Developers on the X1 Carbon - Mechanical Engineering

ThinkPad X1 Carbon

Following on from Developers on the X1 Carbon - Project, we once again hear directly from the developers.

In this third piece we hear from two of the engineers in charge of mechanical engineering. The first is a veteran engineer who designed the X300 and the original X1, and the second is an engineer with experience in mechanical engineering for mobile phones. Together they led the pivotal packaging (chassis design) part of the project.


- In the previous interview we were told that you had some difficulty with the packaging for the X1 Carbon.

Morino: In the planning phase a basic design model based on mechanical engineering was completed. It was close to the current package with a slim front edge, but once we entered the development phase we hit a few hurdles. The first design model completed in the development phase had a thickness of a flat and over 20mm body, which was not even remotely close to the initial plan...

I believe we were thinking a little too pragmatically based on our experience with the X1 and T420s, and we weren't pursuing aggressive enough goals.

Otsuka: Pushing ahead while also thinking about manufacturing, I think the engineering was extremely difficult. It presented a number of challenges we had not faced before.


- So there were a few birth pangs. How did you resolve these problems?

Morino: First, we clarified our goals. These were to "create an overall thin design, and then make the front edge even thinner".

There were two important elements for determining the thickness.
1. The thinness of the part where the ClickPad and battery overlap
2. The appropriate inclination of the battery

To make the point where the ClickPad and battery overlap thinner, we employed a special technique that we had never used with other models.

The larger battery is positioned over the area directly beneath palm rest with the ClickPad and the front edge of the keyboard. We couldn't change the thickness of the battery, so making the ClickPad and keyboard thinner would be effective. However, making the entire keyboard thinner would impact important usability elements such as keystroke, so we avoided doing that.

In light of this, we made the ClickPad thinner by utilizing a magnesium alloy frame and thin glass.

The greatest challenge we faced in eliciting a suitable battery inclination was deciding on the most balanced battery inclination. Basically, to make the front edge thinner all we have to do was increase the battery's inclination -- kind of like a see-saw. However, this makes the back side thicker due to the extended inclination. Despite the machine itself being thin, the back side of the body would stick up making it necessary to have rubber feet touching the desk. The rubber feet would get in the way when putting the product away in a bag, decreasing its portability.

In the end we looked at many ideas while considering the internal architecture, and I think we achieved the best battery inclination with a thin front edge and a suitably thick back edge.

Relationship between  inclination of the battery and thickness of the body


- I heard that there was a major turnaround during development. Did it involve the mechanical engineering?

Otsuka: Yes. I believe it affected the mechanical engineering more than anything else.

There were significant changes after the injection mold and die cast mold were completed. Of course, the changes also affected the product direction and the project as a whole, so all hell broke loose at the Yamato Office. Opinions on the changes were divided even within the company.

However, we took on the challenge that this major turnaround presented.

While examining the product in detail we discovered that we may be able to decrease the size even further, and believing this to be our last chance, we revised the design once more. Collaborating with a range of departments we decreased the size of the battery pack and the sub board and made countless other improvements. I was frankly surprised when we managed to reduce the depth close to 10mm.

However, this was merely a by-product, as the major turnaround involved more significant changes. Looking back now I believe it was the right decision, as the X1 Carbon was improved so much that it became almost a completely different product to the initial plan.

I feel like for this one product we did enough design work for two or three products. I'm exhausted (LOL).


- It's tiring just hearing about it (LOL). Are there any other points that you struggled with or are proud of?

Otsuka: The ThinkPad actually had a "curse" associated with it, and we were able to break that.

This "curse" was the issue with paint coming off the palm rest. This was caused by the sweat from a user's palms passing through the paint to the metal plating, where it would dissolve the metal and create a gas that caused bubbles to form under the paint.

It may be hard to believe, but metal can melt when exposed to highly acidic material like alien blood. Human sweat is normally only mildly acidic, but although it seems medically impossible this issue was actually occurring. So for the ThinkPad we could not use paint on palm rest parts containing metal or metal plating. Alumite treatment using an aluminum alloy has different properties so it is an exception.

The palm rest for the X1 Carbon is magnesium alloy coated with paint. That meant we had a problem&hellihellip;

So we looked into a variety of solutions together with the Manufacturing Technology Department. We considered wrapping the parts with a high-resistance film before painting, but in the end we resolved the issue using a "high-resistance base coating". We apply the final coat of paint after applying a base coat that can withstand even highly acidic sweat. In our tests it could withstand even pH 1 or concentrated hydrochloric acid. It also holds up well against aliens (LOL).

Morino: I am proud of the hinge architecture that opens almost 180 degrees. To my knowledge this is a world first for a drop down hinge.

The X1 Carbon is a "drop down hinge" machine, which is rare in the ThinkPad Classic series. We call it a drop down hinge internally because the hinge itself hangs from the LCD side, and the hinge shaft is on the system side rather than the LCD side.

Most drop down hinge designs only open about 135 degrees, but we made a point of aiming for a design that opens 180 degrees like the normal hinges on other ThinkPad Classic models. However, circumstances forced us to settle for "almost" 180 degrees (LOL).


- As its name suggests, the X1 Carbon is also a new approach using carbon materials, right?

Otsuka: Correct. We're using top-grade carbon for the first time.

As is explained in Lenovo Voice vol. 5 and the additional interviews, we use an even higher grade of carbon than aircraft and Formula 1 cars.

There are many types of CFRP (Carbon Fiber Reinforced Plastic). There are also grades of carbon fiber and there are already many that are very strong. The highest grade carbon fiber is used in fishing rods and is even better than the parts used in airplanes and F1 race cars. However, it is not suitable for mass production in notebook PCs. There are fishing rods that cost hundreds of thousands of yen and are almost works of art. Of course, it is necessary to consider the balance with the cost. There are still many issues to consider, but I think in the near future success is possible.

(Excerpt from Lenovo Voice vol. 5 and Additional Interviews)

As far as I am aware, this mass production of a notebook PC using carbon is a world first. The composition of carbon fiber itself is ideal, characterized by its high density, which enables thin, light, strong parts to be made.

I think in actual fact the X1 Carbon is very thin, light, and strong. In tests where an iron ball was dropped on the product it performed well, with not a single scratch caused. This is despite the test being harsh enough to dent 1.5mm thickness aluminum and magnesium alloys.


- That sounds like an amazing material you're using. Do you have anything to say about the future before we finish up?

Morino: Despite the fact that particular emphasis is often placed on eye-catching features such as new technology and sexy design, I'd like to continue to place importance on the things that are expected from the ThinkPad name.

For example, I think that ease of use, toughness, a spill-proof keyboard, and an LCD that opens 180 degrees are all expected of our products. These are aspects that we improved further with this product while also achieving a thinner body. I believe that there are still many areas other than these where we can make a more easy to use design through incremental innovations in mechanical engineering.

Takayuki Morino holding the ThinkPad X1 Carbon


Otsuka: I'd like to make a successor to the X300.

That may have been Lenovo's goal with the original X1. But personally when I refer to a successor to the X300 I mean a conventional Classic series product with well-balanced attributes.

The X300 has a perfect balance of size and weight, despite providing expandability for the optical disk drive and battery. I'd like to make a product like that. I think that would be a product faithful to the Classic series pedigree.

In contrast, I'd compare the X1 Carbon to a Formula 1 car with leading-edge specs. It can't drive on public roads. I'd like to make the successor to the X300 a compact, all-round sports car that applies Formula 1 technology but can still drive on public roads.

The T4X0s and original X1 were actually products that utilized the technology in the X300. Now with the X1 Carbon we've moved up a step. We still have a lot of challenges ahead of us.

Ryo Otsuka holding the ThinkPad X1 Carbon