My muller build

[Jammer]

That's the best design, you can have one pattern for all 4 sides or you can make another pattern longer or shorter for a rectangle flask. You could even drill holes in the side panels and rebolt the to a smaller flask.

[dallen]

As we all know I have been in the process of building a muller that is suppose to mix and mull petrobond sand, and I have aquired all the needed materials to mix said sand. Only I haven't finished the muller yet, I'm close to that objective now thou with the arrival of the two bearings that I ordered from some Aggriculture outfit that sells tractor parts. What I ordered were to Planter Wheel bearings, I found this info on another thread over on the Alloy Avenue site, guy in Ole Miss is building a muller similiar to mine or I'm building one similiar to his and we're both building similiar to Steve Chastains which I think is way over built.
Anyway I got the bearings and they were a lot smaller in diameter than I thought that they would be. so I grabed up a hunk of 2 inch round bar and went to work with the lathe and turned out a bushing that was wrong on both inside and outside, so I made another one and got it right on that one, had to drive the damn thing into the center hole in the gear that I'm using for a wheel with a sledge hammer, then had to give the bearing a little help with the persuader but it went into the hub, I got every thing in the muller wheel hooked up and damn made the arm too long so I started whacking on it with the torch and made a nice angled offset in it and welded it back together, it needs a spring load on it to keep the wheel pushed down, but it got dark on me and I have to go to Joplin Mo. tomorrow to a job Plant got hit with Lighting, so this is gonna be a fun one.

Anyway I didn't take pictures and I probably didn't get the mix right but it damn sure rams up nice and its nice and pretty like Oklahoma Red Dirt. Its about like the stuff Harry sent me as a sample. I throwed in almost a whole 80 Lb bag of silica sand, probably a third of the powder that I originally ordered from Retco, and a third of abottle of catilayist. and about 6 ounces of Non /Detergent motor oil.

I have a pattern that a friend loaned me some time back to pratice with when I first got started in this and I always had trouble with the sand tearing when I would pull the pattern I rammed it up with what I had mixed up and pulled the pattern it was the prettiest that I had ever pulled this pattern, I mean it pulled clean and with very little tearing, what there was was mostly due to the pattern loosing some of the water putty that was used as a fillet material where it had cracked and falled off.

I'm sorry about there not being any pictures but I will as soon as I get back from joplin, I will do up a video after I fix a couple of items that need taking care of on the muller, 1. and hold down spring, 2, center the drive shaft in the tub, its off about a 1/4 inch one way, 3, fix a scraper/plow on the center tube to throw the sand away from it into the wheel, the wheel is working beautiful its trying to run forward but because of the position its at it smears the sand across the bottom of the tub at the same time as trying to roll forward.

I gotta get in the sack so I will catch back up in a day or two, any questions, thoughts, derogatory remarks, funny jokes, post em I'll try to answer em, but at the moment it looks like I have a muller that will mix petrobond or oil bonded sand with a capacity of some where around a hundred pounds per batch, and the 1 Horse Power drive doesn't back up from it either.

David

[4cylndrfury]

I remember the first pattern I ever pulled in my kbond oil sand, it BLEW MY MIND!!!! It really is a beautiful thing when you see that perfectly shaped void left in the sand....awesome. Looking forward to seeing some pics and vids of your muller, been a long time coming. Good luck on your trip, get back in one piece!

[Harry]

My experience is much the same with the first mold made up with petrobond, it was just so far above anything else I had been able to achieve. I have seen posts by lots of people who get good results with greensand but it simply wasnt for me. Sounds like you muller is working great and that 100 lb batch size is great, my little mixer is about 40 to 50 lbs.

Will look forward to the pictures and your resulting casting. Take care out there in the heat.

[dallen]

its not the heat out on the job but the one arm bandits in the hotel that I gotta worry about, I am about to the point that if one more customer puts me in a casino again I think I'll choke, I already got enough vices to get rid of my money I don't need any more.

Yea it was pretty good feeling after all the work I put in on the thing, to finally get the wheel in it and see it mix what I built it for. I guess I should of weighed the sand an powder but I have found that with greensand that the ratio's don't have to be carved in the side of a flask to work, its more like what does the caster like. I know one guy that he was telling me that my greensand was too dry, but to me it was fine, the way I liked it. They thing that really blew my mind was how little oil I put in, I only poured in about 6 ounces out of a quart. The sand didn't have the gummy feel of the sample that you sent, but it rammed up good. Of course I was handling the sand right then at the mixer, it hadn't had anytime to stabalize so I'm hoping that I will see a differance in it when I get home tomorrow after noon. I am going to ram up a couple of small molds to clean the muller out so I can do some finish up work on it, have to get a plow in to throw the mix away from the drive tube, plus I have to try and flip the thing upside down so I can center the drive tube, so the outside scrapper will do a better job. and I need something to clean the outside bottom corner, of course that corner once full of blended sand will actually be fine.

Just glad that its coming together and working so I can move on to other project, and that the choices I made in building it are working out, without having to go back and use a lot of higher dollar bearings and such.

One of the first casting jobs is going to be to make a new casted wheel arm casted with Cast Iron, so I can get rid of the one I throwed together and butchered last night.

[Harry]

I am surprised less than half a quart even wetted up 100 lbs, most of what I have seen was 2 quarts for 100 lbs. Like you said though, if it works for you then great. I have cut the IFSCO sand about 50/50 with plain sand trying to get it to sieve through a riddle better thinking I could use it as a facing. It seemed to be less sticky but also did not have as much strength, that may or may not matter depending on the pattern and size of the flask. My 15" flask is only 3 1/2" thick and using the block of wood behind the sand as I have been doing it leaves just over 2" of sand. I have had a few drop out on me when closing a mold especially if I take too long lining up pins but I have to say I am impressed on how well that large of a span holds up in general.

[dallen]

I have been all evening trying to get this uploaded and posted here so you guys can see my muller in Action. After taking this video I did some changing to the scraper that runs against the outer tub, and I quickly added another one on the center drive tube its just a piece of a Brush Hog Blade that I welded onto the hub. and from the looks of things I am going to have to add one that will run on the wheel to keep the face clean, what builds up on the out side of the wheel seems to get popped loose after so much sticks that it starts over again. vicious cycle you know.

What you see in the tube is what I shook out of a flask that I poured this morning, sorry for the picxelling of the video guess my camera can't keep up with this thing when it starts. Which reminds me I have to get some kind of a start stop switch on this thing so I can stop pluging it in to turn it on. I have a Hundred Amp starter that I took off of a asphalt plant guess I could wire it up to the 1 HP motor, the starter is worth more then what I have tied up in the muller.

I didn't take any video of the drive setup, I think that we have all seen at one time or another a V-Belt and Chain Drive in motion.

Any Questions feel free to ask, I may not have the right answer but I bet I can come up with one.

[dallen]

Sorry no casting today, been too damn hot. I did do some finishup work on the muller though.
For one thing I was able to find a disconnect switch that I could use for an on/off (not to code)switch but then I don't think the inspector will drop by.
I went downtown was hunting for oil that was compatable with the petrobond recipe, didn't find that but got enough Meythal Alcohal to get my truck and motorcycle really drunk if I want to dump it in the gas tanks, its one of the Chemicals that is used for a Catalyst.
Sorry got off on a differant coon hunt there for a minute. and found this article that I am Quoting

The present invention is related to formulations and methods of use of foundry facing and system sand. More particularly a facing sand composition is provided for the retention of casting detail and reduction in casting defects.

BACKGROUND OF THE INVENTION

The conventional process of sand casting is simply one of forming a hollow mold of a composition of sand and an oil binder and filling it with molten material. A typical casting material is bronze. The binder enables the sand to be molded and to hold its shape as molten metal flows into the cavity defined by the mold. The mold is formed by packing the sand composition about a pattern on a pattern board, removing the pattern to leave a cavity in the formed sand, forming in the sand additional sprues, gates and vents as needed, and pouring the molten material into the cavity. The facing surface of the formed sand dictates the quality or texture of the finished solidified cast product which is ultimately extracted from the sand.

Typically, where it is an objective to produce sand castings having fine surface detail, various difficulties are encountered. For example in the prior art, and as shown in FIG. 1, when using a pattern such as a commemorative plaque having letter or type with partially or tightly facing internal shapes such as "B", "P", "H" and "A", sand can remain stuck in the enclosed spaces upon removal of the pattern with the result that the cast letters fill in during casting. Similarly, detail can be lost for patterns having intricate bas relief designs.

Others have partially alleviated this difficulty through the use of a specialized sand composition facing the pattern that contains a greater proportion of finer sand than the remaining bulk of the sand or system sand. System sand typically has a coarser Grain Fineness Number (GFN) of about 70 while finer facing sand is often between a GFN of about 120 and 180. Such fine facing sands can contain clays and are typically less permeable than system sand. Further attempts to increase the cohesive characteristics of the finer sand further reduces the permeability which impedes the escape of burned oil products during hot metal pours and results in "blows" or voids in the resulting casting. The formulation of a fine facing sand is a balance of conflicting characteristics: finer sand providing lower permeability and the binders and other ingredients needed for such compositions further occluding channels between the particles of sand.

Further, tightly packed facing sand is less subject to washing out when the molten metal flows by. Hard compaction is another characteristic which is in conflict with retaining sufficient permeability to permit the release of generated gases and preserve the integrity of the mold.

While it is known to provide specialized facing sand compositions, there is still a need for economical and robust compositions which result in superior performance and surface finishes and which can also be applied successfully using the tools and techniques of the smaller foundries.

Further difficulties are faced when hand tools are used to form the drag and cope of a mold and the methods of applying and compacting the facing sand and the added system sands can additionally and negatively impact the finish of the cast product. Improved methodology are required to assist the facing sand and maintaining a superior surface finish.

SUMMARY OF THE INVENTION

A sand casting formulation or composition establishes a balance between providing a fine surface for a superior finished surface and providing maximum permeability for enabling release of gas and maintaining integrity of the mold. Additionally, a novel method of sand application and compaction complements the disclosed composition for maintaining the fine surface finish with a minimum of distortion.

In a preferred embodiment, a facing sand composition is provided which comprises a dry mixture of sand and binder, oil and catalyst. Based on fine sand, a dry mixture is prepared preferably comprising 6% wt/wt binder to fine sand, 8% wt/wt green system sand to fine sand and 12% wt/wt burned system sand to fine sand. Once the oil and catalyst are added to the sand and binder, the proportions being about 8% wt/wt oil to fine sand and 0.5% wt/wt catalyst to fine sand. In a preferred order, the fine sand is mulled with the binder. The green system sand and screened burned system are added and mulled with the fine sand. The oil and catalyst are added. Preferably the catalyst is added last or at least after the binder has been distributed throughout the fine sand fine. The mulled mixture is allowed to rest, is mulled again and allowed to rest again before use.

To ensure accurate reproduction of the pattern's fine detail, a preferred method of forming the mold is provided. Preferably the cope is prepared in a cope flask. Then the drag, typically bearing the detail, is prepared by first riddling the novel facing sand in a layer over the detail portion of the pattern and compressing it thereon. The facing sand is then backed by riddling a layer of drier system sand over the facing sand to a similar depth as the facing sand and compressing it thereon. A thick layer of system sand is then applied over the entire pattern including over the sides of the pattern and the thick layer of system sand is compacted about the perimeter of the pattern. A further lift of system sand is then applied to span the entire area of the drag flask and is compacted hard about and over the pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fanciful illustration of a prior art problem, more particularly FIG. 1 is an enlarged perspective view of a sand mold and an extracted foundry letter "A" illustrating how the enclosed center of the "A" inappropriately retains the prior art facing sand and thus fills in the center when cast;

FIG. 2 is a perspective exploded view of a both halves of a conventional cope flask, pattern board and drag flask;

FIG. 3 is a side view of assembled flasks according to FIG. 2 with the cope flask facing upwardly and rammed with sand;

FIG. 4 is a side view of an assembled pattern according to FIG. 2 with the rammed cope flask facing downwardly exposing the drag flask for insertion of foundry sand;

FIG. 5a is a partial close up of a side view of the assembled flasks according to FIG. 2 with the facing sand of the present invention being compressed onto the pattern;

FIG. 5b is a partial close up of a side view according to FIG. 5a having had a further lift of dry system sand added over the facing sand;

FIG. 5c is a partial close up of a side view according to FIG. 5b having had a further lift of system sand added and rammed abut the periphery of the pattern;

FIG. 5d is a partial close up of a side view according to FIG. 5c having had a final lift of system sand added and rammed thoroughly across the drag flask, filled and struck off level; and

FIG. 6 is a side view illustrating the flasks wit the pattern removed and the cope flask and sprue positioned for receiving a pour of molten metal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A facing sand composition for retaining the fine detail in foundry applications comprises a unique mixture of sand, binder, oil and a catalyst. The mixture combines green and burned sand. In use, a first facing sand prepared in accordance with the invention and applied to the pattern is backed with a second dry sand composition, and which is further backed with third conventional system sand composition. The novel methodology of application complements the novel facing sand and results in improved surface finishes without increased susceptibility to defects, and even with reduced defects.

For forming the first facing sand, a fine green sand is prepared and missed with some new green system sand and some burned sand.

The new fine green sand comprises fine silica sand, a binder, oil and a catalyst. For detail having tightly facing internal shapes, even with dimensions as small as 1 mm in relief, it is preferable to use fine silica sand having a GFN of about 120. This fine sand forms the bulk of the facing sand. The binder is a PETROBOND.RTM. binder available from Bentonite Performance Materials, Denver, Colo. According to the manufacturer, this binder is a proprietary mixture of sodium montmorillonite and quaternary amine. The manufacturer recommends use of oil such as a paraffin pale oil although other conventional refined oils without inhibitors or naphthenic oil with a flash points over 400° F. are suitable. Oils having a relatively low viscosity are preferred. An example of such an oil is Chevron Utility 100 oil. A material safety data sheet (MSDS) for which the oil described its characteristics as a severely refined petroleum distillate. Bentonite Corporation provides a paraffin pale oil described in its MSDS as a solvent dewaxed heavy paraffinic petroleum distillate. Suitable catalysts include that known as "P1 Catalyst" provided by Bentonite Performance Materials which is a propylene carbonate. Similarly methyl hydrate is known to serve as a catalyst.

Some second depleted sand is obtained most conveniently from previous casting as burned sand. Such sand is low in oil and binder and contains a mixture of burned first fine sand and burned third system sand. Such sand has had the oil and binder at least partially burned out, or depleted, during a prior pour. The burned sand is screened prior to mixing with the fine green sand.

Some coarse green sand, which is typically available and used as a conventional system sand, is also provided for mixing with the fine green sand. Such system sand preferably comprises silica sand having a GFN of about 70, PETROBOND.RTM. binder and oil. Typical proportions for coarse green sand comprise, for a total weight of 107 lbs., 100 lbs. of coarse sand GFN 70 (92% wt/wt), 5 lbs. binder (5% wt/wt), 2 lbs. oil (2% wt/wt)and about 1 ounce of catalyst.

In preparing the facing sand composition, the fine silica sand and the PETROBOND.RTM. binder together constituting the dry ingredients of the fine green sand, are mixed in a muller. The oil and the catalyst are mulled into the dry ingredients to form a fine green sand. The coarse green sand and the burned sand which complete the ingredients for the facing sand composition are mixed into the mixed fine green sand. The green system sand and screened burned system are added to, and mulled with, the fine sand. The mixture is allowed to rest, mulled again and again allowed to rest before use. On a % of Fine Sand Component Weight. Pref Range % of Fine Fine Silica GFN 120 50 lbs. sand Binder PETROBOND .RTM. 3 lbs. 6% 2.5-3.5 .sup. 5-7% Oil 4 lbs. 8% 2-5 4-10% Catalyst P1 Catalyst 6 oz. 0.8% 5.4-6.6 0.7-0.8 Coarse green 4 lbs. 8% 3-5 6-10 sand Burned sand 8 lbs. 16% 7-9 14-18

The proportions can vary somewhat. It has been determined for the fine green sand, that for each 50 lbs of fine silica sand it is preferred to have greater than 2 lbs. of oil with the preferred quantity being about 4 lbs. Despite some variation in oil fraction, the amount of binder typically does not vary more than about between 2.5 and 3.5 lbs. The fraction of the remainder of the components may vary within 10-25% based on the crude precision practiced in the empirical testing performed in the casting trials.

The mixture can be mulled and remulled according to the preference of the individual craftsman. A successful mixture is one which has an appearance and texture of clay. To achieve this result, the facing sand composition can be mulled for about 20 minutes and then allowed to rest for 15 minutes, mulled for a further 10 minutes, and allowed to rest again for another 30 minutes.

As a result, on a dry basis (less any oil and catalyst), the preferred facing composition is about 77% fine sand, 5% binder, 6% coarse green system sand and 12% burned system sand totaling 100%. Relative dry and wet components are sand (about 93.7% wt/wt total dry components) with 5.8% wt/wt oil and about 6 ounces or 0.5% wt/wt catalyst totaling 100%.

The success of the first facing sand composition to accurately reproduce fine detail is further enhanced by an improved method of forming the mold. The complementary methodology is in two phases: one in the use and application to two different backing sands over the facing sand; and secondly in the method of compaction of the two backing sands.

To ensure accurate reproduction of the pattern's fine detail, a preferred method of forming the mold is provided. As shown in FIG. 2, a typical mold is formed by sandwiching a pattern board between a cope flask C and a drag flask D. The following methodology is known to be suitable for rectangular patterns of up to about 24" by 20" without collapse of the cope. Known techniques for larger areas include additional use of cross bars and chucks in the cope flask C.

With reference to FIG. 3, typically the cope is prepared first. The cope typically contains the back of the casting. Clearly, for patterns having features on both sides, the side having the least intricate features is placed on the cope side. The cope flask C is oriented facing upwardly and system sand is applied. The back of the pattern board may contain the shapes of runners. The system sand in the cope flask C is compressed or rammed hard, 80 to 85 mold hardness or harder, to form the cope. Vent holes are formed in the cope. It is conventional to first apply a good quality system sand in a layer or lift over the back of the pattern board. As system sand is often rejuvenated from used sand, problems and even failures associated with inconsistent system sand can be avoided by applying a first layer of new coarse green sand to the pattern (such as about 3/8"-1/2"), and then filling the remainder of the cone flask C with either of a new system sand or rejuvenated system sand.

After already having prepared the cope, the drag portion bearing the most detailed of the patterns features is prepared so as to minimize distortion and stretch of the detailed features or image in the mold. The following procedure prevents or minimized "ram-away" wherein there is plastic deformation of the sand from around and away from the pattern and detailed features in particular.

As shown in FIG. 4, the mold is turned over to expose the pattern and the drag flask D.

With reference to FIG. 5a, in preparing the drag, a parting compound such as baby powder (talc or less preferably cornstarch) or powdered diatomaceous earth is preferably placed over the surface of the pattern. The fine facing composition of the present invention is then riddled or screened in a uniform layer over the detailed portion and sides of the pattern, the runners and gates. The facing sand is applied to a uniform thickness of between 3/8" and 1/2". The layer of facing sand composition is compressed evenly with a distributed pressure such as by applying a wooden block with hand pressure.

In FIG. 5b, a similar and uniform thickness of second dry sand is riddled or screened over the compressed facing sand composition. The dry sand contains less oil and less binder and is better suited to receive and absorb the gases created during the pour and thereby better avoid the possibility of a blow and the resulting damage to the surface finish of the casting. If the dry sand is barely capable of holding together then it is probably suitable. If the dry sand is cohesive when squeezed by hand then it is insufficiently burned and is too rich in oil or binder.

With reference to FIG. 5c, a thick layer of system sand is applied over the entire pattern. The system sand is compacted hard only about the periphery of the pattern, not over the pattern.

Finally, as shown in FIG. 5d, a final lift of systems sand is applied and is compacted hard about and over the entire drag flask D and over the pattern.

When the pattern board is removed and the molten metal is poured into the mold having utilized the fine facing sand composition and the mold preparation of the present invention, the resulting casting retains all the detail of the original pattern.

The embodiments herein are based on extensive empirical experience used to optimize the proportions of the composition and the procedure for preparing the mold. It is understood that the above embodiments are preferred and that some variations are included in the scope of the invention including variations in composition, and thicknesses and compression. For instance, those of skill in the art are aware of the need to adapt the sand composition, thickness and compression for differences between foundry letters which are 1/8" versus those which are larger. The shapes of flasks C,D and depth of patterns vary and the applied thickness of foundry sand will also vary.

* * * * *

Sorry about it being so long I found it quite a read.
My reasoning for quoting the above paper is because the bucket of Alchoal that I bought today wasn't cheap, of course its 5 gallons, but belive me for 40 dollars if I had a still I could make a lot of Alchoal for 40.00 dollars. One of the things that intriques me is that in the post to threads in the fourms and other things that I have read everyone says that oil bonded sand can be made with readily available ingerdiants, but when you start looking things start getting scarce quick.

Anyway back to the muller. I got a switch on it so that when I need to start and stop it I don't have to drop what I am doing to use both hands to unplug it, this is good.
The other thing is that I added a couple of pieces of just some scraps to the inside of the tub so that as the wall scraper comes around they will knock the materila down that gets pushed up from the bottom.

So far it seems to be working great, I have loaded it up pretty heavy to test the drive, and it has taken everything that I have put in it, up to one whole 80 pound bag of sand petrobond powder and oil and Catalyst it was a pretty sticky mess but I was able to work with it till its in pretty good shape about like the sample that harry sent to me.

Thats about it for tonight I guess, hopefully in the morning I will get to ram up a mold, its been almost hot enough to melt without firing the furnace, just put the ingots in a crucible and set it in the sun.
Like frying eggs on the sidewalk.
DAvid

[4cylndrfury]

I know that real petrobond requires a detergent free oil of a particular weight, which can be hard to come by. In a Pinch, you can use fully synthetic 2 stroke oil, found at any autoparts store. And for catalyst, I just use regular isopropyl alcohol, the lower percentage stuff ( I think thats 70% or thereabouts, more diluted than the 91% stuff you can get at the drug store). The reason for using the lower percentage alcohol is that it will contain slightly more water. Ive been told the alcohol only helps mix the water into the recipe, wherease without the alcohol, obviously the water would be blocked by the oil. The water is what catalyzes the mix from just an oily mess to the doughy consistency of good molding sand. Like I said, that is based on the K-bond recipe, which is in some ways inferior to the real petrobond stuff you guys are using.

[Harry]

The 6 oz of catalyst they mention sounds like a lot but other than that the recipe sounds about like the kent state K-bond recipe.

5 gallons of alcohol should last you quite a long time... Adding it into the sand makes a really big change. When I was making my own sand I found I would need to add a little more from time to time especially in the winter when the sand is cold. It seems to me the sand acts drier when cold.

Since I have been using the IFSCO sand I have not added anything to it at all, for a long time I was segregating the really burned stuff out during shakeout using a putty knife to scrape it away. This had the effect of reducing my heap at a pace quick enough I would add a few scoops of new sand for every 100 lbs or so of castings and this would keep the heap a light brown color. The last few months I have not been cleaning out the burned sand and the heap has taken on a considerably darker color but still more of a brown than black. The sand still works great, my plan is to keep using it this way until I notice any drop in casting quality then change out the entire heap. I believe this is the way BobS runs his heap.

Your muller looks like it is working great, the only thing I noticed in the video that might make an improvement is to get the wheel to roll more along the curve of the circle but then the way you have it looks like it is putting quite the smearing motion on the sand which is probably better than rolling over the sand so maybe not. The capacity is really good also, nice batch size.

I know you have put a lot of work into putting the muller together along with a some $'s, in the end you are going to come out way ahead just in terms of the amount of work getting your sand ready each time you want to pour and even for greensand as you have mentioned earlier it has given you a better quality with that sand and I am sure has been much easier than mixing by hand.