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EF electronic compound guns have a proven track record as the most accurate system available for the application of solvent and water based compounds, and plastisol sealants, on can ends and closures on a wide range of stationary and rotary type compound lining machines.
The original design premise was simple: to maintain very accurate and consistent turns lining and compound weight control, combined with the clean application of all types of compounds and sealant.
Inside each EF compound gun there are two electro-magnetic solenoids. The needle screws directly into an armature positioned between these solenoids. The top solenoid is energized to lift the needle and the bottom solenoid is energized to close it.
Each time a solenoid is energized, the EF control system measures the response time of the solenoid and adjusts the firing time accordingly on the next cycle. If the response time of any solenoid exceeds a pre-set limit the EF controller outputs an interlock signal and displays an error message.
The response times of the solenoids change constantly due to the impact of temperature changes, needle lift adjustment and mechanical friction. However, the control system will always monitor and correct the firing times to maintain very accurate turns lining control. EF compound guns are guaranteed to maintain +/- 0.1 turns lining control.
The closing speed or velocity of the needle is much faster than that achieved with a mechanical spring or air actuated gun. A 24V DC signal is used to energise the open solenoid, and a 12V DC signal to energise the close solenoid.
Both voltages are lowered when the armature starts to move, to protect the solenoids from overheating. The solenoids in the EF electronic compound guns are covered by a twelve month warranty when used in conjunction with the EF control system.
With some compounds it is necessary to achieve an even faster needle velocity to prevent tailing. In this case a 24V DC signal is also used to close the gun. The change from 12V DC close to 24V DC close is effected by a simple terminal change in the EF control cabinet.
The actual amount of compound applied is determined by the amount of needle lift, which is controlled by the position of a mechanical stop.
On the LC gun, the position of the stop is adjusted manually by the operator. There is a dial on the top of the gun, with a scale from zero to sixty, which equates to a maximum needle lift of 1.5 mm. This is increased to 2.5 mm for guns used with plastisol sealants.
On the MK6 gun the position of the stop is adjusted by a stepper motor, which is actuated by the EF controller.
The controller compares measured film weights entered via an operator interface panel to the pre-set target film weight, and calculates the necessary needle lift adjustment to correct the measured weight back to the target weight specification. The stepper motor is then automatically energised to move the stop by the required amount.
For additional set-up modes, test procedures and advanced diagnostics, each system is supplied with a copy of the EF software program and a cable to connect a standard PC to the EF control cabinet.
The functions offered by this software include setting upper and lower limits for machine speed, solenoid reaction times, energising voltages and sensor on/off times. When running, this program also records shut downs and film weight entries with a date and time stamp. Other software features include a library to store settings for different product specifications, password protection and a modem facility for remote access.
Multiple EF systems can be connected to a single PC in a quality control laboratory for example, so that film weight measurements can be entered remotely from a central location.
