Adhesion issue with double Overmold (Pebax)

[Jackson]

Injection Molders-

I've been struggling with an adhesion issue between my 1st and 2nd shot overmolds. Previous attempts to mold have been successful but after recent maintenance to the machine, I cannot seem to find a process to eliminates an adhesion issue between overmolds. Material is Pebax. Running barrel temps around 430 and nozzle around 460. I've been mainly adjusting just the nozzle temperature from 430 to 460. I get better adhesion with hotter temperatures but still have a parting line. I've increased injection pressure to try to push the material in faster and have opened up the mold vents to make sure that I am not trapping air. The increased injection speed seems to have reduced voids. Backpressure and hold pressure do not seem to have a impact. Thoughts?

[kelley]

Can you elaborate as to what maintenance was done to the machine?

[Suhas]

Kelley's question is important - to be followed up with the differences in the outputs in the processes - fill times, cushion values, peak injection pressure, pressure at transfer, and so on.
Also - what are the 2 materials?
Suhas

[rickbatey]

Is this over mold done in one press? Are the parts transferred or using a rotating table to the other cavities?
I ask because if in one press: the interval timer between first component and second component is CRITICAL!! Too long and poor adhesion; too short and you can rupture through the first component skin. Too low steel temp can kill you as well.
Adding grain or texture can help help by increasing the surface area.
What is the other resin? Is it made to bond to the first? Many of the soft resins bond through chemical reaction and surface energy/temp is crucial.
Rick.