Looking for best rules to follow

[Artefil]

Well, as told in my bio a few days ago, I'm signing a partnership with a company in order to repair and/or refurb/recycle mainly their printers. The purpose is refurb minimum 25%, beginning with 2 shops in my area. In the next future it will grow up to nearly 20. It represents for each shop 2 to 5 printers per week.
I've repaired printers in the past having time enough for doing it, but today I'll have max 90 minutes for each. I must resend each printer with one year warranty (buyer mandatory).
I think (maybe I'm wrong) I should follow the same rules for each one. What will be your best advice, which piece will you replace or clean for each. Which rules will you follow (the more you repair the more you earn).
For example todays printers are :
MG3650S
MX475
MP620
MG5650
MG3650
MX715
MG7550
What checklist will you suggest I put in place. (Globally I have no spare parts problems) But I just have a couple of weeks determining the best way and strategy. I look forward to your suggestion.

 

[Ink stained Fingers]

I would advise you to get the service/maintenance manuals for these printers, and the resp. software tools

 

[Artefil]

Thank you for this advice, but I am rather looking for a preventive maintenance methodology that allows customers to be assured of the proper functioning of the equipment. Which parts would you change, which would you repair, which would you clean, regardless of the printer model. For example, would you always empty the waste ink tank ?
Anyway all errors will be removed and factory settings restored, firmware updated etc. That part I know.

 

[Ink stained Fingers]

to repair and/or refurb/recycle mainly their printers.

I'm not clear about your business model, prev. maintenance is not part of your original posting, that's more typical for large format printers.

 

[Artefil]

I'm sorry maybe I haven't enough explained what I'm looking for. The purpose is : the customer won't have any problem during the one year warranty. For me repairing may include prev. maintenance in order to be sure of the printer. It's what I do when I'm repairing computers. A sort of renew condition. Is it more clear ?