Last updated 23rd January 2002

Two case studies have been selected to illustrate a number of important points about the Powermiser system.
The first study is that of a 37kW Powermiser unit fitted to a 200T Metalmeccanica press at the Plastics Centre in Teesside Tertiary College.
This installation allowed us to conduct a number of experiments under carefully controlled conditions to prove the level of savings we could achieve with Powermiser and monitor the effect on product quality.
The second study we have chosen is that of a 75kW Powermiser system fitted to a 500T Krauss Maffei press at the Hartlepool works of Stadium Group PLC.
This demonstrates Powermiser in action in a real production environment.
The contrasting studies help illustrate that the Powermiser system is just as applicable to 'toggle-lock' and 'direct-lock' machines, works well even for machines fitted with variable displacement pumps and does not impact upon either cycle time nor product quality.
200T MetalMeccanica.
This press is of the 'toggle-lock' variety with dual fixed displacement pumps driven by a single 37kW motor.
The SEF100 control system implements closed-loop control of the moulding process using a single proportional flow valve and proportional control of the pump discharge pressures.
The Powermiser interface was mounted inside the existing cabinet of the SEF100 controller and seamlessly integrated with the proportional and directional valve control electronics.
The Powermiser drive was floor mounted just in front of the machine at the motor end. This provided easy access for demonstration purposes.

Tests on two different tools were organised and monitored by the Centre's senior polymer consultant, Jerry Reeves.
The first test used a 6-impression cold runner tool with a total shot weight of 93gms (including sprue and runner) moulded from polypropylene.
The component produced had a typical wall thickness of 2mm with a 3mm thick centre boss. The cycle time was just under 50s.

A run of fifteen shots was carried out with the Powermiser system switched off. The fifth and fifteenth shot were weighed and the total electricity consumed by the motor during the run was logged. The total time to produce the 15 shots was measured using a stopwatch.
The process was then repeated with the Powermiser system enabled.
The whole experiment was then repeated and the results are shown below:

Powermiser	Weight of Shot #5	Weight of Shot #15	Total Time	Power Consumption	% saving
Off	92.77g	92.76g	749s	3.83kWh	-
On	93.63g	93.48g	748s	1.52kWh	60%
Off	93.08g	93.12g	743s	3.77kWh	-
On	93.10g	93.50g	746s	1.66kWh	56%

The test demonstrated that components produced with the Powermiser system enabled were no different to those normally produced and the cycle time was unaffected.
The energy required to mould using the Powermiser system was, however, approximately 58% down from that required for normal operation.
A second test was performed using a single impression 'disc' tool with a centre direct sprue feed and a shot weight of approximately 400g in ABS.
This was almost the maximum shot size for the machine.
An experiment was carried out as before and the measurements taken proved the moulding process was not being unduly affected by the Powermiser system.
The percentage energy saving with the Powermiser system enabled dropped to 37% but the actual amount of energy saved increased.

Tool	Average Hourly Consumption Without Powermiser	Average Hourly Consumption With Powermiser	Units of Electricity Saved per Hour	Percentage Energy Saving
Six Cavity Tool	12.10kWh/h	5.06kWh/h	7.04kWh	58%
Large Disc Tool	20.07kWh/h	12.67kWh/h	7.40kWh/h	37%

Shown below are graphs of the instantaneous power consumed by the motor (kW) with respect to time (s) over two shots for both tools.

The green trace represents power consumption with the Powermiser system enabled and the blue trace represents normal consumption.
As can be seen the Powermiser trace keeps pace with normal operation but during large parts of the moulding process the rate of power consumption is dramatically reduced.
500T Krauss Maffei.
This press is of the direct-hydraulic-lock type with a single 75kW motor driving one fixed displacement and one variable displacement hydraulic pump.
The MC3 control system implements closed-loop control using a system of proportional flow and pressure regulation.
The Powermiser interface was neatly mounted inside the existing control cabinet and interfaced to the directional and proportional valve control cards.

The Powermiser drive was floor-mounted at the rear of the machine close to the motor.
Motor power consumption was recorded over successive samples of ten shots of a medium sized tool with the Powermiser system alternately enabled then disabled.

It was found that the average hourly rate of power consumption with the Powermiser system disabled was 37.31kWh / h.
With the Powermiser system enabled this consumption fell to 22.61kWh / h i.e. a reduction of just over 39%.
Stadiums maintenance manager decided to make his own energy measurements over a period of one month with and without the Powermiser system enabled.
This took into account normal production stoppages, tool changes etc.
His independent measurements indicated an average saving of 43% with the Powermiser system.
The graph below shows the instantaneous power consumed by the motor (kW) with respect to time (s) over a two-shot window.

The green trace represents power consumption with the Powermiser system enabled and the blue trace represents normal consumption.
As can be seen significant savings are made when the Powermiser system is enabled.