Tip of the Day 31: How to deal with No Injection Forward Signal

First let me say that this is NOT the preferred method of hooking up eDARTs in permanent installations. It can be workable for demonstrations and such. But in the long run and especially with Valve Gate control leaving off injection forward can lead to future failure.

That being said sometimes you cannot get an Injection Forward signal from the machine. Either it is not there or you are in a hurry to do a demonstration without any sequence signals. Here is how it works.

The Next Best Thing: LER-30 Stroke Encoder

On: The sequencer looks for a slight forward motion of the screw and considers that the start of injection (Machine Sequence / Injection Forward ON). The “Injection” tab on the Sequence Settings will show a box for adjusting just how much motion counts as a start. This rarely needs to be adjusted.

If you have a Seq. Module Input / First Stage signal the rising edge (off -> on) of that signal will count as the start of injection instead of the stroke motion.

Off: If there is a Seq. Module Input / Screw Run and injection pressure then the sequencer looks for the “step” in injection pressure prior to the start of screw run. This is done with some averaging and thresholding whose settings that appear on the Sequence Settings. Fortunately the first guesses I made for the variables have seemed to work well without any adjustment. Heaven help us if it ever needs to be changed.

If there is no injection pressure then the sequencer tries to look for the first jump back in the screw position that is followed by at least ¾ second of continuing backward motion.

Second Best: Injection Pressure Alone (no Stroke)

On: Set with a pressure threshold. Note that this must be changed to be above the backpressure and the “Off” pressure or you can get multiple On/Off cycles of Machine Sequence / Injection Forward during the cycle.

Off: Similarly set with a falling threshold. This must be set below any “dips” in the injection pressure profile to prevent multiple sequencing.

Last Resort: Seq. Module Input / Mold Clamped or Limit Switch / Mold Clamped

On: Machine Sequence / Injection Forward comes on at a fixed time after Mold Clamped. You set this time in the Sequence Settings.

Off: Machine Sequence / Injection Forward is on for a set time also set in Sequence Settings.

Tomorrow: The Sumitomo Oscillograph Interface

Some Graphical Aids

Stroke / Volume, Injection Pressure and Screw Run

Stroke / Volume and Injection Pressure

Stroke / Volume only

Injection Pressure Only

Mold Clamped Only