I searched and found it but no info on chemical composition. One of the features of ceramic fiber board is that is unwetted (meaning no-adhesion) by aluminum and non-ferrous metals which is quite helpful for re-use. Is this also the case with this material? 2732°F is an impressive number for this type of material. Best, Kelly
For the main structure I used fibre board.... Then applied a thin layer of the ' Calofer' One of its components is Sodium Silicate...water glass That's all I found about it. Some cracks developed while drying so gonna apply another layer today.
Sodium Silicate explains the higher refractory. Hopefully the aluminum will not adhere to it when it freezes. I turn my cups over after extraction to let the molten metal run out. After it coolsd there is just a thin foil that can be folded inward and extrated with needle nose pliers. The "cradle" for my mid sized cup is just a piece of sheet metal bent in a U-shape that straddles the central part of the cup cavivity. The ears on the U-bend protrude above the cup so they can be grasped with pliers for extraction, though I must say, the folding handle on my large cup is very convenient. It's a good looking cup Koen. I think you'll be very happy you made it and will be very helpful for maintaining a continuous uninterupted pour. Best, Kelly
If you haven't used those materials with molten aluminum contact before, you might to try a small test peice first. If the aluminum sticks you might be able to coat it with graphite or mix graphite in with the sodium silicate for release agent.....if needed. Best, Kelly
The idea is to do a test poor anyway. I milled a brake light housing which is ideal as a test for my system. Today I made a bigger crusable.... it's the biggest size which goes in my meltingoven. The new crusable has a diameter of 16o mm and a hight of 260mm ...which increases the volume with 3.8 kg making the total amount of molten alluminium about 14kg (5.2 liters). It still needs finishing.( later this week). My vibrating table should be fine. The dieselburner is fixed too. One step at the time... Keep you posted. Koen
Hi, Did the coating today. I used a product named " joint filler" not certain its the same as the US dry wall mud but it acted as expected. I started early, (the home made apprentice was still in pyjamas). I kep the pattern mounted on the wooden stand and scooped the mud into the 6 tubes first....then filled the top. Poored the rest out in a plastic planter I borrowed from my neighbours (hard to find big cheap planters in Balen DC in december). I "scooped" as much areas as I could reach (using a soup spoon) before letting it dry for a while.....then took the pattern off and repeated the proces. The inlet sprue was coated separately. I dipped the test piece too. I'm gonna leave it to dry now for a couple of days. Meanwhile I'll make the sandbox. The idea was to make a straight box which I will tilt to get the proper angle. That way I won't need that much of sand. I was thinking of pooring the aluminium at 700°C ....is that the proper heat or do I have to make it hotter? Chat soon, Koen
Is it the non-setting type? Setting will solidify like Plaster of Paris, whereas non-setting can be stored indefinitely for later use. This was a good strategy. The coating looks good and usually looks even better when dried. Temperature and air movement will dramatically affect the rate of drying and not in a linear fashion. Don't heat the wet pattern over 100F/40C. I have a bathroom in my shop that has a heater vent and if I shut the door, it becomes a perfect drying room in the winter. At room temp, just point a small fan at the coated pattern for gentle air movement and it will also significantly improve drying. For very isolated interior features, sometimes the air may need to be directed. Almost anything will adequately dry in 2-3 days with no special care though. A conforming flask can work and has several advantages. It uses less sand as you note and also menas the mold has lower mass which makes it easier to vibrate and pack. There are some cautions. It needs to be rigid. The sand pressure can easily move large flat walls so a stiffening ribs/boards may be advised. I would provide at least 3 inches of sand between any wall of the flask and the casting. Even so, expect the wood box to get very hot. My barrel flask molder can tilt, but it's very easy to distort your pattern because of uneven sand settling. -Give this due consideration. My advice would be to construct the box with all sides attached (screws) except the longest top side, then fill and vibe/pack the mold tightly to the top with the pattern in the position of your last picture above. Strike off the sand, attach the last side, place it in the preferred position then vibrate again in the new position. Then remove the end where you will pour from, place the pouring cup, complete filling and vibe again. You will need a level surface for the cup and you need to fill sand to very near the top of the cup to prevent the metal from escaping at the interface with the sprue. The pouring height can be quite tall. You might try a dry run to see if you can manage a full crucible at that height. You can expect the pour to last 20-30 seconds. If you fill your crucible with sand it will be about the same weight as aluminum, and it will be a good test to see if you can hold it steadily for that long. If not, you might consider a "steady rest" to assist with the weight. Things are much higher risk when you have 30lbs of molten metal plus the weight of your pouring shank and crucible and it's not the time for surprises. -It pays to practice with "dry runs". You should always pour at the lowest possible temp that avoids cold shuts, but as hobby casters, and especially LF/expendable pattern casters, we get one chance and fails can be quite painful. There is always a trade off between achieving best metal quality and probability of success. Pouring hot improves probability of a fully formed casting. Of course, superheating the aluminum increases the probability of H2 porosity, especially in a fuel fired furnace. Make sure you have a very lean flame. Lost foam typically requirtes about +100F/40C pour temps compared to conventional open cavity sand casting. I'd recommend 760C for your pour. Good luck! Best, Kelly
Hi Kelly, Thanks again for the advice! Highly appreciated! I think the stuff I used is the setting type... will try to source that other one later. Gonna start eating extra portions of bacon to increase my chance on succes. As its an air intake and for my own private use I'm not bottered with the risk of some porosity...760°C it will be! Keep you posted! Koen
Here in the US it is called lightwieght joint finishing compound, or top coat. It's the finishing layer for taped gypsum/dry wall board joints. I found the ingredients that makes it light weight and easily smoothed also make it easier to coat patterns and more porus when dry. Best, Kelly
It's called "a test run" .....it was a sunny Sunday in Balen-sûr-Nethe ...so why not do it now ....can't pospone it for ever, can I? ....what could possibly wrong ? Got my vibrating table out...it's dodgy I know and will probably eat itself at some point ...hope it will behave this time .... Made a cradle for the new pooring cup And got everything going... I used ingots I made earlier so not to much dirt in the aluminium.... I put the test piece in, a brakelight housing...vibrating went ok. Pfew. At 770°C I turned off the burner and poored at 760°C aprox....as advised But then the " what the heck?"-feeling popped up. The aluminium began to cook ( bubbling) in the pooring cup. I just continued pooring....no turning back now...not too much smoke or flames. I instantly realised i did forget to bake the new cup first, like I did with the Franken-cup.... The test piece isn't big at all so the poor wasn't long nor difficult. Demolding went good, the sprew broke so I gave it a couple of minutes extra. Then dumped it in water.... I expected the mud would be baked but it was mushy ...dont know if that is normal? The surface must have been full with air bubbles ....( i did put some drops of soap in the mud) ....not the biggest problem.as most of it needs to be turned down on the lathe... So to conclude: need to bake the pooring cup and test again. The mud is probably not the correct one but as I already have dipped the big inlet in it I will have to learn to live with it .... And the big box I made for the inlet will be pretty heavy so I will need to replace the vibrating motor on the shacker. I will be forced to poor on the shakertable too as the box will be way to heavy to handle on my own.... Keep you posted, Koen.
Thank you Koen for the report from Balen-sûr-Nethe. I was once in Aachen so maybe 110km away? The lens look good in the housing, did you get the fit you wanted? You may want to try dipping the pattern in water with soap before the joint compound. The fact that the mud did not burn or bake might be a sign that is it really a non-setting type which is good. I have only done a handful of pieces, so not an expert, just excited to see your results.
Most likely caused by the Calofer not being fully cured. It looks like a lot of the Calofer came loose from the cup. It may not be up to the task. Other than the inital reaction from the cup coating, it's a good thing that there was little to no smoke/fire. -I strive for none. Your casting actually looks pretty good. I do have a spray bottle full of soapy water I apply to the pattern prior to coating to act as a surfactant. The coating viscosity and thickness can have a significantaffect on the amount of bubbles. Good luck with the pour of you manifold. Good vibe/packing will be key as well as insuring a continuous, uninterupted pour. After you initially fill the cup with molten metal, anticpate and be ready for it to rapidly take metal. The infamous lost foam "pause" gets a lot of casters. Best, Kelly
Update from Balen DC! The plan was to get the poor of the inlet manifold done before 2024....well....that didn't happen.... During the last testpoor I witnessed my funky pooring cup creating bubbles...because I had forgotten to cure it....not gonna happen twice! So I bought another fire resistant paste and started all over again. Slight uprising of stress levels when I noticed I dropped something on my foam pattern while it was laying to dry in my indoor workshop !!! Some gating was broken, a crack in one pipe and a lot of the dried slud had fell off. Restored it and tried not to think about it too much.. While the cup was drying I put the foam part into the sand ... the dodgy vibrating table didn't fell apart but I had to weld on aditional weight to get its vibrating more intense .....as suggested I vibrateded first horizontal then put the box on an angle.... By the time I got the box filled it had become a pretty heavy unit. Poor weather conditions made me decide to do the poor inside. Not ideal I know but .... I filled up my new crusable with cold aluminium to see if I was capable to fysically do a steady poor....phew! To deal with the weight of the flask I build a small plateau (out of pavement tiles 12cm) to stand on and a steady support for the cup (clamped on the sandbox). On the support I used two rounded nuts which centered the pooringcup without gripping....not gonna risk getting sloppy when I'm over there! So that being done it was time to cure the cup..... put it in the crusable and got the oven at about 950°C. (after fiddling about 3 days to get the oil burner going again) ..... eeeeek...the cup was falling apart....but the actual inside was okay and all its parts were still there....I had the option to use my Franken-cup but decided to go on with my better looking and bigger one....It had its steel cradle and would be submerged in the sand ...solid ....or not ...soon to find out... Ones the cup was in the sand I was ready to melt the aluminium..... Got it at 780°C . All went surprisingly smooth ....no smoke no flames and it took about 80% of my aluminium ...which was exactly as planned but far from expected. Demolded it and it was actually looking 98% the same as the pattern!!! Wooooheeee!!!! There is a gap in one of the tubes, actually the first tube I made on the mill...probably too thin....not centered properly when I turned it over. There are also a lot (millions) of tiny bubbles...because of surface tension... I did use the original inlet gasket to see if my shrinkage compensation of 1.5% was ok ...only 1 tube is out about 1 mm. I still have to learn a lot and I realize I was lucky on numerous occasions but overall ...pretty happy!!! Lost the pooring cup though...an offering to the gods of liquid aluminium I guess Thanks for the support and suggestions! Some pictures ....
I've broken patterns (usually gating) while dipping them due to byant forces and had to make in process repairs. It has influenced how I gate some patterns, especially larger ones. Wow, I bet the aroma will be reminder of the pour for a while. That is a good indication you had a good gating strategy and executed the pour well. Cast a small matching section and use it as a patch to TIG weld it closed. A little work with a burr and abrasive roll and you won't even know it happened. Did you wet the pattern with soapy water from a spray bottle before coating? It can be more of a challenge with thinned coatings that have high water content. Brushing the slurry/coating on the surface also breaks the surface tension. Then you can immediately reapply the coating by redipping or re-ladling. -A bit tedius for large patterns with internal surfaces. You can also brush coat in several stages if convenient, with a thicker brushable slurry. Use 1.3% not 1.5%. It's a small difference but enough to explain the 1 mm. Depends upon how much casting you plan to do, but making expendable cups from resin bound sand may also be an option.....but the ceramic fiber cups are hard to beat. That's a very challenging part to cast. I think you've done very well, especially if this is earlier in your lost foam casting experience. As you have probably learned, things become much more difficult to manage in a hobby environment as part size increases.....namely, pattern coating, mold size/weight, and molten metal management. How much does the casting with gating weigh? Congratulations on your success! Best, Kelly
Thanks Kelly, Appreciate the support! The gatingstragety is mainly yours, as temperature settings. I did learn A LOT and planning on casting more stuff in the near future....it needs a lid !! The total weight was 8 kg Keep you posted, Koen
Status update Balen DC! I'm told you guys like pictures ...soooo Lately I have been doing bits and bobs: Some milling and cleaning up the inlet manifold...getting rid off the thousands of tiny balls caused by the surface tension. I prepared 6 raw shapes ( which look like lollipops) to create rear light holder out off....dipped them in a bucket of soapy water...still used the (the wrong) mud. I also tried to learn some scanning .... The plan is to make a headlight holder which fits perfectly in the van's body .... and I started drawing the lid of the air intake (not finished) .... it will get connected to an old school air filter ( oil) by a flexible tube ... Best Koen
Thanks for the post and wonderful pictures Koen! I have a similar scanner. Sometimes it is trouble, but when it works it's pretty amazing.
I bought some Chinese magnetic reference points to stick to the body which helped A LOT. Still learning though.
I like the Grumman kurbside stepvan a lot! but I've ended up with a Ford.... which is not catastrophic at all as most of its rusty bodywork needs to be reworked anyway. This week I've been mostly busy with a headlight housing. I did scan its body to help me design the housing but in the end I just did cut a hole in the body, shoved the cilindrical styrofoam housing in to mark its edge, cut that edge and glued on the front flange.... I used "joint finisher" instead of " joint finisher" and put the piece through a soapy bath before dipping it into the mud. I needed to make a new sand box too...on a budget as always... I used a wooden pallet ...to prevent my sand leaking out I put in some plastic..... which in the end was a bad idea.. I did put in the styrofoam under an angle and used a sand cup. I left the box on the shaker.....another bad idea... On the wooden box I installed a steel bar to rest the crusable on. Could have saved aboud 4 inches in height if I just started from a flat surface instead of the pallets base. I poored at 780°C. During the poor I was to much focused on not setting fire to the box/ plastic which made me getting messy....a hessitation for a second got me a tiny error at the bottom of the flange....
