Eileen Yu, Vice General Manager
Published 3 min readTechnology
A parison that drifts to one side, or plastic that sticks on the die tip, is a process fault to record before anyone changes the machine. The checks below stay outside electrical cabinets and controller menus. Menu paths differ by generation, and this page does not publish them.
The background article implementing wall thickness control explains the idea of a parison program. Point counts in that older article are not the specification of the controllers below.
When the parison will not stay centered
Stop and look before you adjust anything. From a safe position, with guards in place, note whether the parison leaves the die toward one side and whether the die gap looks uneven. Check the die and mandrel for a nick, a bent edge or a piece of plastic caught on the lip. Do not open electrical panels, and do not move a servo or a hydraulic valve to “see what happens.”
A short video of the parison, taken from the operator side, is more useful than a description. Include the machine serial number from the nameplate when you write to Tongda.
When material sticks to the die tip
Sticking is usually a temperature, contamination or tip-condition problem. Look for degraded plastic, dirt or a damaged tip, and note whether the melt looks unusually stiff or unusually fluid. Do not scrape a hot die by hand, and do not publish or copy a setpoint from another product. The temperature that suits one resin and one die is not a number for every machine.
If the tip is damaged or the build-up returns as soon as you restart, stop and ask for service rather than running through it.
Wall-thickness programs
Tongda fits a MOOG parison wall-thickness controller that supports up to 200 points. Tongda also offers a whole-machine wall-thickness controller co-developed with Siemens. That Siemens controller is mainly for all-electric machines.
A point count is the number of positions along the parison where the gap can be set. It is not, by itself, the weight of the container. Ask a technician to watch the program on a dry cycle before you judge a new profile on production resin. This page does not describe the buttons or menus used to enter those points.
All-electric machines are listed under fully electric blow molding machines.
When to contact Tongda
Send the serial number, the resin, what the container is doing, and a video of the parison or the die tip through the contact page. Spare parts and visits are described on warranty, spare parts and after-sales.
What should I check before calling about a parison that runs off center?
From a safe position, note whether the parison leaves the die to one side and whether the die or mandrel is nicked, bent or carrying plastic. Do not open electrical panels or follow a controller menu from memory. Send a video and the serial number through the contact page.
Why does plastic stick to the die tip?
Sticking is treated as a temperature, contamination or tip-condition question. Do not scrape a hot die. Record what you see and ask Tongda if the build-up returns.
Which parison controllers does Tongda use?
A MOOG parison wall-thickness controller supports up to 200 points. A whole-machine wall-thickness controller co-developed with Siemens is mainly for all-electric machines. This page does not list controller menus.