hotzn Posted January 1 Report Share Posted January 1 Hi there, happy new year! I am a novice, happy to learn from some threads here so far =) I'm thinking about starting a clay project I have in mind for a few years. Therefore I am trying to find the best way of manufacturing a battery of parallel pipes that should have none or almost no draft angle at the inner walls of the pipes. Additionally, the ends of the pipes should have a defined shape too, one side even closed off. I thought about different ways to solve it: Extrusion of modeling clay mass (-> no draft) + slip casting of front and bottom of pipe battery (can modeling clay mass be combined with a slip cast process?) Slip casting with minimal draft angle (0,5° or even less? polish the plaster for easier demolding?) . Plaster mold resembles the inner shape of the tubes and slip builds up to the outside. (Is it a problem that the drying clay will shrink onto the inner mold - maybe even leading to cracking? Slip casting with normal draft angle (2-3°?) and using drill(?) to drill out the draft into a even hole before firing(?) or is the slip cast elastic enough to be streched/widened to a homogenous inner diameter of the pipes somehow? Form pressing of clay mass. Not sure about possibility of 0° draft. Don't know of a reference of form pressing clay yet. Maybe you have one? Looking forward to reading your thoughts! Quote Link to comment Share on other sites More sharing options...
neilestrick Posted January 1 Report Share Posted January 1 Can you please define draft angle? And will this be sculptural or will it serve a function? A drawing, maybe? Quote Link to comment Share on other sites More sharing options...
Jeff Longtin Posted January 2 Report Share Posted January 2 Hello Hotzn, Welcome to the Forum. Your questions are a bit too technical for easy answers. You would really need to decide which clay you want to use and then run your own tests to determine "draft angle". ("Draft angle" = the taper necessary to allow for one piece to be pulled from another.) Different clay bodies have different levels of shrinkage. I'm not sure which would be more advantageous for you, clay bodies with lots of shrinkage or clay bodies with less. Those factors then affect how easy the body is to keep in suspension. (On a consistent basis.) Years ago 3M had an Industrial Ceramics division and they commissioned me to make a simple mold for a simple piece.(For engine cylinder liners.) We never got into clay formula discussions. Years later, when I reached out to my contact to ask a technical question, I learned that he had retired and that they sold the division to a company in Mexico. More recently another local company, a branch of a Dannish company, approached me about making molds for silicone carbide kiln furniture. That project never got off the ground but they did show me the process for making another ceramic product they made. (Deisel engine air filters.) The "clay" was black and made with silicone carbide powder. They extruded the forms in a very precise extruder device. They fired it, however, in a nitrogen fueled "kiln" and fired them to 3000 degrees. Thats what I envision you're looking for but that's super technical stuff and I have no idea how where you'd begin on that. Good luck. Min 1 Quote Link to comment Share on other sites More sharing options...
Mark C. Posted January 2 Report Share Posted January 2 Jeff (They fired it, however, in a nitrogen fueled "kiln" and fired them to 3000 degrees) this is how recrystallized silicone carbide is made in a Nitrogen rich oxyegen free environment .Often electric arc furnace. All my kiln shelves are made from this process (advancers or Baileys). I have a pile of soap bricks (like a while brick cut in half the long ways) made from same material. Its the stongest material at high temp and never warps at say 2400 (cone 11 ) and keeps warm a long time and glaze will not stick to the surface as its smooth and not porous. You can look it up say on Alibaba and see some interesting forms made in China same way. By the way that nitrogen rich 3,000 degree furnace costs an arm and leg to fire and maintain . There are very few of them around. the globe. Saint Gobain headquatered in France is one of the older doing this (they make Advancers) the Bailey clay ones come from Germany and now China has a few plants as well. This is the feild of industrial ceramic engineering. Way above my pay grade.I have a funny story about one of these guys-maybe another time-they made electric arc furance lids for the tops of crucibles. Jeff Longtin 1 Quote Link to comment Share on other sites More sharing options...
PeterH Posted January 2 Report Share Posted January 2 (edited) Are you trying to make a set of panpipes or a high-tech industrial component? It would help if you gave us an idea what you are trying to make, and the use to which it will be put. This gives the experts some criteria to judge the merits of alternatives production techniques. Two minor points. - If you use multi-part moulds don't draft-angles become irrelevant, although parting lines may require tidying. - Is extrusion an option? Edited January 2 by PeterH Quote Link to comment Share on other sites More sharing options...
hotzn Posted January 2 Author Report Share Posted January 2 Hello you all and thanks a lot for starting the discussion! I'll upload some sketches to clarify a bit. The part can have quite some tolerances and is no technical part. I need no fancy clay or high temperature firing. It should be possible to handle the process and materials with "normal pottery equipment". I'm just worried about the draft angle, as one major requirement is a quite consistent inner diameter. As the inner contours (bores) are deep and not that wide I can't go more than 0,5° for a draft angle. If 0,5° is not possible, another step in manufaturing is needed to hone out or strech the cavities. Shouldn't be too complex to manufacture though! 9 hours ago, PeterH said: - If you use multi-part moulds don't draft-angles become irrelevant, although parting lines may require tidying. Please note that the pipes/tubes are arrayed not only linearly but also in the depth which makes molding from the outside of the tubes impossible. Here some visuals to my inital ideas on manufacturing: 20 hours ago, hotzn said: Extrusion of modeling clay mass (-> no draft) + slip casting of front and bottom of pipe battery (can modeling clay mass be combined with a slip cast process?) 21 hours ago, hotzn said: Slip casting with minimal draft angle (0,5° or even less? polish the plaster for easier demolding?) . Plaster mold resembles the inner shape of the tubes and slip builds up to the outside. (Is it a problem that the drying clay will shrink onto the inner mold - maybe even leading to cracking? Slip casting with normal draft angle (2-3°?) and using drill(?) to drill out the draft into a even hole before firing(?) or is the slip cast elastic enough to be streched/widened to a homogenous inner diameter of the pipes somehow? 21 hours ago, hotzn said: Form pressing of clay mass. Not sure about possibility of 0° draft. Don't know of a reference of form pressing clay yet. Maybe you have one? Quote Link to comment Share on other sites More sharing options...
neilestrick Posted January 3 Report Share Posted January 3 @hotzn I'm still not understanding. Is this a sculpture or is it functional in some way? What will the final product look like? How many pipes will there be? Why is this draft tolerance needed? Can they be joined after forming or do they have to be formed together? What are the dimensions of each pipe? How large is the grouping? What shape is the grouping? Are they all connected at the bottom, top, sides? What are the total dimensions? The function of the final product will determine which type of clay you need to use. There's also issues of warping in drying and firing, etc. "Normal pottery equipment" is not really good for things that require precise tolerances since things move. Is clay the best material for this project? Hulk 1 Quote Link to comment Share on other sites More sharing options...
Mark C. Posted January 3 Report Share Posted January 3 With slip/clay shrinkage precision is very hard-lots of factors to work through to get to a known point. I'm pretty new to ceramics ,only have a bit over 50 years under my belt and still do not know what ( "Normal pottery equipment" ) is? How about a metal casting process its much more precise. neilestrick 1 Quote Link to comment Share on other sites More sharing options...
Jeff Longtin Posted January 4 Report Share Posted January 4 Just a few thoughts...I remembered the proper description of the diesel engine thing the company produced...they made diesel engine particulate filters. Simply put the filters are these ceramic things, 3" wide by 14" long, that have a 1/4 radius cylinder shape, and have 99 little holes that trap diesel fuel particulate as the exhaust fumes pass through. The extruder that creates the holes is made up of 99 little tubes (I think?) that push through the clay and leave it with 99 little holes all the way through the 14" length. The holes were 1/16" if I recall. Truely amazing feat. The extruder form was metal. And I think it was heated? (for lubrication perhaps?) Maybe this is the key to this situation. Rather than think of terms of plaster/cement molds think about heated metal molds? Extruded rather than cast? Magnolia Mud Research 1 Quote Link to comment Share on other sites More sharing options...
PeterH Posted January 6 Report Share Posted January 6 On 1/1/2024 at 10:59 PM, hotzn said: Is it a problem that the drying clay will shrink onto the inner mold - maybe even leading to cracking? Yes -- and it will probably be impossible to de-mould. ... although I have a very vague memory that I seen mention of a sacrificial "core" -- which burns-out/crumbles during the firing -- being used in some circumstances. Somewhat tongue in cheek, a picture of ancient Peruvian pan-pipes from https://digitalassets.lib.berkeley.edu/anthpubs/ucb/text/nap002-003.pdf My understanding of the paper is that the pipes were cast individually and then joined by adding additional clay by hand (although the set of individual pipe moulds for a complete panpipe were held in a common mould structure). Seriously, what is the intended usage of your end-product. It will enable us to understand the importance of the precision you seem to be demanding. It might also mean that the inevitable shrinkage & warpage of clay products during both casting and firing may render your product unusable for your intended purpose (a point already raised by Mark). Quote Link to comment Share on other sites More sharing options...
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