ALAN LI

Have you ever felt frustrated having to change mechanical pencils every time you want a
different writing thickness? Have you ever been annoyed by not having the right lead size when
your mechanical pencil runs out of lead? The D­1 mechanical pencil is the solution to your
problems.

 

What is the D­1 mechanical pencil?

“D­1” stands for “all dimensions in one”; it is a mechanical pencil compatible with a continuous
range of lead sizes, and it is just as easy and comfortable to use as a traditional mechanical
pencil. You insert the lead rod, click on the top button a few times, and the lead will come out
from the front tip. But this time, there is no need to worry about lead jamming due to
incompatibility.

 

Why should I use it?

The D­1 mechanical pencil will save your time by eliminating the annoying search for correct
lead sizes, and will help you get back to concentrating on the work under your pencil tip quickly.
There is no need to look for the little “0.5mm” or “0.7mm” printed on the body of the pencil; pick
up a size you like, and D­1 will work for it.

 

How does it work?

In contrast to the flat tips used in traditional mechanical pencils, the tip of the D­1 mechanical
pencil has slanted faces, which slide against the outer case to create a larger hollow space
when a larger lead rod is pushed against it. The expansion of the spring will contract the tips to fit
smaller leads and press against the lead rod to provide frictional force while the advancing
mechanism is activated.

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1: Sketch of the tip fitting with different sizes of lead

 

Where are we in the development of D­1 mechanical pencil?
We’ve gone through several iterations to generate divergent ideas to achieve the goal of
expanding the compatibility of mechanical pencils. From all of these ideas, the one shown above
was chosen, and a prototype was built with cardboard to show that the sliding­expanding
process of the tips will work under the pushing force exerted by the user’s click, as
demonstrated in the video.

 

For the details of the design, we have chosen polypropylene plastic for the tip and an open and
ungrounded music wire compression spring for the spring shown in the drawings to minimize
the cost of manufacturing.

 

Risk and challenges

Although the concept of the D­1 mechanical pencil has been materialized, we still need to design
other details before D­1 can be put into production: Up to what exact range of lead sizes should it
be compatible with? What shape and grip it should have?