Molding and casting revisit
Luciano explained some design guidelines when think of making something from a mold. I am a mechanical engineer and I knew most of it already but I had never put them to practice while designing yet and to make it in fablab. It was a good reminder, from now on I will increasingly integrate these guidelines in my designs.
Some design feature you could add to the design of a mold are the draft angle, clearance area on top of a mold, consideration regarding tool size and bed size of the machine you are going to be using, Consideration of tools you thin will be appropriate- if the solid model consists mostly of planar surface with only fillets and other non essential features being curved you would want to use flat end tool for both roughing and finishing, use ball end for heavily curved objects, Another common sense logic about molding and casting plastics is that, you would want to make a cast of a soft material then your mold needs to be hard and vice versa. This make total sense and might be uncommon enough that it can be called common sense. Common sense is not common after all. When I say soft it means rubber and hard is not necessarily hard to machine but it is rigid enough that it doesn't compress much on loads to which the soft material tend to comply with.
Now if you want to make a single hard product then you will have to make a positive of it in the hard wax in a pocket and then you pour a soft plastic into it to have a mold on to which you can cast a hard plastic. But to make the multiple number of hard plastic you can use the same soft mold. The soft mold might have lesser casting cycles before it gets damaged. You can choose a higher grade rubber resin if you want to produce more copies of the plastic.
Luciano explained some design guidelines when think of making something from a mold. I am a mechanical engineer and I knew most of it already but I had never put them to practice while designing yet and to make it in fablab. It was a good reminder, from now on I will increasingly integrate these guidelines in my designs.
Some design feature you could add to the design of a mold are the draft angle, clearance area on top of a mold, consideration regarding tool size and bed size of the machine you are going to be using, Consideration of tools you thin will be appropriate- if the solid model consists mostly of planar surface with only fillets and other non essential features being curved you would want to use flat end tool for both roughing and finishing, use ball end for heavily curved objects, Another common sense logic about molding and casting plastics is that, you would want to make a cast of a soft material then your mold needs to be hard and vice versa. This make total sense and might be uncommon enough that it can be called common sense. Common sense is not common after all. When I say soft it means rubber and hard is not necessarily hard to machine but it is rigid enough that it doesn't compress much on loads to which the soft material tend to comply with.
When you want one rubber(soft)
product then you make a negative of that product in wax (hard) on a wax
slab. But If you want multiple copies of the soft product you need a
permanent hard mold to which you can cast multiple number of times. The
hard plastic might eventually wear out and then you'd have to make
another a hard plastic, but the hard plastic mold is a long term
solution for it. So in order to make the hard plastic mold you need a
soft product to begin with but we will mot mill a rubber since it wont
give a good finish. We always mill the wax. So we mill a negative of the
product inside the wax, pour the soft plastic resin into it and now
when we have a soft product with us we place in a pocket and pour the
hard plastic resin around it to take its shape. You will have to either
mill or make an enclosure that doesn't let the resin flow out when
poured and can be broken easily to get the resin of may be allow the
plastic to be permanently embedded
there if you like that. Place the product intelligently so that it can
be taken of easily from the resin after it gets cured and the cast can
now be used as mold for soft materials.
Now if you want to make a single hard product then you will have to make a positive of it in the hard wax in a pocket and then you pour a soft plastic into it to have a mold on to which you can cast a hard plastic. But to make the multiple number of hard plastic you can use the same soft mold. The soft mold might have lesser casting cycles before it gets damaged. You can choose a higher grade rubber resin if you want to produce more copies of the plastic.
