Color shift issue. Need help ASAP

[krimol]

This is a problem I've had since I've owned my machine.I have a Roland VP540i. I'm using 3M 180. I have a 4 color design. This is a repeat customer (my best customer) and everytime they get new trucks in I go to print using the same material, same profile, same everything and the gray comes out different every time. I have to spend hours tweaking the color to match the original, then change the file to the new colors. Today, I spent several hours doing that. I got a gray the was "close enough" , changed the design file to the new gray and printed it and it was noticeably differerent. I then reprinted the test print again and it was different from the first test. So I have 3 different grays: the first test print, the file print and the second test print. Nothing has changed... same roll of material, same temperature in the room, same profile. I double checked everything. I'm at my wits end. Please help.

It's more noticeable in real life than it is in the picture, but you can see the difference

 

[Solventinkjet]

Due to many factors, printers will drift in color over time. There's a process called, "linearization," that allows you to bring it back it's original state but that requires a spectrophotometer. I've even seen two of the exact same model printer, in the same room, installed on the same day, same file and media etc. and they printed different colors.