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HOME FOUNDRYThe journal “modelist-Konstruktor” I write a since 1985 and have never regretted it. Read everything from the first page to the last. Very useful and interesting publication. And though time is now difficult, and the cost of the magazine is not so low, will it write in the future, because I believe that the value of the log above its price. The journal regularly and in sufficient volume published drawings of armored vehicles, planes, cars. But, unfortunately, rarely describes the production technology of models and designs equipment and devices, without which hampered their establishment.

A few years ago in one of the rooms “Modeller-designer” was published a description of the equipment with which it was possible to cast plastic parts for models. I liked the idea: taking it as a basis, I produced a variant of the casting machine, which offer the readers of the magazine.

Injection molding machine consists of three parts: a frame; the upper part, which includes foundry with the press; the lower it is represented proformae and the mechanism of their connections/disclosure.

In the drawings, the injection molding machine is missing some dimensions — for example, the height of the smelting chamber, its diameter, etc., I do not put down deliberately in one case some of the details used ready (of course, modified) in another because they can vary depending on available materials.

 

Docking a movable plate with a movement mechanism

Docking a movable plate with a movement mechanism:

1 — movable plate; 2 — slide; 3 — screw; 4 — steel rivet (4 PCs); 5 — uterine nut (from a car Jack. 2); 6 — bracket (St3, the thickness of the uterine nut, 2 pieces); 7 — carrier (St3, the sheet s8, 4x); 8 — bolt M10 with nut (6 pieces); 9 — guide rail (cylinder rod of cambina “field”, 2 PCs.)
 

Melting chamber to the injection cylinder

Melting chamber to the injection cylinder:

1 — rod; 2 — camera-cylinder (cylinder harvester “Niva”); 3 — piston; 4 — output (St3, rod d10); 5—insulating layer (mica); 6 — spiral; 7 — heat-resistant coating (silicate glue with a little asbestos, asbestos sheet)

 

Base frame welded from tubes of rectangular cross section 60×30 mm. Average the item is made extended to the end of its continuation is welded to the support arm, made of a propeller shaft of the car. The connection is reinforced by the gusset plate. Outside to base at the corners of the attached stand, made of 36×36 mm. area on Top of the rack cover is fitted which fixed the smelting chamber. Frame cover made from a steel angle 25×25 mm, and the flooring is better to make ie steel sheet with a thickness of 2-3 mm (it is wooden). The cover is attached to the uprights with bolts M8. On the cover free (with bolts and not end up curled nuts, through increased than normally required, holes) is mounted melting chamber. This is necessary in order to docking semi-form die was in the center Gating system. After the nuts are tightened to the end.

Melting chamber is made of a hydraulic cylinder of the combine harvester “Niva”. Looking ahead, I note that the guides of the movable plates is made of a rod of the cylinder.

 

Melting chamber serves both as a pressure cylinder. The piston and rod is also taken from the mentioned techniques, only the diameter of the rod reduced. To create the required pressure to the piston rod attached to the lever.

In the bottom of the cylinder of the smelting chamber is mounted a die through which molten plastic is supplied under pressure to the form. The form consists of two semi-molds, each of which is attached to its movable plate. P/Gita made of steel sheet with a thickness of 5 mm. They are part of the mechanism of Assembly and disassembly semi-molds and suspended on two General guides on the uprights of the frame. To avoid bending the plates when you move to each is attached two slides. The movement of plates is a special screw through the fallopian nuts (these details from Jack) attached to the lower edge of the plates. I have them attached by leashes, but it’s easier nuts to the plates to weld. The screw on one half — right screw-thread, the other left. Its ends are fixed in the bearings, housings which are attached to the frame. The rotation of the screw is performed using a handwheel with a handle.

 

Injection molding machine

Injection molding machine (parts 3,4,9 — harvester “Niva”):

1 — lever (steel strip 25×4); 2 — bearing of the lever (propeller shaft from the car); 3 — piston rod; 4 — the smelting chamber; 5 — cover (steel area № 2,5 and Board s20); 6 — die; 7 — movable raft (St3, the sheet s5,2); 8 — the RAM (St3, 4 pieces); 9 — guide rail (2 PCs); 10 — frame (steel pipe 60×30); 11 —screw(Jack); 12 — handwheel with handle (milling machine); 13 — front (steel, area 36×36, 4 PCs.);

The technology of manufacturing plastic parts the following. The piston rises to its highest position. Pre-crushed polystyrene (or other plastics) is poured through the feed opening into the cylinder of the smelting chamber and is heated to the melting temperature (for polystyrene to about 180° C). Before filling the form you have to prepare — lubricated with silicone grease (better to use one that is sold in aerosol packing). The willingness of the plastic to the fill is determined by the beginning of its leakage from the die. By this time it should rotate screw to bring the plate to connect the two halves of the form. The upper part of the sprue channel should be tightly pressed to the polymer. Further, the melt under the pressure created by the lever and piston to sharply escalate in the form. After the plastic hardens, the mould is opened by turning the screw in the opposite direction and it is removed from the finished casting.

Injection moulding machine produces parts of almost equal quality to industrial.

 

V. YATSURA, H. Chernoluchinsky, Volgograd region

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