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1 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
arvidj
Mark,
Was this the "flour" you used ...
Laguna Silica, 200 Mesh in Bulk ...
I am in search of "flour" locally and need to have something as an example as "quartz flour" is getting the deer-in-the-headlights look when I ask about it.
Thanks,
Arvid
This is what I got:
Laguna Custer Feldspar in Bulk
FYI, After looking grading curves and reading the giant thread, I ended up using displacement measurement to come up with the following for a mix. I really wanted to use local aggregates wherever possible to save shipping and reduce overall cost. Empirical observation and practical considerations are the basis for the mix:
Attachment 272692
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1 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Update:
I have washed all of the aggregate and have it drying spread out on tarps. For anyone wanting to work with epoxy granite, wash, clean and dry the aggregate. I had issues on a test without doing this.
I washed it by filling 5 gallon buckets with material and then stuck a hose into it and washed it until the water cleared. The larger stones weren't bad but the decomposed granite is really dirty. Anyway, I think you need to remove the moisture out and have things clean when you go to cast.
It is taking longer than I thought to dry - I have raked it out to rotate stuff each day when I come home from work. Looking forward to casting the base this Sunday...
Attachment 273094
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
I used some fine powdered alumina which was left over from my foundary furnace build. I bought it at a local pottery shop. Unfortunately the mesh size is not stated, but it has that fine powder feel like icing sugar.
I added a little laser printer toner to the 10% epoxy test, as it make the E/G look cooler.
You have a nice grading there. I only used 5 different aggregate sizes. 12-14% resin is lot. My test peices were with 10%% and 8% epoxy, and the ten percent was easy to vibrate, but the 8% settled as well with good vibrations. The Youngs modulus of the 8% measure nearly 20% higher (on my limited, poorly controlled experiment).
The scientific papers I have browsed on the web agreed that the aggregates need to be really dry, otherwise the strength dropped something like 20-30%.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
I am shooting for a lower amount but I haven't seen the impact of the mineral flour on viscosity. Made test batches with everything else and was happy at 8%. The base is really over built so If I have a higher epoxy level, I think it will be okay and I would prefer not to have any inclusions in it.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
The jump from 8% to 10 % was significant in how quickly it sagged under vibration (I just tapped that test mould on the floor for a couple of minutes. The 8% needed the rivetting hammer on the mould. I can imagine that 14% would be very wet, and leave a thick layr of epoxy on top once it settles.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
That thick layer of epoxy that has floated to the top is called waste of money. It is the result of too much epoxy used, which, once the aggregate is fully saturrated, just floats to the top, creates a shinny flat surface that adds little to no increase in the rigidity. Sometimes it's just better to use less and work a little harder or longer and end up with little waste.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
G59
That thick layer of epoxy that has floated to the top is called waste of money. It is the result of too much epoxy used, which, once the aggregate is fully saturrated, just floats to the top, creates a shinny flat surface that adds little to no increase in the rigidity. Sometimes it's just better to use less and work a little harder or longer and end up with little waste.
Thanks for the feedback. I have 2 people coming over this morning and should be mixing and casting in a few hours...
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Please post some in-process pix! I am considering using EG as an addon to a steel I-beam build I am considering. Would love to have some of you learnings to save me some headaches!
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8 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
On to it:
First off, weight for all materials for the mill base was 737 lbs/327kg
This doesn't include the sub base which I am still working on for a design- leaning towards 1/2" thick 4" square tube welded frame...
Finished mounting 70 feet of rebar in the casting:
Attachment 273566
Attachment 273568
Next we mixed the epoxy in a five gallon bucket with a drill rotary mixer. Added the epoxy to 130lb batches of aggregate. The epoxy and hardener weighted 13lbs for 10% epoxy by weight. I went a little higher because of the mineral flour and chopped carbon I added to the mix and it seemed about perfect. It wetted out and yet left no epoxy pooled on top. Mixing:
Attachment 273570
Here is a close up of the mix:
Attachment 273572
We tamped the mix with a dirt tamping tool- basically a 8" square of steel on the end of a pole. I didn't get a pic of the tool but here is the result:
Attachment 273574
We vibrated the mold by bolting a bench grinder with an eccentric weight- this made a big difference and parts of the mix dropped as much as 3/4":
Attachment 273576
I would say definitely vibrate your molds...
After vibrating and adding more mixed aggegate, we screeded the top to provide a flat top surface:
Attachment 273578
End result was flat and I was very happy with my mix and the epoxy ratio as well as the US composite 635/slow hardener epoxy system. We had time to mix 4 batches, pack the mold and vibrate and weren't rushed. Temp was 70F/21C btw.
This what it will look like for the next 4 days during cure. I checked 3 hours later and things were warm to the touch and setting up nicely:
Attachment 273582
I read somewhere here that post cure at elevated temps by putting a box with a small heater can add to strength I will look for a box and maybe do that tomorrow. Now I just have to wait..
Thanks for looking
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Great work Mark! Can't wait to see the de-molded result :)
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
Voyager77
Great work Mark! Can't wait to see the de-molded result :)
FYI I rolled it out so it could bake in the sun (socal and all) and everything was already setup. I tapped on it and it was really solid the epoxy is already hard- still going to force myself to be patient.
I am very happy with the aggregate blend and US composite 635/slow hardener combo because I had enough time to do the pour and it seems to have cured properly
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
This looks good.
I am interested in what your final results re: mass and rigidity become.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Awesome job, thanks for updating the post!
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Nice work. I like your bench grinder vibration solution.
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1 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Update:
I came home and the slab was baked by a full day in the sun and solid, so I took a peek by removing a corner. Good news it is really tough- inadvertently smacked it a few times with sledge hammer removing the mold material and it didn't even dent, let alone crack. The 4lb sledge fairly bounced off of it. The part I removed looks good - feels and acts like a solid rock. I took a grinder to it and it grinds like a rock too- you can see that part on the upper right part of the pic.
The bad news is I didn't use enough wax or a proper mold release. Fortunately I taped the entire saddle section and all corners which are radiused and those areas are coming off easy- the flat side- not so much. I spent an hour with a chisel and crow bar with the sledge to remove the end and a little part of the long side. Any secrets to making this easier?
Attachment 273834
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Maybe a belt sander with the roughest belt you can find?
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3 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
gt40
Update:
I came home and the slab was baked by a full day in the sun and solid, so I took a peek by removing a corner. Good news it is really tough- inadvertently smacked it a few times with sledge hammer removing the mold material and it didn't even dent, let alone crack. The 4lb sledge fairly bounced off of it. The part I removed looks good - feels and acts like a solid rock. I took a grinder to it and it grinds like a rock too- you can see that part on the upper right part of the pic.
The bad news is I didn't use enough wax or a proper mold release. Fortunately I taped the entire saddle section and all corners which are radiused and those areas are coming off easy- the flat side- not so much. I spent an hour with a chisel and crow bar with the sledge to remove the end and a little part of the long side. Any secrets to making this easier?
Attachment 273834
It's just wood, no? Particle board in fact? Straight edge and cheeeeeeeeap circular saw blade. Take care of the sides in no time. Hit the epoxy/granite with wet diamond blade on a grinder after that. Watch some videos on grinding concrete countertops.
Or, soak it those areas with water, the particle board will expand and break apart leaving only that which is truly attached. At least that's what anything particle boardy around here does.
Router was my first thought. Parallel pipes/boards in the same plane as the stuck wood and shave it down to the epoxy. That's when I thought circular saw and 4" at a time is better than 1/2" per pass.
If you go with water, cut slitting groves for better penetration.
One of these
Attachment 273892
or
Attachment 273894
Maybe even
Attachment 273896
Down around the 40-60 range.
[edit]router as a planer
Joint and Thickness-Plane with a Router - YouTube
Looking at this I thought of a table with 4 legs
simple Router Planer Jig - Woodworking - YouTube
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3 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
It isn't too bad- making progress- this was done in a half an hour...
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Not sure but on the photo it looks like the bottom left did not compact very well. Are there voids in the surface?
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
Voyager77
Not sure but on the photo it looks like the bottom left did not compact very well. Are there voids in the surface?
Yeah, there are a few spots with small voids. No major inclusions though. I have gotten most of the mold off and it is pretty consistent. I made some test pieces also and it looked prettier with more epoxy but was not nearly as durable as the mix I ended up with that you can beat, drop and abuse without issue. It is a balance getting a large piece to optimum 8-10 percent epoxy levels - at 14% everything is really nice looking but not nearly as durable...
I figure I can fill in the voids with quartz flour and epoxy mix and do a final coat to make it all shiny and smooth if it still bugs me. Lessons learned are vibrate more if you can and use enough/proper mold release. We will see more after I flip it and finish the demolding. I need a crane at this point just to do that...
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4 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Update:
I was able to rent a giant hoist for cheap and flipped the base and went to work removing the mold material. I even managed to alarm the wife dangling a 700 lb block over our driveway :p
I was really concerned whether all the work to use ground steel plates and pre-drill the mounting holes for the rails would be messed up by the epoxy. Good news, rails bolted up on a test fit and without even trying, are only .0242" off over the full length before even starting- casting does not seem to move ground steel plates. I had previously aligned things with a granite surface plate between the ground steel bars. It is a lot easier to mount things before you pour...
Couple of quick pics before I clean everything up this weekend.
I am happy things fit and the alignment works. Hopefully it will start to make sense because up till now, everything has been upside down for casting purposes...
3 foot base for the linear rail:
Attachment 274196
Mill base with servo and ballscrew sub bases + rail mounts:
Attachment 274198
Test fit:
Attachment 274202
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
all can be said is well done
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Do those rails sit proud of the epoxy (just thinking it will be easier to grind or scrape)?
Nice work
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
700lb is a lot of mass. Did your vibrator still move that as the last batches were going in?
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1 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
pippin88
Do those rails sit proud of the epoxy (just thinking it will be easier to grind or scrape)?
Nice work
The ground steel bars are flush and the epoxy granite doesn't protrude. Based upon indicating the bar yesterday, I don't think I will need to scrape at all.
Here is another pic:
Attachment 274298
Quote:
Originally Posted by
RotarySMP
700lb is a lot of mass. Did your vibrator still move that as the last batches were going in?
The vibrator shook pretty strongly but I wish I had bolted at least one more to the other side. There were no significant voids on the entire piece so it worked partially. I was also trying to go for the lowest level of epoxy I could get away with. 2-4 bench grinders bolted to each side with eccentric weights would be the way I would do it next time...
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
How did you get such precise positioning of the inserts prior to the pour? I assume that was done at this point, right:
http://www.cnczone.com/forums/attach...098893&thumb=1
I would think the melamine/particle board would not provide enough stability to hold the parts in a .001" tolerance over too long a distance, is that not correct? Or did you clamp them to ground gauge blocks to keep them a precise distance apart? Or ???
Looks great, just trying to think of how to do mine...
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
mcphill
How did you get such precise positioning of the inserts prior to the pour? I assume that was done at this point, right:
http://www.cnczone.com/forums/attach...098893&thumb=1
I would think the melamine/particle board would not provide enough stability to hold the parts in a .001" tolerance over too long a distance, is that not correct? Or did you clamp them to ground gauge blocks to keep them a precise distance apart? Or ???
Looks great, just trying to think of how to do mine...
I through bolted 1 ground steel bar to the melamine board with coupling nuts and bolts. Then I used a verified square granite surface plate and aligned the other ground steel plate to that, prior to bolting.
As you might surmise from the above pic, I started loose and then moved the granite from one end to maintain the same distance from the first keeping it tight to one side. Kind of a giant heavy witness block. After I was done, you could slide the granite surface plate from one end to the other with zero gaps and both steel plates parallel as a result. Bolting the melamine to the ground steel bars every 80mm/3.14" keeps everything pretty straight and the steel bars are 3" wide. I was going to bolt precision ground stock as crossmembers to keep it aligned but after indicating the 2 bars bolted to the melamine, I didn't need to- the epoxy granite will hold everything anyway. Hope that helps
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
gt40
Hope that helps
Certainly does, thanks!
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
I forgot to mention do the alignment with the melamine on a flat surface before you tighten the steel plates down
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
How flat are the bars? Melamine is rarely flat.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
The bars are precision ground to .001" on all sides and are 1/2"x3"x36" O-1 from Starrett.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Instead of bench grinders, you could of used a couple of orbital sanders mounted to the bottom of your mold. Contrary to what most think, you don't need a large offset mass to create strong vibrations. A lot of it has to do with the frequency of the vibration.
I wish I had the time to test this out in the real world, but I would mount two palm sanders on the bottom and have them turned on the minute the epoxy is poured in. Once the mold is filled, vibrate for an additional 5 minutes and then I would run a palm sander over each side of the mold for a few more minutes.
On another note, I like the look and color of your mill's base. This is the biggest one I've seen on the forum and I hope everything turns out as you planned.
The bar stock idea seems to have worked, I'm just not sure if repeatability can be had that way.
Keep up the great work.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
ger21
How flat are the bars? Melamine is rarely flat.
With 700lbs, it's the shape of what it's sitting on.
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2 Attachment(s)
Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Update:
I got everything de-molded and was able to test fit the linear rails. I was able to indicate them parallel to 5 decimal places and about 7 thousands variance on height so the ground steel inserts worked as a design element. I will shim and grout for the final install but sweeping the full length of the ground steel bar embedded in the base measured only .007" height difference. Interestingly, my linear rail has some variance independent of this also.
Here are a couple of pics. I had only one significant void on the corner that was noteworthy and only cosmetic. The base is fully functional and bomb proof.
Attachment 274834
Attachment 274836
It was a real pain to remove all the molding material- a few moments spent with mold release would have saved hours- lessons learned. I am working on the x axis next but I will be busy with the day job for the next week...
Thanks for looking
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Hoping for an update, get any work done over the weekend?
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
mcphill
Hoping for an update, get any work done over the weekend?
I have been busy and not able to work on things - hope to do more by the weekend.
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
serpvect
Any progress?
Sorry for the lack of posts. We had a change and I am moving up to Seattle area and am getting a larger shop to boot. All busy though getting the house ready for sale so it will be a few months. Basically the base is done and I bolted the linear rails to it.
I hope to restart mid-summer...
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Re: Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build
Quote:
Originally Posted by
gt40
I am only 4 years into cnc and it is at the serious hobby stage. I want to make some 3d stuff in limited quantities in steel and I want it to be more accurate than my RF45 clone- these things are the basis for doing this build. In a perfect world, I would have Brother Speedio but as the wife won't sign off on that just yet, this is the current upgrade.
I'm not sure this machine will get you there. I think you are missing some important points. The number one point is that mass isn't everything. The first consideration is that you need securely mounted rails and frankly I'd be worried about the machine tearing out your rail mounting plates.
Quote:
As far as the design, I am trying to keep each major components at 700 lbs / 300 kg. It will also be bolted on a much larger subframe that will add considerably to the mass I expect the full mill with the subframe( still finalizing the design) will be around 2500 lbs/1130 kg. I got all my rails, thk and nsk 32mm ballscrews and basic materials for 2k so far. Add my time and spindle + electronics pneumatic draw bar and I hope to be well under 10k. I think if I can achieve this price point with the components I am using it should be a major step up from my current mill and hard to beat in terms of cutting ability, accuracy compared other mills in this price.
I am still tweaking the vertical column. 11x12x36 is the current dimensions and re enforced with large steel tube cast inside. Should be about 480lb with the steel inside. This is alot better than the 100Lb or so weight of the RF45 column but it could be bigger.
why not place the square column on the onside and machine it to mount the linear rails.
Quote:
Most important, when I finish, I will know the machine inside and out and be able to maintain and fix it if need be. Modern VMC's can be very complex and expensive to fix and there is the learning curve. I also would rather start with new stuff than learning fix someone elses mess.
To your comparison with an RF45, I am not sure how familiar you are with these machines. The column is 7x9 tapered hollow cast Iron, as is the base. I can pick up and move the column, the base or the table by myself. The whole machine is only around 800 lbs/350 kg without the motor and stand. Going from a RF45 to this build will allow me to replace dovetails with THK linear rails, 3 times the mass and the room to fit proper sized ballscrews and servos.
Again mass isn't everything. To function better the machine needs to be structurally stronger. In this regard I'm not getting good vibes about this machine.
Quote:
I am still tweaking the vertical column. 11x12x36 is the current dimensions and re-enforced with large steel tube cast inside. Should be about 480lb with the steel inside. This is alot better than the 100Lb or so weight of the RF45 column but it could be bigger.
You brought up an interesting point on the steel rails. I tested a 1/2"thick piece a foot long cast at the bottom of a box mold placed on a granite surface table. It was dimensionally unchanged. The ground steel will be through bolted to the mold and cast in a horizontal position with the epoxy granite on top in the same manner as my test. We will see for the bigger piece. I guess I will scrape or grout as needed.
For my part, the biggest thing I am trying to work out is mixing 3 - 4 cubic feet of epoxy granite per pour for each section. I have planned for a total of 25 gallons.
Thanks for the challenging questions!
Get a cement mixer!