Large Scale Central

Foam board engraving

Precision Board is a very high density urethane foam material used for signage. It’s usually cut with a router, but is also touted for lasering. Basic engraved linework seems to be straightforward enough: you set the power lower and / or the speed higher to get the penetration you want. This is what I did with shingles and wood grain with acrylic, and the process seems similar with PB.

The thing I’ve been wanting to understand though is how to get different depths in the surface. I got a small sample last week for testing. Yesterday I read a little, did a simple test pattern in CAD, made a JPG of the image, and imported it to the laser software. Without much effort. this is what resulted.

In a nutshell, the laser software I use (RDWorks) has vector and raster modes. In raster (they call it “scan”) the software interprets the image’s darkness with power level. So lighter areas are shallower. I was pretty excited to see something come out. But I also noticed that the effect isn’t linear. As you can see, the really shallow passes don’t do much. But then a certain power threshold breaks through and eats deeply. I suspect the surface of the PB is a little tougher / denser, causing this effect. No big deal though.

In the above test, I blended the raster jpg with a vector line drawing of the borders. That way, after the depth-cutting was done, the vector linework layer (set to high power / slow speed) kicked in, and cut the material. That took 2 passes though, because of the thickness. But this mixing & overlaying of files was difficult, even in this simple test. Complicated buildings, with cuts and deepened areas, would be a pain to register.

However, I noticed something interesting in the software settings: that you set your resolution in terms of density of laser passes. Like, if you set the density to .12mm, that’s the distance between passes. So I figured, why not make a hatch pattern in CAD that has the right line density? That way, all the graphic commands can be done in the same CAD vector file, without messing with JPG’s and all that. Here’s the first test I did like that.

The upper left two boxes were done with a simple cross-hatch in CAD: .005 & .010 spacing, set to power & speed as noted. And it came out just like the jpg (raster) areas in the other 6 boxes.

So that was exciting. I ran a few more tests, to judge the differing effects of speed, power and nozzle gap from the material surface.

This one was all vector file (lines in CAD), comparing power / speed.

You can see the lines in the foam.

I mainly need a couple of depths, just to give some sense of texture. And from these tests, that seems quite workable. These cuts are about 3/32 and 3/16 deep.

Why is this making me hungry?

===:>Cliffy

Cliff
You are a WHOLE lot more technical type of a guy than I am. I am a guy that tries something to see
if it works if so I seldom try something different. The lap siding effect I do the table saw.
Dado head at 5/16" wide, angle the head at 12 degrees, and move the fence a 1/4" at a time.
Very clean results and 50 times quicker than the laser, and very easy and very clean.
When I want to raster to a lower level like my doors, I just run that area 1st, and second, if needed deeper. The raster does leave a little fuzzy surface, a small wire brush removes the fuzz very
quickly, and easy.
Food for thought, when doing multiple layers, you may want to adjust your focus to the area of your surface.
When vectoring set your focus at 1/4" deep, That will help to either speed up the cut or may
allow to cut in 1 pass.
With the above said, please carry on with your experimentation, you have very great ways in details, I might learn something new that works better.
Dennis

Untitled by Dennis Rayon, on Flickr

Untitled by Dennis Rayon, on Flickr

Untitled by Dennis Rayon, on Flickr

Untitled by Dennis Rayon, on Flickr

Untitled by Dennis Rayon, on Flickr

Before the sign

Untitled by Dennis Rayon, on Flickr

After the sign

Untitled by Dennis Rayon, on Flickr

These are just a few of the things that I have done with the PB

Not sure Cliff if this helps, but I am very happy with the results with PB and the laser

Dennis

Oh Cliff

I laser everything at 200DPI, speeds everything up a bunch

Dennis

Thanks Dennis for those photos of your fantastic work. Some of it I know of from your threads, but now after experimenting some I’m armed with a better appreciation, and better questions.

Your suggestion of putting the head 1/4" against the foam is interesting; I’ll sure try that.

'll have to look for a DPI setting…

How were you registering your deepened raster areas with your vector scribes & cuts? Still in CAD, or…?

On that last photo, you were hand-gouging the foundation stones, right? And hand-scratching your wood grain maybe?

Are you using 1/2 or 3/4 PB?

For your overlaid brick trim around doors & windows, is that another thickness of 1/2"? And what cement do you use for that?

Thanks again Dennis! Great work!!

[I confess: I keep having more questions and re-editing this]

Cliff

I use 1/2" thick.

the brick around the window and door was 1/4" thick I sawed with band saw. then lasered.

My lasers are run by Engravelab, i set the heat and speed through it.

The depth of cut is based where I set it.

I use a wire brush in a dremel for the stones, the laser made the motar lines

wood grain is made with a hand wire brush, fairly stiff bristle

i use another smaller wire brush for lighter detail

Thanks for that information Dennis, I own you one.

Well, I owe you a whole lot more, not sure what the tally is!

But thanks again my friend, that helps a lot.

Cliff

You had asked about glue, Titebond 3 with headless pins, I use pins a lot.

All the corners have pins going in both on a 45-degree cut, holds everything for the glue to dry.

The pins hold more than most people think they do.

Dennis

Thanks Dennis, that’s great to know. I’ll do the same.

Been following along with interest. I don’t have access to a CNC Laser, but I do have limited access to a CNC Router. The detail I wanted in the brickwork for my Mik 2019 entry McGillicuddy’s supply, was just too much to do by hand. I’ve discussed it with our router guru and the issue will be locating bits fine enough for the grout lines. The laser engraving looks promising.

There are plenty of fine bits, that could be adapted …

https://www.riogrande.com/category/tools-and-equipment/burs-and-drills/burs

Scroll through for sizes and shapes.

Right, or Dremel bits even, if the router could accept 1/8" shanks.

Thanks John - I will check that source out. I believe due to rotational speeds they need to be certified by the machine maker: Gerber.

and Cliff… Nah - needs to be 1/4" shank.

I just checked Gerber’s bit catalog and they have standard bits in diameters as small as 1/16 which I think is a little heavy for brick mortar lines. They have engraving bits that go much smaller - just need to see how they work in th HDU foam.

I did a cnc router for my first couple buildings, I used 1/8" shank, not sure but i think I used .040 diameter cutter. Did a good job, I prefer the laser just because it is easier in the

all around performance and variety. But if i did not have a laser I would cnc router all of what I would want.

Have fun is the key.

Dennis

I did some more experimenting today, using an alternative to Precision Board called SignFoam. I’m trying to get proper samples to play with, but I’ve been sent 3 artsy samples like this.

These are 3/8" thick, CNC routed. Notice how fine their engraving is, at least as thin as 1/32.

The reason I’m interested is that this is more easily gotten for me, with free shipping (from Harbor Sales). They don’t like to deliver to residences, so I might have to meet the driver in some parking lot. But that’s a lot better than the high costs I was quoted for PB (139 per 4x8 sheet, 1/2", 15 lb; plus $259 shipping, plus tax). Harbor sales price for same in Signfoam: $129 per sheet, free delivery, no sales tax.

I decided to use these small SF samples for some testing today. I wanted to check the flame-retardancy (they claim self-extinguishing), and see how it took to engraving bricks & grain. Also nozzle distances, and more on the effects of speed and power settings, like Dennis suggested.

It seems to do just as well as Precision Board, with one difference: there wasn’t that surface layer that was hard to break through (but maybe that was an older PB sample, who knows).

My fave was this one, ran with a 1/2" gap from nozzle to material.

Of course, the effects can be easily lessened (this grain is too deep). But the mortar lines are really crisp, 1/32 wide and and 1/32 (lower far corner) to 1/16 (upper far corner) deep.

I’m relieved it didn’t want to cat fire (I really tried to light it, but it wouldn’t take). So Signfoam and Precision Board seem to be safe in this regard. BUT, other brands of HDU board WILL torch right up. I tried this with Corafoam and Jasper. Those cannot be used with lasers; but they’re cheaper though, and can be routed and used outside.

One issue with painting Signfoam is proper priming to close the cells. In our shop it takes 2-3 coats of a specialized primer (don’t have details at home). With that in mind, exaggerated cuts may be best as the primer will fill them in a bunch. The primer could stand in for mortar if the brick faces are then painted with a pad or very fine roller.

Jon, is Signfoam any worse than Precision Board in that regard? I’m looking at samples of the two, they seem optically identical in regards to porosity, with SF looking less so.

Thanks for the width / paint buildup tip!

Jon Radder said:

One issue with painting Signfoam is proper priming to close the cells. In our shop it takes 2-3 coats of a specialized primer (don’t have details at home). With that in mind, exaggerated cuts may be best as the primer will fill them in a bunch. The primer could stand in for mortar if the brick faces are then painted with a pad or very fine roller.

Honestly I think it’s called Sign Prime (hehehe) seriously though

I’m not certain. We work with a couple of different suppliers of HDU foam board and buy whatever is least expensive on any given day. I have not seen (that I recall) the brand name Precision Board on any. Is it more green? We do occasionally get a greenish one that seems to be a finer foam.

I guess what I am trying to say is that before you lock in your settings; try painting your samples and see where it goes. A standard acrylic primer like 123Plus should work for you.

Rooster ’ said:

Jon Radder said:

One issue with painting Signfoam is proper priming to close the cells. In our shop it takes 2-3 coats of a specialized primer (don’t have details at home). With that in mind, exaggerated cuts may be best as the primer will fill them in a bunch. The primer could stand in for mortar if the brick faces are then painted with a pad or very fine roller.

Honestly I think it’s called Sign Prime (hehehe) seriously though

It might be in your part of PA. The one we get is a regional product mixed up by a cottage industry sign carver. It has no MSDS and no ingredients listed on the can. The first time I used it I wasn’t sure what to thin it with so I experimented with everything and found it to be water based. Label says DO NOT THIN, but it was too thick to get through my HVLP gun with a 2mm tip!