HP Designjet 750c, cutter question.

[Hansoon]

HP Designjet 750c, cutter question.

Customer replaced himself the printhead drivebelt. Since than the cutter doesn't function anymore

The printhead carriage moves too far to the right (I think) causing the cutter to be latched and unlatched at the same time. I understood it should function as follows: The printhead carriage should move to the right just under the blade spring of the cutter to latch in and pick up the cutter to drag it to the left cutting herewith the paper. After cutting, both units are moving back to the very far right thereby unlatching the blade spring of the cutter.

Question: Is the amount of travel to the right, home position of the cutter, determined by the encoding strip and sensor system in the carriage or is there a separate sensor detecting to where and how far the carriage must move to latch and unlatch the cutter respectively?

Hans

[jeff33]

Yes the cutter home position is determined by the encoder strip. On this model it is very easy to install the cutter in the wrong position, ask him to see if the cutter moves easily by hand, if not it is installed wrong and must be reinstalled or the cable for the control panel is in the wrong position not allowing the cutter to be all the way to the right.

[Hansoon]

According to customer cutter hasn't been touched.

Question again: What determines the latching / unlatching action of the cutter. The amount of how far the carriage pick up arm moves under the cutter blade spring isn't it? This distance between the latching and unlatching position is how detected? The encoding strip or a separate sensor?

If I move by hand the carriage a certain distance to the right the cutter is being picked up. If moved too far to the right it first catches and than releases immediately.

I will check tomorrow if the ribbon cable is obstructing the cutter to find its far right home position. Good tip, thanks.

Hans

[jeff33]

There is no other sensor only the encoder. I don't know of any way to change the belt without removing the cutter. You might want to make sure the encoder is clean.

[mo0651]

you may want to check if the belt teeth are in the carriage correctly. half the belt has teeth. The other half smoooth. May not get far enough over to grab cutter. Just a thought with belt replacement

[Rob Sandberg]

Please correct me if I am wrong but don't you have to remove the cutter before the carridge can be removed.
When reinstalling the cutter it needs to be place back properly. I have done it wrong before and the above problems happened.
The cutter should move freely when installed properly.
Again it has been a couple of years so I might be wrong about this.

Rob S

[Hansoon]

.
Replaced today the Carriage Ribbon Cable and everything is working fine.

Thanks for your input guys.

The only thing left is that sometimes it doesn't recognize the black cartridge (machine is using monochrome black only) switching between new and older cartridges does the trick most of the time. I cleaned already all contacts from both Cartridge holder as well as the cartridges itself but problem still occurs from time to time. This problem was there before customer started to mess himself. Any idea's

Hans

[jeff33]

Your problem is the carriage. Please explain how the trailing cable affects the cutter.
Thanks
Jeff

[Hansoon]

Please explain how the trailing cable affects the cutter.

Obviously the signal from the Encoder Strip Sensor is going through the cable to the logic of the machine. The position of the carriage is determining when the cutter is latched or unlatched.

Hans

[jeff33]

The encoder controls the position of the carriage if the trailing cable is bad you will have more problems then the cutter not latching.