Cost improvement of deburring equipment for PPS moldings

SANKO GOSEI
May 8
3 min read

PPS (polyphenylene sulfide) is a peculiar material among high-performance engineering plastics and is prone to burring (flash) for the following reasons.

✅ Reasons why PPS is prone to flash:

Low viscosity and high fluidity PPS is a type of resin with relatively low viscosity and smooth flow.　This ‘good flowability’ is a detriment, and leads to the phenomenon that resin tends to leak out from the gaps in the mold = burrs easily appear.

High molding temperatures Moulding temperatures for PPS are usually quite high at around **300-330°C**.　Due to these high temperatures, the molds also tend to expand thermally, which can result in small gaps on the mating surfaces. As a result, burrs are likely to occur there.

Insufficient gas venting PPS is also a resin that tends to release a lot of gas.　In some cases, if gas venting is not done properly, the internal pressure increases and burrs are more likely to occur.

Although PPS is a material that makes manufacturers weep, in recent years it has been widely used in automotive parts for the following reasons.

Reasons why PPS is chosen for automotive parts

1. high heat resistance (extremely resistant to heat!)

　PPS can withstand continuous operating temperatures of around **200-240°C**.

　In EVs and hybrid vehicles, the temperature around motors and inverters tends to be high.

　PPS can be used in ‘hot workplaces’ without a care in the world.

　Examples of applications: motor insulation parts, connectors around inverters, etc.

(2) Excellent dimensional stability (straight and tight)

　Water absorbency is extremely low and dimensional changes rarely occur.

　Even in the presence of humidity and temperature changes in the engine compartment and cabin, ‘warping’ and ‘distortion’ of parts is minimised.

　is minimised. 3.

3. chemical and oil resistance (resistant to chemical attack)

　PPS is extremely resistant to chemicals such as oil, coolant and fuel.

　This means ‘no corrosion!’ even when ‘covered in oil’. In other words.

　Also very successful in powertrain components.

4. high flame resistance (naturally self-extinguishing)

　PPS is **self-extinguishing (UL94 V-0)** and flame retardant without additives.

　It is useful as a ‘flame-resistant material’ in EV high-voltage systems and around connectors.

5. meeting the need for weight reduction (also replacing aluminium)

　As a substitute for metal parts, it contributes to improved fuel efficiency and CO₂ reduction through weight reduction.

　Rigidity can be further increased by mixing glass fibre, etc.

　There are examples of replacing aluminium die-castings with PPS.

In this issue, we introduce an example of an improvement in the deburring process of a PPS resin molded product that we are working on.

Deburring methods, generally speaking, automatic deburring machines are blast machines that use shot blasting. The cycle time is quicker and there is some flexibility in changing the media to be shot. The advantage is that the same quality can be guaranteed as they are often used by the customer.

However, blast machines are expensive, and if they are not matched by production numbers, this can lead to increased production costs...

Alternatives to using a blast machine are

Nylon brushes are attached to an air router to remove burrs.

However, the adjustment of the rotation and the hardness of the brushes did not match and even the product was scraped!

This would result in a poor appearance even if burrs could be removed.

So we changed to an electric drill with a lower rotational speed than the air router, and also changed the diameter and roughness of the nylon brush. (from 1500 rpm)