Use of servopumps

The topic energy efficiency gains more and more importance because of climate protection and rising energy costs. The injection moulding machine has strong influence on energy consumption and cycle times, and thus on the whole efficiency of production. By using servopumps (servomotor with constant pumps) we not only bring your older injection moulding machines up-to-date but we make for a significant energy saving. Replacing the conventional control pump combination by an actual drive system, Hemscheidt injection moulding machines have been provided with a servopump system offering the replacement of the pumps as well as an upgrading of the injection moulding machines. Using a servopump, the energy consumption of the drive will be reduced, shorter cycle times are possible and the noise emission will be considerably reduced.

The following results have been obtained with a machine HPM 500H (drive 90kW with RKP250) by face-to-face comparison:

Mould: Bowl (18l) with sprue gate, D=420mm, wall thickness=2 – 3 mm, moulding mass=665g/PP

RKP250Servopump 200Servopump 125
Energy consumption kWh/kg0,7120,4630,364
Cycle time in s565252
Noise emission in dBA756060
Energy saving in %3549

These values have been found out with similar machine settings and thus indicate the direct energy saving without optimisations still possible. Assuming 300 days of permanent operation, the following energy consumption can be calculated for this case of application:


69shots/h x 8000h =552000 x 0,665kg = 367080kg x 0,712kWh/kg = 261360,96 kWh

Servopump 200

69shots/h x 8000h =552000 x 0,665kg = 367080kg x 0,463kWh/kg = 169958,04 kWh

Servopump 125

69shots/h x 8000h =552000 x 0,665kg = 367080kg x 0,364kWh/kg = 133617,12 kWh

Assuming an exemplary price of 0,10€/kWh, the following potential for savings will be the result:

RKP250261360,96kWh x 0,10€/kWh = 26.136 €
Servopump 200169958,04kWh x 0,10€/kWh = 16.996 €
Servopump 125133617,12kWh x 0,10€/kWh = 13.362 €

Other advantages of this modern solution for a machine drive are an ameliorated precision of the pressure regime of the plant, less air-conditioning and longer service life of the oil.