My HP F4180 prints bad in Black almost every document

[CASC2017]

Since 3 years , my HP have printed bad my documents. They can be a .PDF, a .DOC or another extension. And I have changed the inks all this time, but the problems haven't been solved.

Here are some examples:

This is  part of a PDF

 
And this one is the original JPG/PNG of some options from an Electric Oven with its result:

What can I do now?

[Raj_05]

Hi @CASC2017,

Welcome to the HP support community.

Please help us with your HP unit serial number or the product number on a private message for further assistance.

Here is the link to find the product number:- Click here

In order to access your private messages, click the private message icon on the upper right corner of your HP Support Community profile, next to your profile Name.

Alden4

HP Support 

[CASC2017]

Thanks for your reply.

Ok, i found the serial number and sent it to you in a Private Message.