Determining optimum gate size

My team is currently tasked with specifying dimensions for a twenty year old tool under reconstruction. We are only just beginning to put GMP in place where tribal knowlege had ruled. A 1980 tool print calls out a .035 diameter sub-gate with typical geometry. Original design personnel are history and this six cavity tool with two, 180 deg. opposed gates per cav. has a range of openings .053-.078. A co-relation has been shown between those cavities with the largest gates to be most prone to failure in a test mode designed to expose susceptability to linear cracking of the glass-filled nylon parts. Processing data for previously acceptable parts does not exist. We had been wingin' it. Any suggestions that would lessen our trial/test/repeat steps would be greatly appreciated. Thanks. May the Force be with you.

 

[visitor]

try changing gate location and enlarening vents at knit lines

 

If you can give me some more specific info about your part I could give you a good estimate for gate size. Also, always start small - this leaves you "steel safe" and most tool shops will resize the gate for no charge as part of typical mold trial/tuning.

What is the part material?, part volume?, length of runner?, part wall thickness? cavity surface area?

If I know this information I will estimate the gate and runner size for you.

Respectfully,

Eric Fehrman
Fehrman Tool & Die, Inc.

http://www.FTDINC.com