In prototyping,

you can choose the material.

You can choose the operator.

You can apply it slowly.

You can use only the good ones.

If there is a problem, you can redo it.

That is why a very good state can be created.

But in volume production,

material lots change.

Operators change.

Equipment condition changes.

Production speed also rises.

In other words, more variable factors come in than in prototyping.

One was made cleanly.

All ten passed.

This is important.

But in volume production,

1,000 units,

10,000 units,

100,000 units

are made.

The larger the quantity, the more small variations that were invisible during prototyping appear.

In other words, prototype evaluation only looks at a tiny part of the volume production distribution.

In prototyping, a single material lot is often used.

But in volume production, multiple lots are used continuously.

Even with the same part number, there may be some variation in

thickness,

hardness,

adhesive strength,

peel force,

and surface condition.

The lot used during prototyping may have happened to be easy to handle.

In other words, in volume production, it is necessary to look not only at the average performance of materials, but whether the process holds up across the entire range of material tolerances.

For example, there is a structure of

TIM ±0.05 mm,

insulating film ±0.02 mm,

adhesive layer ±0.02 mm.

Each individual tolerance is small.

But when laminated, the thickness variation of the finished component becomes larger.

Furthermore, the mating parts also have dimensional tolerances.

Then the final amount of compression ends up

large in one product

and small in another.

In other words, in volume production, it is necessary to look at the worst-case condition obtained by adding up the tolerances of each part.

For example, the design gap is 1.0 mm.

The TIM thickness is also 1.0 mm.

On the drawing, they match perfectly.

But in reality, there may be variation such as

gap 0.8–1.2 mm,

TIM 0.9–1.1 mm.

Then

combinations that are sufficiently compressed

and combinations that barely make contact

may occur.

In other words, in volume production design, it is necessary to consider not the average, but even the combinations of maximum and minimum.

Volume production equipment runs every day.

Dies.

Rollers.

Suction heads.

Guides.

Blades.

These wear little by little.

The equipment on day one and the equipment after processing hundreds of thousands of units are not exactly the same.

That is why in volume production, what matters is not only

“it can be made when the equipment is normal,”

but also

whether quality can be maintained even amid equipment changes.

When a die-cutting die wears,

burrs increase.

The outer shape changes.

Hole positions change.

Cut surfaces deteriorate.

Such changes may affect

insulation,

application position,

automatic recognition,

and contact condition.

In other words, die management ultimately also becomes functional quality management.

With a new die, it is good.

But as it wears, quality gradually declines.

The question is at what stage to replace it.

Replacing it only after it has become completely defective is too late.

That is why changes in

burrs,

dimensions,

and appearance

are monitored, and it is replaced preventively.

In other words, volume production quality is also connected to equipment maintenance.

In prototyping, units can be processed slowly one at a time.

In volume production, speed is increased.

Then

material behavior,

adhesive behavior,

peeling behavior,

heat,

and tension

change.

In other words, volume production speed itself becomes a new process condition.

Adhesives are viscoelastic materials.

The contact state can differ between slow application and high-speed application.

In prototyping, it wets out well.

In high-speed volume production application, air remains.

This can also happen.

In other words, even the same material changes performance depending on speed.

In prototyping, you can

hold it down for several seconds

and press it repeatedly with a roller.

In volume production, there is a takt time.

Sometimes several seconds cannot be spent on one unit.

Then, even with the same pressure as in prototyping, the contact state may change.

In other words, it is necessary to look not only at pressure, but at pressure × time.

Depending on the material, behavior changes in

summer,

winter,

and the rainy season.

Adhesives become softer.

Film dimensions change.

Static electricity increases.

Peel force changes.

The prototyping room had stable air conditioning.

The volume production site has large seasonal differences.

This can also happen.

In other words, environmental conditions are also part of process design.

Materials are used right after delivery.

Used after being stored in a warehouse for several months.

Stored refrigerated.

Stored at room temperature.

The material condition may change depending on this.

Especially with

adhesives,

thermosetting materials,

and hygroscopic materials,

storage conditions become important.

In volume production, it is necessary to consider even the history from material receipt to use.

Once-opened material may change in condition depending on whether it is

used immediately,

used the next day,

or used a week later.

Moisture absorption.

Surface contamination.

Changes in adhesive strength.

These are examples.

In other words, in volume production, not only the “material part number” but also management of the material’s condition is necessary.

In prototyping, the developers themselves assemble.

They know the material properties well.

But in volume production, many operators are involved.

Even with the same work instructions,

application angle,

pressing force,

and peeling speed

differ subtly.

That is why processes that depend only on operator skill tend to vary in volume production.

In volume production,

no matter who does the work,

and no matter which shift,

the quality must be the same.

That is why

jigs,

positioning,

application sequence,

and pressing method

are standardized.

In other words, it is necessary to transfer the skills of experts into the process.

In prototyping, one can work by feel, such as

“pressing about this much is fine”

and “apply at about this speed.”

In volume production, these are converted into

pressure ○ N,

speed ○ mm/s,

time ○ seconds,

position ±○ mm.

In other words, establishing volume production is also converting conditions based on feel into controlled conditions.

With automatic machines, everything will be exactly the same.

It is tempting to think so.

But equipment also has

positional accuracy,

pressure accuracy,

tension fluctuation,

and temperature change.

In other words, automation is a means of reducing variation, but it cannot make it zero.

What is needed is to design the process including the variation of the automated equipment itself.

In the morning, the equipment is started.

Motors and rollers are cold.

It runs for several hours.

The equipment temperature rises.

Then

tension,

dimensions,

and adhesive behavior

may change slightly.

In other words, in volume production, it is also worth checking the difference between right after startup and stable operation.

There is one prototyping machine.

In volume production, multiple units of the same equipment are introduced.

Then

Machine A,

Machine B,

and Machine C

may have subtly different conditions.

Even with the same settings, the actual pressure and positional accuracy differ.

In other words, in multi-line deployment, reproducibility between machines is also necessary.

Volume production was established in Japan.

It is then transferred to an overseas factory.

Equipment,

material suppliers,

temperature and humidity,

operators,

and transport conditions

change.

Then quality may change even with the same drawing.

In other words, transferring the drawing does not mean the volume production conditions are transferred too.

At the time of processing, the component is good.

But when it reaches the customer, it may

warp,

have deformed adhesive,

shift in position,

or have a collapsed reel.

High temperature,

high humidity,

vibration,

and long-term storage

may have an effect.

In other words, volume production quality is established only when it is maintained not at factory shipment, but until the moment the customer uses it.

At shipment, the pitch is correct.

But during transport, the reel gets hot and the carrier stretches.

Or the winding pressure changes.

Then the pitch may shift on the customer’s equipment.

In other words, for reel products, it is necessary to check not only processing accuracy but also the logistics environment.

For example, thermal evaluation was performed at room temperature.

The actual product is used in an 80°C environment.

Or it is also used at minus 20°C.

In prototyping, it is horizontal.

In actual use, it vibrates.

In prototyping, the material is new.

In actual use, it is used for five years.

The evaluation conditions are different.

In other words, it is necessary to check whether the conditions under which performance was achieved in prototyping are the same as the conditions under which the customer uses it.

In prototyping, good conditions can be created.

Choose the material. Choose the operator. Apply slowly. Redo it if there is a problem.

But in volume production, that is not possible.

Material lots change.

Tolerances stack up.

Dies wear.

Speed increases, and pressing time gets shorter.

Material behavior changes between summer and winter.

Storage period and time after opening also become conditions.

Operators change.

Even automatic machines differ between right after startup and continuous operation.

With multiple machines, differences between machines appear.

Transferring overseas changes the entire environment.

And components also change during transport.

All the variable factors that were not present in prototyping come into volume production.

In other words,

prototyping is the process of confirming “whether it can be done,”

and volume production is the process of proving “whether the same thing can continue to be made.”

In Part 2, we look at how to prove it.

Looking at worst-case values. Having design margins. Managing by process capability.

And actual failure cases, and the areas a processing company can take on.

 

Column Supervisor: Koji Kakumoto (President, OTIS Co., Ltd.)

After studying abroad and working in planning and development at a trading company, he joined OTIS Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as President, working to drive business growth and strengthen the organization.

 

This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.