Neo900 Stacking and Measurements

The following images show parts of the vertical stacking of Neo900, and various measurements of the geometry of N900 elements that affect this stacking. The raw data is from meshes obtained by 3D scans (repository). The measurements were taken with the "meme" mesh measurement program. MeshLab was used for 3D rendering of the mesh.

In the screenshots below, the mesh is shown in grey, with darkness indicating depth. Where the contrast is increased to better show fine structures, parts of the mesh exceeding the available range of grey tones are shown as yellow. Blue lines at the bottom and the right side are sometimes added to show the height profile along the axes of the cursor (red).


Vertical stacking

The following drawing shows part of the vertical stacking of Neo900, including the PCBs, the upper edge of the case, and the slider mechanism of the display module.

All dimensions are in millimeters. The following sections explain how the measurements used in this drawing were obtained.

Case edge height (rear side)

The following set of measurements shows the height of the case edge over the top surface (S2) of the PCB. The green measurements lines indicate the pairs of points whose Z difference is being measured.

The result is that the case edge is typically between 1.9 to 2.0 mm above the PCB surface.

Case edge height (front side)

We repeat the same measurements on the front (keyboard) side.

The case edge is typically about 2.0-2.2 mm above the PCB surface. The "step" on which the keyboard frame rests has a depth of about 1.1 to 1.2 mm and is thus roughly 1 mm above the PCB.

Case wall thickness (rear side)

For designing the side walls of the spacer frame and for calculating clearances (in the next section), we need to know the thickness of the case wall.

The measurements are between opposite points where the sensed height markedly falls off, and suggest a thickness of 1.4-1.5 mm. Given that the top of the wall is slightly curved, which can cause a drop to appear in the scan before the wall falls off in reality, some measurements are likely to be too short by up to one grid step (0.1 mm). We therefore consider the nominal wall thickness to be 1.5 mm.

PCB to case clearance (rear side)

This set of measurements shows the horizontal clearance between the PCB (LOWER) and the case. The green measurement lines show the distances being measured.

The result is that the clearance varies considerably but is never smaller than 0.5 mm.

PCB to case clearance and wall thickness (front side)

This set of measurements shows the horizontal clearance between the PCB (LOWER) and the front side of the case, and it also shows the thickness of the wall. The green measurement lines indicate the distances being measured.

We obtain an overall wall thickness of 1.5 to 1.6 mm, and a "step" width of 0.4 to 0.5 mm. The PCB is closer to the wall than on the rear side, only 0.3 to 0.4 mm.

Location of rear (button) side features, vertical clearance near wall

This set of measurements show there where features on the rear side are placed along the X axis. It also indicates the vertical distance between the top of the case wall and the most prominent rear-side features.

The first 0.5 to 0.6 mm below top of the case wall are unobstructed. Then the IR window begins, followed by the volume button with a peak at about 0.75 mm and the rest at 1.3 mm, and the camera button at about 0.9 mm.

Location of front (keyboard) side features

The following set of measurements shows where features on the front side are placed along the X axis:

The middle "hook" seems to be centered at the middle of the case. Most of these measurements are between edges that not perpendicular to the measurement direction and sometimes even rounded, and may therefore be fairly inexact.

Vertical structure of the slider

The height (or depth) of details of the metal structure of the slider mechanism is examined in the following set of measurements. Special attention is given to the height of the bends at the upper end of the slider. The measurement lines indicate the points whose heights are being compared.

The general observation is that that basic shape of this metal structure is a plane with some cut-outs into which shallow details have been stamped, and from which larger structures protrude. We can therefore measure all heights relative to this plane.

The following different features are being measured here:

Spacer on light spreader

The outlier observed above can be explained by closer examination of where the spacer touches the PCB. The following image zooms into the PCB-with-case scan we have used before, showing the lower right corner, right above the keyboard:

At this location, the spacer is not in contact with the PCB directly, but rests on the light spreader, which has a thickness of about 150 μm. One can also see that the spacer has compressed the light spreader by about 50 μm.

Slider to case clearance

In order to explore possibilities for adding stabilizing elements to the spacer frame, we need to determine the horizontal gap between case and slider mechanism. We measure this indirectly by determining the distance between the steep outer side of the display and the edge of the slider. Using the case wall thickness, the gap between slider and wall can then be calculated.

These measurements show a systematic difference to the wall thickness of 1.5 mm. This can be explained by the shape of the display case, which transitions from the plateau to the wall through a small step. This step is almost invisible in the mesh at the top edge but can be clearly seen at the bottom edge:

With the scanning equipment equipment used, such a step is difficult to measure accurately due to the conical shape of the scanning needle. Combining results from the top and the bottom edge (below), we estimate the step to have a width of about 0.4±0.1 mm.

We show distances corrected for the step width in parentheses after the original measurement. The minimum distance between slider metal and the case is thus 0.1 mm, with the gap sometimes growing to about 0.5 mm (zones A a and B) or even 0.8 mm (zone C).

The measurements also show a significant difference between the distance between slider and the outside wall of the display on the left and on the right side. We did not examine this further, but consider it possible that the difference may have been caused the 0.4 mm step entering some of the measurement while being absent from the others.

Location of slider features

The following set of measurements shows where features on the slider are are located along the X axis. While some measurements were made between points that also differ in the Y direction, we only use the X difference.

Note that, while the scan shows a clearly visible rotation in the XY plane, its effect on measurements is negligible. (E.g., the real distance between the two columns is only about 0.02% larger than its X distance.)

2016-10-26 23:39:12 UTC