first session BREAK! After the break: part design H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 23

24 idealized workflow concept assembly level decomposition into set of parts part level detailed part design thin walled $ yet strong and stiff equal wall thickness free of error H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 24

25 Shortly after injection: both products are still fully plastic (not solidified) solidification, shrinkage H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 25

26 A couple of seconds later: the left product has soldified completely, the right one not yet. solidification, shrinkage interior of part: continues shrinking H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 26

27 solidification, shrinkage Spuitneus komt rechtstreeks in de holte uit If the gate freezes (solidifies) too soon, no further injection of material is possible. However: the product will continue to shrink. This will result in a faulty product, having not the correct shape and dimensions. H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 27

28 thin-walled design When the goes then: wall thickness cooling time products per hour part cost profit Example: Nokia mobile phone top part H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 28

29 consequence of uneven wall thickness H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 29

30 consequence of uneven wall thickness Spuitneus komt rechtstreeks in de holte uit H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 30

31 consequence of uneven wall thickness Spuitneus komt rechtstreeks in de holte uit H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 31

32 consequence of uneven wall thickness Spuitneus komt rechtstreeks in de holte uit H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 32

33 consequence of uneven wall thickness Spuitneus komt rechtstreeks in de holte uit H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 33

34 consequence of uneven wall thickness Spuitneus komt rechtstreeks in de holte uit H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 34

35 consequence of uneven wall thickness Cause #1 Spuitneus komt rechtstreeks in de holte uit relatively thin layer which hasn t soldified yet relatively thick layer which hasn t solidified keeps shrinking for a longer time H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 35

36 consequence of uneven wall thickness Cause #2 Spuitneus komt rechtstreeks in de holte uit quickly solidified: mainly amorphous slowly solidified: semi-crystalline: denser, more compact structure H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 36

37 sink marks Spuitneus komt rechtstreeks in de holte uit Sinkmarks are localized depressions in the product s surface. They make the product looking low quality and cheap. H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 37

38 sink marks Spuitneus komt rechtstreeks in de holte uit IPod: absence of sinkmarks give the sensation of a quality product. H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 38

39 sink marks Sink marks typically occur in locations where there is a lump of material: H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 39

40 sink marks Sink marks typically occur in locations where there is a lump of material: H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 40

41 sink marks Excessive shrinkage in the lump might even cause voids, compromising the strength of the product. vacuum H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 41

42 sink marks Design rule: no sink marks when H < 0,60 x T H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 42

43 sink marks H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 43

44 sink marks excessive amount of material cycletime > 10 min H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 44

45 sink marks thin walled product with ribs cycle time 35 secs H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 45

46 sink marks Shrinkage prediction using Moldflow software H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 46

47 avoiding sink marks h < 0,6t t h H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 47

solid looking part for instance a handle, or Lego trees

48 use of ribs Ribs are being used: to increase the product s stiffness to fix other parts onto to make a thick solid looking part for instance a handle, or Lego trees H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 48

49 Approximate Young's Moduli of Various Solids use of ribs Material Young's modulus (E) in GPa Rubber (small strain) Low density polyethylene Polypropylene Polyethylene terephthalate Polystyrene Nylon Oak wood (along grain) High-strength concrete (under compression) Magnesium metal (Mg) Aluminium alloy Glass (all types) Brass and bronze Titanium (Ti) Carbon fiber reinforced plastic (unidirectional, along grain) Wrought iron and steel Tungsten (W) Silicon carbide (SiC) Tungsten carbide (WC) H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 49

50 conclusion balance the cost of the parts against the cost of the assembly co-operate with mold engineers: use their experience! H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 50

51 the end Thank you for your attention, and see you in Rotterdam! H R O R o t t e r d a m B r n o U T j o i n t p r o j e c t 51

Chapter 2: Energy and the 1 st Law of Thermodynamics. The Study of Energy in Closed Systems

Chapter 2: Energy and the 1 st Law of Thermodynamics The Study of Energy in Closed Systems Topics 2.1 Mechanical Concepts of Energy 2.2 Broadening Understanding of Work 2.3 Broadening Understanding of