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.
Hi, made that sign some years ago. Cut from ColorCore Plastic, that material I also used for my office sign for >5 years w/o any yellowing or bleaching.
The inlays (orange, yellow) are made from colored acrylic.
I know I tried some glues, and one failed dramatically, the other held like welded, I do not remember what was what, would need to try again. The one was two component epoxy (I think that failed), the other was IPS Weld-On 3 Acrylic Plastic Cement ( methylene chloride), what can be used to “weld” acrylic, the latter is also available in thicker gel kind of glue.
I know there is still some room for improvement, but the sign was made very quick, and rotates in the wind above a coffee shop door now for some years, and will not be inspected by customers very closely.
Oh perfect thank you. I have some areas that I would engrave to utilize the 2 color properties of the color core, but then other areas that would just be 1 color so this looks great for those areas. Thank you!
Thanks so much for your response - your sign looks really great! I didn’t consider colored acrylic but I like how vibrant it is. Our neighborhood logo has red and yellow also, so I want them to stand out. Did you use any type of top coat or sealant? How did you align the design elements before attaching them to the backer?
The main sheet is white-brown-white, so I cut away the white layer to get to the brown, on both sides, the orange and the yellow “steam cloud” are just inlays into the cut out white layer, the door knob and the yellow curl were glued on the brown layer “freehand”
I just learned there is multilayer acrylic. I love to work with acrylic because “welding” it with the specific glue is fun. I did not try it yet, but certainly will consider it. HDPE was difficult to glue. Rowmark | DurMark
And: always cut plastic in a way that you cut chips, not let it melt.
How dos plastic melt? With high temperature. Extruded acrylic (covered with clear foil) has a lower melting point, so for CNC cutting cast acrylic (covered with brown paper stuff) is almost a must.
And consider how to get a contact between the cutter and the stock hot: rub it as long as possible, means to keep it cool have as little contact as possible for the shortest time possible.
Means: as less cutting edges as possible, “O”-flute is by far the best, the only I cut thermoplastic with. Also a v-carve with just one cutting edge would make it, I have no experience with those on plastic. So the rotation speed should be as low as possible, really ridiculously slow.
And now you have to get the heat away from the cutting site as fast as possible: the feed must be as fast as possible.
long story short: rub as little as possible on one place. Means: low speed, fast feed for thermoplastic. It is worth to spend one hour or two and one bit or two to experiment before one ruins the rather worthy plastic stock.
I have used multi layer acrylic for projects on the laser. I am not sure it would work well in the CNC unless you could find some with thicker layers. The stuff for the laser has super thin layers. I just did a project with a white surface layer then blue and then black. It looks cool.
Cullen: for me quite the opposite Works well with the CNC, and yes, you are right, the layers should not be too thin. AFAIK there are max. 3 layer multicolor sheets available for CNC (3 layers for two sided projects, 2 layers for one sided),
The multi layer acrylic is really easy to work with, but I don’t think it’s the right choice for a large “dimensional” sign. I’ve seen ¼" as the max thickness, but I can’t even find anything thicker than ⅛" now.
Have you considered PVC? It paints and glues easily.
I haven’t but just because I don’t have a lot of experience working with plastics. I was hoping for something that I wouldn’t have to paint but if the end result is nicer and lasts longer it might be the best choice. What type of glue do you use for PVC? Any exterior paint recommendations?
Super glue works, but I’d use PVC cement for an outdoor sign.
I don’t like painting either, but it takes paint really well. I use outdoor Rust-Oleum. There’s a version specifically for plastic that also provides some UV protection, but most of their exterior spray paints are good on plastics.
Note that unless you get special PVC cement which has a longer open time the stuff is fast. Touch it together and it’s done. I did a project recently using it where I used pegs to help me align the pieces so that i wouldn’t mess it up.
At least consider HDU. You will find that most professional carved/painted signs these are made from it these days. Extremely easy to work with, it will last a long time (we are repainting some where I work that are 12 years old and still in very good shape). It is a little more fragile but it cuts CLEAN!
Here are some examples I’ve done in the last couple months.
Works well with the CNC, and yes, you are right, the layers should not be too thin. AFAIK there are max. 3 layer multicolor sheets available for CNC (3 layers for two sided projects, 2 layers for one sided),
