US20150000855A1

US20150000855A1 - Holder block system and methods for metal casting

Info

Publication number: US20150000855A1
Application number: US14/314,091
Authority: US
Inventors: David SCHWAM
Original assignee: Case Western Reserve University
Current assignee: Case Western Reserve University
Priority date: 2013-07-01
Filing date: 2014-06-25
Publication date: 2015-01-01

Abstract

A holder block system suitable for producing metal castings. The holder block system includes a holder block primary mold that has one or more cavities that accept a sub-mold that incorporates the features of the part to be cast, wherein the sub-mold can be produced utilizing 3-D printing. Methods of preparing holder block patterns and cast objects are with the holder block system disclosed.

Description

FIELD OF THE INVENTION

The present invention relates to a holder block system suitable for producing metal castings. The holder block system includes a holder block primary mold that has one or more cavities that accept a sub-mold that incorporates the features of the part to be cast, wherein the sub-mold can be produced utilizing 3-D printing. Methods of preparing holder block patterns and cast objects with the holder block system are disclosed.

BACKGROUND OF THE INVENTION

Sand casting is a popular method utilized to produce metal components having various geometries. Sand molds that are destroyed in order to remove the cast part are utilized.
With the advent of 3-D printing, 3-D printers have been utilized to print molds suitable for use in sand casting. However, producing cast materials with 3-D printed molds can be quite expensive, at least in part because of the potentially large amount of printing material and long time needed to produce a mold and in some cases a large print size required. 3-D print materials are also relatively expensive.

SUMMARY OF THE INVENTION

In view of the above, a problem of the invention is to provide rapidly producible, yet cost effective metal cast components.
The problem of the invention is solved by the holder block system of the present invention which includes a holder block primary mold, preferably formed by traditional, inexpensive sand molding methods, that includes one or more cavities that accept a sub-mold that includes the features of the component or part to be cast, wherein the sub-mold is produced utilizing 3-D printing.
Yet another object of the present invention is to provide a holder block primary mold that includes one or more cavities, with a sprue, well, runner and ingate.
Still another object of the present invention is to provide a unitary, single piece, 3-D printed sub-mold that is free of a separate core.
A further object of the present invention is to provide a holder block system including a primary mold including a cavity which contains a sub-mold, wherein the compositions of the mold and sub-mold are the same or different. In a preferred embodiment, the materials of the primary mold and sub-mold are different, with the holder block primary mold fabricated by a traditional no-bake or a similar sand-molding process. Utilizing a traditional primary construction, mold preparation time is relatively short and also is relatively inexpensive. The sub-molds prepared by 3-D printing take relatively longer time to prepare and also require special materials.
Yet another object of the present invention is to provide a method for providing a holder block system comprising the steps of providing a primary mold having at least one cavity and one or more of a sprue, well, runner and ingate; providing a 3-D printed sub-mold including an interior surface having a shape of an object to be molded; inserting the sub-mold into the cavity of the mold; and adding a molten metal to a portion of the mold such that a molten metal flows into the sub-mold from the mold.
Still another object of the present invention is to provide a sub-mold that is formed as a single piece, utilizing 3-D printing, wherein the sub-mold is free of a cope and drag.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other features and advantages will become apparent by reading the detailed description of the invention, taken together with the drawings, wherein:

FIG. 1 illustrates one embodiment of holder block system which includes a sub-mold ready to be inserted into a holder block primary mold; and

FIGS. 2 a and 2 b illustrate a top view and a bottom view, respectively, of a cast part made with the holder block primary mold and the 3-D printed sub-mold shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

A holder block system is disclosed comprising a holder block pattern including a primary mold that has one or more cavities that accept a sub-mold that incorporates the features of a part to be cast. The primary mold does not contain any features of the part to be cast, in a preferred embodiment. Advantageously, the sub-mold is produced with a 3-D printer. Methods for producing metal castings with the holder block system of the present invention are disclosed.
Primary Mold Production
The holder block system of the present invention includes a holder block pattern comprising a holder block primary mold. The primary mold has one or more cavities that are designed to accept one or more sub-molds. As illustrated in FIG. 1, the holder block system 10 includes a primary mold 20 and a sub-mold 40. Primary mold 20 includes a form such as a flask 22 into which a molding composition 24 is placed. Any suitable composition known to those of ordinary skill in the art can be utilized. Molding compositions typically comprise sand, e.g. silica sand (SiO₂), which is preferably mixed with a binder or other material that aids in maintaining the shape of the mold cavity 26 and/or any other desired features. Sand is relatively inexpensive and resistant to the temperatures at which metal parts are cast and molded. Various additives that can be utilized with the sand, include but are not limited to, various resins, clays, water, and oils.
The molding composition is added to the flask 22 and placed around a pattern, which is preferably in the form of a replica of the external shape of the sub-mold. The pattern can also include a gating system 28. In other embodiments the gating system is formed separately. The gating system includes one or more of a sprue 29, well 30, runner 32 and ingate 34, for example as shown in FIG. 1. Various types of molds can be created, for example green sand molds, no-bake molds, air set molds, dry sand molds, cold box molds, vacuum molds or the like.
In view of the use of a sub-mold, the holder block mold is free of any part-specific features. Thus, the holder block pattern primary mold 20 includes one or more generic cavity blocks or cavities. The generic cavity or cavities 26 created in the holder block mold 20 accepts a smaller sub-mold or several small sub-molds, each made to fit into the cavity. Thus, the holder block mold provides all the features necessary for casting a high-integrity part and at the same time, allows the sub-molds to incorporate only the features of the part to be cast.
Sub-molds
As indicated herein, the sub-mold is produced by 3-D printing. The outer dimensions of the sub-mold 40 are adapted to be placed in at least a portion of the cavity 26 of mold 20, for example as illustrated in FIG. 1. The sub-mold 40 includes an ingate 42 adapted to align with gating system 28 of mold 20 and thereby accept the molten metal into the interior cavity of sub-mold 40.
Various techniques and procedures have been developed which utilize 3-dimensional printers to form components such as molds, models and prototypes using 3-D design data. 3-D printers are available from various sources, including, but not limited to, 3D Systems, Inc.; EOS GmbH; Prometal, a division of the Ex One Company; Stratasys, Inc.; and Z Corporation.
According to the present invention, a 3-D printer is utilized to print a sand sub-mold directly onto a print bed. As known to those of ordinary skill in the art, 3-D printing provides a process for making a 3-dimensional object of virtually any shape from a digital model. 3-D printing utilizes an additive process where successive layers of material are laid down in different shapes. According to the present invention the sub-mold 40 includes a printed exterior surface 44. The interior surface of the sub-mold includes at least a negative image of a component to be cast. The 3-D printing process excels in creating complex molds and eliminates entirely the need for cores. Thus, in one embodiment, the holder block system of the present invention is free of a core.
After the sub-mold 40 is formed, it is placed within the mold cavity 26 such that the holder block pattern can be subsequently cast.
Pouring
After the holder block system 10 has been assembled, a desired alloy composition is poured into the mold. Various molten materials, preferably metal as known to those of ordinary skill in the art can be utilized. Generally, molten metal is ladled or poured from a holding container into the sub-mold through the gating system of the base primary mold 20. A suitable amount of molten metal is poured in order to fill the entire cavity of the sub-mold 40 and preferably the gating system 28.
Finishing
After the desired component has been cast in the holder block pattern 10 of the present invention, conventional steps can be taken to produce a finished component. For example, the mold is opened after a suitable cooling time has elapsed. In order to remove the cast component from the holder block pattern, the sand-based molds are generally broken and the casting removed therefrom. Excess material can be trimmed from the casting through any suitable process such as cutting, sawing, trimming or the like.
FIG. 2 illustrates a top view and a bottom view, respectively of the cast component formed utilizing the holder block mold 20 and sub-mold 40 illustrated in FIG. 1. It is noted that the “FEF” logo plaque is the usable casting that was inside the 3-D printed sub-mold. The casting also includes the sprue, fanned ingate and riser, all necessary to obtain a desirable plaque.
While in accordance with the patent statutes the best mode and preferred embodiment have been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.

Claims

What is claimed is:

1. A holder block system, comprising:

a primary mold comprising a cavity; and

a 3-D printed sub-mold located in the cavity, the sub-mold having an outer surface adapted to mate with at least a portion of the cavity, and wherein an interior surface of the sub-mold includes at least one negative image of a component to be cast.

2. The holder block system according to claim 1, wherein the sub-mold is formed as a single piece.

3. The holder block system according to claim 1, wherein the primary mold comprises a gating system, wherein the sub-mold includes an ingate adapted to align with the gating system on the primary mold and thereby accept a molten metal into an interior cavity of the sub-mold.

4. The holder block system according to claim 3, wherein the sub-mold is free of a separate core and a cope and drag.

5. The holder block system according to claim 1, wherein the primary mold does not contain any features of a part to be cast utilizing the holder block system.

6. The holder block system according to claim 1, wherein the sub-mold is formed from a different material than the primary mold.

7. The holder block system according to claim 1, wherein the primary mold comprises a flask and a molding composition located within the flask, with a cavity being present in the molding composition.

8. The holder block system according to claim 3, wherein the primary mold gating system comprises one or more of a sprue, well, and runner.

9. A method for producing a holder block system, comprising the steps of:

providing a primary mold having at least one cavity and one or more of a sprue, well, runner and ingate;

providing a 3-D printed sub-mold including an interior surface having a shape of an object to be molded;

inserting the sub-mold into the at least one cavity of the primary mold to form the holder block system.

10. The method according to claim 9, further including the step of forming the primary mold by adding a molding composition to a flask and incorporating a pattern into the molding composition in the form of the at least one cavity.

11. The method according to claim 10, further including the step of forming a gating system in the molding composition that includes one or more of a sprue, well, runner, and end gate.

12. The method according to claim 11, further including the step of forming an ingate on the sub-mold and aligning the ingate with the gating system of the primary mold.

13. The method according to claim 12, wherein the primary mold is formed so that it does not contain any features of a part to be cast with the holder block pattern.

14. A method for producing a metal casting, comprising the steps of:

obtaining a primary mold having at least one cavity;

obtaining a sub-mold including an interior surface having a shape of an object to be cast, wherein the sub-mold is 3-D printed and has an external shape adapted to be placed in at least a portion of the cavity of the primary mold;

inserting the sub-mold into the at least one cavity of the primary mold; and

adding a molten metal to a portion of the primary mold such that the molten metal flows from the primary mold into a cavity of the sub-mold including the interior surface.

15. The holder block system according to claim 14, wherein the sub-mold is free of a separate core and a cope and drag.

16. The holder block system according to claim 15, wherein the primary mold comprises a gating system, wherein the sub-mold includes an ingate aligned with the gating system on the primary mold and thereby accept the molten metal into an interior cavity of the sub-mold.

17. The holder block system according to claim 16, wherein the primary mold does not contain any features of a part to be cast utilizing the holder block system.

18. The holder block system according to claim 17, wherein the sub-mold is formed as a single piece; and

wherein the primary mold gating system comprises one or more of a sprue, well, and runner.