Casting Metal: the Basics

[Music] I guess there's a lot of people when they were younger went to the beach and made sandcastles first of all you need a bucket and the first thing you do after mom and dad deport you that is run onto the beach and try and make the sand castles as quickly as you can when you first go on the beach you're up a long way from where the CSB and the sand is very dry it doesn't really make very good sand castles because it just pours almost like a liquid so after a while you run down by the sea where the waves are coming up and you try again but that sound is too wet and you find that it sticks to the side of the bucket but between the two sides of the beach you'll find the sand that's just right where it's bang together with water so that it will form a perfect sandcastle they always have a slope on the sides the reason for that is once you've filled it you give it the customer a couple of hats that releases the bucket and then it will lift cleanly off the sand rather than using water to bind the sand together this sand is bound with oil so that it will bind together and hold the shape really well using oil means that can use a finer grade of sand which will give a better quality of car stick we're going to make our sand mold in a metal box known as a flask this is a two-part box which has locating pins so that they can be taken apart and locate accurately each time the top is known as the cope the bottom is known as the dragon today we're going to make two products the first one is a small cylinder or bearing block and we'll use sand welding to produce that the second product is a small coin a supermarket trolley so that you don't have to leave your pan bin at the supermarket to make a simple object such as this little number plate it's quite easy to just make it as a one part patent which can easily be produced and removed from the sand it does have sloping sides it has the draft angle just like the slope on your sandcastle bucket some more complex shapes are difficult to take out of the sound even a simple cylinder once you've buried it in the sand you wouldn't be able to remove it without breaking the sand or if you were trying to draw it out vertically it would break the mold unless you put a taper on it and then you wouldn't have a cylinder this can be overcome by splitting the pattern into two parts so that you mold two parts separately and they locate together using pins in the same way that the pins locate the boxes in the flask we've already thought about using the split pattern so that you can take the two halves separately but how can we produce the hole through the middle without having to drill it out in industry obviously producing something and having to machine a lot of the metal away is time-consuming and cost consuming so producing it with the hole already in place is an advantage so we're going to use a pattern again it's a split pattern but it forms together to produce the outside shape but it has these locating bosses on the ends which are known as core prints they're painted black because that's a visual clue to the people in the foundry that they know they've got to add a core to the mold so if we take the COPE off the top of the flask and set that to one side and turn over the drag we often refer to that as an inverted drag and add the first part of the pattern one side has locating pins so it sits flat we'll use the side with the holes face down in the molding box this has been set so that nothing touches the sides of the molding box and there's a space in the corner for us to complete the molding work we give a quick sprinkle of parting powder and it's just used to help remove the pattern from the sand when we're opening the mold because the sand has oil you may want to wear gloves to protect your hands or use a barrier cream particularly if you're using replaying second-hand and sand we start off by sprinkling the sand breaking it up as we go just like making a rhubarb crumble topping and we partly fill the box we never fill it in one go if you fill it in one go you'll be able to form a very hard surface but where you need the strength of the mold around the pattern will be compromised so we just use our fingers to press the sand down to hold the pattern in place the sand now needs to be rammed down more tightly this is a typical ramming tool with a flat end on one side and a tapered end to get into corners I find these are sometimes too large with the small boxes that we're using just a piece of broom handle with a tapered end works particularly well the tapered end is used to get into the corners you don't need to go crazy it's not a competition for the world's strongest man you just add some more layers of sand build it up it might paint 2 or 3 layers as the sand compresses down we now need to level off the sand and that's just done with a piece of bar the process is traditionally known as Strickling so the tool we use is known as a Strickling bar and if we use a soaring action and take it off a piece at a time we end up with a nice flat firm surface and turn things back over and now you can see we've got the pattern surrounded by sand and we can just run our fingers to make sure that it is firm that won't do any harm at all we now take the second part of the pattern and locate that in place we at the cope we have another dusting a parting powder this time the parting pair deserves two processes firstly to release the pattern from the sand and also to stop the two layers of sand from sticking we need to find a way to introduce the metal into the cavity of the mold we do that by adding a runner if we were doing a pattern which needed it or if you were doing an educational course you would always need to talk about having a riser which is a second channel on the opposite side for this particular task we only need to have a runner I use this tapered wooden pin known as a sprue pin and I place it in the corner of the box if it touches the pattern it will damage the outcome if it touches the flask the heat from the molten metal will sink out and it will start to solidify before it has completed the task we repeat the process maryberry would be proud of me doing this pressing the sand there and using the ramming tool again to firm the sand the ramming tool doesn't fit down into the corner but that doesn't matter you can use any old thing I'm using the Strickland bar the sand on the second box the cope doesn't need to be quite so firmly round as in the drag we use the Strickland bar just trickle off the top the best we can and then to remove the sprue pen we just give it a tap twist it and because it's tapered it releases easily out of the sand I know to use a trowel take the top off around the pouring hole and make sure there's no loose sand which would wash into the mold we also produce something called a pouring Basin which makes it easier to pour the metal it gives you a larger target but it also reduces the flow rate of the metal going into the mold so you get less erosion of the sand as you pour good practices to add some vent holes just by pressing in a piece of wire which allows any air to escape and any small amount of smoke that may be produced by the oil burning out and we can split the two halves of the flask the patterns now need to be taken out that can be done just by giving them a gentle tap and then lifting the pattern clean the out we've got a good impression in the sand the same with the other half that's come out quite well there's a little bit of looseness there nothing to worry about that can be repaired by hand we can see there's a small impression on the sand left by the sprue pin that gives us a good indication of where we cut a small bowl the final piece of molding work we need to do is to cut a gate we know what gate is it's where you go into something working away from the mold cavity and we need to ensure that there is no loose sand a good way of doing that is to blow and it's sensible its pop on the pair of got goggles to make sure that nothing blows back into your eye [Music] so that is the basic model produced we just need to produce the core to lay across so that we can form to help the whole through the middle of the casting we use the two parts block introduce and hook it down and run it to give it some strength make sure it's full trim the top and thereby giving it a tap it should release the core which you can carefully lay across the prints the two halves go together again just checking for loose sand okay to pin put it together and that's ready for pouring because we're going to be using molten metal we have a bit of health and safety going on a leather apron saves any splashes to the body suitable gloves and finally a full face visor to keep things nice and tidy so after a break of a 5-10 minutes we now have a pot of molten metal I'll just turn the burner off nice long tongs so that I'm well away from the heat just rest it move the tongs down and then pour the metal into the pouring Basin so that it gently flows [Music] the top of the metal is slightly convex when you first pour it but as things cool down the casting contracts the metal will feed in and we'll see as it becomes concave and dips in the middle of the runner it may be that you need to provide surplus metal within the mold so that it will keep feeding you might have to add maybe up to 50% more metal to the mold than you're going to use in your final casting okay so we've let the mold cool down for 10 or 15 minutes so hopefully when we open it up we'll have the magic over decent casting in there [Music] it's filled well on the bottom part of the mold because we've only used a low temperature metal the sand hasn't really been compromised we can now break out the casting it is still hot you still have to be remembering that it will hurt you if you pick it up and then we can just take the sand from the core just poke that out and there we have the hole right through the casting and it's come out and quite nicely aligned on the joints we just have to cut the sprue off and that can be remelted for the next job there's very little waste in the foundry industry so now we're going to look at die-casting this is a nice simple die made out of MDF laser-cut to produce the supermarket shopping tokens it can be produced out of MDF with the laser cutter channel for the metal to form and the shape of what you're doing the two slices that go on the outside of the sandwich one has got text which has to be a mirror writing and the other in this case has got a little shopping trolley logo but there are events to allow the air to escape as the metal runs in they locate together and have a board backwards and forwards just so that you've got some way to pour the metal it's held in a machine vise so that it's nice and stable and we've got a bit of tape around just a secondary clamping so that nothing explains apart when the metal is pulled in and this time it takes quite a steady hand as we're dealing with a fairly small target to pour this metal and then just to make sure that there aren't any air bubbles a few gentle taps will hopefully give a good result all right so you're giving this a few minutes to cool down I'll just take that little bit off there and then we can release the tape under the vise and start taking things apart so they've got the three parts of the die and they should pay the way things are still warm inside so I'll try not to touch the metal and you can see that the text is formed nicely everything's filled well on the second half you can see that we've got a nice clear impression of the shopping trolley where the air vents ran you can just see a very small amount of metal just started to but there's no problem with that on this product it's just a simple matter of breaking them off the main feed and then a quick touch with the file or a bit of Emery cloth will give it the finish that we're looking for okay so just a couple of last safety things to think about don't pick anything up without knowing that it's call the burner switched off but this set up will probably take twenty minutes to cool down so you can comfortably handle it without safety gloves don't go and put it in the back of your car don't stand it on the table that will be affected by the heat things might not look hot that they probably are make that assumption so hope that you've learned something from what we've been looking at today whether you're watching this as a hobbyist or was thinking about a career in the foundry industry or whether you're approaching it in the school environment I hope that you gain something from it and have fun but be safe thank you [Music]

Channel: undefined

Views: 162,034

Rating: 4.9178514 out of 5

Keywords: casting, cast metal, foundry, foundries, metal, metal work

Id: 2CIcvB72dmk

Length: 15min 20sec (920 seconds)

Published: Thu Nov 22 2018