VBLOG 17 Test Furnace Demonstration.

Maybe i should have made a video on the why an wherefor's of the test furnace first.  Its been a while and there are new subscribers.






OBSERVATIONS

1. I should have arranged the mold to make more room for a decent pour basin.   The aluminum escaped and ran into the top of the cylinder I was pouring.
2. Need to judge pour temperature better.  I am new to casting aluminum with gas.
3. Surface could be better. But it was just a billet for machining and I did not properly blow out the mold.
4. Would like to improve how the spru connects to the runner.
5. Would like a model for the pour basin.
6. I could have poured at about 30 minutes but added more aluminum I did not need then waited too long.
7. Additional melts would be shorter.  Need to batch work.  I don't like this part.

The new flask and shank worked well if a bit difficult to lock closed.  The cobbled together cheek worked well.

The refractory in the cylinder seems to be holding up.   Will need to see how it is after extended use.

Green Sand Binders, speciffically dextrin

Optimizing the green compression strength and permeability of green sand made from Epe silica sand

Effect of varying binders (bentonite and dextrin) and water on the properties of recycled foundry sand made from silica sand mined from Ilaro Silica sand deposit in Ogun State Nigeria and have been used in several cycles for production of cast iron was examined. The used sand was washed in hot water, dried and the sieved for grain distribution. Varying bentonite and dextrin contents were added together with water to portions of the silica sand and thoroughly mixed. The moulding sand properties (permeability, green strength, compatibility, shatter index and moisture content) of the recycled foundry sand were determined. It was observed that the recycled Ilaro sand (after several cycle of usage) has grain Fineness Index (GFI) of 50 and that it can still be reused by minimum addition of binders. It was concluded that the optimum green strength and permeability for the recycled sand was achieved when 12g of bentonite, 8g of dextrin and 12cm3 of water were added to 200g of recycled sand.

I think the key here is 8 parts dextrin to 12+12+200 parts by weight.

Elsewhere I have read the ratios for such binders is .5 to .75%.   The above ratio is 3.6%. 

Currently I am having problems with edges and plan on trying to mix a small quantity of facing sand by adding dextrin in the 8/224 ratio.  Then applying this sand where I think it is needed.

Adding this tiny amount of dextrin should not significantly effect the sand in future castings.  

Placed 262 of green sand in the toaster oven to dry it out.  The dextrin will mix better in dry sand.  It will be interesting to see what the water ratio is.  Have not looked at that in a year.  Have been 'adjusting to taste'.

262g x 0.005 = 1.2g

Well that did not got well.  The new scale has a 1 gram resolution.   Need to use the little precision scale if I make another tiny batch.  But its made and it smells like dextrin.  Works and feels different.  Put it in a zip lock.

New steel cruciables

My friend dropped by on request and welded my new crucible, on the right,  that fits the test furnace.  He was also kind enough to fix the leaky one I welded some time ago.

The crate behind contains rockwool.  Its a bit nasty having spent a few years outside.  Still good enough for testing, maybe more.

Refractory on Rockwool

<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZRxN5Dki8p9aiTykoy0fUjjf-bOB20uP_b2RiDN1wIVgR6G-i61XURx2YLFjh6cV1EgB4uMX14GwEtlQhHcMQe63ciKV5nE5pKFzJ_-usD-r1oa24wFeLcGBSoDHAwk5Z8uXwB2yCkyPW/s1600/IMG_8323.JPG" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZRxN5Dki8p9aiTykoy0fUjjf-bOB20uP_b2RiDN1wIVgR6G-i61XURx2YLFjh6cV1EgB4uMX14GwEtlQhHcMQe63ciKV5nE5pKFzJ_-usD-r1oa24wFeLcGBSoDHAwk5Z8uXwB2yCkyPW/s320/IMG_8323.JPG" width="240" /></a>About a week ago I coated this sample of rockwool with my refractory.&nbsp;&nbsp; The goal is to test how well it bonds to the fibers.&nbsp; If this works maybe it will make a good hotface for ceramic blanket. Much tougher and thicker than satanite.<br />
<br />
This morning I removed the refractory on rockwool test sample from its zip lock bag.&nbsp; The bottom side is smooth from resting on the paper.<br />
<br />
Its easier to cure the concrete in a zip lock bag with a tablespoon or two of water then the larger chamber I was using.<br />
<br />
<br />

Lathe tool bit trays

Figured it would be nice to organize the carbide lathe bits.

This was made using the top from a project TV.  The material is best described as paper fiber with a wood grain veneer.  The sides are plywood.

The large tray has 49 compartments the smaller has 28.

The pockets are 0,4 inches.   The space between pockets are large enough to prevent the its from touching.

I have about 6 1/2 inch bits that will not fit.  Making the pockets large enough to accomadate them would have made them too large for the smaller 5/16".

I am not sure about the use model.  Maybe keep the larger one in a tool cabinet and the smaller near the lathe.  Will have to see what works.

Cleaned in the wood shop today.   Added a splice box behind the stationary table so I can run power to the outlet behind it.  This table has been pulled away from the wall for far too long.   Once there is power I can set it in place and pull it back out when I work on the window opening and insulate etc.

After cleaning up the table I had room on it for the small band saw.  That allowed me to get rid of the table it rested on freeing up more space.  With the wood shop and foundry in a 2 car garage it is tight in there.


Days Later:

The garage shop, woodshop/foundry, wiring is done but for one outlet and the overhead lights.  Filled in the overly large window opening I created last summer with recycled plywood from an old storage cabinet.  The rest of this wood was used to build a casting sandbox.

More cleaning.   Made a holder for the cordless drills and added a shelf below it which now hold air nailer nails and staples.

Furnace Failure again, What a day

The plan was to pour new pulleys for the master mill.  Put the cruciable in the furnace.   Started to ram up the mold then realized the flask was to shallow to do it as I wanted.  So I made a flask extension.











Then I noticed the furnace/oven was not heating.   The coil repair, weld had burned away.  It was not just the weld point but the most of the exposed wire around the weld. Hmm 



I pulled the heating elements, ceramic plates.  This time I am trying a small screw to hold the wires together.




About now I noticed one of my DIY bricks had disintegrated!  It  came out whole but was clearly comprimised.  It did not take much to crumble it.

Needless to say this was disapointing. An OH SHIT moment even!   But I realized that the brick that died was an early brick, one without lime put it as a test.  Sheesh.

This brick was a bit short and I had filled in the area above it with the mix including lime but not perlite.  It looks very sound.  In fact so much so that I am starting to think that the perlite is a bad deal.  Yeah I know it insulates.   But maybe on an electric over where you need groves for the coils it should be emitted from that layer of refractory.



I recently learned that adding larger particles to a mix reduces its fluidity.  So you need a higher ratio of cement because you need to coat these, larger particles.  So I am wondering if maybe I should up the cement ratio in my mix.  Well thats what experimenting is all about.

The UPS man delived a tub of Rutland 601.  It only needs one day to air dry.  So I maybe using that.

Foundry furnace burner.

Opted to build a naturally aspirated burner along the style of a Reil.

Tip.
I used to make PCBs and have a good number of .030" carbide drills.  It is very difficult to drill steel with these.   A small hole was drilled in a 1/8" cap.  The hole was soldered shut and drill with the PCB bit.   While not as fast a change as mig tips it is not all that hard to resize the hole.




Input flare.
Lost foam casting was used to make the flare.  Several Styrofoam cups were stacked to approximate the shape. 

 

 The casting was drilled to take the 3/4" pipe which threaded into the unthreaded drill hole.   The inside and outside shape were refined on the lathe.

The burner is running rich.  I may replace the 1/8" pipe cap with something that does not block so much air.  It is defeating the cone.

Tub Muller cylinder cut to size.

It was a bit too cold to run the lathe today so I cut down the tank I plan to use for the sand muller.  I made the sides 15" tall and the tank is 30" in diameter. 

If I mount it on the frame I have repurposed the top of the tub will be at 43".

Need to remove the legs and cut a trap door to remove the sand.  Need to research this.  Recall someone had a slide door that did not bet fouled by the sand.

The double worm reduction I found earlier.  150:1 so a 3450 RPM motor will result in 22 RPM.  Still thinking about using a garden tractor variable speed between the motor and the gearbox so I can use a 1725 motor and dial in the speed. Just thinking.

Also have the 23" x 1.5" shaft with bearings but it maybe too short.
 

Centrifugal casting

Found the part I cast a replacement for.  It is about the same fit as my version so it can be used if I finish its fabrication.

The Old

 The nose cone directs metal into the investment filled flask.  The cone on this crucible is broken off.

 I am not sure but think the bottom heat shield is always present.  But just the same its a good idea.

The New Casting

Now that I have a factory example I may try this again.    But no real need just now.

Now I need to make up something in wax to cast.  Hmmm...

Changes to the cure box Seven days to furnace!

Replaced the 250 watt aquarium heater with a light bulb.  Not sure on the wattage will have to check.  Soldered to the button on the bottom of the bulb and wrapped 12ga solid copper wire to the threads and soldered to the wire.  The metal threads would not take solder.   Dipped the base of the bulb in plati dip to insulate and water proof.     This will eventually be used in a paint locker and not immersed in water.

The wattage seems to be a good match.  Pattern is nearly at sine wave at freezing.  Outdoor temperature on the right side of the graph is over 60F.  The right hand gauge and graph below it are from a sensor sitting in the shop window.

The furnace is drying on a shelf in my office.  Has about a week to go air drying.

Looks a bit pocky but should be ok.  Need to look for an electric knife at the thrift store to make a vibrator probe to settle the refractory.  But the consistency I am using now maybe too stiff for that to work.    Something else to play with.

Need to figure out something small I to centrifigual cast in brass.  

Cast crucible cradle for centrifugal caster.

Unfortunately I overestimated for shrink between the two uprights and they are too loose.  Although far from perfect castings they would have worked other than that.

There was some shrinkage on the very center of the parts underside but it would not have effected operation.

I will hang on to these but may make a new pattern and try again.

However I have a built up a version from stainless steel sheet and mild steel bar that I most likely be using in the near term.

The built up version is preferable because the uprights can be formed/bent past 90 degrees which will cause them to grip the crucible yet flex if it expands while heating.

CBox aka Cure Box Display

Still needs a bit of touch up.  Temperatures are in C.  Week graph only has a few hours of data.