I might be doing an HDU sign. How much difference is there between the differing densities? Is #30 30 lbs. per cubic foot in weight? Will 18 0r 20 lb. hold up as well over the years? Is the difference the quality finish from smaller cells? I'm accustomed to working with wood.
Posted by Dan Sawatzky (Member # 88) on :
In the heavier densities the thickness of the walls of the cells changes with the weight. 30 lb foam is 30 lbs per cubic foot. 20 weight is 20 lbs per cubic foot.
In our shop we use 30 lb most of the time and go through a ton of it regularly. Occasionally we will use 40 lb for something like a door skin that will get a lot of traffic.
Precision Board also makes a 25 lb board now that we will be giving a try soon. It feels good to the touch and may be a perfect compromise between 20 (which I don't care for) and 30 lb.
While 20 lb and 30 lb are routed at the same speeds on the CNC you will notice a big difference working it by hand. 30 lb would be like carving oak compared to cedar which would be similar to 20 lb.
If you contact the good folks at Precision Board they will send you out some samples.
-grampa dan
Posted by Joe Cieslowski (Member # 2429) on :
20 lb Duna, (Corofoam) is the best for hand carving.......closest to wood. For sign work you don't need anything harder.......IMO.
Joe
Posted by John Smith (Member # 1308) on :
hi Rick - what is the sign? are you going to sandblast or carve it? my way of thinking, it is not the HDU foam itself that suffers from UV and age, but the primer and paint itself. we are always called out to refresh paint but never for HDU deterioration (unless the top coats have been compromised). what size is it, single or double sided, and how will it be mounted ? 99% OF the signs I made were of 15-18#.
Posted by Rick Sacks (Member # 379) on :
First sign will be a shape cut around 4'x5', D/F, and painted in a dark color so it will be subject to movement from temperature. I figure on using a couple sheets of 1 1/2" glued back to back with some 1/2" plywood sandwiched inside. I'd also have some wooden blocks below the surface in the needed locations around the edges for mountings. Not yet decided whether to blast or carve...that will depend on the weather at the moment.
Posted by John Smith (Member # 1308) on :
Rick - I think that you will be comfortable with the 18-25# which would be like carving & blasting redwood, of which you are very familiar with. sandblasting will require the wire frame to simulate woodgrain: do you have one? like Dan said; the heavier you go in density, the harder it gets.
[ February 16, 2021, 03:34 PM: Message edited by: John Smith ]
Posted by Rick Sacks (Member # 379) on :
I have a wireframe. I like to be able to twist the wires in places to resemble knots. As far as brands of foam, I'll be at the mercy of the suppliers. I think there are only two major suppliers now in the SF bay area. Seems they get big and then merge into one company.
Posted by John Smith (Member # 1308) on :
when I was sandblasting HDU signs, I loved the "craftsmanship" of adding the natural elements such as knots. if it was as a one sided sign, I would use the rubber Faux Graining tools to make the back look like laminated boards with glue lines and wood grain. a trick I learned was to make the faux knots out of wire clothes hangers and solder it into shape. then, you can put that anywhere in the wire frame for knots that blend in with the blasted grain pattern. I miss the work - but I enjoy retirement better.
[ February 18, 2021, 05:55 PM: Message edited by: John Smith ]
