(1)	Cross-section of runners
	A runner of round cross-section is the most advantageous, but grooves must be machined in both the stationary and movable platens. If a round runner cannot be used, a trapezoidal runner is suggested. Avoid semi-round runners. An example trapezoidal runner is shown in Fig. 7-1.
(2)	Runner size
	Although a wide runner is advantageous in terms of preventing cooling of material and pressure loss, the runner size is determined in consideration of economic aspects such as reducing the amount of material molded in runners.

Fig. 7-2 is a diagram for simplified runner design. This figure shows that required runner diameter can be estimated from the longest runner length. This figure serves as a guide for a runner size.

(3)	Runner lay-out
	A multi-cavity mold is designed with equal runner lengths and runner sizes so that the resin fills all the cavities simultaneously, and runners are laid out symmetrically. Example runner lay-outs are shown in Fig. 7-3. When runner lengths to cavities are not equal (runners of unequal length), or when cavity volumes differ in family molding, the runner size is adjusted for simultaneous filling.

7.2Draft

Since the mold shrinkage of Duracon is relatively great, a smaller draft can be used in comparison with amorphous resins. However, in view of mold release it is desirable to apply as large a draft as possible within the allowable range.
	At least 1/4to 1/2is recommended. If possible, approximately 1is favorable.
The knock-out method, the position and number of knockout pins are taken into full consideration for improving mold release.

7.3Undercut

Although in principle shape design without undercut is desirable, an undercut design may be unavoidable for molded parts that are to be assembled by means of snap fitting. In case of cylindrical molding, undercuts are as follows
	M90: up to 2.5-3%
	GH-25: up to 0.5%

7.4Gas Vents

Since improper design of gas vents may cause gas burn marks and mold deposit, full consideration should be taken for gas vent design. With structures in which gas is expelled from the parting line, a gas vent as shown in Fig. 7-5 is effective, as gas can be expelled from the entire circumference of the molding.
	The mating surface of the mold is roughened over several mm from the circumference of the cavities to a depth of 1 / 100 to 2 /100 mm, and grooves of a depth of about 1 mm are machined from that section to the outside of the mold.

7.5 Gates
7.5.1 Gate Size
(a) Gate Size

From the standpoint of quality, including appearance, strength, etc., the gate size should be as follows.
	Gate depth should be 60-70% of the thickness of the molded part.
	Gate width should be 1 to 1.5 times of gate depth (in case of a side gate)
	Shorter gate land is preferable (in case of a side gate)
However, if no quality problems result, a smaller sized gate can be used to improve molding cycle, automation of gate finishing work, etc. Gates of 0.8-1mm depth can be used for molded parts of up to approximately 3 mm in thickness. Although a much smaller gate of 0.5-0.6mm depth can also be used, this requires careful selection, since there may arise problems such as increased dimensional variance and decrease of impact strength.

(b) Gate Position

	Set at the thickest section of the molding.
	Set at the position where appearance of the molding is not affected
	Do not set at the section where the molding receives a load.
	When the weld line presents problems, take these problems into consideration.

(c) Gate Structure

Since Duracon does not require a special gate shape, a common gate shape can be used. However, when a pin gate or tunnel gate is employed, improper degating may occur in some shapes. Notes are shown in Fig.7-4.