CN101623907B - Method for preparing three-dimensional photoelasticity analysis model by applying fast-forming plaster mold technique - Google Patents

Abstract

The invention discloses a method for preparing photoelasticity analysis model by applying fast-forming plaster mold vacuum pouring technique, comprising three parts of manufacture of wax pattern female die used for moulding, manufacture of fusible pattern plaster die and vacuum pouring epoxy resin. The concrete steps are as follows: 1. converting the three-dimension CAD model of the part to be manufactured into STL format data, and manufacturing with a laser selection precinct sintering technique to form the wax pattern fast; bonding wax gate stick on the wax pattern female die and hanging the wax pattern female die in the mid air in the container; 2. adding filler and additive in semi-hydrated gypsum powder to be evenly mixed with water, pouring into the container, keeping the distance between the wax pattern female die and the wall of the container to be uniform, and standing for 10h until the plaster mould is solidified; placing the plaster mould into a drying furnace for drying, de-waxing, baking and the like, and placing into a vacuum pouring machine after cooling; and 3. adding solidifier and plasticizer into the epoxy resin, heating by water bath, placing into the vacuum pouring machine for de-gasifying, pouring into the plaster mould and placing into the drying furnace for solidification.

Description

The method of applying fast-forming plaster mold prepared three-dimensional light elasticity analytical model

Technical field

The invention belongs to Rapid tooling, be specifically related to the method that applying fast-forming and gypsum mould vacuum injection molding technique prepare the photoelastic analysis model.

Background technology

Experimental technique with optics Research on Principle Elasticity Problems is called photoelastic method; It is that the transparent plastic with birefringence effect is processed component model; Place polarized light field to read interference fringe pattern analysis; To study all concentrated zone and three-dimensional internal stress problem of the stress distribution of the member of more complicated, particularly stress of geometry and load-up condition.Gypsum mould technology is mainly used in industries such as medical treatment, bronze ware casting and building, closely also is applied to the hot investment casting of high accuracy complex parts decades.Realize copper aluminum precision casting through making steps such as prototype, configuration gypsum slurry, pouring gypsum mould, gypsum mould shrink sclerosis, casting and casting cleaning.

Application of epoxy prepares the die model that the main method of photoelastic model is elder generation's making part at present; Moulds such as the die made with lowmelting point alloy of making withdrawing pattern somatotype, silica gel mould, plaster mold; Pouring carrying out epoxy resin pattern is shaped, and also has during the model of labyrinth to adopt piecemeal to make the bonding one-tenth adult model in back.Such process characteristic one is that model accuracy is low, and die model is made precision and received the influence of machining accuracy and somatotype positioning accuracy big; The 2nd, the manufacturing cycle is long, and particularly for the labyrinth part, mould structure is complicated, and the process time is long; Partitioned organization is many etc.; The 3rd, the model with complicated inner cavity structure, the depanning difficulty, it is bonding more often to need piecemeal to make, and can not satisfy the conforming requirement of material fully.

Summary of the invention

The objective of the invention is, a kind of process of using rapid prototyping and fusible pattern type gypsum mould making three-dimensional photoelasticity model is provided, model accuracy can reach IT5 level casting dimension accuracy.

This method comprises molding with the making of quick shaping wax pattern master mold, the making of fusible pattern plaster mold and vacuum pouring epoxy resin three parts, and method is mainly following three processes:

One, applying fast-forming fabrication techniques part wax pattern master mold:

(Rapid Prototyping, RP) technology is to take manufacture a product the fast process of brassboard of layering manufacturing, discrete stacking method to quick shaping, can directly make part prototype exemplar by part three-dimensional CAD mathematical model applying fast-forming special equipment.Adopt selective laser sintering (SLS) fast shaping technology to make wax pattern in this patent, former type material is paraffin, plastic powders mixture, is used to make the master mold prototype of fusible pattern plaster mold.Concrete steps:

(1) three-dimensional CAD model that will desire workpieces is converted into the STL formatted data, uses selective laser sintering (SLS) technology and makes quick shaping wax pattern master mold;

(2) wax gate stick on bonding on the wax pattern master mold, cup diameter 20～30mm;

(3) will assemble unsettled being placed in the container of part master mold wax pattern of gate stick.

Two, use foaming plaster and make the fusible pattern plaster mold, comprise configuration gypsum slurry, assembling sprue gate, processes such as pouring gypsum mould, dewaxing and gypsum mould dehydration.Install part quick shaping wax pattern additional sprue gate, the unsettled appropriate size that places encloses in the case; In semi-hydrated gypsum powder, add suitable filler and additive, to improve plaster mold intensity, reduce the crackle tendency and to increase gas permeability and collapsibility; The preparation gypsum slurry; Pouring foaming plaster mould in enclosing case, plaster mold is inserted in the drying oven after solidifying, and the high temperature oxygenating is to remove wax pattern master mold in the plaster mold; Low temperature-high temperature drying technology with a definite sequence in drying oven is carried out drying and roasting, processes the fusible pattern plaster mold.Concrete steps:

(1) preparation gypsum slurry: select α type or beta-type semi-hydrated gypsum powder for use, in 100 parts of alpha semi-hydrated gypsum powder, add 20～40 parts of (weight ratios of silica flour; Kaolin or 35～50 parts of bauxites, 15～25 parts in magnesium sulfate down together); Evenly be mixed and made into gypsum slurry with water, the ratio of water and solid is 0.8: 1～1.5: 1, slowly pours in the container; Keep the wax pattern prototype apart from the chamber wall distance evenly, the slurrying and the duration of pouring are no more than 10 minutes.

(2) leave standstill more than 10 hours, gypsum mould solidifies and discharge section moisture;

(3) plaster mold is inserted in the circulating atmosphere drying oven, dewaxing dry to plaster mold and roasting, in 100～700 ℃ of temperature ranges, heat up, insulation and cooling about 25-30 hour, process anhydrous foaming plaster mould.The dewaxing of wax pattern master mold is included in plaster mold drying and the roasting process.

(4) plaster mold is cooled to 30～50 ℃, inserts in the type vacuum injecting and forming machine.

Three, vacuum pouring epoxy resin

Place vacuum pouring indoor the fusible pattern plaster mold of processing; Earlier with photoelastic resin material proportioning, mixing, the degassing, nearly vacuum (＜1kPa) be poured in the plaster mold under the state, recover atmospheric pressure during casting complete; To guarantee that resin is full of die cavity, model is evenly closely knit.In drying baker, carry out one-step solidification.Concrete steps:

(1) preparation epoxy resin: in 100 parts of (weight ratio, down together) epoxy resin, add 30 parts ± 5 parts of maleic anhydrides, face 2 parts ± 1 part of dibatyl phithalate; 0.1～0.2 part of dimethylaniline, water-bath are heated to 80～100 ℃ of mixing, insert in the type vacuum injecting and forming machine; Keep absolute pressure＜0.01bar in the vacuum chamber; The degassing also is poured in the plaster mold, and recovering vacuum chamber pressure behind the casting complete is atmospheric pressure, takes out plaster mold.

(2) plaster mold was inserted in the drying baker 48 hours, the drying baker temperature keeps 50～55 ℃, and model is cured;

(3) take out plaster mold, insert in the pond and soak, treat the soft back removal of gypsum gypsum;

Clear up gypsum at last, the arrangement model.In water, soak the light and handy plaster mold in back, remove gypsum material, after obtaining resin mould and removing the sprue gate, accomplish photoelastic resin mould.

The specific embodiment

Below through specific embodiment this bright method is done further explanation.With the engine piston model is example.

One, molding is made with the wax pattern master mold:

(1) will have this part three-dimensional CAD model; Spare part outside measurement is 150 * 150 * 165mm; Be converted into the STL formatted data, (Selected Laser Sintering, SLS) technology making quick shaping wax pattern is the piston prototype that molding powder mixes with paraffin to use selective laser sintering.Wax pattern prototype dimensional accuracy is ± 0.2mm 2 days Production Times;

(2) wax gate stick on bonding on the wax pattern master mold, cup diameter 20mm;

(3) 40 * 40 * 40 centimetres of side's buckets of the sheet iron system of enclosing are with unsettled being placed in the bucket of piston wax pattern master mold that assembles gate stick;

Two, the fusible pattern plaster mold is made:

(1) preparation gypsum slurry: select the alpha semi-hydrated gypsum powder for use; Additive is a weight ratio; 100 parts of land plasters, 20 parts of silica flours, 20 parts in bauxite powder, 8 parts of talcum powder, 18 parts in magnesium sulfate; Add 240 parts in water and be mixed and made into gypsum slurry and slowly pour in the container, keep the wax pattern master mold apart from the container side wall distance evenly, the slurrying and the duration of pouring are no more than 10 minutes;

(2) leave standstill 10 hours, gypsum mould solidifies and discharge section moisture;

(3) plaster mold is inserted in the circulating atmosphere drying oven 130 ℃ and continue 6 hours; Rise to 700 ℃ with 60 ℃ heating rate per hour then, kept furnace temperature 5 hours; Temperature to 300 a ℃ maintenance naturally cooled to normal temperature after 5 hours in the mild reduction stove.

(4) plaster mold is cooled to 30～50 ℃, inserts in the type vacuum injecting and forming machine;

Three, vacuum pouring epoxy resin

(1) preparation epoxy resin: in 100 parts of (weight ratio, down together) E-44 type epoxy resin, add 32 parts of maleic anhydrides, face 3 parts of dibatyl phithalates; 0.2 part of dimethylaniline, water-bath are heated to 90 ℃ of mixing, insert in the type vacuum injecting and forming machine; Keep absolute pressure＜0.01bar in the vacuum chamber; The degassing also is poured in the plaster mold, and recovering vacuum chamber pressure behind the casting complete is atmospheric pressure, takes out plaster mold;

(2) plaster mold was inserted in the drying baker 48 hours, the drying baker temperature remains on 55 ℃, and model is cured;

(3) take out plaster mold, insert in the pond and soak, treat the soft back removal of gypsum gypsum;

(4) cut the resin gate stick with handsaw, keep outer surface of piston complete smooth;

(5) cleaning components model makes not have gypsum ash and wax on the model, and high pressure gas dries up model.

Characteristics of the present invention and usefulness are: it is high to make photoelastic model precision degree, and fabrication cycle is short; Mould making process is simply effective, and depanning is convenient, and the complex model that is particularly suitable for thin-walled or inner-cavity structure is made.This method also can be used for preparing fast the epoxylite model of other purposes (like BUILDINGS MODELS and handicraft model etc.) labyrinth.

Claims (1)

1. use the method that the plaster mold vacuum injection molding technique prepares three-dimensional light elasticity analytical model, it is characterized in that method comprises molding with wax pattern prototype, the making of fusible pattern plaster mold and vacuum pouring epoxy resin three parts, concrete grammar such as following steps:

One, applying fast-forming fabrication techniques wax pattern master mold:

(1) three-dimensional CAD model that will desire workpieces is converted into the STL formatted data, uses selective laser sintering technology and makes quick shaping wax pattern master mold;

(2) wax gate stick on bonding on the wax pattern master mold, cup diameter 20～30mm;

(3) will assemble unsettled being placed in the container of part wax pattern master mold of gate stick;

Two, the fusible pattern plaster mold is made:

(1) preparation gypsum slurry: select α type or beta-type semi-hydrated gypsum powder for use, in 100 parts of alpha semi-hydrated gypsum powder, add 20～40 parts of silica flours, kaolin or 35～50 parts of bauxites, 15～25 parts in magnesium sulfate; Evenly be mixed and made into gypsum slurry with water; Aforementioned proportion is a weight ratio, and the part by weight of water and solid is 0.8: 1～1.5: 1, slowly pours in the container; Keep the wax pattern prototype apart from the chamber wall distance evenly, the slurrying and the duration of pouring are no more than 10 minutes;

(2) leave standstill 10 hours, gypsum mould solidifies and discharge section moisture;

(3) plaster mold is inserted in the circulating atmosphere drying oven, in 100～700 ℃ of temperature ranges, heat up, be incubated and lowered the temperature 25～30 hours,, process anhydrous foaming plaster mould plaster mold drying, dewaxing and roasting;

(4) plaster mold is cooled to 30～50 ℃, inserts in the type vacuum injecting and forming machine;

Three, vacuum pouring epoxy resin

(1) preparation epoxy resin: in 100 parts of E-44 type epoxy resin, add 30 parts ± 5 parts of maleic anhydrides, face 2 parts ± 1 part of dibatyl phithalate, 0.1～0.2 part of dimethylaniline; Aforementioned proportion is a weight ratio, and water-bath is heated to 80～100 ℃ of mixing, inserts in the type vacuum injecting and forming machine; Keep absolute pressure＜0.01bar in the vacuum chamber; The degassing also is poured in the plaster mold, and recovering vacuum chamber pressure behind the casting complete is atmospheric pressure, takes out plaster mold;

(2) plaster mold was inserted in the drying baker 48 hours, the drying baker temperature remains on 50～55 ℃, and model is cured;

(3) take out plaster mold, insert in the pond and soak, treat the soft back removal of gypsum gypsum;

(4) cut the resin gate stick, keep the part model outer surface complete smooth;

(5) cleaning components model makes not have gypsum ash and wax on the model, and high pressure gas dries up model.