The geometrical precision of the silicone matrices to the manufacturing of the models of the gear

Transcription

1 ARCHIVES of FOUNDRY ENGINEERING Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences ISSN ( ) Volume 9 Issue 2/ /2 The geometrical precision of the silicone matrices to the manufacturing of the models of the gear G. Budzik a, A. Marciniec a, T. Markowski a, M. Oleksy b, M. Cygnar c a Department of Machine Design, University of Technology in Rzeszów, Avenues Powsta ców Warszawy 8, Rzeszów b Cathedral of Technology and Chemical Science of Materials, University of Technology in Rzeszów, Avenues Powsta ców Warszawy 8, Rzeszów, c State Higher Professional School in Nowy S cz, Address: Staszica 1, Nowy S cz gbudzik@prz.edu.pl, amarc@prz.edu.pl, tmarkow@prz.edu.pl, molek@prz.edu.pl, mcygnar@pwsz-ns.edu.pl Received ; accepted in revised form: Abstract The article presents the researches of geometrical precision of silicone casting form manufactured with using of the process of rapid prototyping of the tools (RT Rapid Tooling). The testing casting form is applied to the production of prototypes of sprockets with the polymer resins and also the casting waxes. The determining of real geometrical precision of silicone form in the relation to the theoretical assumptions determined on the basis of the parameters of the material card of applied silicone was the purpose of researches. Silicone form was created on the basis of the stereolitographic model of sprocket. The coordinates measurable machine WENZEL LH 87 was applied to researches. The measurements of form and also base model were executed in the scanning mode on the basis of model 3D-CAD of sprocket. In purpose of the acceleration of measurable process of base model, silicone form and also prototypes manufactured in form, the special program CNC was written. Program enables the executing of measurements in automatic mode. Measurements enabled determining of precision of manufacturing of form in the relation to nominal model 3D-CAD and also in the relation to stereolitographic base model. The next stage of the research works will concern of the execution of geometrical measurements of prototypes casted in silicone form with chosen materials: casting waxes, the polyester, the epoxy and polyurethane resins. Executed measurements will enable on determining of real precision of prototypes manufactured in silicone casting forms. The problems concerned of determining of geometrical precision of silicone forms and manufactured in them prototypes are considered seldom in the analysed literature from the range of rapid prototyping. From this reason presented researches in article create the original work in the theoretical and practical aspect. Keywords: non-destructive researches, geometrical precision, rapid prototyping, silicone matrix, gear Manufacturing of the high quality casts requires of using modern research and the productive methods [1, 2, 3, 4]. The systems of rapid prototyping are more and more often applied in production of the casting components [5, 6],. The some additive systems of RP enable on manufacturing of casting models used to production of casting forms [7, 8]. Additionally it is possible to use directly systems of RP to production of casting forms for the low-fusible alloys (method 3DP) [9]. It is possible to obtain the large extension of the possibilities of applications of rapid manufacturing by means of using of methods Rapid Tooling [10, 11]. One from methods of Rapid Tooling is method of manufacturing of silicone matrices and prototypes under the ARCHIVES OF FOUNDRY ENGINEERING Volume 9, Issue 2/2009,

2 lowered pressure in the technology Vacuum Casting. Silicone forms enable on production of model with casting waxes, the polyester, epoxy and polyurethane resins [12]. The precision of prototypes manufactured in silicone matrices is dependent from manufacturing of them. It is possible to estimate precision of manufacturing of form with using of the coordinates measurable technique. The literature describes methods of manufacturing of silicone form, omitting very often of them dimensional shapely precision. From this reason presented in title of article the research problem was considered. On the basis model 3D-CAD prototype of wheel was manufactured by means of technique of stereolitography (fig. 2). Silicone form applied in researches was manufactured on the basis stereolitographic model of sprocket. Matrix applied in researches was made with silicone type MM240 TV A+B (fig. 3). 2. The creation of silicone form Manufacturing of testing model 3D-CAD sprocket was first stage of creation of silicone form (fig. 1). Testing model was created in the manner enabling executions of measurements by means of coordinates measurable machine in the programmable automatic model CNC. The center of the system of coordinates of model 3D-CAD was placed in the axis of the turn of sprocket. It was possible thanks this the precise adjustment of the system of coordinates of model 3D-CAD to the system of coordinates of the program environment of coordinates measurable machine. Fig. 3. Testing of the silicone form This is two-component transparent additive forming silicone, which after finishing of process of the hardening achieves the durability properties of the elastomer. Main properties of silicone are: the dimensional stability, the small manufacturing cramp (0,08%) and the large chemical resistance. Silicone is transparent what helps in the cutting of form. Process of manufacturing silicone form with elements about the complex shapes was described in detail in literature [12, 13, 14]. 3. Execution of measurements 3.1. Preparation of measurable machine Fig. 1. Model 3D-CAD of the testing wheel The analysis of geometrical precision of stereolitographic model of sprocket and silicone form were executed with using of coordinates measurable machine WENZEL LH 87 (fig. 4) having the standard software Metrosoft CM3.8 [15]. The general conditions of executing measurements are presented in works [16-19]. Process of the preparation of the things contained in researches: preparation of coordinates measurable machine, fasten and base elements for measured model of sprocket, the calibration of measurable head, the reading of model 3D-CAD of measured sprocket and determining of the measurable points, determining of mode of executing of measurement (point, scan), determining of the speed of the moving of the measurable head in mode CNC, the writing and the running of program CNC to measurement of sprockets on base of model CAD, execution of measurements. Fig. 2. Model SLA of the testing wheel 138 ARCHIVES OF FOUNDRY ENGINEERING Volume 9, Issue 2/2009,

3 Fig. 6. Measurement of the model SLA Fig. 4. View of the measurable post It exists possibility of measurement of base model and made on his base of the matrix with using of the same model 3D-CAD. In this case before measurement of form in program environment of measurable machine it is necessary to set the direction of coming of measurable head to the measured element. Figure 7 presents measurement of silicone form in scan mode. It is possible to indicate measurable points individually on the surface of model 3D-CAD or in form of the path created as result of cutting of model by means of the measurable plane (fig. 5). Figure 6 presents measurement of SLA model in scan mode. Fig. 7. Measurement of silicone form 3.2. Analysis of results of measurements Fig. 5. Measurable path of the sprocket s outline Software of coordinates measurable machine Metrosoft CM 3.8. Wenzel Metromec enables the observation of the deviations during executing of measurement. It enables also the geometrical interpretation in the relation to nominal model (3D-CAD) [15]. ARCHIVES OF FOUNDRY ENGINEERING Volume 9, Issue 2/2009,

4 Fig. 8. Protocol with measurement of the model SLA Fig. 9. Protocol with measurement of the silicone form 140 ARCHIVES OF FOUNDRY ENGINEERING Volume 9, Issue 2/2009,

5 Measurements were made by the measurable ending having the slug about the diameter 2 mm with the speed of scanning 4mm/s, with the step of scanning equal 0,5 mm. Measurable path contained 1601 points. It is possible to analyse results of measurements along whole measurable path or in interesting points. Figure 8 presents the measurable protocole of model SLA of sprocket. Figure 9 presents measurable protocole of silicone matrix s socket applied to production of casting models of sprockets. Protocols contains charts of deviations along measurable path and also the detailed values of deviations in chosen points. It is necessary to notice on the basis of analysis of measurements of model SLA, that model was created very precise i.e. on the whole length of measurable path set value of the tolerance did not exceed (±0,1mm). Maximum deviation of the measured outline does not exceed 0,07mm. This is result of elaborated and applied in The cathedral of the construction of the machines procedures incremented precision manufactured models SLA by means of the appliance SLA 250. Results of measurements of silicone form confirm good precision of the imitation of the geometry of model in silicone form, however this precision is smaller than precision of model SLA. Maximum deviation of dimension of matrix in the relation to dimension of nominal model is equal 0,152mm. To take the shape and dimensions of form and also set by producer theoretical cramp of silicone (0,08%) into consideration deviation of dimension of the form s socket in the relation to base model should not exceed 0,04mm. Results of measurements show the large exceeding of set theoretical value. From this reason in the case of manufacturing of silicone forms of elements about complex shapes it is necessary to apply the individual constructional assumptions with the supplementary data with coordinates measurements. 4. Conclusions Coordinates measurable technique enables on the estimation of dimensional shapely precision of silicone casting forms. Results of measurements show, that real dimensions of the silicone matrix s socket differ in the large degree in the relation to theoretical dimensions, which they would result with set processing cramp of silicone. This fact argues about the large influence of shape of form on her dimensional precision. From this reason manufactured silicone forms applied to production of the precise products should be control individually with using of coordinates measurable technique. Dimensional shapely precision of prototypes manufactured in silicone forms is the separate problem. In this case precision of prototype is resultant of mistakes of base model, mistakes of socket s form and also manufacturing cramp of the cast material in silicone form. Silicone forms can be applied among others to manufacturing of waxen casting models applied to production of shell forms in technology of precise casting. In next stages of research works it will be planned execution of measurements on next stages of process of manufacturing of prototypes or waxen measurements of casting models and final casts. These information are applied to the calculation of the coefficients of the compensation, which must be considered during of manufacturing of model 3D-CAD. Scientific works financed with the means on science in years as the research developmental project (N R /2008) and also in years the research project (4T0B ). Bibliography [1] N. Homburg, E. 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