The models were HP Deskjet 5150 and Deskjet 656C.
|HP Deskjet 656C straight outta garbage.|
After all the trouble of carrying them home, I noticed they both had plastic optical guides next to the printhead pulley system. At first I was thinking "why do they need optics to guide steppers?" Then I understood the grave situation. There were no steppers. It seems that HP has found a cheaper way to get their precise printhead movement. They use DC motors with optical linear encoders to give feedback on the printhead's position.
|HP's optical guide for the printhead.|
I decided anyway I would gut the both printers for parts. I would probably be needing them for the mechanical construction.
You need a torx screwdriver set to open these things. Every screw on these seems to be a torx. I needed at least the T10, T15 and T20 to open the printers.
|My trusty screwdriver set.|
At this point I want to make it clear that opening printers is MESSY! Be prepared to get ink everywhere.
|A partially gutted HP Deskjet 5150.|
I found another optical guide on the Deskjet 5150. It's a rotary encoder that gives the printer feedback on the paper feed DC motor's position. Again they have saved on steppers.
|An optical rotary encoder.|
|The first stepper motor I found!|
I took out the stepper and googled it's model PML55L-048-HPG9. The first search result gave it's data:
Nominal voltage: 24V, Steps / revolution: 48, Step size: 7.5 degrees. Everything I need to drive it, I quess! I've never used stepper motors in my projects before...
|This one will come in handy.|
Even without google it's easy to distinguish a stepper motor from a DC motor. Stepper motors have 3-6 wires on them while DC motors have only 2. For more info on the various motor types, here's a great tutorial page: Jones on Stepping Motor Types.
So here's the conclusion: if you're looking for steppers: Deskjet 5150's got zero, 656C has one.
But the Deskjet 5150 sported something else I'm sure I'll find useful: a screw-mountable metal rod that the laser head can travel on.
|I'm planning to use this rod in the CNC build since it's got some convenient screw holes.|
OK, that's it for today! At least some progress.