“Arctic Erosion” Table

Supplies

Total Boat Thick Set Epoxy Resin

Blue Transparent Pigment

Vacuum Pot

Vacuum Pump

Torch

Epoxy/Plastic Polish

Fine grit sandpaper (to 2000 grit)

GFRC Concrete Mix

AR Glass Fibers

Cake Fondant Tool for perfect edges

Helical Mixing Paddle

Concrete mixer

Concrete pigments

1-part concrete sealer

Black 100% Silicone Caulk

Paste Finishing Wax

‚ÄúFrom Scratch‚ÄĚ GFRC Recipes

Hopper Spray Gun (for spray-on face coat)

Air compressor (for spray gun)

 MATERIALS

Foamular

Melamine Sheet

CNC

Inventables X-Carve CNC

Spektra Compression Bit

OTHER TOOLS USED

SawStop Table Saw

Kreg Miter Sled

Fine finish miter saw blade

Melamine blade

DFM Toolworks Mini-Square

Spektra Compression Bit

Hikoki / Metabo HPT Cordless Circular Saw

Hikoki / Metabo HPT Cordless Angle Grinder

Hikoki / Metabo HPT 36V Impact Driver

Hikoki / Metabo HPT 12V Impact Driver

Hikoki / Metabo HPT Random Orbit Sander

Heat Gun

Step 1: Making the Concrete Form

A. CUT THE MELAMINE PIECES

You can use a table saw or¬†buzz saw¬†to chop¬†your pieces to size. You‚Äôll likely want¬†to regulate¬†the dimensions¬†of the table, but here is what I cut for a 48‚ÄĚx22‚ÄĚx8.5‚ÄĚ concrete slab (conveniently, ‚Äú4×8‚ÄĚ melamine sheets¬†are literally¬†49.5‚ÄĚ wide, so¬†you’ll¬†just use¬†the complete¬†width of them¬†to save lots of¬†time). Note that I only made it 8.5‚ÄĚ tall, because we‚Äôll be making a 5.5‚ÄĚ tall wood base for it¬†to take a seat¬†on.

(2x) long sides 49.5‚ÄĚx 9.25‚ÄĚ

(2x) short sides 24‚ÄĚx9.25‚ÄĚ

(1x) base 48‚ÄĚx22‚ÄĚ

B. CUT FOAM

Note: if you don‚Äôt have a CNC,¬†you’ll¬†just print out the SVG file, and use it as a template¬†to chop¬†the froth¬†pieces with a jig saw or band saw. If¬†you would like¬†to travel¬†super budget,¬†an electrical¬†turkey knife also works well for cutting foam.

I decided¬†to form¬†my very own¬†topographic shape from scratch. So, I first had¬†to make¬†a digital sketch of how I wanted the layers¬†to seem¬†. I used Affinity designer¬†to get¬†the 2D vector file of the layers, but¬†you’ll¬†use any software¬†which will¬†create SVG files, like Adobe Illustrator or Inkscape. I then imported the SVG file into Inventables Easel software. In Easel, I separated out each layer so I could cut the layers individually. I‚Äôm cutting each layer from ¬Ĺ‚ÄĚ rigid foam, so when 8 ¬Ĺ‚ÄĚ layers are stcked to¬†the froth¬†form¬†are going to be¬†4‚ÄĚ tall. Foamular¬†are often¬†cut really fast with a CNC. I did ¬ľ‚ÄĚ deep passes at about 60 inches per minute, so each layer only took¬†a couple of¬†minutes to carve on my X-Carve.

After each bit was finished on X-Carve, I used a 150 grit sanding pad to quickly sand off the tabs.
C. ASSEMBLING FORM

I attached one melamine end of the shape to the melamine base. Note that I’m getting to attach the opposite 3 sides after I’ve glued the froth to the within of the shape , which you’ll do after attaching the top .

To secure the froth , I just used some general purpose spray adhesive. I glued rock bottom piece to the shape first, then glued the layers on one-by-one, to create up the 3D foam shape. I’ve been told that heavier duty spray adhesive can cause issues with concrete forms (e.g., erosion at them). the overall purpose spray adhesive I used had many hold, and didn’t dissolve the froth , so i like to recommend sticking with it.

I then applied a couple of coats of polycrylic to the froth . This helps a touch to stop concrete from seeping into it and end in a cleaner surface. I’m told that brushing on a think layer of epoxy, and covering that in paste wax or another release agent, works better. So you would possibly try that if you are doing this, since I ended up having a good amount of froth to scrape off the concrete.

After gluing the new foam knockout, I sealed the shape by caulking the seams. I even have a process that folks seem to like for getting perfect caulk lines, so I’ll share it here. I apply a layer of paste wax to the melamine, lay down a generous line of 100% silicone caulk, and run a metal fondant ball tool over all the caulk lines. The fondant tool pushes excess caulk to the edges to go away a clean line over the seam. And, the layer of paste wax makes it easy to peel the surplus caulk away once it cures, leaving an ideal caulk line.

Step 2: Concrete Spray & Pour

I used¬†optical fiber¬†ferroconcrete¬†(or ‚ÄúGFRC‚ÄĚ for short).¬†inspect¬†my previous Instructables on GFRC concrete for more details on mixing. However, for this project I made it easier using Fishstone’s just-add-water GFRC mix.¬†you combine¬†it by adding 1 gallon of water¬†for each¬†50 lbs (one bag) of mix. For this table, I needed about 170 lbs in total (between two face coats and back coats).¬†the quantity¬†you‚Äôll use will vary¬†counting on¬†the dimensions¬†of your table, but figure 11 lbs per¬†sq ft¬†of table at 1‚ÄĚ of concrete, and you‚Äôll be good¬†to travel¬†.

A. Face Coat

The first coat is sprayed on¬†to supply¬†a ‚Äúbeauty‚ÄĚ coat or ‚Äúface‚ÄĚ coat, with no glass fibers. When mixing the face coat,¬†you would like¬†to¬†draw a bead on¬†pancake-batter consistency, but¬†it’s¬†important¬†to not¬†add¬†an excessive amount of¬†water,¬†which can¬†weaken the concrete. If the recommended amount of water isn‚Äôt enough, I add a superplasticizer¬†rather than¬†more water,¬†to urge¬†it right. If you scoop¬†the combination¬†with a trowel and hold it vertically, it should slide off the trowel, but leave a 1/8‚ÄĚ layer on the trowel ‚Ästthis suggests¬†it’ll¬†be thin but still¬†stick with¬†the edges¬†of¬†the shape¬†once you¬†spray it.

I used a hopper gun to spray the face coat, spraying corners first, then sides, then¬†the center¬†of¬†the shape¬†. I started by spraying with¬†the shape¬†oriented vertically so¬†it had been¬†easier to coat the tiered foam knockout. We then placed¬†the shape¬†horizontally on¬†the bottom¬†so I could spray¬†the remainder¬†of¬†the shape¬†.¬†you would like¬†to spray¬†during a¬†U-pattern, towards the portion of¬†the froth¬†that’s¬†already covered, to avoid sand particles¬†aged¬†the unsprayed surface.

After spraying, we brushed within the face coat with a chip brush, just to make certain there have been no trapped air bubbles.

Optional: wait until face coat firms up but¬†remains¬†damp¬†to the touch¬†, then spray second layer of face coat. If doing this, make each face coat layer no¬†quite¬†1/8″ (so 1/4″ total).

Wait for the face coat to arrange before adding backer coat. you would like it to be firm but still wet, so you cannot erupt it easily together with your finger, but it still sticks to the rear coat.

B. Hand-Packed Back Coats

The timing of your backer coat is vital , so confirm your face coat has firmed up enough (but not completely dried out), before you begin your backer coat. Usually this only takes 30-60 minutes.

You can wait until the face coat¬†is prepared¬†to start¬†mixing your back coat,¬†goodbye¬†as¬†you’ve got¬†everything measured¬†call at¬†buckets (so mixing only takes¬†a couple of¬†minutes).¬†the method¬†is analogous¬†to mixing the face coat, except you add¬†optical fiber¬†to the GFRC bag mix (between 1.0-1.5 lbs per 50 lb bag of mix). Also,¬†you would like¬†to use less water and plasticizer,¬†therefore the¬†back coat is thicker¬†and may¬†be hand packed ‚Äď it should be¬†almost like¬†playdoh or clay. (Again, see my previous instructables on GFRC for more details on the recipe and mixing process for¬†the rear¬†coat.)

I mixed one 50 lb bag at a time, and packed it in by hand, working it into the concrete¬†that’s¬†already¬†within the¬†form. To avoid slumping on the vertical surfaces, I only packed in about ¬ľ‚ÄĚ at a time. In total, we did 4 thin back coats,¬†build up¬†slowly until the concrete was ¬ĺ‚ÄĚ thick on the verticals.

Optional: After the primary layer was packed against the face coat, we added an alkali resistant (AR) glass mesh, which is formed out of an equivalent alkali resistant glass because the AR fibers within the mix. This mesh adds strength and also helps to stay slumping on the vertical surfaces to a minimum, making subsequent layers easier to pack in.

Step 3: Inner Base Support

Before flipping over the form, it was time to address the issue of how we would attach the inset base to the hollow table. Since the wood base will be inset from the edges of the table, you can‚Äôt rest it on the edges. The solution we came up with was to make inner cross pieces using construction lumber and 1‚ÄĚ steel tube.
The steel cross braces will be supported by 2×4 or 4×4 lumber. I used a miter saw to cut scrap pieces of 4×4 and 2×4 to the size (sneaking up on the size by testing the fit in place).
I then cut the steel tube to length using my angle grinder. We used a drill press to create ¬ľ‚ÄĚ holes on the bottom side of tubes, and to drill larger holes on top of the tube. The larger hole on top allows the entire ¬ľ‚ÄĚ bolt, including the ¬Ĺ‚ÄĚ head to be inserted into the tube, so it be bolted to the lumber via the smaller ¬ľ‚ÄĚ holes on the other side of the tube.

Step 4: Demolding the Concrete

I usually¬†attempt to¬†scrape of¬†the surplus¬†concrete on¬†the highest¬†edges of¬†the shape¬†at 6-9 hours after pouring, when¬†it’s¬†semi-hard, but timing didn‚Äôt¬†leave¬†it¬†this point¬†.

When we came back subsequent day, the concrete was rock hard. I started trying to wet grind with an angle grinder, but quickly realized the duster would blind us before we could finish, if I continued. So we took a few chisels and began chiseling…for over an hour. As we labored, we felt a touch like Michaelangelo’s assistants, doing the grunt work so he could come and shape certain important parts of the David.

Once most of the sting was chiseled off, I could then use the angle grinder to grind the sides perfectly level with the shape , for a clean crisp bottom table edge. Then we evacuated the shop my air cleaner did its work on the cloud .

Next it had been time to flip the shape and demold. this is often pretty simple. Just remove the drywall screws and pry the edges off.

Note that the froth stuck to the concrete a touch quite expected. i feel I should have put another layer or two of polycrylic thereon , and doubtless used some form release spray, since parts of the froth stuck to the concrete.

Step 5: Pre-Finish the Concrete

To patch some imperfections in the concrete, I used a concrete slurry coat, which is just the same GFRC mix and white pigment as the face coat. I rubbed it in by hand, using circular motions to push it into holes in the concrete.
I let the slurry cure overnight, then came back and wet sanded with 400 grit sanding pads, and rinsed the table thoroughly. I then applied an acrylic sealer to the concrete. While I will be sanding and sealing again after epoxy, pre-sealing will help prevent any overflow epoxy from bonding to the concrete, and allow it to be more easily chiseled off.

Step 6: Epoxy

Before pouring the epoxy, I applied paste wax to the concrete at the open end of the topographic cavity, then used silicone caulk and a scrap piece of melamine to seal off the top of the topographic reservoir to carry the epoxy.

For this project, I used Total Boat‚Äôs new thick set epoxy, which allows for much deeper pours. I used Fusion 360 to calculate¬†the quantity¬†of the topographical cavity ‚Äď it came¬†bent¬†be 3.1 gallons.

I started by mixing up one entire 1 and 1/3 gallon kit of thick set. This was far and away the most important amount of epoxy I ever mixed directly . I added blue transparent pigment to the epoxy, mixed thoroughly, then poured most of the epoxy back to a smaller bucket that slot in my vacuum pot.

Using the chamber will pull the bulk of the bubbles out of the epoxy, and reduce the probabilities of getting bubbles trapped in it. I’m told it isn’t necessary with thick set, but I wanted to try to to everything I could to urge clear epoxy for this project. After letting the air pump run a couple of minutes, its time for the primary pour.

After pouring and waiting¬†a couple of¬†minutes for any leftover bubbles to rise through the epoxy, I came back with a torch to pop the few bubbles that weren‚Äôt removed¬†within the¬†vacuum pot.¬†the primary¬†pour ended up being about 2.5‚ÄĚ at its deepest point,¬†and that i¬†ultimately did two more pours to fill it up, letting the epoxy cure for 12 hours between pours.

Note that the painter’s tape I wont to protect the concrete from epoxy clothed to be unnecessary. a number of the epoxy still got on the concrete. However, i used to be pleasantly surprised to seek out that, because I pre-sealed and waxed the concrete, the cured epoxy popped off really easily with a chisel, with no noticeable effect to the concrete surface.

When I removed the melamine from the top of the epoxy, I got another surprise, but this one wasn’t so pleasant. I’m unsure exactly what happened, but since the melamine only stuck within the deepest section that gets the most well liked during curing….I think the epoxy actually melted the melamine and got into its MDF core. It wasn’t chiseling off….until I discovered that I could use the warmth gun trick to melt the epoxy therefore the melamine might be removed. to form things harder , the chisel gouged the surface, which meant I had to travel back use some fast-setting epoxy to patch things up.

Step 7: Finish the Epoxy & Concrete

To finish both surfaces, I started by dry sanding the concrete and epoxy from 120 grit up to 240 grit. I then wet sanded both surfaces to 400 grit. Since 400 grit is as high as I want to go on the concrete, I paused here to apply sealer to the concrete. (Note: if you sand concrete past 400 grit, some concrete sealers don’t take as well.) I let the concrete sealer cure overnight, then returned to finish the epoxy by wet sanding up to 5000 grit, and then using a plastic polish for the final shine.

Step 8: Make the Wood Base

The base is just a simple box, inset by 3.5‚ÄĚ on the long sides, and 5‚ÄĚ at the ends. I left one side open and added two dividers so you can store magazines or books under the table. I used butt joints and assembled with glue and brad nails. After filling nail holes and plywood sides with wood filler, I used white spray paint to paint all the exposed surfaces of the base.
Here is the cut list for a 38‚ÄĚx15‚ÄĚx5.5‚ÄĚ base made from ¬ĺ‚ÄĚ plywood.
(2x) 38‚ÄĚx15‚ÄĚ ‚Äď top and bottom
(2x) 4‚ÄĚx15‚ÄĚ ‚Äď side pieces
(2x) 4‚ÄĚx 14.25‚ÄĚ middle dividers
(1x) 36.5‚ÄĚx4‚ÄĚ inset back

Step 9: ENJOY!

SOURCE —————— www.instructables.com

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