Cumsa Controlled vacuum for better part quality in injection moulding

Editor: Rosemarie Stahl

The Double Action Vacuumjet and the Smart Vacuumjet are two new vacuum devices made by Cumsa. Compared to other Cumsa vacuum systems, they are able to create vacuum (60L/min) in the mould cavity and also blow off (6 bar) through the same channel.

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The Double Action Vacuumjet and the Smart Vacuumjet are the latest additions by Cumsa to its Vacuum series.
The Double Action Vacuumjet and the Smart Vacuumjet are the latest additions by Cumsa to its Vacuum series.
(Source: Cumsa)

The developers at Cumsa, a manufacturer of standard parts for mould-making, have launched two vacuum devices that add new features to the company's current Vacuum products line, the Double Action Vacuumjet (VB) and the Smart Vacuumjet (SV). According to the company, all of its vacuum models are built on the Venturi principle, which only requires compressed air connected to the device at six bar (90 PSI), with a vacuum capacity that can extract gases at up to 60L/min.

The new units allow for the removal of trapped air from the cavity of the mould through the Cumsa Vacuum Valve and/or the ejector pins, thereby creating benefits such as better part quality, reduction of sink marks, shorter cycles, lower injection pressure, etc., as with previous versions. Additionally, it is now possible to blow off the lines after every cycle through the same vacuum channel.

The Double Action Vacuumjet (VB) extracts the gas from the mould during the injection process. The unit is activated by compressed air when the mould closes and runs until the plastic part is ejected. This product is particularly unique in that it features porous inserts and/or laminar vents, conveniently located in the critical areas of the mould where the plastic fills last. These porous inserts help to extract the gases produced during injection. Thus, the plastic has less resistance to flow and fills faster. After the injection and during the ejection, the compressed air will help to clean the inserts or laminar vents after every cycle. The VB can be installed as a standalone unit or in combination with any of Cumsa's other vacuum devices.

Full control of air removal

The Smart Vacuumjet (SV) is a fully automated device, Cumsa states. The unit needs to be hooked up to 24V for optimal working of its internal solenoid and needs the compressed air connected to start the process. The solenoid controls the opening and closing of the vacuum valve typically located in the mould cavity. The SV operator should be set up only once, when installing the unit in the mould, using the selector placed on the back to set up the vacuum level by selecting one of the four different vacuum levels (from -600 to -900m bar). Once the mould closes and the compressed air starts flowing, the device sends a signal to open the vacuum valve and starts to extract the air from the cavity up to the defined vacuum level. Once the pre-set vacuum level is reached, the SV displays the amount of vacuum achieved with green numbers and sends a signal to close the vacuum valve.

The injection starts while the air is being removed through the ejector pins and vents. At ejection, the device produces the blow-off and purges the channels, cleaning the insert or laminar vents after every cycle. If the desired vacuum level cannot be achieved after five seconds, but is over -200m bar, the SV will close the valve and start the injection, indicating in the display the maximum achieved vacuum with red numbers. If after five seconds the vacuum level does not reach at least the -200m bar, the unit will not send the signal to start the injection to avoid the production of low-quality parts. The display will then indicate the cause.

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