Dukane 6000 Series User Manual page 126

Linear Vibration Welder 6000 Series
Weld Amplitude
Amplitude has less effect upon the weld strength than weld
time. Figure 9 -2 shows the relationship of weld strength for
generic POM as a function of weld force for a fixed weld
depth and two different amplitudes. Higher weld strength
occurs at lower clamping pressures because the weld time
is longer and the penetration distance greater. However as
clamping pressure increases to shorten the weld time, the weld
strength decreases more rapidly for the low amplitude weld
joint. Figure 9 -3 shows the relationship of weld strength of
different thermoplastics as a function of weld depth (collapse
distance) for a fixed weld amplitude and weld pressure.
Weld Force
Increasing the weld force increases the collapse but not the
weld penetration. The welding force required for different
materials is determined by a combination of the polymer's
melt flow index, the glass transition or crystallization
temperature and molecular weight. The approximate melt
index range for some common thermoplastics and their
welding pressure range are given in Table 9-I. Since there
is such a wide range of melt flow rates for even common
polymers, depending upon their molecular structure, the
welding pressure required can initially only be estimated.
The optimal values must be determined experimentally.
Pressure is force per unit area, so the weld force setting is
the desired welding pressure multiplied by the total effective
joint area. Remember to keep the units of measurement
consistent (pounds and inch
2
meter ) when calculating the desired weld pressure.
Hold Force
Clamping under pressure while the bond hardens, corrects
warping problems by forcing the parts into the proper
geometry. Decreasing the welding pressure at the beginning
of the hold cycle can reduce the flow of molten material and
thus reduce the size of the weld bead or flash. In addition, this
can reduce shear thinning to create stronger welds. The hold
time must be long enough however, so that the temperature of
the weld seam is below the glass transition or crystallization
temperature. A holding time of between one and five seconds
is usually enough.
Page 120
User's Manual
2
, Megapascals or newtons and
Material – POM (Acetal, Delrin)
Weld Distance = 1.0mm
15
10
5
0
1 2
Pressure (MPa)
Figure 9 - 2
Relationship of Weld Strength as a
Function of Weld Pressure
Weld Pressure – 2MPa
Amplitude 1.0mm
20
15
10
5
0
1.0
Weld Depth (mm)
Figure 9 - 3
Relationship of Weld Strength as a
Function of Weld Depth
Thermoplastic
Abbv
Chemical Name Trade Name
Acrylonitrile Lustran
ABS
Butadiene Styrene
Nylon 6
Polycaprolactam
PA6
Nylon–6/6
Polyhexamethylene–
PA66
adipamide
Polycarbonate Lexan
PC
High Density Chevron
HDPE
Polyethylene
Polymethyl Lucite
PMMA
Methacrylate
Polyoxymethylene Delrin, Acetal
POM
Polypropylene Herkulon
PP
Polyphenylene Ether
PPE+SB
+ Styrene/Butadiene
Polystyrene Styron
PS
Styrene–Acrylonitrile Lustran
SAN
1 psi = 6.895x10 -3 MPa; 1 MPa = 1.450x10
Table 9- I
Approximate Welding Pressure for
Common Thermoplastics
Dukane Manual Part No. 403-619-00
Amplitude 1.4mm
Amplitude 1.0mm
3 4 5
POM—Acetal,
Delrin
PPS—Fortron, Techtron
PBT—Celanex
LCP—Vectra
1.1 1.2 1.3
Melt Flow Rate Welding Pressure
3
(cm /10 min) (psi) (MPa)
2–50 145–290 1.0–2.0
18–110 145–290 0.5–3.0
10–180 72–435 0.5–3.0
3–12 145–290 1.0–2.0
0.1–80 72–1160 0.5–8.0
1–25 145–290 1.0–2.0
1–40 145–580 1.0–4.0
1–100 72–580 0.5–4.0
8–270 145–870 2.0–6.0
3–25 145–580 1.0–4.0
8–25 145–290 1.0–2.0
2 psi; 1 MPa = 1x10 6 Nt m -2