CNC Foam Reliefs for Insulation and Decoration

Our boat is to be a work boat and industrial by function, but its also our home and we want it to reflect our sense of beauty and comfort. The majority of the cruising boats we have seen follow a uniform decor guideline similar to homes in a homeowner community.  We want something difference, which is part of the reason a junk sailboat appealed to us.  We also have no fascination with any particular style or culture.  Our little house and its decor is a blend of Columbian, Mexican, African and our boat will be a blend of the things we like as well.  So the plan is to exploit our CNC table toward that end. We plan to spray the interior of the hull and pilot house with the traditional insulating foam, and then add in metal, wood or fiberglass fixtures. The fixtures will be trimmed with CNC cut foam.  Any remaining wall spaces and all of the ceiling will be covered with CNC carved foam reliefs.  To protect the surface of the foam, we can coat it with epoxy, StyroSafe or StyroShield or StyroSpray 1000 Examples of StyroSpray   It runs $120 for 2 gallons.  Two coats on a 4×8 sheet will cost about $18.

We did some testing with StyroSpray 1000 and found it to be a good adhesive and sealer for the exterior.  It would take a lot of time to apply sufficient coats, but it would make a durable exterior coating.  However it would be too long of a process to add sufficient coats in order to allow it to be machined.

Shop Bot Carving

Shop Bot Carving

“Styrospray can be sprayed with a regular hopper gun (spray the inside of your hopper with furniture wax first) or it can be brushed on and is available from Industrial Polymers. I use epoxies in various forms, depending on the application and have found this to be the best when preserving detail. I use what stucco guys call “browncoat” very often. This gives a hard but “elastomeric” finish to the foam. It can be sprayed on repeatedly, and can be carved, sanded and detailed. There are other coatings like Vanillacryl which are water based and do a nice job where constant handling is not a problem. Use Enerfoam spray glue system to glue up your pieces.” — Darrell Blanton, ( ShopBot forum: )  Vanillacryl and it’s replacement: “Foam Coat”

Example wire frame for carving

Example wire frame for carving

Styrene foam billets were also on the shopping list in order to make a large gunnel for our dingy that will at as flotation and a bumper. An old dock laying out in a field provided 360 cubic feet of styrene foam billet for $50.  It’s rough but a hand saw and a wire cutter will clean it up.

STL files can be imported into CAM for the tool path generation.  Larger carvings using try a 1/8″ ball end. Polygons should be no larger than 0.05″.

Foam Suppliers

$50 for plenty of used foam

$50 for plenty of used foam

Universal Construction Foam
HIGHLOAD 60, 60 psi @ 5% Compression 2″ or 3″
Trymer 3000 Green – 4’x8’x6″ is $528!  🙁
Flying Foam  Good explanation of Foam Types
Fiber Glass, Foam:
Diversified Foam Products  Selection Guide  CertiFoam 60

Clamping it Down

We use a vacuum table, but this is a great idea from Scott for clamping down your work piece. These are called “blind nuts” and the local hardware store will have them if they are worth their salt.

CNC Router for 3D Relief Carving

Good Explanation:

1.  3D CAD Model
2.  3D CAM Cut Path Software generates a Part File – PartWorks 3D $795 – Cut3D $299
or  ArtCAM Pro — Interprets 3D from grayscale.

Some of Our CNC Router Work


Routing Acrylic

#20 Chain Sprockets

#20 Chain Sprockets

For good quality cuts use a 3/8″ or 1/4″ diameter bit.  If a smaller tool is required then use one with a single spiral flute. As a rule of thumb, the following feed rates are good starting points if the goal is optimum edge finish. A constant spindle speed of 18,000 rpm and a depth of cut equal to the cutter diameter is assumed.

1/8” Diameter Tooling: 75-100 ipm
1/4” Diameter Tooling: 100-200 ipm
3/8” Diameter Tooling: 125 ipm to 250 ipm
1/2” Diameter Tooling: 150 ipm to 300 ipm

These are a sprockets routed from 1/8″ thick Plexiglas (acrylic).  The software used to design the sprockets was Sprocketeer 2.0 from ..and it’s FREE!


Our router is a Porter Cable Model 7518, and it draws 15 amps at 120v.

Supplies — Bits and precision Porter Cable collets.   — Router bits for plastic:    — Affordable ball mill bits

3D Laser Scanner  $2500 $250 Scan Software + $20 Green Line Laser + $80 1224×768 USB Camera Stitch Software (free)