Using a Ceramic Filter to Prescreen An Iron Pour

Denis, I haven't been there in five years, and they were not interested in shipping to me after I moved to Reno. Oakland used to have a lot of foundries, but now mostly art foundries.

 

I followed Billy's suggestion to widen the inflow to my filters so as to improve flow through them. Lo and behold it worked! I made spruies that seemed way too large and more or less square in cross section begiining as almost 1" in diameter and tapering until only 1/4" of sand held the filter down so that about 2" x 2" of filter had flow of iron more or less straight into it. The metal poured about twice as fast as prviously though I neglected (dang) to video it. That would have allowed actually measuring pour time. I know for sure that it was considerably faster.

Here are some pics of the sprues, pouring basin and splash basins and runners. The castings were free of any pits. Nice!


Here are a few pics of the 36" casting sprue and filter. Maybe it is not obvious that the square filter is the widest part of the sprue. this is the under side of the pouring basin and sprue.

This si the upright basin, filter, sprue.



The overall view of the underside


The underside of the 18" casting


By accident I postioned the pouring basin right above the blind riser.
Got lucky and the 1/4" thick top of the blind riser cavity did not collapse

The inside of the casting formed by a sodium silicate-bound core.

The top of the blind riser. It is interesting that ususally there are what appear to be blobs of molten metal that must get extruded from the riser top though cracks in the skin (I am making this up---guessing) as the riser cools and contracts.

There are going to be more filters in my future. I will be cutting generous sprues down to them to allow full use of the filter area. The filters do not slow flow very much. I poured at 2550 iummediately after innoculation of FeSi so the metal should have been quite fluid. You can see it flowed up 1/8" diameter vent holes in the blind riser of the 36. The 18 has no vents.

Side note: there was about 2-3 inches of snow on the ground as we got a surprise dump of snow yesterday.

Denis

 

Well done Denis!

I really appreciate the knowledge that you share and the quality of your work.

Excellence in everything!

Cheers Charlie

 

Gee, um thanks---slightly embarrassed.

Denis

 

It will be easier and more consistent for me to use a sprue/filter form to install a filter in my molds. So here is what I will try out in an hour or two. Will pour tomorrow.
The square portion is just a 64th or so larger than the actual filter. I've found that simply placing the filter in the recess and then pressing the sand around the recess with my thumb seems to deform the sand enough to lock the filter in place. Once set in place the cope can be inverted and the filter will not fall out of the recess and won't float in iron if it is sitting in the bottom of a pouring basin (a different configuration than the form is used for).



Denis

 

Is the white finish on that pattern lacquer? If so, what kind?

 

Stuff like that is where the 3D printer is going to come in really handy!

 

Yes, Rustoleum. On real porous stuff, like end grain or MDF, I often seal with something like cyano glue or epoxy glue as first coat. Then shellac for a coat or two and then lacquer.

Denis

 

Could be.
I used the form two days ago on a couple molds I plan to pour 3 hours from now. Worked fine for molding.

Denis.

 

It did? But I thought patterns needed to be as smooth and as slick as glass to pull cleanly! That one shows sanding marks!

Of course, that might be due to my trying to work around crumbly non-mulled sand, too...

 

But, that pattern intentionally has a ton of draft so that finishing could be as quick and crude as possible. Still, perfection is not required. Pretty good and SLICK is. Graphite rubbed into the surface helps slickness.

It probably took 10 mins to cut out the pieces on a table saw, sand the taper into the stem on a 80 grit disc sander, and cyano glue the together. A quick fillet of Bondo and it was ready to knock off the high spots and paint.

Denis

 

That's another portion - draft is usually 3 degrees or less.

Will try to get seed-slik soon. Already have the "mop" style brush.

 

These are the “tools” I use to apply graphite—-a paper towel for flat surfaces and a short bristle calligraphy brush for letters.

Be aware that Slip Plate sells pure graphite as well as mixed products with similar appearing labels. Just be careful which you order. I almost got caught on that.

Denis

 

Ordered graphite. Made sure it was the right stuff, like in the picture.

 

Just a note on a refinement I made to the sprue form shown above. I trimmed it just a hair so that the largest dimension of the base of the form just equals the filter dimension. Since the form has draft, the filter now snugs into place without any pressing of nearby sand. It slides in just right to hold itself in place firmly enough so that it does not fall out due to gravity. This feels like the ideal fit.

Denis

 

We just had a shoulder that held it in place. About what you are describing I think. Sounds like you about have it down pat. Nice!

 

I use a shoulder in the drag to support the filter. But I place the filter in the cope. So, while positioning the cope on the drag something has to hold the filter against gravity. The snug but not tight fit does just that.

Your advice on sprue shape etc. has helped me get this dialed in fairly well now.

Denis

 

Here was todays pour using filters in each mold. They do not imnhibit flow rate significantly as I throttled the pour somewhat by decreasing the size of runners I used previously. The prior pour was quite a bit faster (uncomfortably so) as I overcompensated for imagined inhibition from the filters. Once I did what Billy suggested and allowed the metal to "see" the entire area of the filter, it flowed through just fine.

Here is a video of today's pour. the first mold takes 37 pounds of iron and poured in about 15 seconds---probably about as fast as I can comfortably pour. The second takes 10 seconds for 25 pounds. The temp was 2580F as I lifted the crucible out of the furnace. The commentary was extemporaneous as a couple neighbors stopped by and I tried to give them an idea what was going on and why.

I'll open the molds in the morning.



Denis

 

Too cool! I love your setup! I am working on my setup very very slowly...my first priority was to prove out my furnace and this weekend I poured aluminum and brass. Took me about four melts to pour a brass bell but I finally figured out how to tell when the brass is about hot enough.LOL I may be able to get up to cast iron with this furnace but it sure does eat the propane. I think I will be working on an oil drip burner soon. I have gathered enough sources for free fuel to keep it running...and should be able to do some building this week and experiment this weekend. Let us see how those turned out....looks like they poured well.