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Residence Time ∓mp;

Percentage Utilisation of Machine shot capacity

                    K x Max. Shot Volume or weight of Machine    
Residence Time = --------------------------------------------- x Cycle Time
                     Actual Shot Volume or weight of Mould

                  K x Cycle Time
Residence Time = --------------------------------------------------
                  Actual Shot weight of Mould / Max. Shot weight of machine

                  K x Cycle Time x 100
Residence Time = -----------------------------------------------------
                  Percentage utilisation of max- shot capacity of machine

                                               K x Cycle Time x 100
Min.%age UTILISATION of shot capacity of m/c = ----------------------------
                                               Permissible residence Time


Consider Max Shot Weight of m/c=200grm. ∓mp; Thermal sability is 200 sec for melt.

Actual shot weight of mould 50 grm with Cycle time of say 30sec.

It was found practically that K=2 for 50 dia screw of L/D=18.

Residence time=(400/50) 30 = 240 sec. If thermal stability is for 200 sec at moulding temperature then melt would degrade. However if cycle time is 20 sec then residence time would be 160 sec. This cycle time would be workable with out degradation.

If actual shot weight of mould is say 70grm, then residence time=(400/7)30=

say 6 x 30=180sec then it is possible to run with out degradation. It would degrade only if there is interruption during production run resulting in increased residence time.

Also seeThermal Stability

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