JPS5937702B2 - How to join evanescent split models - Google Patents

Abstract

PURPOSE:To bond split patterns readily and rapidly with good dimensional accuracy by forming a groove in the faying parts of horizontal dies, injecting hot-melt type adhesive agent and allowing the same to set. CONSTITUTION:Edge preparation 3 of U-, V- or I-form is applied to the faying parts of the precision-casting extinctable split patterns 1, 2 to be bonded and a hot- melt type adhesive agent 4 having been heated to melt is injected into this groove 3 and is allowed to set through cooling. The extinctalbe split patterns to be used refer to those of heat-elution type and do not include those of water soluble type or heat burn type. Known hot-melt type adhesive agents composed primarily of polyamide resins and phenoxy resins are used for the hot-melt type adhesive agent, wherein the most desirable is polyamide-base resins.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of joining and integrating fugitive split models used for precision casting, and in particular, a method that allows easy and quick joining without impairing the dimensional accuracy of the models. Moreover, it relates to a new joining method that enables the reuse of model materials.

Wax-based, naphthalene-based, polystyrene-based, etc. are known as fugitive models used in precision casting, and integral models are used if the shape is relatively simple.

However, when the shape becomes complex, it is extremely difficult to produce a one-piece fugitive model, so a method is adopted in which a fugitive split model is used and then joined together with an appropriate adhesive when making a mold. .

As this type of adhesive, solvent-based adhesives such as vinyl acetate adhesives are mainly used, but conventional adhesives
Sufficient adhesive strength cannot be obtained, ■ It takes a long time to harden and workability decreases, ■ Naphthalene-based disappearing models are sublimable, so if it takes time to bond, dimensional accuracy will decrease, ■ After the model disappears Since insoluble adhesive solid components are mixed into the model material, it is difficult to recover and reuse the model material, which is a serious problem in the practical application of fugitive segmented models. There is.

The present inventor has focused on the above-mentioned circumstances and has conducted extensive research in an attempt to develop a bonding method that can eliminate all of the drawbacks (1) to (3) mentioned above with respect to solvent-based adhesives.

As a result, they discovered that the above objectives could be achieved by using a hot-melt adhesive, and finally completed the present invention.

That is, the configuration of the joining method according to the present invention is to form a groove in a U-shape, V-shape, single-shape, etc. at the joint part of a fugitive split model for precision casting, and to apply hot-melt adhesive within the groove. The gist is that the agent is injected and cured to join and integrate.

The dissipative splitting model used in the present invention refers to a heat elution type, and does not include an aqueous elution type or a heat dissipation type.

In addition, hot melt adhesives include polyamide resin,
All known hot melt adhesives whose main components are phenoxy resin, polyester resin, polyisobutylene resin, etc. can be used, but there is a correlation with wax, polystyrene resin, naphthalene, etc., which are the most commonly used raw materials for fugitive split models. Among these, polyamide resins are most preferred.

When carrying out the present invention, as shown in Figs. 1 to 3 (all cross-sectional explanatory views), a U
A groove 3 in a shape of a letter, a V-shape, or a letter 1 is formed, and hot-melt adhesive 4 heated and melted is injected into the groove 3 and allowed to harden by cooling.

In the case of a single-shaped groove, hot-melt adhesive 4 may be applied to one or both of the opposing surfaces of the domain models 1 and 2, and the opposing surfaces are brought together as soon as possible and cooled and hardened. can.

Since the time from injection or application of the hot melt adhesive to cooling and hardening (completion of bonding) is several seconds to several seconds, the relative positions of split models 1 and 2 should be firmly fixed in advance in preparation for bonding. In addition, in the case of butt joining, preparations must be made so that the relative positions of both can be accurately secured.

After the joining is completed, the adhesive protruding from the groove 3 may be cut off to make it smooth.

By employing this method, the divided models 1.degree. 2 can be firmly joined and integrated in an extremely short period of time.

In the illustrated example, we have explained the case where three types of groove shapes are adopted, but the groove shape itself is not limited, and can be changed depending on the shape of the model, the workability of the groove processing, dimensional accuracy, etc. It is possible to change it as appropriate.

In this way, it has been determined that all of the drawbacks of conventional solvent-based adhesives, such as ① lack of adhesive strength, ② long bonding time, and ② low dimensional accuracy, can be solved.

Furthermore, the fugitive model bonded according to the present invention is made to disappear by heating and eluting after the mold is prepared, and at this time, the hot melt adhesive is also eluted into the model raw material.

However, hot-melt adhesives are compatible with model raw materials and have heat-melting properties themselves, and since the amount used is extremely small relative to model raw materials, the eluted material can be reused as is. Can be used as model material.

Therefore, the above-mentioned disadvantage (2), which was pointed out to solvent-based adhesives, namely, "impossibility of reusing model raw materials", could be solved at the same time.

In the present invention, the injection temperature of the adhesive is 2 times lower than the melting point of the adhesive.
The temperature is preferably 0 to 30°C.

At temperatures below 20℃, the adhesive and model will not melt well, and the temperature will exceed 30℃.
There is a drawback that the adhesive ability decreases when the temperature exceeds ℃.

The present invention is roughly constructed as described above, and has completely solved all the problems related to joining and integration, which have been a bottleneck in effectively utilizing evanescent segmented models, and has great practical value.

Next, examples of the present invention are shown, but the following does not limit the present invention, and the model raw materials, the type of hot melt adhesive, the groove shape, etc. are changed in accordance with the purpose of the above and below. It is also possible to carry out the invention as described above, and all of them are included in the scope of the technology of the present invention.

Example A naphthalene-based (containing 1 to 3 styrene resins) fugitive segmented model was used, and polyamide resin (A or B in Table 1 below) was used as a hot melt adhesive.
The split models are joined using the groove shape shown in the figures (the unit of dimensions in each figure is mm).

Bonding is performed by injecting heated and molten adhesive into the groove (for grooves, apply adhesive to both opposing surfaces and press them together within 5 seconds), and then holding the pressure for 20 seconds. Ta.

Using the obtained bonded piece, the strength was measured when a downward bending load was applied with the groove facing upward, and the results shown in Table 2 were obtained.

[Brief explanation of drawings]

1 to 3 are cross-sectional explanatory views illustrating groove shapes employed in the present invention. 1.2... Vanishing split model, 3... Bevel, 4...
Hot melt adhesive.

Claims (1)

[Claims] 1. When joining fugitive split models for precision casting, a groove is formed at the joint of the model, and a hot-melt adhesive is injected into the groove and hardened. How to join split models.