Multi-color plastic sign making

Hi all, I have done a lot of work with wood and clear acrylic on my S5 Pro, and want to branch out into cutting colored plastics and would appreciate some advice as I am having a hard time finding good info online.

I want to make a 3 or 4 colored and multi-dimensional sign for the entrance to our neighborhood. I am ok with trial and error as I work through the learning curve, but ideally I would like the final result to be something that will last ~10 years.

  • Is color core HDPE the best material for outdoor signs?
  • If I want to cut shapes/letters out of the material and attach to another sheet of HDPE acting as a backer, what is the best method to attach that will last in the elements? I have seen super glue recommended but not sure if mechanical joinery is needed as well.
  • Do I have to finish the plastic with any sort of sealant? I would like to use colored plastic so ideally I don’t have to do any painting, but I don’t know if a clear coat would help with longevity.
  • If my plan is to cut out the shapes/letters and attach to a backer, what strategies have you used to make sure the final layout is perfect? I have seen people recommend using a laser level but I am wondering if it would make more sense to (very shallow) pocket out the backer where the letters and shapes will go so everything is aligned by computer. I have tried using a level to attach wooden letters to a wooden backer and they never come out perfectly for me.

Any advice or resources would be very much appreciated!

Sorry, can’t help with the first three bullets but for the alignment question on bullet four I would do as you say, make a shallow pocket, or using dowels from the rear milled into the letters. The dowels could be short and made from the HPDE, however it would take some flipping of the letters for dowel centering to match the dowels drill into the sign face itself.

ColorCore is great but from what you describe you may want to check out color board:

I don’t think you would need any sealant. Not sure how you could bind things.