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Za formanje z bentonitno peščeno mešanico običajno uporabljamo lesene ali kovinske modele. Izdelava in obdelava le teh modelov je dolgotrajna in običajno tudi draga. Izbor materiala velikokrat temelji na tem, koliko form bomo z modelom izdelali. Za majhna podjetja, ki imajo majhne serije ulitkov, so ti postopki preveč zamudni, zato bi 3D tisk lahko bil dobra rešitev. Tehnologije 3D tiskanja se hitro razvijajo in postajajo bolj dostopne tudi osebnim uporabnikom ter manjšim podjetjem. Zato sem preizkušal, ali lahko modele natisnjene na 3D tiskalnikih uporabimo pri formanju z bentonitno peščeno mešanico, namesto klasičnih lesenih ali kovinskih modelov. Ko poskušamo model odstraniti iz forme, se nam le ta lahko poruši. Problem se lahko pojavi zaradi premajhnih livarskih kotov, zaradi neprimernih lastnosti peščene mešanice ali zaradi površine modela. Zato smo izdelali tri modele z različno kvaliteto površine, za testiranje smo izbrali štiri različne vlažnosti bentonitne peščene mešanice v območju optimalnih trdnostnih lastnosti za dano vsebnost bentonita in modele izbrali tako, da imajo čim več različnih livarskih kotov, a še vedno zadoščajo livarskim pogojem. S tem smo preverili, kako kvaliteten mora biti tiskalnik in posledično 3D tisk. Preverili smo tudi, kako pomembne so vlaga, lastnosti peščene mešanice in pri katerih kotih se začnejo forme rušiti. Po večkratnem formanju različnih modelov pri različni vlažnosti peščene mešanice smo ugotovili, da se forma v večini primerov lepo izdela. Vlaga ima velik vpliv na formo, saj se peščeni mešanici močno spreminja oblikovalnost. Pri nizki vlažnosti je peščena mešanica zelo suha in se forma, iz katere izvlečemo model, hitro poškoduje. Obratno se pri visoki vlažnosti peščena mešanica lahko prilepi na sam model in se forma poškoduje, ko odstranimo model. Največkrat se je forma okrušila pri najbolj navpični stranici, ali pa pri modelih, ki so imeli napako zaradi 3D tiska. For moulding with bentonite sand mixture or green sand, wooden or metal patterns are usually used. The production and processing of these models is time consuming and usually also expensive. The choice of material is often based on how many moulds we will build with the pattern. For small businesses that have small series of castings, these procedures are too time consuming, so 3D printing could be a good solution. 3D printing technologies are rapidly evolving and becoming more accessible to both personal users and smaller businesses. That's why I tried to test whether models that are printed on 3D printers can be used for moulding with bentonite sand instead of classic wooden or metal patterns. When we try to remove the pattern from the mould, it can be broken. The problem can arise due to insufficient pattern angles (sides are too vertical) due to the inappropriate properties of the sand mixture or the surface of the model. Therefore, we have developed three models with different surface quality, selected four different moistures in the range of optimum strength properties for the sand mixture with given bentonite content, and selected the models so that they have as many different casting angles as possible but they are still sufficient for casting conditions. By doing this, we checked the quality of the printer and consequently 3D printing. We also checked the importance of moisture, properties of the sand mixture, and the angles at which moulds begin to crumble. After repeated sampling of different models for different moisture content of the sand mixture, it was found that the mould is well maintained in most cases. Almost all samples, where we had errors in the mould, collapsed at the most vertical sides or at patterns that had a 3D printing errors. |
