Though there are many types of gates used in the manufacture of

plastic parts they all have these basic components: Land, height,

width.

They also have the same function and that is to act as a conduit

of flow for the plastic material into a cavity so as to form the

part.

Finally they also act as a dam between the runner and the part.

Hopefully being the thinnest area it freezes first. This may be

a time to state that whichever is thinner, height or width will

control the freeze time of the gate. Land length typically will

have the biggest effect on pressure drop.

Sub characteristics of the gate is that it acts a regulator or

the source of shear upon the material. When you look at the

formula for shear it is the volume of material pushed though a

said orifice in a said period of time. One way of classifying

gates may be to state they are either restricted or large. This

may be determine by the material itself as to what is classified

as viscous and non-viscous.

So when designing gates some rules of thumb are involved such

as:

a) Land length of gate at maximum of 1 mm / 0.040"

b) Height and width at 40% of the wall thickness to start.

c) Location, location, location

d) Impinge flow into something, unless you enjoy

    worming and other issues

e) The smaller the diameter of the gate the more shear,

    quicker freeze time and in some cases the fill, pack

    and hold are all in the fill stage of the process due

    to this small gate.

Do you know what the shear rate of your gate is? Have you run a

relative viscosity study on your part (gate), what about a

pressure drop or gate freeze study?  Before opening up the gate

please run studies as to what is going on. Recently we had a

nozzle which was the restriction, being a smaller O than the

gate diameter.

It is amazing how many times the first thing out of the

processors or tool maker mouth is open the gate. The issue

continues to multiply from that standpoint. Things such as we

can't fill the part, we have a longer cycle time now; we have

bubbles, the size changed on my part. The funny thing is I can

understand as we are all under pressure to perform as quickly as

possible to solve an issue at hand. But if we take some time

to perform basic study, scientific data gathering we than

can achieve better results in a shorter period of time.

1-      Troubleshooting:  assisting in the processing

a.       Over the phone, or by E-mail.

b.      At your plant, (minimum of 4 hour charge)

2-      Design review of parts, prints, molds.

3-      Plant Audits,

a.       Review of  process setup

b.      Review your cooling program via basic numbers

c.       Material handling system

d.      Observations of  plant operations and flow

Plant audits can be done in either a 1 day quick observation or a multiple day detailed observation and review done on a machine by machine basis. Initially a 1 day quick observation gives the basis of what is going on. This does include a written report.

4-     Training / education programs. (many more than shown)

a.       Scientific Molding:   The principles and details to molding by results.

b.      Mold design and part design..  understanding the basics

c.       Materials, selecting materials and understanding data sheets

d.      Plant the cooling system, layout and efficiencies

e.       Customize training / education programs developed.

5-      Mold optimizations / new mold trials

a.       Develop optimum fill speed and time

b.      Understand the pressure drop of your tool

c.       What is the gate freeze time

d.      What needs to be changed based on data.

e.       Record a process that is repeatable and consistent. If we can't than the why not.

6-      Other services

a.       program management

b.      testing of materials (we can arrange)

d.      BRT Melt Flipper