RUBBER SURFACE PROBLEM

[AKHILESH MAURYA]

I HAVE SOME ROUGH DOTS ON COOKER RING.It is not regular problem sometime occur sometime not. molding temperature 180 time 24sec.Formulation
nbr sibur 3345 100 phr
carbon 550 40 phr
calcium carbonate 35 phr
steric 3 phr
zinc oxide 6 phr
dop 6 phr
After that mixing i separately add sulphur zdec tmtd
sulphur .430 phr
tmtd .151 phr
zdec .164 phr
I have already checked by decreasing zinc oxide to 3 phr or decreasing or incresing accelerater but is of no use.... wher ia the problem ?

 

[btrueblood]

How is the molding accomplished, is it transfer, injection, or straight compression molded? How many bump cycles, and does the mold pressure decay with time? Looks like trapped air to me.