Front- or Rear Service for DLP Rear Projection Videowall Cubes?

Some manufacturer of large video cubes promote front access systems, where you can open the cube screen from the front, but is this really a good solution?

Large screen systems that have rear access for service and maintenance have fixed screens and therefore a maximal gap of 0.68-0.8 mm between the individual modules (this gap is necessary to allow for temperature-caused variations of the materials). Frontal maintenance requires movable screens. This mobility of the screens is only possible with wider gaps between the cubes. The width of the gap between two front-maintenance cubes is up to 2 mm, so we cannot talk of a „seamless" video wall anymore. The distance from pixel to pixel can be up to 1 mm with conventional rear maintenance-access, and this gap can be up to 2 mm with front-maintenance cubes (pixel to pixel).

Mechanical Reliability (Limitations)
Since the screen frame has to be moved for service and maintenance works, it must be guaranteed that its construction and installation is done in a very stable and accurate manner. Repeated opening and closing of a low-quality construction will lead to maladjustments of the screens, which will result in a loss of sharpness for the entire video wall. Already, variations in distance of only a few tenths of a millimeter can affect the sharpness of the entire system. Maintenance (exceptions with front-maintenance access):

The service staff has to stand in front of the video wall to do their work. This means they have to stand directly in the view of the people who are watching the video wall, so the operation of the entire wall is disturbed for a while.
Video walls with rear-access for service works can be repaired while the wall is in normal operation, except for the cube being repaired.

Advantages
Saves space, no space for service and maintenance work behind the video wall required.
No rail-system needed, which compensates for the higher price of the cubes.
Electronic geometry adjustments with remote control or keyboard.

Disadvantages
Wider gap between the cubes, up to 2 mm instead of 0.68 mm with conventional cubes.
Difficult to service in operation, service staff disturbs the view on the video wall.

Danger of damages and scratches that may happen to the screens of larger video walls, if the screens are not handled with adequate care.
Servicing larger walls may require the use a scaffolding or an elevating platform, which leads to higher costs.

Even though eyevis prefers rear maintenance systems, frontal-maintenance systems are available for some of the rear projection cubes. eyevis has always given special attention to important matters such as the mechanical stability and accuracy of its products. This guarantees that there are no image distortions with eyevis frontal-maintenance solutions when they are appropriately handled. In order to have the same minimal gap as with rear-maintenance systems, eyevis developed rail systems for their entire cube range. The purpose of the rail system is the possibility to mount the video wall directly in front of the wall of the building. For service and maintenance works, the rails simply have to be fixed to the basement, in order to drive the wall back and forth. The basement is made of a distortion-free steel frame with linear driving ability. The mechanism of the rail system allows the cube wall to drive back and forth without any tilting. There is no readjustment of the cube wall necessary after the movement. The large screen wall can be locked in end position.