LFMC
13 - Hollow Straw Feeder...
...and now for something completely different!!!
Finally something new to contribute!!!
This is a technique that is as significant as moving to plaster casting. The basic premise is to feed the mold with disposable thin walled drinking straws...
Shown to the right is an assortment of straw diameters ranging from 0.180 through to 0.5" in diameter.
These are courtesy of my ever-loving wife & twins... some are from beverages, others are the spares typically found in the bottom of the Burger & Fries bag...
Between other jobs I grabbed some blanks that were kicking around and slid in 2 plaster jobs that are design concepts that were more so Foam prototypes before the master mold is cut.
A typical mold seems to take 2 to 3 Foam patterns before the bugs are worked out in the GCode and a repeatable pattern code is ready for production.
One of the procedures that is high on labour, low on interest and least rewarding is cutting the casting from the feeders.
Up till now I always fed a pattern with 1" square foam runners. They seemed so flimsy when foam, but proved to be rather solid when rendered in Aluminum.
Typically an hour of grunting and sweating is the order of the day for a 2 to 3 feeder casting before starting on the finish.
I laid-up an assortment of straw diameters and feed locations... spend a few hours over the course of a week thinking like a liquid... do not "be of the casting", but rather "be the casting". After all the whole point of this exercise is to be immersed in the task at hand.
We're on familiar ground here, the blanks are placed on a layer of sand that's approx an inch thick to protect the wooden flask.
The sand is loosely poured in over the mold and shaken to settle after the molds are covered with at least 2 to 3 " of sand.
Funnel Cans are added for the last 3 to 4" of sand with the straws as close to the center as possible.
The bow-tie is flawless, even though only 3 of the 5 feeders held their 0.25" diameter.
The one thing I doubt that I'll ever know for sure is whether the feeder flows and eventually clogs or clogs on the get go.
This HD Blank is fed with 0.180" diameter Flex elbow straws.
It had 3 dead stops on the feeders, but there is a fill pool shadow in the sand that stuck to the foam.
I spent over an hour examining each casting before wire-brushing to try and visualize how the pattern filled.
This pattern filled out with some flaws...
The feeders are almost 3/8th" in diameter, but were placed to far inward and should have been placed closer to the outer most extremities of the arms that radiated out from the center.
Also I will in the future double-up the feeders for more flow.
What's coming down the pipe???
These are "Master Molds" that are finally ready to cast. As this is being written the plaster is curing since being carefully laid-up onto the molds.
The Sunset plaque is actually 3 (three) separate 8" patterns that have been glued together... Each piece takes approx 3 to 5 hours to mill, but can be left virtually unattended for up to 30 minutes at a time...
With a 24" casting being by far the largest casting from my foundry to date, I'll have to build a special deep flask to hold over 100lbs of sand. At least I have some new ideas for additional content to be posted through out the summer...
But for now I have 36hrs of socialization and unwinding to engage, as well as a reasonable helping of fishing as Bass Season opens today (June 19th 2004)
theworkshop.ca over & out...
Disclaimer
(an unfortunate necessity)
All
Rights Reserved theworkshop.ca © November 05, 2004.