Crucibles did fine. All seemed to come with the same 'instruction card' , but each is a unique shade of lighter gray than when they arrived. So maybe same wholesaler and different potteries? Or different levels of reduction/oxidation in the smelter? Waiting on weather to not be rain or snow and some sieves to better sort-clay-temper my homemade green sand...but still hoping to pour in the next day or two using the 10# of 130 mesh Petrobond I also bought. Two of the 3 PLA 3D printed patterns got painted, all are waxed and graphite coated per Denis' notes on another thread.
In a nutshell, I got around to it...a round tuit...well, you know what I mean. Object is 4oz, 6oz with sprue and riser. Put 10.2 oz in the smallest flask. It took about 20 minutes to come up to pouring temp (no pyrometer). Used a welding helmet without the tinted glass as face shield was AWOL. Heavy boots, gloves, jacket (P-coat, go Navy), jeans. No real incidents of note other than burning the flask with the side of the crucible and the old pottery wheel table under the factory-supplied white plinth. Waited about 1/2 hour to de-flask. Picked out the worst of the burnt sand and put the rest in a jar to put back in the bag. Thanks for all of the tips! I am especially liking the combination of wax+graphite+parting dust as it played out in the Petrobond today. Once I 'fix' my green sand I will try it again and see how it goes with the same parting compounds.
First pour? Looks good! A couple of observations. First picture of the casting seems to have pores in it. Lean your burner out. What is the ingot pan made out of? If it's Teflon coated, bad juju. After burning most of my flasks, I made some sheet metal guards.
Nice job! I do think you can skip the riser. This is a thin flat casting. So, as it cools the top and bottom surfaces can easily approach each other allowing for shrinkage. Obviously, the riser did no harm. It just involves extra work finishing the casting and requires extra melted metal. On occasion such a riser can suck metal from the casting since this riser arrangement solidifies last near its center of mass. Denis Added: Thinking some more about the riser question, the one thing you might do is to enlarge the splash basin as it essentially adjoins the edge of the casting as part of the gate. Right where a gate enters a casting like this is the hottest part of the casting and the last to solidify. It is possible to get a vacuum defect right at the edge of a gate if the last spot to solidify is the junction of the gate and casting. By increasing the size of the splash basin a bit and maybe thickening the gate you can move that solidification point into the basin which will itself be acting like a riser. Then the vacuum defect can occur in the splash basin and who cares about that?
Thanks Everyone! Fish, so just reduce the propane leave the air? This one struggles a bit, pops and chugs sometimes instead of just whooshing all the time. I don't think it has the best venturi action since it only has a slide and no horn. It would be sort of ironic to cast one to fix it... The egg poacher pan was a 50 cent secondhand store gap-filler find. The two cavities I poured damaged the coating for sure, it almost looks like paint rather than 'normal' Teflon. Should I not use the pucks from those? Denis, I see your point, riser is more of a liability than an asset in this case. By thickening the gate, is that the width, depth, both? I was going to print a new version of the diamond pattern but am about 20% short on filament. So I took a saw and hot glue gun to the old one to remove the acute angles casused by the tabs and filled in the holes I caused yesterday by not being ready with pre-drilled holes for my pattern removing screws.
I guess I’d do both and just a little more than what you have which may already be adequate. At least give it a try and see how it works. With respect to leaning out your flame, the exhaust coming out of the furnace will have a yellow flame if rich and will gradually reduce in color as you lean it out. I think I would lean it out until there was no visible flame and maybe just a tweak more. Also a clean piece of metal held in a rich exhaust will soot up up. A lean exhaust will not deposit soot. Denis
Yes, it doesn't take much tweaking to get it right. A slight adjustment usually works. I produced much worse melts when starting out. Got caught up in the 'my furnace can melt a pot in X amount of time'. Everyone was talking oxidizing and reducing flames. I understand rich and lean better. The light went on when I needed extra time to check a flask before pouring,. I turned the burner way down and ended up with my best melt ever. The pucks will be fine, it's your lungs that will suffer. I use cast iron muffin/corncob pans. Just preheat to drive off the moisture after they rust up a little.
Thanks Everyone! Fish, I was hoping to find those 'corncob' pans too. Back to work today, tomorrow evening looks good weather-wise for another go. I will work the air-fuel mixture some more as suggested.
I took the casting to work and sanded it a bit on a belt sander in the machine shop at the gate and riser locations, enough to feel better about it but not enough that I'll get confused with anyone that knows what they are doing.... Both of the machinists I talked too had tried sand casting once in high school but never since. I did not have the energy to set up the furnace or pack flasks so I did the next best thing: played with even more sand. I went back through the rest of the raw sand that was either winnowed or 'screen door-ed' (approx 10 mesh) and ran it through a shiny new 40 mesh kitchen screen. Out of 24.2# I kept 14.7# and rejected as too coarse 9.5# between 10 and 40 mesh. I did a mix adding 7% clay and then 5% water to the sum of clay+sand. The clay was 1/2 calcium bentonite (southern low swell) and 1/2 sodium bentonite (western more swell). I used a sprayer and that helped me avoid the little 'tarballs' from last time but my mix still felt a little 'sticky' at the end. Last time I left the lid off the bucket with low humidity in the house and the next morning it was better.
The reason it's better is that it takes time for the clay to absorb the water. After it's sat overnight is the time to mull it to coat all the sand grains with the clay. Greensand is not a mixture of clay and sand, it's coated sand grains. If you do 50 pounds at a time without a muller, you do the 'tarp stomp'. Spread the sand on a tarp, sprinkle on the clay, spray it with water, fold the tarp over it and do a dance on it. Next day do it again and again and again.
Thanks, the new mix is already feeling better after sitting for a day. That stomping thing...like this?
Odd weather patterns this weekend. Unseasonably warm, windy, wet yesterday causing heavy condensation in the garage. Cooler drier today and still windy. Unseasonably cold tonight and for the next few days. I worked on batch #2 of sand yesterday while cleaning the garage and doing other things. We got to discussing a boat part on another forum and I decided to make 3D printed patterns based on the CAD I had proposed. I was going to do a match plate then decided to crawl before walking and made a plain 2-piece pattern with a removable riser section. The trick seems to be including some .125" (3.2mm) holes in the pattern for dowel pins and for extracting screws. I painted the PLA+ filament last night, sort of heavy and also in high humidity, and it was not fully cured when I applied the beloved #2 paste wax today. The wax started taking off the paint. I decided to push forward regardless, and wiped off the excess tainted wax and did a 'shake and bake' of graphite and patterns in a plastic bag and then rammed it in Petrobond 130 and gave it some vents as the plumbing looked tight. I also thought I'd try some sand from batch #1 as an 'open faced' mold of a diamond badge as a curiosity inspired by my ex-foundry buddy. It seemed to ram OK, maybe a little dry(?) but I got enough to keep going (furnace was already charged,melted, and waiting). I had 3D printed a horn or venturi gizmo for the air intake and added markings 0-10 (based on length of the 3 air slots) and 11 (for overkill). Furnace ran good at 6. The only time it pop-popped was lighting it with the intake set at at 10. No soot seen at several samplings. I picked up a couple of scrap stainless rods and an old file cabinet part from work to use as stirring sticks and a flask heat shield. I had calculated metal needed at 8oz and melted 11 something. Turns out I only needed 2.5oz and should have only made 5 or 6. The part discussed was bronze and I had CAD set to report as bronze so my weights were coming back nearly 4x over. How do you folks do guesstimates? Volume through experience? I poured the Petrobond flask and it filled faster than expected. I went to the open faced one and poured my glob of leftovers but it did not have enough gusto to engage the sand. All this before I figured out the metal weight error. I thought the 2 small parts were going to be rejects as I did not see the vents fill but they turned out fine. The open face was a flop, sort of a vintage weathered look. It will most likely go back in the crucible sooner than later. De-flasking the badge, top of sand was dry, bottom of sand was wet. Is this normal or an indicator of needing some mulling? I did not mull, stomp, bend, fold, mutilate, or spindle (for those old enough to remember computer punch cards ?!?) that sand. I probably should have tried the fresher worked sand from yesterday first. Very happy that I was able to go from design to metal so quickly, still need to work out bugs with green sand. Speaking of sand, my big-box store sells a bag of sand that is quite clean, flows 100% though a 40 mesh but hangs up in a 60 mesh. Is this worth trying to make into green sand or does one need finer particles and more varied particle size for good green sand? My first batch of sand is only culled at 10-15 mesh 'screen door' and ny second batch is culled at 40 mesh, both including fines not impaired by any mesh. Or am I really better off, without a muller, to use Petrobond type sands?
Fast forward to the end...here are the dogs drilled and tapped with 3/8 -16 UNC threads.. Since these are proof of concept and not for a boat this is as far as they go.
