PDT317-INJECTION MOLD DESIGN MOULDING MACHINE SIZE PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM Email: shayfull@unimap.edu.my (019-4728377)

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.

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

PDT317-INJECTION MOLD DESIGN MOULDING MACHINE SIZE Example-1: For a 20 cm diameter plain disk, the projected area is 314.16 cm2. However, if the disk has a single 10 cm diameter through hole in any position, what is the actual projected area?.

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

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 :

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

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

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)

PDT317-INJECTION MOLD DESIGN MOULDING MACHINE SIZE

PDT317-INJECTION MOLD DESIGN MOULDING CYCLE TIME PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM Email: shayfull@unimap.edu.my (019-4728377)

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

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.

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)

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.

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

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

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:

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

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:

PDT317-INJECTION MOLD DESIGN Q&A

PDT317-INJECTION MOLD DESIGN SEKIAN TERIMA KASIH PREPARED BY: EN. SHAYFULL ZAMREE BIN ABD RAHIM Email: shayfull@unimap.edu.my (019-4728377)