Shear Stress and Shear Rate Information

<< Click to Display Table of Contents >>

Navigation:  Getting Started > Defining Injection Molding Components in SYNC > Moldex3D Material Wizard >

Shear Stress and Shear Rate Information

Plastic flow undergoes shear effects during filling. Shear effects are relative to flow rate and pressure drop. With too high shear stress or shear rate, degradation and cracking may happen to the part. The cross section area of the gate is often the smallest over the part, and thus the shear around this area is the highest.

Shear rate at the gate is relative to gate dimension and flow rate. It can be obtained using Moldex3D. Meanwhile, most of material manufacturers provide shear rate limits on the plastics. As shear rate is under the limits, product defects and problems can be reduced.

The below table is the Maximum shear stress limits applying to products and Maximum shear rate limits applying to gates.

 

Maximum of shear stress and shear rate

 

 

Maximum of Shear Stress, (MPa)

Maximum of Shear Rate, (1/sec)

PP

0.25

100,000

HDPE

0.08

40,000

LDPE

0.08

40,000

EVA

0.30

30,000

PS

0.25

40,000

HIPS

0.30

40,000

SAN

0.30

40,000

ABS

0.30

50,000

ABS (Platting Grade)

0.30

30,000

PMMA

0.40

40,000

PPS

0.50

50,000

PA6

0.50

60,000

PA66

0.50

60,000

PA612

0.50

60,000

PA12

0.50

60,000

POM

0.45

40,000

PET

0.50

50,000

PBT

0.40

50,000

PPO

0.50

35,000

PC

0.50

40,000

PC/ABS

0.40

40,000

TPU

0.40

20,000

PC/TPU

0.40

10,000

PUR

0.25

40,000

s-PVT

0.30

20,000

r-PVT

0.30

20,000

PSF

0.50

50,000

PES

0.50

50,000

LCP

0.50

60,000