| nico le fay | 27 Jan 2013 10:33 a.m. PST |
… during the mould making process ! And I'm majorly "bleep"ed right now, to put it mildly. Not only did I lose half a day's work but also a handful of decent masters. Cooked the mould at 180°C(~360°F) (organic rubber) and the metal masters just warped. At 170°C everything was fine. Wasn't too hot, was it ? (Under standard conditions) the melting point of the alloy should be around 230°C.
Did anyone else experience something similar ?
Cheers …
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| RavenscraftCybernetics | 27 Jan 2013 11:06 a.m. PST |
It happens. master metal is generally harder than production metal. unfortunately with lead free alloys thats no longer the case.
i feel your pain. |
14Bore  | 27 Jan 2013 11:28 a.m. PST |
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| nico le fay | 27 Jan 2013 11:39 a.m. PST |
Thanks Ravenscraft. I used a lead-containing alloy but it seems it wasn't tough enough. Did it go like this? Pretty much – except there's not even a broomstick left. |
| headzombie | 27 Jan 2013 1:39 p.m. PST |
I don't think I have ever cooked an organic mold above 320. Maybe yours differs. |
| Dr Mike Salwey | 28 Jan 2013 3:58 a.m. PST |
Last year the Ottoman artillery masters I did for Baccus met the same fate turning into blobs in the mould making process. We had identified it as a problem with me having cast in my quality 'old figures' lead pot which some elements of the alloy I now learn have quite a low melt point. Fortunately for me however is I had done a persoanl cold cure of the masters first! If I had not I could imagine your pain! |
| IUsedToBeSomeone | 28 Jan 2013 4:02 a.m. PST |
180 degrees seems high for a mould – I never run mine above 150 for organic rubber. Mike |
| altfritz | 28 Jan 2013 5:50 a.m. PST |
It seems that mold making and casting are more a Black Art than Science. There are so many mold tpyes and processes used in different parts of the world. Some mold makers seem to prefer pewter masters then their regular alloy for production castings. |
| LeonAdler | 28 Jan 2013 3:09 p.m. PST |
I use nowt above 140 here, 180 seems very high, way to close to melting point for my liking and remember 'melting point' can mean different things. Is it the point at which the metal is castable or merely liquid'ish ( sorry to use technical language lol). Check your heating platerns are working evenly. Vulcanising is pretty much done after 10 mins the rest of the heating is just curing the rubber.
'Warped'? If you mean you got dud cavities need to check your pressure too.
I too feel your pain I remember a whole mould of 15mm masters going the same way when a hydraulic seal failed………
L |
| allthekingsmen | 30 Jan 2013 5:16 a.m. PST |
I don't know what rubber you're using, but 180C sounds extremely high for cooking molds. I top out at 300F (60 degrees lower than your target). Also, check your actual platen temps versus what the dial on your vulcanizer reads. You'll need a long-stem thermometer. To calibrate it, insert it in boiling water to ensure that it reads 220F/100C (modified accordingly by your elevation above sea level). Close the platens of the vulcanizer on the stem and hang around while your machine processes through its high and low temps. If you have an old vulcanizer, the temp dial and reality will be very different. |
| allthekingsmen | 30 Jan 2013 5:22 a.m. PST |
My apologies… 212F for water boiling, or 210 at 1000-foot elevation here in Atlanta. |
| nico le fay | 30 Jan 2013 7:39 a.m. PST |
Wow, seems I should set the temperature limit a lot lower – appreciate all your feedback ! "Warped" meant to describe the way they melt down. Rather than turning into blobs, the masters look like something tried to suck the "fluid" out of them, what's left is a weirdly deformed sheath. @allthekingsharm: I'm using home-built equipment. Until now, no problems occurred. Cheers |
| LeonAdler | 30 Jan 2013 1:34 p.m. PST |
Your mould supplier should have specs for the rubber he is supplying.
L |
worries about not losing his rules stuff.
