Greetings everyone. A newbie here. I have pretty extensive experience in making 3D prints and silicone molds. Now I want to try to make some rigid molds using resin casting, and then expanding polystyrene pellets inside the molds using steam. The goal is to then burn them out with lost foam casting. If anyone has any experience (good or bad) doing this, I welcome your input.
Welcome to the forum. A previous watersports hobby had me dealing with large billets of expanded polystyrene and composites and I still have a couple big chunks taking up space. I never had a hankering to expand PS pellets in a home-built mold. Are the resin molds you're planning capable of the heat and pressure and releasing the cast/expanded pellets? Having a CNC setup for lost foam is the bee's knees, my last project was only in the machine for 12-15 minutes per part before I had them hot glued and dipped in the right kind of drywall compound. Extruded polystyrene seems to be the preference of the regulars with expanded being used for sprues and gating. PS the mold-making process you describe fascinates me, several of the folks here have experience mad skills that way. I have never had a project come about that would have me do down that road...yet...
I will be using SiryaTech resin. It is a resin that is used for making molds for plastic injection molding, so yes. it will stand up to the temperature and pressure to make the styrofoam.
Hi Wader and welcome. You should read this thread and more importantly the threads linked within it. Intended Experiment With Raw Expandable Polystyrene Beads | The Home Foundry In short, pre-expanded material is difficult to obtain, has a very short usable life, and getting a consistent result as far as pattern density more difficult than you might expect. Though the process is used in commercial production setting, IMO it's not worth the effort in a hobby setting. If production it needs to be a complex part that takes advantage of evaporative pattern casting else other processes are more practical and effective. I have a ~400 page book on lost foam casting piublishged by AFS. Half the book describes and is dedicated controlling this pattern making process and the other half to all the other related LFcasting processes.....if that tells you anything. Best, Kelly
