Originally posted by jonnytrooper@Jul 23 2005, 08:08 PM
Hey, if you need any help, I can stop by sometime this week.Â Did you ever cast them in resin, or did you decide to vacuform the little greeblies?
Originally posted by star-art@Jul 24 2005, 01:41 PM
Well, without trying to reinvent the wheel, there are basically three approaches that have been done in the past:
1. Turn a very large disc out of Renshape or other wood substitute. Requires very expensive special equipment, limited by the size of dish needed.
2. Make radial ribs, fill in with foam, then sand to shape. Difficult to get a perfectly even surface this way, but you can work in any size.
3. Build a custom rig and turn the shape from hydrocal. This is what Custom Replicas did with their big 5.5-foot model. It works. And hydrocal should make a good master for vacu-forming -- just watch out for shrinkage. You might try to avoid making the plaster too thick so it won't crack or shrink. Place it on a strong backer board as well that won't flex under pressure and allow it to crack.
Renshape is one of a family of mastering materials intended to replace wood and aluminum, made of a filled urethane it comes in various thicknesses and densities. Model Plank, from BJB is a similar product but not as expensive as RenShape. That being said...Originally posted by DarthJRW@Jul 25 2005, 01:33 AM
Originally posted by CaptCBoard+Jul 24 2005, 11:39 PM--><div class='quotetop'>QUOTE(CaptCBoard @ Jul 24 2005, 11:39 PM)</div>i finally figured it outÂ
i have the blueprint for the 3 footer and i used basswood for the basic disk shape then im carving the details such as curves domes ect, out of carving foam and its working great ....
i will post pics shortly
<!--QuoteBegin-DarthJRWRenshape is one of a family of mastering materials intended to replace wood and aluminum, made of a filled urethane it comes in various thicknesses and densities. Model Plank, from BJB is a similar product but not as expensive as RenShape. That being said...@Jul 25 2005, 01:33 AM
I really hate to say this, but if you don't know about the plaster technique and you don't know what RenShape is, you probably don't have enough expertise to pull the job off without a whopping huge amount of experimentation. My recommendation is to find someone who already knows how these parts should be made and have them do the mastering. And second to that suggestion is, in the case of this particular part, you should definitely NOT be trying to vacuform over a postive master, but pulling the plastic into a negative. Getting the pull out of the negative will not only be much easier (basically it'll just jump out) but if you put any detail on the 'positive', it will come out much crisper since the finished surface of the plastic will have been against the finished surface of the mold. Pulling plastic over the positive itself means the contacting surface is on the inside and any detail will be 'mushed' due to the thickness of the plastic (even if its really thin...). Even if there isn't any detail being formed other than the general shape, its still better from a production standpoint to pull the plastic into a negative mold-- the parts will be very easy to remove and the mold will hold up much longer as there are no shrinkage stresses building up on it. If you are only making a few (less than 5 or 6) of these parts, it probably won't matter. But if this is going to be a kit where you make more than that, this is a consideration you need to be aware of.