I'm getting black smudge marks on copies. After

Imaging unit is the problem. It's made for 100k but often there is a problem very soon after replacing. There is a belt in this unit and he has a lenght enough for two pages A4. Thats why you have problem on every second page. Try to reassembled it and see what is wrong inside ot imaging unit.
If you ask me...buy new mashine. This one have a hundreds of problems by default.
Pifonski

try to stop the sheet just before it enters the fuser and see if the marks are on the paper already. if not then it has to be the fuser if they are them you have another issue.

Not an expert on this brand of printers but it looks like dirty feeder rollers to me. Try cleaning them and Print a Blank document and see if the marks show up

Problem is either the cartridge or the fuser.
Put paper in the manual feed tray(tray 1)
Print something. When the paper gets 1/2 way into the printer, open the
top cover. Pull out the toner, look down at the paper.
If it has the smudge replace the toner. If no smudge, replace the fuser.

clean d parer feed rollers if not repaired then clean d pcu

Hello sir;The streak line from printing also should be from copy, because the line come from imaging unit, check the meter count if close to or over 50,000 then replace drum and drum blade, it will take care the problem.
The brother printer you need to replace imaging unit( drum unit).

OK, from the desciption i can assume several things here are some option.
If by receipt you are talking about the confirmation the unit prints the the problem is likely dirty glass.
You would also get the lines when you make a copy using the ADF.
Open the lid there are two areas of glass the thin strip is likely dirty and needs to be cleaned.

If by receipt you mean pages you receive from someone else, and not printed or copied on your machine, then their machine has the condition described above.

If everything has the lines then you have a toner or fuser problem:
This is the test to determine toner or fuser issue.
Print a test page
When you hear the paper feed into the machine open the top to stop the machine
Remove the toner cart.
You should be able to see the page with printing on it. (This is before the page hits the fuser)
If you can see the smudge or marks on the page the problem is most likely the cartridge but NOT the fuser.
If the page is clean the problem is most likely the fuser.
Hope this helps

- Try to reallign the cartridge, run a print test, after that if the issue still persist - uninstall and reinstall software - run test and re-allign again the cardtridge using software. run print test again.

Are you sure this is a Designjet 450 (large format printer) and not a Deskjet 450 (portable printer)? The following assumes you have wispy black streaking on the printed side of the paper. If the streaking is on the back side then post more details of the printer model and the issue.

In either case the most likely cause is a buildup of fibers on the underside of the printheads or carriage, causing wisps of black ink to be dragged on the paper when the carriage reverses direction. You can clean the printer as shown at the following (though the details will be somewhat different for the Designjet or Deskjet....).

Regards,
Bob Headrick, MS MVP Printing/Imaging

Can only be two things the drum or the fuser. More than likely drum they last about 4 toners i think.

Learn the art of getting a page to stop halfway threw printing, you want to stop the page after the drum has put a image on the paper but before paper has gone threw the fuser (hotbit).

Once you have mastered the position correctly by stopping the printing by opening the door and removing drum/toner cartridge, to reveal the paper that is printed but can be rubbed off, we will know if marks are coming from the drum (you will see them) or from the fuser, if print is fine.