1. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM
( )

2. PDT317-INJECTION MOLD DESIGN COURSE CONTENT & COURSE OUTCOMES
14-15
CHAPTER 6: Injection Moulding Calculation
CALCULATE and COMPARE the shot and plasticizing capacity, the cycle time, the clamping force and mould cost.
CO1: Ability to define and describe basic terminology process
in plastic injection molding and mould design.
CO2: Ability to define and describe the procedure of designing
plastic products for injection moulding process.

3. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
Determination of the appropriate size of an injection moulding machine is based primarily on the required clamp force which depends on:
the projected area of the cavities in the mould
the maximum pressure in the mould during mould filling
The projected area of the cavity is actually the projected area of the part, or parts if a multi-cavity mould is used, and a runner system, when viewed in the direction of mould opening
The value should not include any through holes moulded in the direction of mould opening

4. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
Example-1:
For a 20 cm diameter plain disk, the projected area is cm2. However, if the disk has a single 10 cm diameter through hole in any position, what is the actual projected area?.

5. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
ANSWER (Example - 1: )

6. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
The size of the runner system depends on the size of the part. Typical runner volumes as a percentage of part volume are given as :

7. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
Related table to calculated Moulding Machine Size :

8. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
Related table to calculated Moulding Machine Size :

9. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE
As a general rule, approximately 50% of the pressure generated in the machine injection unit is lost due to the flow resistance in the sprue, runner systems and gates
Example 2:
A batch of 10 cm diameter disk with a thickness of 8 mm are to be moulded from high-density polyethylene in a 6-cavity mould. Determine the appropriate machine size?. (Given that, approximately 50% of the pressure generated in the machine injection unit is lost)

10. PDT317-INJECTION MOLD DESIGN
MOULDING MACHINE SIZE

11. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM
( )

12. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
Define as time taken to produce 1 unit product
started from injection until ejection and resetting
Consist from 3 stages :
EJECTION /RESETTING
INJECTION/FILLING
COOLING
MOULDING CYCLE

13. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
After the appropriate machine size for a particular moulded part has been established, the moulding cycle time can be estimated
i. Injection Time
A total time requires for polymer to flow through the runners, gates and fulfil the cavity passages.

14. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
Injection time (filling time) is given by:
sec
Where:
Vs = required shot size (amount of material) m3
pj = recommended injection pressure N/m2 (table-8.5)
Pj = injection power W (table-8.4)

15. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
Example 3:
Calculate the estimated injection time for the 10 cm disks moulded in a 6-cavity mould as in Example 2.

16. MOULDING CYCLE TIME PDT317-INJECTION MOLD DESIGN
Refer Table 8.4 for Injection Power, Pj and
Table 8.5 for Injection Pressure, Pi

17. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
ii. Cooling Time
It is assumed that cooling in the mould takes place almost
entirely by heat conduction
Cooling time (filling time) is given by:
Where:
hmax = maximum wall thickness mm
Tx = recommended part ejection temperature oC
Tm = recommended mould temperature oC
Ti = recommended injection temperature oC
a = thermal diffusivity coefficient mm2/s
TABLE – 8.5

18. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
iii. Resetting Time
The summation of mould opening, part ejection and
mould closing times is referred to as the resetting
time and have been suggested by Ostwald as:

19. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
Mould resetting time is given by:
sec
Where:
td = dry cycle time sec
Ls = maximum clamp stroke cm
D = depth of part to be moulded cm
TABLE – 8.4

20. PDT317-INJECTION MOLD DESIGN
MOULDING CYCLE TIME
Example 4:
Assume that 10 cm diameter plain cylindrical cups with a depth
of 8 cm (same as an example 2) are to be moulded in a six-cavity
mould. Calculate the mould resetting time.
Answer 4:

21. PDT317-INJECTION MOLD DESIGN
Q&A

22. PDT317-INJECTION MOLD DESIGN
SEKIAN TERIMA KASIH
PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM
( )