HP 7000 slow printing

[issa2011]

i have hp printer 7000 its cartidge 920
after continuous printing (30 paper of A4) its become slow and finally stopped!

i try clean printhead with hot water to remove clogs ......
please if any one have any idea tell me anything that can help
*sometime used original ink sometimes refilling
after let printer for 20 minutes it will print normally again but of course in smae problem

 

[Alex Hold]

It sounds like a design fault.. is it a brand new printer? The hp 7000 should have no problem whipping out 30 pages a minute at least.