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Photo printer taps micromechanics

Posted: 02 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:photo printer? PictureMate Deluxe Edition teardown? electromechanical assembly?

Epson's PictureMate Deluxe Edition printer is a toaster-sized box that prints photographs from almost any input source, easing the path to photo-lab-grade prints so winning pictures don't lie around in cold storage. The unit purchased for this teardown cost only $79 and included the printer, ink and starter pack of paper.

Unlike a general-purpose printer, the PictureMate handles only photo-grade 4 x 6-inch paper sheets (glossy or matte). Able to accept picture files from USB sources (host PC, CD-ROM, thumb drive or direct connection to a digital camera) and memory cards of all stripes, the Epson prints with appropriate control inputs to the array of buttons on the top surface. A 2.4-inch QVGA LCD screen is included for image review and the roughly 3kg design has a carrying handle for portability.

Rather than dispense ink by heated bubbling, the Epson printhead employs piezoelectric (piezo) micropumps at each nozzle in the 90 x 6 array to eject precise droplets onto paper. While some printers include a new printhead with every cartridge, the Epson printhead is intended to last the lifetime of the printer. An internal apparatus regularly cleans and wipes the printhead surface as part of normal operation. Each nozzle has a ceramic piezo element that warps on application of a control pulse, with the piezo displacement ejecting a droplet from the appropriate orifice formed in the front metal plate covering the piezo array. By controlling pulse amplitude and duration, the amount of ink dispensed can be precisely regulated. The system employs variable-sized dot dispense to trade off speed and precision, using large drops in regions of continuous color and going with finer-grained dispense in areas of detail.

A six-line fluids cable (one for each color) plumbs ink from the ink cartridge to the printhead. A pump near the cartridge creates a pressure head to fill the ink lines, exerting a squeezing force on the individual color sacks through a common bladder. The bladder pressure is provided by a peristaltic pump that is integrated into the same electromechanical assembly as the printhead cleaner.

While printhead motion covers one axis of printing, the indexing of paper from the tray through the printer provides the other. Careful coordination of printhead activity with paper transport is clearly necessary to get the interleaving of horizontal and vertical displacements perfectly aligned for band-free, void-free, continuous prints. The maximum 5,760 x 1,440dpi resolution represents a 4:1 asymmetry, probably due to disparities between the precision of vertical paper indexing and the pitch of the horizontal printhead orifices.

None of the fluidics or electromechanics can be put into action without supporting electronics. Along with reading data files from disparate sources, mapping image data to the printhead drive, controlling system motors and sensors, as well as displaying images on the LCD, the single controller board also accepts user input.

Belkin's USB Hub and dongle

Epson's PictureMate Deluxe Edition printer is a toaster-sized box that prints photographs from almost any input source
(View Epson's PictureMate Deluxe Edition printer teardown.)

The memory card reader subsystem is based on a multistandard connector block with slots for memory cards. An ASIC manufactured by NEC and branded with Epson markings (E09A568BA) provides the translation hardware to map differing physical card interfaces into a source for consistent printable data files, and also likely handles some aspects of control. A more complex Epson ASICthe E01A63BA, also made by NECis probably tasked with the image processing needed to convert a range of input picture formats and resolutions to a rasterized and printable form. Two 16Mbyte Samsung SDRAMs support the image processor, with an 8Mbyte Oki PROM used for system control code. The USB interface is also handled in this larger processing ASIC.

Other devices unique to the printer's needs include an Allegro motor control ASIC (A6628SEDT) and another Epson-branded (but Sony-manufactured) two-chip TSOP, thought to provide LCD power and clocking support.

Perhaps the most custom of all the semiconductors is the driver chip for the piezo printhead array. While the driver gets its data and commands from the image processor, it must ultimately modulate the micropumps with precision.

Parts from Linear Technology, National Semiconductor and Texas Instruments handle power management and voltage conversion, the latter for charge control of an optional, $49 Li-ion battery for portability.

Given the printer's complexity, it's doubtful the $79 purchase price tops the cost of production. Epson is almost certainly pinning its hopes for profits on the sale of consumables (ink and paper).

- David Carey
President, Portelligent




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