MARTIN FROM THE FIREPLACE

Soldiers, chess pieces, furniture hardware, original buttons, cufflinks, commemorative badges and medals on the occasion of anniversaries of your friends — only a part of the list of products that you can make yourself, casting. This work is quite even those who have not had a similar experience: it is enough to have imagination, to be neat, and of course, to get simple equipment for home foundry.

The first step in the foundry process chain — metal melt. Home the crucible can be done, for example, from a standard heating element from electric fireplace PLI reflector type EKN-0,5. To do this, remove the spiral together with fasteners, through holes in the upper part and the socket housing element sealed with refractory clay. It is better to burn before the start of the first heat! item zagermetizirovat denser.

 
Then in the basement it is necessary to continue with a thin needle file or hacksaw threaded: it will increase heating of the relatively massive part of the basement, and thus obtain a more uniform temperature field around the crucible. Heater will serve as the nichrome wire O 1 mm, laid in the groove. Made the knot tightly wrap 1-2 layers of quartz fabric with low thermal conductivity, or fiberglass, and the ends of the wire output.
For the case of the furnace use a metal tin litre capacity: in its center, put the heating element, and the remaining free volume of the tightly complete the asbestos chips. On top apply a layer of fire clay with a thickness of 5-10 mm. Both ends of the heater you need to withdraw from the case through the ceramic plug from the electric box or similar insulator, cut out under it the corresponding hole.
 
Fig. 1. Mini oven
 
Fig. 1. Mini oven:
 
1 — cover, 2 — casing, 3 — plug box, 4, 7 — asbestos crumbs, 5, 6 — clay veneer, 8 — sealing mounting holes, 9 — silica thermal insulation cloth, 10 — the case of the heating element, 11 — nichrome heater, 12 — panel 13 — sealing cap.

 
Fig. 2. Heating element — the crucible mini-kiln
 
Fig. 2. Heating element — the crucible mini-oven:
 
1 — ceramic crucible, 2 — nichrome heater, 3 — ground part of the crucible.

 
Oven cover is made from the same banks that case, only shortened to 50 mm. on the Inside it is also stuffed with crumbs and be filled with a layer of clay of the same thickness. In the middle of the cap is chosen small five millimeter arch to podlipal flux with the possible ignition of the melt.
 
Useful volume of the resulting Cup will be about 100 cm3. It delivers temperature to 1000-1200° at the heater power of 120-150 watts. The mains supply will be fed through a transformer voltage of 18-24 V.
 
During the melting of brass and bronze, which requires a temperature of 900-1000°, the crucible withstands 10-12 cycles. Time of each heat about an hour. However, do not seek to increase the melting speed — speed furnace from failure due to cracking of the ceramic element, and may result in premature burnout of the heater. When working with metals with high melting temperatures, e.g. tin, can be used heating element with a standard helix with the supply voltage directly 127-220 In power long warm-up it is enough, even if not to isolate the quartz element cloth, and just smear a thick layer of the same clay.
 
Now, about the melting of the products. Usually YUS mould to the finished shape, g made of plastic, metal, wood. First, produce a flask — a wooden box without a bottom. Its dimensions depend on the size of the product, just keep in mind that the distance from the model to the walls must be at least 15-20 mm. it is Better that the flask was split: for this opposite wall connect in pairs on the loops. The lower half of the flask fill with clay — you get the so-called podmogilny Board. But in the corners it is inserted approximately half the length of the metal pins O I—4 mm (for example, but suitable size nails, needles): they serve to fix the positions of the upper floor.
To get started, grease podmodelnuju Board on the sides with a thin layer of vaseline and clamp in the mold. Smooth out the clay, press it to polozeny as a well-oiled model. Next, take gypsum, wetting it with water, carefully stirring at the same time, to make the solution, bringing it to density of liquid sour cream. The initial and subsequent layers of coating applied on the model with a brush, avoiding formation of voids in the corners and the folds, after which the solution is poured to the top of the box. Wait until the plaster hardens. At room temperature this happens the worm for about 15-20 minutes. Turning the flask upside down, remove her podmodelnuju Board: that’s when especially impact the benefits of the split box. Repeat the entire process. If we now remove the flask, disconnect half of the plaster and gently remove the model, then both surfaces will have completed its “footprints” — both moulds. They must dry well: just do it, gradually increasing the heating temperature first hold in the sun or on the radiator, then put in the oven home plate. Here they have to be 3-4 hours at 150-200 degrees.
 
Then proforma preparing the sprue for pouring the metal and heaving through which when filling out the form is a “waste” of air and gases. To do this, connect the two mold halves and drill 5-6 mm O through the channel in the plane of the connector to the volume of the form, — gate, and to behold the opposite side is heaving a smaller diameter of about 1 mm. Receiving the edge of the gate rassverlivajut to make a funnel. (Remember to remove with a soft brush crumbs of plaster after these operations.)
 
Before pouring, put the spongy layer of the separation of lubrication and turpentine mastic for flooring — on all contact surfaces as well as in the form itself, put mold halves together and firmly tie them.
 
Remember that molten metal must be poured in the sprue of a thin continuous stream. Disassemble the mold and remove the mold halves is possible only after the casting is completely cooled.
 
For the manufacture of flat objects, for example, plates used easier in the preparation method of the so-called bas-relief casting. It differs from the described volume — the fact that the model is “recessed” into the clay podmogilny boards completely, that is, the surface of the upper half is left smooth: latest — plaster — simply superimposed on the model, only touching, covering it (it can be prepared in advance). In the same proforma “open way” — with a knife and cut the sprue and heaving.
 
Fig. 3. Molding box
 
Fig. 3. Molded box:
 
1 — outflow, 2 — locking pin 3 — model 4 — loop of the walls of the flask, 5 — podmogilny Board, 6 — off the hook.

 
Fig. 4. Ready drag
 
Fig. 4. Ready to drag:
 
1 — drag, 2 — heaving, 3 — gate 4 — form of the model.

 
Some tips for processing the extracted shape of the products. They need to quickly cleaned from the remnants of plaster with a metal brush and burrs. The last operation is carried out, where possible, carefully chisel., or clippers with subsequent Stripping with needle files. From particles flux burned-on food, oxide films are released by chemical means: the item is coated in mild (5-15% strength) sulfuric acid solution. Small elements bring engraving graver and stonechats. Polishing is performed with various pastes: for solid metal (brass, Nickel silver, silver), use a paste GOI, Crocus, soft (tin-lead) to tooth powder, stir in the melted paraffin.
 
To give the finished product “fashion” is now painting under the old silver, old bronze, gold, and, in addition, to better identify the elevation drawings, they are subjected to electrochemical or chemical oxidation. The most common method is treatment with a solution of sulfuric liver, which is produced by “fusing” sulfur and potash in the ratio 1:2.
 
You can use oil paints, coating them with fixative or varnish for better preservation of the laid layers.
 
And the last one. Any work on the crucible need only if you disconnect it from the mains. Use canvas gloves, protective goggles or a mask. Download charge start only after complete cooling of the crucible and its dry. In operations with chemical substances observe safety precautions.
 
A. TALANOV, B. FEDOROV

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