Tip of the Day 67: Injection Integral Error due to Incorrect Machine Sequence Signal

Tip # 66 explains how Injection Integral values can vary if you change hold time. But…

Mold Transfer between Machines can Change Integral if Signals are Not Correct

When a mold runs on a different machine and you set the hold time “exactly” the same then the two machines must provide the same signal in order to get the same injection integral. We have found that some manufacturers provide an “Injection Forward” signal that goes off at the end of injection pressure (as specified in the eDART “REDI” Kit). Others choose to turn the Injection Forward signal off after screw delay as shown here.

Note that it is the Seq. Module Input / Injection Forward (“SMI”) that is causing Machine Sequence / Injection Forward to go on and off when it does. This is because the eDART’s sequencer assumes that the hard-wired Injection Forward signal is the best choice for knowing when injection ends. Clearly in this case it is not.

A Solution for Incorrect Injection Forward

The eDART’s “Sequence Settings” has a switch that you can use to correct this problem. On the “Injection Forward” tab you can tick the box that says “Ignore Inj Fwd. Seq. Input at… End”.

With that tick box checked the eDART does not use the signal from the machine to decide where the end of injection is. Instead it uses the last sudden drop in injection pressure before the start of screw run. There are some settings below to adjust the way this works but they have never needed adjustment as far as we know. Note that the “ignore end” tick is saved with the machine. So no matter what mold runs on this machine will ignore the end of the injection signal and compute it instead.

On this errant machine, with the “ignore end” ticked the Cycle Graph shows that the Seq. Module Input (SMI), Injection Forward is still incorrect. But now the Machine Sequence (MS), Injection Forward signal goes off at almost exactly the same time it did on the other machine with the correct signal.

The Machine Sequence / Injection Forward is the signal that the eDART uses to compute Injection Integral, Sequence Time / Injection Time and anything else related to Injection Forward.