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thanks for the quick replies
i usually cut all my blanks tube length+3mm so i was planning on making the mold to the same length dimensions
the next thing i was a bit unsure of was the length of the nipple, some of the ones i have purchased only have about a 5-6mm nipple would 10mm be too long to get the cast blank out without tearing a nipple off (thats gotta hurt), i think the 5-6mm ones are a bit short
i am but a padawan seeking advice from the masters:U
MIK
The moulds I make for Marla are of Mold Max 30, by Smooth-On, Tin cured silicone (pink), a US based company, that I can buy locally. I make the nipples .010" to .015" bigger than the inside diameter of the tube. I try for about .100" to .125" longer than the tube at each end and the nipples are somewhere around .500" long. Life of the moulds has been from as low as fifty to over several hundred casts using polyester resin. Life goes down if you add fast catalyst or get the mix ratio off with extra catalyst. Marla doesn't use any mould release and the casts are left in the moulds at least 12 hours before being removed and placed in a warming drawer. It is a metal drawer with an old waffle iron opened flat on the lowest temp (you can hold your hand on it).
Pete
thanks for the info peteQuote:
Originally Posted by QC Inspector
my silicon rubber (as the website calls it) arrived this week, hopefully in the next couple of weeks i will get the chance to make things happen
i was think of making a warming cupboard but now with the filament light globes not available its hard to get something to work for a heater, what does anyone else use or do you just go without
if after 12 hours and the resin is set but still sticky, would it be worth putting mold and all into a warming cupboard, or could this damage the mold
all input and thoughts please
MIK
Marla takes the sticky cast out of the mould, handling it by the ends, and lays it on sticks that are on the open waffle iron. She doesn't put the mould in the warming drawer, although it is supposed to be able to take the heat. You can do two sets of casts every day this way if you have orders to fill. :wink: Lots of people use toaster ovens here for their blanks. We had the waffle iron and an old metal drawer that was meant to screw to the bottom of a work bench, so they got pressed into service. I suppose a small filling cabinet would work if you had one.
Pete
I post cure my casts in the molds for 10min at 100 degrees C. The molds hold the heat and this helps get rid of the sticky bits. It does not damage the molds.
i have got the silicon rubber as described on ebay, now for the masters
the first i plan to make is a new Siera mold
can anyone see any problems with using a full cast of the mold cavity in a resin saver mold, i would then redrill the holes for nipples to the larger size needed
if i use these then they are shaped perfectly for whats required
MIK