1. PDT 317-INJECTION MOLD DESIGN
PART DESIGN GUIDELINE
PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM
( )

2. PDT 317-INJECTION MOLD DESIGN COURSE CONTENT & COURSE OUTCOMES
6-7
CHAPTER 3: Designing Product with Plastics
DEFINE, EXPLAIN and DISCUSS in selected suitable type of polymeric material for producing product, product design consideration, product defect after injection process.
CO2: Ability to define and describe the procedure of designing
plastic products for injection moulding process.

3. UNIFORM WALL THICKNESS
PDT 317-INJECTION MOLD DESIGN
UNIFORM WALL THICKNESS
Plastic parts may be considered to have a shell type
configuration with a basic surface and features which are
attached to it to meet functional requirements.
Guideline
The basic wall of the part should be kept uniform.
Basis
This provides for even flow
of the melt during injection.
Even cooling and shrinkage
that controls part warpage.

4. UNIFORM WALL THICKNESS - TRANSITION
PDT 317-INJECTION MOLD DESIGN
UNIFORM WALL THICKNESS - TRANSITION
“Transition should be made gradually, on the
order of 3 to 1.”

5. EJECTION Ejection Remember!!! PDT 317-INJECTION MOLD DESIGN
The designer needs to consider how the mold will design in appropriate draft.
Remember!!!
Normal practice
Cavity Side = 3° to 5°
Core Side = 1° to 3°
Draft is required to release part
from mould and to avoid pull/drag mark

6. PDT 317-INJECTION MOLD DESIGN
PARTINGLINE
A “parting line” in mould making is the place where two or more parts
of the mold meet.
When the mold halves do not meet with enough precision or injection
pressure is high, material will creep into the space between the molds -
burr/flashing.
Flashing

7. PDT 317-INJECTION MOLD DESIGN MOULD FOR INJECTION MOULDING PROCESS
PARTINGLINE
MOULD FOR INJECTION MOULDING PROCESS

8. PARTINGLINE-MISMATCH
PDT 317-INJECTION MOLD DESIGN
PARTINGLINE-MISMATCH
Guideline
Specify mismatch on the
parting line.
Basis
Note establishes what is
acceptable to the engineer for
the molder.
Guideline to determine the parting line
try to choose the flat parting line
minimize undercuts
make sure the part not stick at the cavity
side when mould open

9. PDT 317-INJECTION MOLD DESIGN
PARTINGLINE
Guideline
Redesign holes in the side
walls so reducing the need for side action in the mold.
Basis
Taking advantage of design
flexibility can simplify the
mold, reducing initial costs
and minimizing maintenance
throughout production.

10. PDT 317-INJECTION MOLD DESIGN
PARTINGLINE
Internal snap feature
- required use of ???
Mould movement
Molded slot
No special mould actions required
Molded hole
- Required ???
Internal snap
No special mould action required
when slot is added

11. PDT 317-INJECTION MOLD DESIGN
RIBS-THICKNESS Rt Wt
Guideline
The thickness of the rib at the intersection with the nominal wall should be 50 to 60% of the nominal wall.
Basis
Rib thickness more than 60% of the wall thickness resulted sink on the
wall opposite the rib.
Rt – Rib Thickness, Wt – Wall Thickness

12. PDT 317-INJECTION MOLD DESIGN
RIBS-HEIGHT
Guideline
Maximum rib height, h = 3x
nominal wall thickness.
Basis
Deep ribs become difficult to
fill, may stick in the mold on
ejection, and with draft they
can generate a material mass
at their base.

13. PDT 317-INJECTION MOLD DESIGN
RIBS-DRAFT
Guideline
Typical draft for ribs is 1 to
1.5°. Minimum draft should
be 1/2° per side.
Basis
Draft is necessary to aid
ejection of the part.

14. PDT 317-INJECTION MOLD DESIGN
GUSSET
Gussets may be considered a subset of ribs and the guidelines
for ribs apply to gussets.
Guideline
The thickness of a gusset at the intersection with the nominal wall should be 50-60% of the nominal wall.
Basis
This will keep the gusset from reading through the nominal
wall as sink.

15. PDT 317-INJECTION MOLD DESIGN
BOSSES-SIZE
Guideline
Typically the boss OD = 2 ID.
Basis
This is the general rule of
thumb which allows the wall
to increase as the size of the
boss increases.

16. PDT 317-INJECTION MOLD DESIGN
BOSSES & SCREW SIZE ØD
Guideline
The ID should be
0.8 x nominal screw diameter.
Ø0.8D
Basis
This is the proper dimension for a screw to tap threads in a boss.
Self-Tapping Screw

17. BOSSES – SCREW ENGGAGEMENT
PDT 317-INJECTION MOLD DESIGN
BOSSES – SCREW ENGGAGEMENT
Guideline
Screw engagement should be a minimum of 2.5 times the screw diameter.
Basis
Shorter engagement lengths risk stripping the threads during assembly and pull out
strength may be reduced.

18. PDT 317-INJECTION MOLD DESIGN
BOSSES – HOLE DEPTH
Guideline
The depth of the cored hole should be in (0.813 mm) greater then the screw length when fully engaged.
Basis
This avoids bottoming the screw causing undo stress and allows room for displaced
material from the self tapping screws, primarily thread cutting screws.

19. PDT 317-INJECTION MOLD DESIGN
BOSSES – GOOD LEAD
Guideline
A chamfer at the top of the
boss is a good lead in for the
fastener.
Chamfer around
Basis
The designer can speed the
assembly by adding lead into his design.

20. PDT 317-INJECTION MOLD DESIGN
BOSSES - DRAFT
Guideline
Draft on the OD is 1/2°
minimum.
Guideline
Draft on the ID is 1/4°
minimum.
Basis
Draft is needed for release
from the mold on ejection.
With proper ejection and polishing on the mold, the small draft angle can be accommodated.

21. PDT 317-INJECTION MOLD DESIGN
HOLE AND DEPRESSIONS
Guideline
The distance between two
holes or one hole to the edge
of the surface should be at least
2 x the nominal wall thickness.
Basis
Adequate material around
a hole is needed for strength
particularly when knit lines
are likely to be present.

22. PDT 317-INJECTION MOLD DESIGN
CORNER RADIUS
Guideline
The outside corner radius
should be equal to the inside
radii plus the wall thickness
(R = r + t).
Basis
This practice keeps a
uniform wall thickness at
the corner and reduces
stress concentrations.

23. PDT 317-INJECTION MOLD DESIGN
APPEARANCES PART
Guideline
To maintain a Class A surface (cosmetic surface) on a molding, the side behind the Appearance surface must be free of projections and depressions. If a projection can not be avoided, then the maximum thickness at the intersection is half (50-60%) the nominal wall thickness.

24. PDT 317-INJECTION MOLD DESIGN
APPEARANCES PART
Guideline
Sometime styling line can be make to cover the plastic defect, but its depend on the customer approval.

25. APPEARANCES PART-TEXTURING
PDT 317-INJECTION MOLD DESIGN
APPEARANCES PART-TEXTURING
Guideline
Textured surfaces stop a
preferred in (1.524 mm) or a minimum of in (1.016 mm) from any parting line.
Basis
Terminating the texture
improves the durability of
the parting line.

26. APPEARANCES PART-DRAWING
PDT 317-INJECTION MOLD DESIGN
APPEARANCES PART-DRAWING
Guideline
Print notes for appearance parts. Locate knockouts, gates and insert lines away from identified appearance surfaces. Specifications include color number, gloss number or texture specification. All appearance and post finish surfaces are identified.
Basis
To communicate clearly on the part drawing information with regard to appearance.

27. PDT 317-INJECTION MOLD DESIGN
Q&A

28. PDT 317-INJECTION MOLD DESIGN
SEKIAN TERIMA KASIH
PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM
( )