So this is the start. We'll start building the dolly-frame next week. Would have started today except that Superior Metals Centre was closed.
Saturday, December 31, 2011
The Backyard Foundry - Some Concept Plans
Been thinking about how I would go about building my backyard foundry. Starting with Dave Gingery's book on "Building A Gas-Fired Crucible Furnace" (aka "How To Build Big Bertha!"), I modified things a bit to come up with this concept.
So this is the start. We'll start building the dolly-frame next week. Would have started today except that Superior Metals Centre was closed.
So this is the start. We'll start building the dolly-frame next week. Would have started today except that Superior Metals Centre was closed.
Friday, December 30, 2011
Screw The Core Boxes, Eh!!
One of the tricks-of-the-trade I learned with the Sodium Silicate/ CO2 experience was a better way to make core boxes. My first attempts resulted in a core box built in two pieces with wooden pegs to join the together - the same way you join the two halves of a split-pattern.
That was a complete failure - for two reasons. Firstly, trying to pull apart two halves of a 3-sided core box (one end, half of one side and half of another side) didn't work. The sand core got stuck in the core box and had to be broken out. Secondly, without realizing it, one of the core boxes had an extremely large "undercut" (remember this was my first experience making sand cores!). I ended up with a solid chunk of sand stuck in this angled core box. The only way to get the sand core out was to dig it out with a screwdriver. So much for that idea!
Then I hit upon the idea of joining the sides of the core box together with screws. When the sand core had solidified, it was a simply matter of undoing the screws.
The solidified sand core easily released from the sides of the core box as each pair of screws was undone. I could then give the sand core an extra couple of shots of CO2 with all 6 sides of the sand core exposed.
All in all, a great first-time experience. No muss, no fuss, no cleaning up my wife's oven, eh!?
So let's get down to building our backyard foundry!
That was a complete failure - for two reasons. Firstly, trying to pull apart two halves of a 3-sided core box (one end, half of one side and half of another side) didn't work. The sand core got stuck in the core box and had to be broken out. Secondly, without realizing it, one of the core boxes had an extremely large "undercut" (remember this was my first experience making sand cores!). I ended up with a solid chunk of sand stuck in this angled core box. The only way to get the sand core out was to dig it out with a screwdriver. So much for that idea!
Then I hit upon the idea of joining the sides of the core box together with screws. When the sand core had solidified, it was a simply matter of undoing the screws.
The solidified sand core easily released from the sides of the core box as each pair of screws was undone. I could then give the sand core an extra couple of shots of CO2 with all 6 sides of the sand core exposed.
All in all, a great first-time experience. No muss, no fuss, no cleaning up my wife's oven, eh!?
So let's get down to building our backyard foundry!
Sand Cores Using Sodium Silicate and Carbon Dioxide (CO2)
Sand, when mixed with the correct ratio of sodium silicate, rammed into a core box, and then exposed to carbon dioxide (CO2), will result in a very hard and durable sand core. Never having used sodium silicate (and never having made sand cores before!), this was an excellent lesson in learning what works and what doesn't.
PQ Corporation is the largest manufacturer of sodium silicates, one of the most widely used chemicals in the world. Their brochure on sodium silicate has this table which describes the various strengths of sodium silicate available.
N-Grade Sodium Silicate
The key measure of sodium silicate is the weight ratio of its two major components - Silica DiOxide (SiO2)to Sodium Oxide (Na2O) (the column titled "Wt. Ratio SIO2 / NA2O"). The most commonly available sodium silicate has a weight ratio of 3.22 parts of Silica DiOxide to 1 part of Sodium Oxide with a solids content (active ingredients) of 37.6% (8.90+28.7=37.6 from Table 2 above). The rest (62.4%) is water. This is sold as "N" grade sodium silicate and is NOT the best choice for making sand cores as it doesn't provide very good strength to the sand core. The sand core will slowly disintegrate when handled. This type of sodium silicate has the viscosity of a cheap liquid dishwashing soap. Table 2 above describes it as a syrupy liquid.
I made the mistake of using the 3.22 N-grade sodium silicate (it may even have been a weaker solution) with very poor results. Even after 24 hours and constant exposure to CO2, the sand cores wouldn't hold together. For those that did stick together, I would end up with loose sand grains in my hand whenever I handled them.
RU-Grade Sodium Silicate
The best type of sodium silicate for making sand cores has a weight ratio of 2.40 parts of Silica DiOxide to 1 part of Sodium Oxide with a solids content (active ingredients) of 47.05% (13.85+33.2=47.05 from Table 2 above) - a 25% increase in active ingredients over the N-Grade stuff!! This is typically sold as "RU" grade sodium silicate and has the viscosity of concentrated liquid laundry detergent - it pours very slowly. Table 2 describes it as a heavy syrup.
I got some 2.4 RU-grade sodium silicate from CM and today mixed up a batch of sand to make some sand cores.
Mixing The Sand And Sodium Silicate
I first got all of my supplies, cups, bags, and stir sticks together and laid them all out on a sheet of plastic to make the cleanup easier. (The McDonald's cup is my supply of sand - easier to pour from a small cup than from a 25 kg bag, eh!?) I then put a smaller sheet of plastic down on top of the larger sheet so that I could easily recover any spilled sand.
To make the sand cores, I first filled the core box with dry 90m silica sand and poured it into a Ziploc bag. I added about 10% more dry sand as it will compact more when the sodium silicate is added to the mix.
Using my Canadian Tire "Star-Frit" scale, I weighed the baggie at 376 grams.
I put an empty plastic cup (clean and dry!) on the scale and zeroed it out.
I next decanted 38 grams (10%) of 2.4 RU-grade sodium silicate from my large supply bottle into the cup.
I poured the liquid into the bag of sand and rolled the sand, sodium silicate, and bag between my hands until the sand and sodium silicate were well and uniformly mixed. The mixture felt only slightly damp but would clump together when squeezed.
Stuffing The Core Box
To make sure the CO2 would penetrate the sand core, I placed 1/4" steel rods into the middle of the core box so that I would have holes through the middle of the sand core. I spooned a small amount of sand mix into the core box and rammed the sand mix around the sides of the box and the steel rod.
More sand mix, more ramming until the core box was filled to the top. I struck the sand mix level with the top of the core box and lightly patted the sand mix so that it was firmly compacted across the top. With a twist, I removed the steel rods from the middle of the sand core leaving nice 1/4" holes through the middle of the sand core.
Using The CO2 Gas
I wouldn't have believed it if I hadn't seen it in person but.... it only takes a few seconds of CO2 gas to turn the loose sand into a hard sand block!! The secret is in how the CO2 is applied to the sodium-silicate-sand mix.
On the right-side of the photo above, you can see a block of wood with a couple of holes in it. And, in the photo below, you can see a plastic container with a hole in the top. Using my blow gun attached to the CO2 cylinder, and pressing down on the top of the plastic container, I slowly gave a 2-second shot of CO2 into the container. This immediately hardened the surface of the sand core.
Removing the plastic container, I then placed the wooden block on the top of the core box, aligning the hole in the wooden block with the hole(s) in the sand core. I slowly gave each hole a 2-second shot of CO2.
I then undid the screws of the core box. Voila, the sand core easily separated from the sides of the wooden core box. In less than 20 seconds from the time of applying the CO2 to starting to undo the screws, I had a solid sand core! Whoodathunkit, eh!!??
I then repeated the CO2 process for my second sand core. The solidified sand core easily slid from the core box.
Ratio of Sodium Silicate To Sand (By Weight!!) Is Very Important!!
The whole secret in using sodium silicate is in the sand mix and the application of the CO2.
In my first try at using sodium silicate, I was short about 3 tablespoons of sand mix. I hastily mixed up a small batch that had about 30% sodium silicate. Bad news!! It wouldn't hold its strength even when repeatedly exposed to the CO2. The sand core was still as soft as when I had rammed it into the core box. I presume the extra liquid prevented the CO2 from penetrating the sand core. So, whether you use a 6% ratio or a 10% ratio, the relative ratio (by weight) of sodium silicate to sand is very important. It doesn't take a lot of sodium silicate.
How You Apply The CO2 Is Very Important!!
While CO2 is heavier than air, my first attempts at using sodium silicate weren't that good. I placed the wet sand cores into a plastic bag and applied the CO2. On my trip to Alumaloy Castings, I saw how they applied the CO2 to the sand - a small cup-like device attached to their CO2 hose, and a piece of wood with a hole in it held on top of the sand core and aligned with the holes in the sand core. A couple of 2-3 second shots of CO2 and the sand core was as solid as a rock.
It was obvious I needed to apply the CO2 in a more "aggressive" fashion. So I modified my process using a 1-litre plastic container with a hole drilled in the top. I was then able to drive the CO2 right into the exposed surfaces of the sand cores.
To get the CO2 into the holes created by the 1/4" steel rods, I simply drilled a couple of holes into a piece of 1/4" plywood so that I could drive the CO2 right through the middle of the sand cores.
Bigger sand cores? Simply use a bigger plastic container. These sand cores were almost instantly as hard as a brick with very smooth surfaces and sharp edges.
In any event, I'm very pleased with the results. Now we go into full-scale production with the sand cores using sodium silicate and CO2.
Next up: An easier way to make the core boxes.
PQ Corporation is the largest manufacturer of sodium silicates, one of the most widely used chemicals in the world. Their brochure on sodium silicate has this table which describes the various strengths of sodium silicate available.
The key measure of sodium silicate is the weight ratio of its two major components - Silica DiOxide (SiO2)to Sodium Oxide (Na2O) (the column titled "Wt. Ratio SIO2 / NA2O"). The most commonly available sodium silicate has a weight ratio of 3.22 parts of Silica DiOxide to 1 part of Sodium Oxide with a solids content (active ingredients) of 37.6% (8.90+28.7=37.6 from Table 2 above). The rest (62.4%) is water. This is sold as "N" grade sodium silicate and is NOT the best choice for making sand cores as it doesn't provide very good strength to the sand core. The sand core will slowly disintegrate when handled. This type of sodium silicate has the viscosity of a cheap liquid dishwashing soap. Table 2 above describes it as a syrupy liquid.
I made the mistake of using the 3.22 N-grade sodium silicate (it may even have been a weaker solution) with very poor results. Even after 24 hours and constant exposure to CO2, the sand cores wouldn't hold together. For those that did stick together, I would end up with loose sand grains in my hand whenever I handled them.
RU-Grade Sodium Silicate
The best type of sodium silicate for making sand cores has a weight ratio of 2.40 parts of Silica DiOxide to 1 part of Sodium Oxide with a solids content (active ingredients) of 47.05% (13.85+33.2=47.05 from Table 2 above) - a 25% increase in active ingredients over the N-Grade stuff!! This is typically sold as "RU" grade sodium silicate and has the viscosity of concentrated liquid laundry detergent - it pours very slowly. Table 2 describes it as a heavy syrup.
I got some 2.4 RU-grade sodium silicate from CM and today mixed up a batch of sand to make some sand cores.
Mixing The Sand And Sodium Silicate
I first got all of my supplies, cups, bags, and stir sticks together and laid them all out on a sheet of plastic to make the cleanup easier. (The McDonald's cup is my supply of sand - easier to pour from a small cup than from a 25 kg bag, eh!?) I then put a smaller sheet of plastic down on top of the larger sheet so that I could easily recover any spilled sand.
To make the sand cores, I first filled the core box with dry 90m silica sand and poured it into a Ziploc bag. I added about 10% more dry sand as it will compact more when the sodium silicate is added to the mix.
Stuffing The Core Box
To make sure the CO2 would penetrate the sand core, I placed 1/4" steel rods into the middle of the core box so that I would have holes through the middle of the sand core. I spooned a small amount of sand mix into the core box and rammed the sand mix around the sides of the box and the steel rod.
Using The CO2 Gas
I wouldn't have believed it if I hadn't seen it in person but.... it only takes a few seconds of CO2 gas to turn the loose sand into a hard sand block!! The secret is in how the CO2 is applied to the sodium-silicate-sand mix.
On the right-side of the photo above, you can see a block of wood with a couple of holes in it. And, in the photo below, you can see a plastic container with a hole in the top. Using my blow gun attached to the CO2 cylinder, and pressing down on the top of the plastic container, I slowly gave a 2-second shot of CO2 into the container. This immediately hardened the surface of the sand core.
I then undid the screws of the core box. Voila, the sand core easily separated from the sides of the wooden core box. In less than 20 seconds from the time of applying the CO2 to starting to undo the screws, I had a solid sand core! Whoodathunkit, eh!!??
The whole secret in using sodium silicate is in the sand mix and the application of the CO2.
In my first try at using sodium silicate, I was short about 3 tablespoons of sand mix. I hastily mixed up a small batch that had about 30% sodium silicate. Bad news!! It wouldn't hold its strength even when repeatedly exposed to the CO2. The sand core was still as soft as when I had rammed it into the core box. I presume the extra liquid prevented the CO2 from penetrating the sand core. So, whether you use a 6% ratio or a 10% ratio, the relative ratio (by weight) of sodium silicate to sand is very important. It doesn't take a lot of sodium silicate.
How You Apply The CO2 Is Very Important!!
While CO2 is heavier than air, my first attempts at using sodium silicate weren't that good. I placed the wet sand cores into a plastic bag and applied the CO2. On my trip to Alumaloy Castings, I saw how they applied the CO2 to the sand - a small cup-like device attached to their CO2 hose, and a piece of wood with a hole in it held on top of the sand core and aligned with the holes in the sand core. A couple of 2-3 second shots of CO2 and the sand core was as solid as a rock.
It was obvious I needed to apply the CO2 in a more "aggressive" fashion. So I modified my process using a 1-litre plastic container with a hole drilled in the top. I was then able to drive the CO2 right into the exposed surfaces of the sand cores.
In any event, I'm very pleased with the results. Now we go into full-scale production with the sand cores using sodium silicate and CO2.
Next up: An easier way to make the core boxes.
Mold Making 101 - Colours For Patterns
Patterns are usually made of wood and finished with smooth painted surfaces. In addition to providing a smooth finished surface that allows the pattern to be removed from the mold, the paint is used to identify the different part of the pattern (pattern, core prints, surfaces to be milled). The American Foundryman's Society has adopted the following colour codes for painting patterns.
Nonferrous
Pattern - yellow
Coreprint - black
Machined areas - red
Loose piece mating areas - yellow with red strips
Gating for mounted patterns - yellow
Ferrous
Pattern - black
Coreprint - yellow
Machined areas - red
Loose piece mating areas - yellow
Gating for mounted patterns - yellow
There are other colours for other types of metals.
Next up: Making sand cores using Sodium Silicate and Carbon Dioxide (CO2)
Nonferrous
Pattern - yellow
Coreprint - black
Machined areas - red
Loose piece mating areas - yellow with red strips
Gating for mounted patterns - yellow
Ferrous
Pattern - black
Coreprint - yellow
Machined areas - red
Loose piece mating areas - yellow
Gating for mounted patterns - yellow
There are other colours for other types of metals.
Next up: Making sand cores using Sodium Silicate and Carbon Dioxide (CO2)
Mold Making 101 - Sand Core Basics
Simple Patterns
Just to recap on our previous post we placed our PATTERN on a MOLD BOARD in the middle of the bottom half of a FLASK which is called the DRAG. We then RAMMED green sand around the PATTERN, levelled or STRUCK off the excess sand and then flipped the DRAG over. We next put on the top half of the FLASK (which is called the COPE), dusted on some PARTING POWDER, inserted a SPRUE PIN, filled the COPE up with green sand and RAMMED the green sand. We then removed the COPE off of the DRAG, made some GATES and VENTS so that the molten metal would flow into and out of the hollow MOLD. We next removed the PATTTERN, producing a reverse image of our pattern in the form of a hollow MOLD.
Complex Patterns In our previous post, we were molding a simple pattern. However, very few patterns are that simple. In the majority of cases, patterns are usually irregularly shaped with hollows and cavities in the middle. We therefore have limitations when we want to make castings that have hollows and cavities in the middle.
We can usually get around this problem by inserting a core of solid sand into the mold. If we can make this core of solid sand into the shape of our hollow or cavity, when the molten metal is poured into our mold, it will flow around the sand core. When the metal solidifies, we simply break out the solid sand core and...... voila!..... we have our hollow or cavity.
Split Patterns
Wherever possible, patterns with an irregular shape are made in two halves called a SPLIT PATTERN. With a SPLIT PATTERN, we place the bottom part of the pattern face-down in the DRAG. We then ram green sand around the pattern, flip the drag, pattern, and rammed-sand over. We then place the top-half of the pattern on top of the bottom-half, place the COPE on top of the DRAG, ram green sand around the pattern, insert/cut in some SPRUES, GATES, and RISERS. We then lift the COPE off the DRAG, remove the patterns and complete the rest of the mold (SPRUES, GATES, and RISERS) so that it is ready for pouring.
In the graphic below, we have the SPLIT PATTERN for a hollow pipe with flanges on each end. The pattern can be split in half along a "PARTING LINE". The two halves of the pattern are kept aligned by holes in the bottom half of the pattern and wooden dowels that protrude from the top half. The wooden dowels align with the holes in the bottom half of the pattern. Here's what our pattern would look like.
Split Patterns & "Core Prints"
However, our pattern doesn't account for the hollow centre of the pipe. To create this hollow centre, we make a cylindrical SAND CORE that we insert into the mold to create the hollow centre. In order to ensure that the SAND CORE is properly placed in the mold and kept there, we add CORE PRINTS to each end of our SPLIT PATTERN.
Now that we have added CORE PRINTS to the PATTERN, we place the bottom-half of the pattern face-down in the drag, and ram the drag with green sand.
We then flip the drag and bottom-half of the pattern over on the mold board, place the cope on top of the drag and set the top-half of the pattern on the bottom-half, using the alignment pins and holes that we have built into the SPLIT PATTERN. We then ram the cope with green sand.
We lift the cope off the drag and remove the patterns from the mold. We add the sprues, gates and risers (not shown). We now have the external shape of the casting we want to make, including two round voids at each end that will hold our SAND CORE in place.
Adding the "Sand Core"
We now insert our cylindrical SAND CORE which will give us a hollow centre when we pour our molten metal into the sand mold. Notice how the SAND CORE fills the voids made by the CORE PRINTS in the green sand.
Wherever possible, when we are making patterns, we'll use a SPLIT PATTERN and SAND CORES to create the holes that are required to complete the casting.
Just to recap on our previous post we placed our PATTERN on a MOLD BOARD in the middle of the bottom half of a FLASK which is called the DRAG. We then RAMMED green sand around the PATTERN, levelled or STRUCK off the excess sand and then flipped the DRAG over. We next put on the top half of the FLASK (which is called the COPE), dusted on some PARTING POWDER, inserted a SPRUE PIN, filled the COPE up with green sand and RAMMED the green sand. We then removed the COPE off of the DRAG, made some GATES and VENTS so that the molten metal would flow into and out of the hollow MOLD. We next removed the PATTTERN, producing a reverse image of our pattern in the form of a hollow MOLD.
Complex Patterns In our previous post, we were molding a simple pattern. However, very few patterns are that simple. In the majority of cases, patterns are usually irregularly shaped with hollows and cavities in the middle. We therefore have limitations when we want to make castings that have hollows and cavities in the middle.
We can usually get around this problem by inserting a core of solid sand into the mold. If we can make this core of solid sand into the shape of our hollow or cavity, when the molten metal is poured into our mold, it will flow around the sand core. When the metal solidifies, we simply break out the solid sand core and...... voila!..... we have our hollow or cavity.
Split Patterns
Wherever possible, patterns with an irregular shape are made in two halves called a SPLIT PATTERN. With a SPLIT PATTERN, we place the bottom part of the pattern face-down in the DRAG. We then ram green sand around the pattern, flip the drag, pattern, and rammed-sand over. We then place the top-half of the pattern on top of the bottom-half, place the COPE on top of the DRAG, ram green sand around the pattern, insert/cut in some SPRUES, GATES, and RISERS. We then lift the COPE off the DRAG, remove the patterns and complete the rest of the mold (SPRUES, GATES, and RISERS) so that it is ready for pouring.
In the graphic below, we have the SPLIT PATTERN for a hollow pipe with flanges on each end. The pattern can be split in half along a "PARTING LINE". The two halves of the pattern are kept aligned by holes in the bottom half of the pattern and wooden dowels that protrude from the top half. The wooden dowels align with the holes in the bottom half of the pattern. Here's what our pattern would look like.
However, our pattern doesn't account for the hollow centre of the pipe. To create this hollow centre, we make a cylindrical SAND CORE that we insert into the mold to create the hollow centre. In order to ensure that the SAND CORE is properly placed in the mold and kept there, we add CORE PRINTS to each end of our SPLIT PATTERN.
We now insert our cylindrical SAND CORE which will give us a hollow centre when we pour our molten metal into the sand mold. Notice how the SAND CORE fills the voids made by the CORE PRINTS in the green sand.
Mold Making 101 - Very Basic Instructions
1.1 Parts of the Mold.
Castings are made in a 2-piece wooden box called a FLASK. The bottom part is called the DRAG. The top piece is called the COPE. The DRAG does not have a bottom. Instead, it is placed on a MOLD BOARD which is an oversized piece of 3/4" plywood on two skids. LOCKING PINS allow the two sections to be separated and then later re-joined in perfect alignment. The joint and surface separating the COPE from the DRAG is called the PARTING LINE.
To recap.
A CASTING is made from a MOLD. The MOLD is made in the FLASK from a PATTERN using GREEN SAND to create a hollow cavity that is in the shape of the PATTERN. To make a mold:
The pattern is placed top-down in the DRAG on a MOLD BOARD. The DRAG is filled up and tightly packed or RAMMED to the top of the DRAG with GREEN SAND. The excess sand is struck off with a straight edge which produces a flat surface on the DRAG.
A second MOLD BOARD is placed on top of the leveled sand. The DRAG, along with both MOLD BOARDS, is flipped over. The top MOLD BOARD is removed so that the top surface of the pattern is now exposed. This surface now forms the PARTING LINE.
The PARTING LINE is next dusted with TALC so as to allow the COPE to be separated from the DRAG when it comes time to remove the PATTERN.
The COPE is then fitted to the DRAG using the LOCKING PINS.
Tapered SPRUE and VENT PINS are then pressed about 1"-2"into the green sand of the DRAG. The SPRUE and VENT PINS will form openings through the sand in which to pour the hot metal and to allow the hot gasses to escape.
The COPE is filled and rammed to the top with green sand. The excess sand is struck off with a straight edge.
With the COPE and DRAG tightly packed with green sand, the PATTERN next has to be removed or DRAWN from the MOLD. The SPRUE and VENT PINS are removed from the COPE, the LOCKING PINS removed, and the COPE lifted off the DRAG. The PATTERN is lightly RAPPED so that it can be loosened from the green sand and lifted out.
The green sand in the DRAG between the SPRUE and VENT holes and the hollow impression left by the PATTERN is removed using a spoon-like instrument called a SLICK to form channels called GATES which will allow the molten metal to flow into the MOLD and the hot gasses to escape.
The COPE is then re-placed on top of the DRAG using the LOCKING PINS.
Hot molten metal is then poured into the SPRUE hole until the metal returns to the surface by the VENT hole.
When the metal has solidified, the FLASK is upturned off the MOLD BOARD. The green sand is then knocked out of the FLASK to expose the CASTING. The SPRUE and VENT holes, which are now filled with metal, are next cut off of the CASTING.
Next up. Sand cores, core prints and core boxes.
Castings are made in a 2-piece wooden box called a FLASK. The bottom part is called the DRAG. The top piece is called the COPE. The DRAG does not have a bottom. Instead, it is placed on a MOLD BOARD which is an oversized piece of 3/4" plywood on two skids. LOCKING PINS allow the two sections to be separated and then later re-joined in perfect alignment. The joint and surface separating the COPE from the DRAG is called the PARTING LINE.
To recap.
- FLASK – a 2-piece wooden box.
- DRAG – bottom half of the FLASK
- COPE – top half of the FLASK
- MOLD BOARD – oversized thick plywood on skids that the DRAG rests on.
- PARTING LINE – joint and surface which separates the COPE from the DRAG.
A CASTING is made from a MOLD. The MOLD is made in the FLASK from a PATTERN using GREEN SAND to create a hollow cavity that is in the shape of the PATTERN. To make a mold:
The pattern is placed top-down in the DRAG on a MOLD BOARD. The DRAG is filled up and tightly packed or RAMMED to the top of the DRAG with GREEN SAND. The excess sand is struck off with a straight edge which produces a flat surface on the DRAG.
A second MOLD BOARD is placed on top of the leveled sand. The DRAG, along with both MOLD BOARDS, is flipped over. The top MOLD BOARD is removed so that the top surface of the pattern is now exposed. This surface now forms the PARTING LINE.
The PARTING LINE is next dusted with TALC so as to allow the COPE to be separated from the DRAG when it comes time to remove the PATTERN.
The COPE is then fitted to the DRAG using the LOCKING PINS.
Tapered SPRUE and VENT PINS are then pressed about 1"-2"into the green sand of the DRAG. The SPRUE and VENT PINS will form openings through the sand in which to pour the hot metal and to allow the hot gasses to escape.
With the COPE and DRAG tightly packed with green sand, the PATTERN next has to be removed or DRAWN from the MOLD. The SPRUE and VENT PINS are removed from the COPE, the LOCKING PINS removed, and the COPE lifted off the DRAG. The PATTERN is lightly RAPPED so that it can be loosened from the green sand and lifted out.
The green sand in the DRAG between the SPRUE and VENT holes and the hollow impression left by the PATTERN is removed using a spoon-like instrument called a SLICK to form channels called GATES which will allow the molten metal to flow into the MOLD and the hot gasses to escape.
The COPE is then re-placed on top of the DRAG using the LOCKING PINS.
Hot molten metal is then poured into the SPRUE hole until the metal returns to the surface by the VENT hole.
When the metal has solidified, the FLASK is upturned off the MOLD BOARD. The green sand is then knocked out of the FLASK to expose the CASTING. The SPRUE and VENT holes, which are now filled with metal, are next cut off of the CASTING.
Next up. Sand cores, core prints and core boxes.
Thursday, March 10, 2011
Putting It All Together
Now that all the parts are fabricated or modified, it's time to put it all together.
Here's a close-up of the air intake slots with the accelerator in place.
Next step is to fit on a ball valve, run some hosing to the gas regulator which we connect to the propane tank.
