PU coated rollers also called polyurethane rollers or urethane rollers. Normally they are made of a metallic core coated with polyurethane rubber.

Like this:

Or like this:

PU coated rollers are widely used in industry, mining and machinery etc, sometimes they could be a very small tiny component, sometimes could be a huge machine part.

No matter what their size is, they play an important role in the transmission process.

In most cases, we can manufacture all kinds of PU coated roller, but today we are going to share the case of roller which needs to be light (weight reduction).

#### Here is the case:

We got an inquiry from a customer, name called R in this study.

R: Can you tell me the pricing and current availability for the two rubber rollers of dimensions which are specified in the attached pdf drawing? I would like to purchase a testing sample of two of the long rollers and four of the short rollers.

Just like the usual requirement drawing, but there is something missing in the file, what is it?

The thickness of the polyurethane coating.

So we make another adjustment drawing (with PU coated thickness) according to the size that R provided.

From the above information, we can calculate the approximate weight of the roller.

Volume formula

First, we need to calculate the volume.

V=π r² h

π=3.14

h=length of roller

r=radius of roller (normally size is shown as diameter, radius=half of diameter )

Weight Formula

Then calculate the weight, as we know the formula.

m=pV

m=mass (consider as weight)

p=density

v=volume

But wait! We know the density between polyurethane rubber and metal is different, we should calculate their volume separately. SMART!

There is an easy way to do that.

We can separate the rollers into three parts, the whole roller (blue+yellow), the metal core (blue), the polyurethane part (yellow). Shown as below:

Roller Volume

First, the whole volum=3.14 x 1.75² x 20 = 192.325 cm³

Second, the blue volume=3.14 x 1.4² x 20 = 123.088 cm³

Third, yellow=whole-blue,192.325 – 123.088 = 69.237 cm³

So we already got the blue and yellow volume, we can calculate their weight separately.

Roller Weight

The core material is stainless steel density=7.85g/cm³ and polyurethane density=1.2g/cm³.

Blue = 7.85 x 123.088 = 966.2408 g

Yellow=1.2 x 69.237 = 83.0844 g

Oh, don’t forget the long handles on both sides, size is diameter 5mm, length 15mm

two handles volume=2 x 3.14 x 0.25² x 1.5 = 0.5888 cm³, weight=7.85 x 0.58888 = 4.6227 g

Total blue + yellow + handles = 966.2408 + 83.0844 + 4.6227 ≈ 1054 g

Once samples were finished, we send them to customer for testing. after some tests, R writes us feedback.

R: we need the rollers to be lighter. Much lighter. 50-60% weight reduction for both pieces is what we are after.

With this information, we know the target weight is 422.8-527g. Change the size of the roller won’t fit the weight reduction, so we first discuss changing the core material to aluminum (Green color shown below). Aluminum density = 2.8g/cm³

Green = 2.8 x 123.088 = 344.6464 g

Yellow = 1.2 x 69.237 = 83.0844 g

Two handles = 2.8 x 0.58888 = 1.6489 g

Total 429.3797 g. Bingo! That is almost a 60% reduction!

Of course, we can do more reduction like cutting to the size of aluminum to get lighter. But we suggest keeping enough space of the core to Get enough power and friction.

By the way, most customers care more about the price after changing the material while aluminum is expensive than stainless steel.

But in this case, after cutting 60% of the weight, the price only increasese 15%-20%, which benefits more if you have much more weight limitation.

#### Now You Try It

We hope you can see the potential of The case study for your solution and your business.