Laser Shutter Arm for Laserjet 4000/4050/4100

This is a replacement for the laser shutter arm on HP Laserjet 4000/4050/4100 and possibly the Laserjet 5000. The equivalent HP part number is RB1-8700-000CN. This is a 23 year old printer (2000) so generally only used parts are available. Luckily we have 3d printers.

It is common for this part to break resulting in blank pages. The arm is actuated by a fin on the toner cartridge. The arm presses a lever to open a dust cover on the laser scanning assembly. The laser is blocked when the lever is broken, resulting in the blank pages. My hypothesis is that it breaks if the toner cartridge is installed with too much force.

The part is located under the top cover plastics on the left side of the laser scanning assembly, #17 in the diagram. It is normally black plastic, but the replacement part is shown in blue. Check the "HP LaserJet 4000 & 4050 Series Printers Service Manual" for how to remove the top plastics. I found a PDF online pretty easily.

It wasn't too complex, four screws and some plastic clips. Pages 6-6 through 6-11 cover this.

The pivot point on the part fits into a notch on the left side of the printer. There is a hole in two plastic bosses on both sides of the pivot point which the arms slot into. Squeeze the arms inward to get the pivot point into the round part into those holes. The side of the part with the bigger horn faces the front of the printer. The back of the part goes through a slot when the toner cartridge is removed. See pictures below

Don't forget to reconnect the little arm to the right of the toner cartridge to the door like I did. The toner cartridge won't install with it in the down position. Whoops.

Print Settings

Printer: Ender 3 Pro w/ direct drive
Rafts: No
Supports: Yes, use auto supports (supports everywhere in Cura). Print in the default orientation.
Resolution: 0.16-0.2mm
Infill: Not applicable due to thickness
Shells: 2+
Material: PLA/PETG (Anything will work)