Arw Posted February 12, 2019 Posted February 12, 2019 Hey allI searching about hemisphere planI just find http://www.pendicular.net/shellmap.phpbut its not give a good hemispherecould you give me a nice hemisphere map?
Arthur Posted February 12, 2019 Posted February 12, 2019 There is no map/drawing on flat paper that will give a nice spherical hemisphere without a round pattern or mould.
Arw Posted February 12, 2019 Author Posted February 12, 2019 There is no map/drawing on flat paper that will give a nice spherical hemisphere without a round pattern or mould.I have a PolyEthylen mold that don by CNC and I make 600 hemisphere but this map not good enough.I wish you have better one
Fulmen Posted February 12, 2019 Posted February 12, 2019 As I understand it the math behind the program is sound. It can be tweaked with regard to the number of petals and the amount of overlap, the fit will improve as the overlap goes towards zero and the number of petals goes towards infinity.
Arw Posted February 12, 2019 Author Posted February 12, 2019 As I understand it the math behind the program is sound. It can be tweaked with regard to the number of petals and the amount of overlap, the fit will improve as the overlap goes towards zero and the number of petals goes towards infinity.yes overlap is the problemwhat do you think about 6 petals?how should i design?can I find a ready map?
a_bab Posted February 12, 2019 Posted February 12, 2019 Just get some commercial shells or hemis and reverse-engineer the hemis pattern (aka: soak them in water overnight then spread and dry).This will give you the real deal.
Fulmen Posted February 12, 2019 Posted February 12, 2019 (edited) Arw: The script works best under Linux, you can run it from a LiveCD or install it under VMware. I found my VM from years ago, so just let me know what you need. Here's a 100mm, 6 petal 0 overlap map.map.pdf Edited February 12, 2019 by Fulmen
Col Posted February 13, 2019 Posted February 13, 2019 (edited) yes overlap is the problemwhat do you think about 6 petals?how should i design?can I find a ready map?There is a hemi template generator in the files sectionhttps://www.amateurpyro.com/forums/files/file/113-hemi-printing-templatezip/ Template hemi`s vs chinese hemi Edited February 13, 2019 by Col
Mumbles Posted February 17, 2019 Posted February 17, 2019 Are you forming into a female mold, or trying to form over a male mold? In my experience pressing into a female mold works best.
Arthur Posted February 17, 2019 Posted February 17, 2019 Each layer of paper on the mould really needs to be a different size, to account for the progressive size change from layer to layer. Sometimes you just have to pull and push the damp paper leaves into the shape needed.
Mumbles Posted February 17, 2019 Posted February 17, 2019 No they don't. You'll never have a perfect shape at the end and will need to trim regardless. 2
Arw Posted February 22, 2019 Author Posted February 22, 2019 Arw: The script works best under Linux, you can run it from a LiveCD or install it under VMware. I found my VM from years ago, so just let me know what you need. Here's a 100mm, 6 petal 0 overlap map.unfortunately does not work but its better There is a hemi template generator in the files sectionhttps://www.amateurpyro.com/forums/files/file/113-hemi-printing-templatezip/ Template hemi`s vs chinese hemi That's a web page that doesn't exist anyway Are you forming into a female mold, or trying to form over a male mold? In my experience pressing into a female mold works best. both together a female down and a male mold on upEach layer of paper on the mould really needs to be a different size, to account for the progressive size change from layer to layer. Sometimes you just have to pull and push the damp paper leaves into the shape needed.its depend to thickness of your hemisphere and your paper
ivars21 Posted February 22, 2019 Posted February 22, 2019 Maybe this is useful:https://pyrodata.com/hemis.php
Col Posted February 22, 2019 Posted February 22, 2019 @ ArwThe webpage is long gone but it was saved to a zipfile so you can use it offline. Extract the zip and click on the index file..
Col Posted February 22, 2019 Posted February 22, 2019 No they don't. You'll never have a perfect shape at the end and will need to trim regardless.I agree, even with die cut discs you still have to trim.
Fulmen Posted February 23, 2019 Posted February 23, 2019 unfortunately does not work but its betterI'm sorry to hear that. But unless you provide more information it is impossible to help you. I can of course make another map, but I would need the specs. Each layer of paper on the mould really needs to be a different size, to account for the progressive size change from layer to layer. Sometimes you just have to pull and push the damp paper leaves into the shape needed.In theory yes. But following the same logic you really need a pattern with an infinite number of petals, and yet you don't. The obvious answer is to use a soft, porous paper that can yield and flow into the desired shape. It would require a closed mold, i.e. the female should be extended to a cylinder with a close-fitting male.
Col Posted February 23, 2019 Posted February 23, 2019 The paper wont flow inside a mold unless its a slurry The hemi`s can be trimmed on a modified pillar drill. The male part of the mold is attached to the chuck and a big bearing is attached to the table. Crank the handle down so the hemi pole is clamped against the bearing and swing a blade in from the side at the correct height to trim off the excess. Its a good idea to include a stop to prevent the blade cutting into the mold.
Fulmen Posted February 23, 2019 Posted February 23, 2019 I disagree, anything will flow with enough force I can't tell how clean the edges are, but at least these ladies seems to manage with a single size of paper:
Col Posted February 23, 2019 Posted February 23, 2019 The 3" chinese hemi`s i soaked and peeled apart had 2 layers
Arthur Posted February 23, 2019 Posted February 23, 2019 What size mould tool do you have? A 3" shell hemi may be 2mm thick but a 16" hemi will be 12+mm thick and made from many layers.
Col Posted February 24, 2019 Posted February 24, 2019 I have molds for 3" and 4" hemi`s The cost of steel molds and press for 16`s wouldnt be worthwhile unless you needed a lot. Even then you could prolly afford to just buy them with the savings made on the smaller sizes
Col Posted February 25, 2019 Posted February 25, 2019 (edited) nope but they dont press and trim them in one operation. two discs are staggered and stuck together in this one and in this one one of these is ideal for mass production Edited February 25, 2019 by Col
Fulmen Posted February 25, 2019 Posted February 25, 2019 In the second video the edges are visibly rough, so they will require a final trim. But I still believe it's possible.
Col Posted February 25, 2019 Posted February 25, 2019 There is a vid showing the trimming operation but i havent managed to find it so far If you figure a way to press a hemi from paper with a perfectly flat rim you`ll save 5-10 seconds of trimming .
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