heat_staking

AMBRELL®

Precision Induction Heating

Heat Staking: Inserting Metal into Plastic

By Dr. Girish Dahake, Ambrell Vice President of Worldwide Applications

for a short period of time. When inserts to be heated to 700°F for

Introduction

the correct temperature is correct installation, so the brass

One of the most common uses

achieved, the insert is pressed inserts must be heated and

for induction heating is the heat

into the plastic. A narrow zone of inserted quickly to prevent

staking of threaded metal inserts

plastic then melts and flows into thread annealing. Brass has low

into plastic. Most thermo-plastics

the knurls of the insert. The electrical resistivity and therefore

are too soft to sufficiently hold a

plastic re-solidifies, resulting in a requires more power to heat with

thread, so brass or steel

complete assembly with much induction than steel.

threaded inserts are added.

better mechanical properties

Post-molded installation is more

than inserts implanted with

1

cost-effective than molding in

techniques. Basics of Metal-to-Plastic

place and induction is a proven

The insert material is usually

.4

way to pre-heat the inserts prior

brass or steel; each has

Simultaneous Heat Staking of

to installation.

advantages and disadvantages.

Three 7

Inserting Metal Parts AccuratelyFor heat staking, the insert is

Brass is non-magnetic and will

..................................................8

preheated with induction and

not corrode as easily as steel.

then pressed into a hole in the

However, brass is a softer

Staking Steel Inserts into a Chair

8

plastic part. This is

material and will anneal at

accomplished by positioning the

temperatures as low as 450°F.,

Staking Steel Inserts into a Chair

induction coil over the hole and

whereas steel starts to anneal at

9

then holding the insert in the coil

1200°F.

Attaching Plastic Handles to

9

Some glass-filled plastics require

Staking Plastic Bearings on

10

Bonding Electrical Connector

10

Inserting Plastic Handles into

Metal 10

Inserting Plastic Handles into

Metal 11

Heat Staking Large Brass

.11

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

1

AMBRELL®

Precision Induction Heating

There are also other factors to

consider: the insert must have

Thermoplastics will flow at

the proper knurl and fin design

elevated temperatures and the

to achieve the desired

solidified polymer can be re-rotational torque and tensile

heated to reflow around the

strength. Most inserts designed

insert. Thermosetting polymers,

for molded-in, expansion,

once the shape has been cast,

ultrasonic or self-threading

will no longer melt or flow on

insertion can be used with the

reheating. Table 1 shows some

induction heating process.

typical temperatures, time and

However, due to the inductively

power required for different

flanged insert

heated insert’s ability to easily

materials, as established in the

reflow plastic, the knurls and fin

Ambrell Applications Lab.

on the insert can be made

deeper for greater holding

The diameter of the insert hole

strength. The material and

must be the correct size to

mass of the insert, together

allow the plastic to flow around

with the available heating time,

the insert. If the hole is too

flush insert

will determine the power

small, extra plastic will be

required to reach the desired

displaced. This displaced

Fig. 2: Different insert types

temperature.

plastic is commonly called

‘flash’. Excessive heat and

A steel insert can be heated

more quickly because steel has

The installation temperature of

pressure may also cause flash.

high resistivity and is harder

the insert is important. Each

If the hole is too large, not

than brass, and there is no

insert must be heated to the

enough plastic will flow into the

concern about annealing at the

same temperature in the same

fins and knurls to achieve the

desired holding strength.

insertion temperature of most

time to achieve a consistent

plastics. However, consistent

process.

With proper fixturing, tight

coating or plated finishing of The critical parameters for a

center-to-center tolerances of

steel inserts, particularly in the

consistent induction insertion

the inserts can be maintained.

threads, can be difficult to process are:

Although molded plastic parts

achieve because steel inserts

• power-on cycle in the

sometimes do not have tight

are typically magnetic and

induction power supply

tolerance, post-molded

oxidize more quickly than

installation with induction

brass. The selection of the

• heat-on time

heating and accurate insert

insert material is dependent on

• tuning frequency

the specific application

• power ramp-up and ramp-location tooling will put the

requirements, but brass is often

down

insert in the same location each

the material of choice due to

• positioning of the insert in

time, even if the holes in the

the coating and plating issues.

the coil

plastic vary in size.

• insertion pressure

• thermoplastic material

Qty. Material

Insert Size; ∅,lg (in) Temp (°F)

Time (sec) Power (kW) Model (kW)

1 brass .33, .50, .17 wall 400 1 .3 1

1 brass

.33, .50, .10 wall 400 .8 .3 1

1 brass

.25, .63 400 2.5 1.2 3

4 steel .63, .50, .12 wall 500 12 .6 1

2 brass .25, .50, .12 wall 350 2 .8 1

1 brass .56, 1.25 700 6 .8 1

1 steel .75, .05 250 2 .7 1

Table 1: Typical heating times, temperatures and power required for different materials

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

2

AMBRELL

There are several methods used

for inserting with induction heat.

An x - y positioning table (see

Figure 3) can be used in

conjunction with a single position

coil when multiple inserts need

to be installed in a single molded

part. The position of the coil is

held constant and the x - y table

moves each insert location

under or above the coil. This

technique provides for a flexible

manufacturing tool that can be

changed by software

programming rather than

hardware tooling changes.

As shown in Figure 4, a second

option for a single position coil is

the use of a robotic arm. The

plastic part is held in fixed

location while the coil and

indexing mechanism can be

moved to each insert location.

Encapsulated heat stations are

available from Ambrell for this

purpose. Small encapsulated

heat stations can be supplied

®

Precision Induction Heating

with 1, 3, 5 and 7.5 kW power

supplies with mounting brackets

to align with robotic insertion

tooling. Location of the coil

relative to the heat station is

custom-designed for each

application.

A multiple-position coil makes it

possible to install more than one

insert at a time into a single

plastic part. Three- and four-position coils have been used for

this application. For this setup,

the coil is normally in a fixed

position and the plastic part is

moved into the coil. The inserts

for each location are heated

simultaneously and then pressed

into the plastic.

For all tooling arrangements with

induction heat, the manner in

which the insert is held is more

important than with other

insertion methods. Using

metallic tools to hold the insert in

the coil will impede the

performance of the induction

power supply. Any tooling in

direct contact with the inserts

should be nonmagnetic and

have the smallest mass

possible. Non-magnetic stainless

steel is often used for the rod

which locates and inserts the

part.

The insert threads should not be

used for holding, as this can

damage the threads during

insertion. Three jaw chucks or a

combination of a locating rod

and vacuum can be used for

holding the insert. With each

method, a taper or some other

centering mechanism should be

incorporated into the design.

Gravity is often used to position

the inserts onto the insert

tooling, and the inserts are

normally pushed upward or

horizontally into the plastic.

Figure 3: Stationary inserter, variable “X” and “Y” table

Figure 4: Stationary table, variable position inserter

Ambrell Companies

Ameritherm Inc.

001.585.889.9000

Cheltenham Induction Heating, Ltd.

00 44 (0)1242 514042

heat_ | © 2007 All information subject to change without notice

Ameritherm France SARL

+33 (0)3 89 76 01 24

3

AMBRELL®

Precision Induction Heating

heat to be generated within the

Basics of Metal-to-insert. The current flows towards

ρthe outside surface of the part

d=3160Plastic Bonding

µf

with most (80%) of it flowing in

where:

Since steel, brass and aluminum

an area known as the skin

d the skin depth in inches

are the materials of choice for

depth. The skin depth is

ρ the resistivity in mΩ-inches

metal inserts for plastic bonding,

dependent on the resistivity and

µ the permeability of the metal

let us look at the relative merits

permeability properties of the

ƒ the operating frequency (Hz).

of each material and see how

material. Table 2 shows the steel

each characteristic effects the

insert with a skin depth of

This formula dictates that in

ability of the material to be

0.0025", compared to the brass

order to achieve efficient heating

heated and inserted into the

of .008", showing that the heat

for small inserts, the operating

plastic part. Material resistivity,

induced in the steel part is

frequency of the induction

permeability, specific heat and

produced in an area 2.5

equipment must be above 50

thermal conductivity are the four

thousandths of an inch in from

kHz. When taking into account

primary properties to consider

the surface, while the brass is 8

the overall size of the insert, the

when heating a metal insert with

thousandths of an inch. This has

available insert length for an

induction. Each of these

several effects on the induction

effective coil and the resulting

materials can be heated by

process. With a steel insert, the

small number of turns and low

induction, but the individual

heat is produced closer to the

coil inductance, operating

material properties will dictate

edge, so care must be taken not

frequencies in the 300 to 450

the characteristics of the

to melt the outer surface during

kHz are required for efficient

induction process. Table 2

fast heating cycles. The heating

coil/part energy transfer.

shows the characteristics of 3/8"

time must be long enough to

OD inserts made from steel,

allow sufficient energy to be

The amount of energy required

brass and aluminum when

transferred to the insert to allow

to heat the insert depends on the

heated with the same magnetic

for proper bonding when

mass of the insert and on the

field produced by a coil with the

inserted into the plastic. The

specific heat of the material

same current passing through it

.008 inch skin depth of the brass

described by the following

and the same number of turns.

insert produces the heat more

equation:

The steel insert absorbs more

into the part but dictates that

power from the magnetic field so

small diameter inserts must be

Q=mCp∆Tit is heated faster than the

heated with higher frequencies

57

aluminum and brass inserts. The

to maintain heating efficiency.

where:

induction process produces heat

For optimum efficiency, the

Q = quantity of heat (kW)

in the insert by creating an

diameter of the insert must be

Cp = specific heat (BTU/lb °F)

electrical current that flows

greater than 4x the skin depth.

∆T = rise in temperature (°F)

around the part. This induced

The skin depth is given by the

m = mass (lbs./minute)

current flows through the

fundamental equation:

resistivity of the material causing

Brass Steel units

Resistivity 1.11 2.76 29.0

µΩ●inch

Skin depth 0.005 0.008 0.0025 in

Specific heat 0.214 0.092

0.118

Cal/gm●°C

Thermal conductivity 211 395 52

Temperature 350

350 350

°F

Time-to-heat 3.2 3.0 1.1 sec

Power absorbed/insert 350 484 560 W

Table 2: 3/8" OD inserts in same magnetic field in a coil with same number of turns and same current.

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

4

AMBRELLThe power required by the

insert is indirectly related to

the time taken to heat it. If the

heating time is increased from

one second to three seconds,

the amount of power required

would decrease to 205 Watts.

Although the power required

to heat the brass and

aluminum inserts is less than

steel, the power absorbed

from the magnetic field as

shown in Table 2 is far less

than the steel insert. So the

steel parts heat much more

efficiently than the brass or

aluminum and require much

less power from the power

supply.

This means that, with the

properly designed induction

coil, a 1 kW induction power

supply can be used to heat

one aluminum insert, two

brass inserts or three steel

inserts at a time.

Having looked at the material

properties affecting the

heating cycle, let us now look

at the material characteristics

which affect the insertion

process. Specific heat and

thermal conductivity are the

primary properties to

consider. Since the induction

process produces heat

towards the outside of the

metal part, the heating pattern

should be considered relative

to the process time.

At the end of the heating

cycle the surface of the insert

is at a relatively higher

Table 3: The amount of power

required to heat 3/8 inch diameter

inserts to 350°F in one second.

®

Precision Induction Heating

Figure 5: Temperature through the cross section of the steel insert, 3/8" O.D. A

specially designed 4-turn double wound helical coil is used on the 1 kW power

supply for the heating.

Figure 6: Temperature through the cross section of the brass insert, 3/8" O.D. A

specially designed 4-turn double wound helical coil is used on the 1 kW power

supply for heating.

thread surface to reach temperature than the inside.

temperature equilibrium. The However, due to the thermal

steel insert will take a longer conductivity of these

25 milliseconds. A short heat materials, the insert quickly

cycle and dwell time prior to reaches a uniform

insertion will minimize the temperature throughout.

When the 3/8" O.D. of a brass possibility of thread

annealing.

insert is heated to 3500°F in

one second, it will only take

60 milliseconds for the center

Aluminum Brass Steel units

Mass 0.0058 0.0184 0.0165 lbs

Specific heat 0.214 0.092 0.118

Temperature rise 300 300 300

°F

Power required 390 535 615 W

Ambrell Companies

Ameritherm Inc.

001.585.889.9000

Cheltenham Induction Heating, Ltd.

00 44 (0)1242 514042

heat_ | © 2007 All information subject to change without notice

Ameritherm France SARL

+33 (0)3 89 76 01 24

5

AMBRELL®

Precision Induction Heating

After the heating cycle, during is pushed into the plastic. The

the insert location and before the temperature of the insert drops The heat content of the metal

actual insertion, the insert loses much more rapidly after insertion insert just before it is pushed in

heat by radiation and because it looses heat in melting the polymer should be sufficient

convection. Heat is also lost to the plastic and by conduction to melt the polymer to a plastic

the fixture holding the insert. As into the plastic. A comparable state and have a good flow

shown in Figure 7, the drop in curve for steel is shown in Figure around the insert. The

surface temperature is almost 8. Steel inserts can be heated interference between the insert

exponential. It is therefore very quickly; due to the poor and the guiding bore in the

important that the insert is thermal conductivity of steel and polymer determines the amount

pushed into the plastic as soon the surface temperature of steel of polymer to be displaced. It is

as possible after the end of the will be at a much higher usually not enough just to heat

heating cycle. A brass insert temperature than the center of the insert to the melting point of

the plastic.

The insert has to be sufficiently

heated so that the heat content

stored in the insert is enough to

raise the temperature of the

polymer at the interface to the

melting temperature, and also

have enough heat to overcome

the latent heat of fusion of the

polymer. The latent heat of a

substance is the amount of heat

Figure 7: Temperature of a 3/8" brass insert in air and when inserted in plastic.

required at the melting

The insert is heated for 1.0 seconds and should be inserted within 5 seconds to

temperature to change the

obtain good capture of the plastic around the insert.

phase from solid to liquid. This

must be inserted within five the insert. As seen in Figure 8,

depends on the particular plastic

seconds of the end of the at the end of the heating cycle

used. A brass insert at 350°F

heating cycle; otherwise the the temperature of the surface of

could not be inserted into a

insert will have lost sufficient the insert drops rapidly as the

plastic which melts at about

200–250°F. The insert must be

heated to a temperature of about

400°F to get a good insertion.

The insert must be heated to a

temperature higher than the

melting temperature of the

plastic to get a good flow of

plastic around it. Yet, the insert

must not be too hot; or the

plastic will burn or boil creating

excessive flashing.

Once the insert has been

Figure 8: Temperature of a 3/8" steel insert in air and when inserted in plastic.

The insert is heated for only 0.4 seconds and then inserted within 3 seconds to

pushed in the polymer, a

obtain good capture of plastic around the insert.

temperature gradient arises in

heat to melt and flow the plastic. heat travels through to the

the polymer; the temperature is

center of the insert until the

hottest at the insert/polymer

Figure 7 also shows the surface whole insert reaches the

interface and drops

temperature of the insert when it

equilibrium temperature (400°F).

exponentially away from it. The

locating fixture should be held

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

6

AMBRELL®

Precision Induction Heating

stationary after insertion for the also be used. With a 1 kW power with good capture of plastic

polymer to re-solidify around the supply, only one aluminum insert around the metal insert.

insert. For the 3/8" brass insert, can be heated, where two of

a hold time of 0.5 seconds is brass and three of steel can be

Simultaneous Heat

Staking of Three

Steel Inserts

There are many plastic molding

applications that require an

assembly with two or three

inserts. By simultaneously

heating the inserts with induction

in a multi-position coil, the

inserts can be pushed into the

part at the same time, optimizing

throughput and yield. An

automotive door handle required

three steel inserts to be placed

Figure 9: Typical coil design and positioning for heat staking

in three separate locations on

the handle. All three locations

usually sufficient to allow the heated in the same time using

were on different plains, but

plastic enough time to re-solidify properly designed coils. Cycle

were inserted from the same

to maintain the tolerance times can therefore be reduced

side. The steel inserts are

required by the insert. The hold by using steel or brass inserts.

relatively easy to heat with

time depends on a number of The insert must be heated to a

induction energy, so a multi-factors: the insert material, the temperature higher than the

position coil designed for the

insert temperature at the time of melting temperature of the

same hole positions as the

insertion, the amount of polymer plastic, and the insert must be

inserts on the handle will heat

displaced and the temperature pushed into the plastic within two

the three steel parts to 375°F in

characteristics of the polymer. to five seconds depending on

2 seconds. The coil is in a single

The melting point and viscosity the size of the insert. Heat lost

plane and the insert push rods

of the polymer will determine the by radiation and convection, as

are designed to correctly place

required temperature for well as the heat lost by

each insert into the door handle

satisfactory insertion. conduction to the inserting

on a five-second cycle time.

fixture, must be accounted for in

These steel inserts have a 0.5”

The process of staking the metal the design of the process. A

diameter flange which has to

insert into the plastic depends good capture of plastic is vital for

seat on the door handle, but not

upon the material characteristics good pull strength and

melt into the surface. By

of both the insert and the plastic. resistance to torque. Thus, the

designing the coil correctly and

During the heating process, a optimum insertion process

properly positioning the part in

proper coil design (see Figure 9) depends on a properly designed

the coil, the body of the insert

is required to transfer power coil, metal insert and the guiding

can be heated to a higher

efficiently and quickly to the hole. The insert must also be

temperature than the flange.

insert. Although steel is easiest heated to the right temperature

to heat, brass or aluminum can to have a good strong product

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

7

AMBRELL®

Precision Induction Heating

inserts can be positioned to molding with a loosely coupled

Inserting Metal

correct the location errors in the two-position coil. A 1 kW Ambrell

Parts Accuratelyholes in the molded part. As the solid state power supply was

heated insert causes the plastic used for this application. Heating

It is often necessary to locate the

to melt and flow, 0.03 to 0.10 the two inserts produced a total

metal inserts in the molded

inch correction in the location of cycle time of one part in every

plastic part with greater accuracy

the insert is achievable. In the five seconds, with the insertion

than is achievable with ultrasonic

application illustrated in Figure and cure time taking an

insertion techniques. Errors in

11, an air nozzle required two additional three seconds. The

the precise location of the holes

inserts to be accurately

inserts were heated to 350°F

in some plastic moldings cause

positioned relative to one face

and the system operated at a

parts inserted ultrasonically to

independent of the molded hole

frequency of 207 kHz with 275

“wander” from the required

spacing. By accurately locating

Watts loaded into both inserts.

location. By using induction

the insert push rods relative to

heating to heat the insert, and

the part, the inserts could be

with accurate insert location,

precisely inserted into the

Figure 11: Accurate insertion metal parts with precision induction heating

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

8

AMBRELL®

Precision Induction Heating

Staking Steel

The plastic re-flows around the

Inserts into a Chair

knurls, cures, and forms a

Attaching Plastic

lasting bond. Once it has cured,

Handles to Steel

Frame

the retention and torque strength

is extremely high, and the

Flatware

Standard office chairs often have

process can be duplicated

The cutlery industry has many

a metal leg assembly with a

quickly and consistently.

requirements for attaching

molded plastic body attached

plastic handles on steel flatware.

with steel fasteners. Metal

In the application illustrated

Many types of pocket knives,

inserts are screwed into the

below, four steel inserts are

dinner knives, forks and spoons

plastic chair body, with the leg

heated simultaneously with a

incorporate plastic handles.

assembly bolting to it.

multi-turn, multi-position coil.

Induction heat is used to heat

Unfortunately, the retention and

The inserts are positioned in the

the tang of the flatware either

torque strength of the threaded

coil using nonmagnetic stainless

before or after attaching the

metal inserts is not very reliable,

steel push rods; and are heated

plastic handle. In one

and the assemblies tend to

to 600°F in approximately

application, a plastic handle was

loosen over time. thirteen seconds, before positioned on a pancake coil and

insertion into the 30% glass-filled the flatware tang aligned at the

When induction is used to heat

plastic chair body at 490°F. The

end of the handle (opposite end

the insert, the insert becomes an

induction heating insert process

of the coil). Power was applied

integral part of the plastic chair

has a much higher retention

to the coil and the tang/ handle

body. The steel insert is heated

strength and positional accuracy

assembly was moved into the

to a temperature high enough to

than can be achieved with the

coil center position. The tang

melt the plastic upon insertion.

threading process.

was pushed into the handle as

the ABS melted, and the entire

assembly was removed from the

coil as the tang fully seated. The

time to complete the operation

was four seconds. This

application required a frequency

of 270 kHz and 200 watts of

power to raise the tang

temperature to approximately

350°F. This allowed the plastic

to form correctly around the

tang, but was not so much heat

that the handle lost its molded

shape. The pancake coil design

was used so the staking process

could be directly incorporated

into the assembly line.

Figure 12: Setup for heat staking steel inserts into a plastic office chair frame.

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

9

AMBRELL®

Precision Induction Heating

supply and an encapsulated heat cycle, a more reliable

Staking Plastic

remote heat station. The heat automated process was

Bearings on Steel

station and coil assembly moved achieved.

over the two steel shafts and

Shafts

heated the ends of the shafts to

1300°F in less than two seconds

Bonding Electrical

With the advances in polymer

before moving back from the

applications for bearing

shafts. The plastic bearing

Connector

surfaces, there are many

assemblies were placed on the

Components

applications which involve the

ends of the shafts, 880 Watts of

Many two-part electrical

attachment of a bearing

power was delivered to each

connectors are held together

assembly to a steel shaft. In the

end, and the total cycle time was

using a mechanical threaded

automotive industry, plastic

approximately 15 seconds. The

screw.

bearing assemblies are often

high temperature of the ends to

used on the end of air spring

allow for cooling after the shafts

0.25 inch OD brass inserts are

cylinders to aid the opening of

have been removed from the

often used to provide the robust

hoods and trunks. In the

coil, the coil moved back and the

thread in the plastic connector

application illustrated below, the

plastic bearings inserted. By

body. Induction heating can be

ends of two steel shafts were

keeping the steel shaft and the

used to heat these with precision

simultaneously heated in a multi-bearing in one vertical plane,

and consistency

position coil with a 3 kW power

and moving the coil and

encapsulated heat station for the

Figure 15 illustrates how a 0.25"

OD 0.625" long brass insert is

heated to 600°F in two seconds

prior to insertion in the glass-filled plastic connector housing.

1225 Watts is delivered to the

part from a 3 kW induction

power supply.

Since the hole in the connector

is a through hole rather than the

usual blind hole, a guide rod can

pass through the plastic housing

to help guide and correctly

locate the insert in the housing.

Figure 14: Setup for staking

plastic bearings on steel

shafts.

Figure 15: Setup for bonding electrical connector

housing components

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

10

AMBRELL®

Precision Induction Heating

Inserting Plastic

handle and the assembly placed

Handles into Metal

over the coil. Power is applied The 9/16 inch diameter brass

and the handle pressed onto the inserts require 475 Watts of

Control Arms

control arm as heating

occurs. In one lab

Agriculture and yard care

application, the steel

equipment often have metal

control arm reached a

control arms with plastic

temperature of

handles. The plastic handles are

approximately 400°F

threaded onto the metal control

and heating times

arms which can eventually

varied from two to six

loosen, and could become a seconds depending on

safety concern if the handle the assembly.

were missing or broken due to

continuous adjustment. With

induction heating, the molded

Heat Staking

handle and metal assembly can

delivered power to reach the

be permanently fused together

Large Brass

required insert temperature of

with a better torque strength

Inserts

700°F within four seconds. Each

than can be achieved with the insert is placed on a non-simple threading technique.

Automobile inlet manifolds are

magnetic stainless steel push

molded from glass-filled nylon

rod which is activated by an air

During manufacture each control

and bolted to the engine using

cylinder. The insert is placed in

arm/handle assembly is

9/16 inch diameter brass inserts.

processed with the same coil

Eight to ten of these large inserts

the coil and heated for four

and power supply, using

are usually positioned on one

seconds before being inserted

different heating times as

plane with a number of smaller

into the manifold. The stainless

necessary. A control arm is

inserts in another plane to mount

steel push rod positions the

inserted into its corresponding

the EGR components and air

insert in the manifold and passes

duct or filter assemblies.

through the coil. Heat is applied

only while the insert is in the coil;

the power is switched off during

the rest of the cycle so as not to

heat the stainless push rod.

Multiple coils are required to

heat the 10 inserts

simultaneously, and these are

located in a “heating plate” that

the inserts pass through. The

coils can be part of a two- or

multiple-position coil, or be

individually driven by 1kW power

supplies. The smaller inserts can

also be inserted at the same

time with a separate coil and

inserter push rod system.

Typical cycle time is 10 to 15

seconds per manifold.

Figure 16: Fixturing table for inserting large brass inserts into engine manifold

Ambrell Companies

Ameritherm Inc. Cheltenham Induction Heating, Ltd. Ameritherm France SARL

001.585.889.9000 00 44 (0)1242 514042 +33 (0)3 89 76 01 24

heat_ | © 2007 All information subject to change without notice

11