I’m struggling with “stringing” while molding Zeonex. That is, as the mold opens, a long thin “string” of plastic is pulled from the nozzle attached to the sprue. Any advice would be appreciated.

Hi John,

Try to lower down the nozzle tip temperature, or melt temperature,
Cooling time too long also may cause this issue

buy a Milacron Roboshot machine and turn on the patented precise metering option. this decompresses both the melt in front of and behind the check ring during decompression by counterrotating the screw, thus eliminating stringing and splay that may happen if too much decompression is used.

Try turning down the front nozzle heat by 20 degrees and add 5 -10 mm of decompression (suck back) after screw rotation.

Not familiar with that resin, but you may not have the correct nozzle tip. You might be better off using the E-tip (I swtiched all of our small machines to them for cold slug control on cosmetic ABS/PC parts), a reverse taper tip (nylon), or the heater band or t/c is too far away from the tip to effectively control the temp. Also a berylium copper tip might be better for this resin. Also extremely large orifices can make it easier to drool.
I also see many people recover far too soon before the mold opens, allowing the nozzle to string. I always finish about 5 seconds before the mold starts to open.

Have you tried the old Dupont heat seal nozzle design ?
Quite often works.
Had this problem with acetals on gear parts going to assembly machines.Tried all the basics I could think of some worked for a while but not consistently.The assembly machine clogged up with what looked like hair balls after a days production. Even put an axtractor over the machine to suck up the strings. Bit the bullet and built a cutter in to the mould.

As mentioned above, reducing the heat to ward the tip and increase decompression, may get you enough time to open & close and reduce strings

you can try with Misumi string eliminating sprue bush for the mould which is easy to replace.(this type have a small metal bridge across the nozzle matching area of the bush)