Date Visited: 12 December 1995

JTEC/WTEC Attendees: R. Aubin (report author), F. Prinz, C. Uyehara

Hosts:

Kenji Otake

President

Eiji Inui

Managing Director

HISTORICAL PERSPECTIVE

Kira is a manufacturing company that was established in 1944. It currently employees 135 people and has annual sales of about $36 million. The company manufactures a variety of metal working machines, including drill presses; CNC turret drill, mill, and tapping machines; robot transfer systems; and a rapid prototyping device called the Solid Center. The Kira Solid Center is a rapid prototyping device intended for office use. It uses a process called Selective Adhesive and Hot Press Process (SAHP). According to an article provided to the JTEC/WTEC team by Mr. Inui,

The SAHP process is based on the photocopy process combined with a hot press. When the inventor of the SAHP process, Noboru Kawaguchi, developed the first photocopy desk-side printer in 1978, he had an idea for a plain paper photocopy 3D printer. His idea stemmed from a desire to improve upon the conventional layering and cutting method employed to create 3D maps.

He restarted the development of a fully automated plain paper 3D printer for office use in 1992 (Inui et al. 1994).

A presentation describing the SAHP process was given at the Fifth International Conference on Rapid Prototyping in Dayton, Ohio, in June 1994.

A patent has been filed in Japan and is now in the open-for-review stage; it is still pending. Production and sale of the Solid Center began in September 1994 with the first machine sold to Tokuda Industries.

METHODOLOGY (COMMERCIALIZATION)

The Selective Adhesive and Hot Press process is intended for operation in an office environment and is driven directly from a computer file using the standard STL format. The SAHP process initially processes 10 sheets of paper to serve as a base for the subsequent part to be build upon. The following six steps describe the process:

1. Print toner (resin powder) onto plain paper. Toner is applied to the paper in the exact position indicated by the sectional data. This is done using a typical laser stream printer and is referred to as the Xerography process.

2. Hot press. The individual sheets of paper begin to create a block as the sheets are printed and then fed to the table. The table is raised to the hot press each time a new sheet of paper is fed to the table. The temperature-controlled hot press (175°C), melts the toner (resin powder), which adheres the sheets together. The hot press also keeps the top surface flat.

3. Cutting the contour. The paper is cut accurately along the contour of the sectional data, and parting lines are cut at the same time.

4. Completed block. Printing, hot pressing, and cutting are now complete.

5. Removal. Excess material is easily removed.

6. Completion. The complete three-dimensional form is revealed.

From both technical and financial perspectives, the Kira Corporation seems well poised to launch and commercialize its SAHP rapid prototyping device. To date, the device is sold exclusively in the Pacific Rim, with a total of 18 systems sold as of December 1995.

The system has similarities to the U.S.-based Helisys Laminated Object Manufacturing (LOM) rapid prototyping system. Both systems use paper and adhesive to construct a laminated object under computer control; however, Table Kira.1 highlights some of the major differences.

Table Kira.1
Key Differences Between the Helisys LOM and the Kira SAHP processes.

The Kira Solid Center is a well designed and nicely packaged rapid prototyping system intended to meet the needs of the modeling or design verification application niche. Because it appears as a larger version of an office copier machine, it would complement any office environment. Mr. Inui noted that the machine uses 50% off-the-shelf products and 50% components designed by Kira. It uses standard A3 size copier paper. Table Kira.2 provides additional specifications for the Solid Center.

Table Kira.2
Kira Solid Center Machine Specifications

The toner particle size is 100 microns. The rationale for using a printer to deposit the toner is cost. There are three types of toner deposition:

1. Broad lines about 3/16 in. wide. These are used for the actual border of the part.

2. Thin grid lines about 1/2 in. space apart. These are used for external support (outside the part boundary).

3. Thin grid lines about 1/16 in. apart. These are used for internal adhesion.

Mr. Inui confirmed that Kira has no intention to build a larger machine.

MATERIALS

The only material used in the Kira machine is paper. Mr. Inui noted that a plastic/paper sheet was experimented with, but cost was a limiting factor, and Kira has done no work with ceramic materials.

APPLICATIONS

Although the primary application intended for the Kira Solid Center is modeling for design verification, because of "hardened applications," there is now high interest in vacuum castings.

Castings

A number of Kira customers are now using Kira models as patterns for the MCP vacuum casting process to make plastic/resin duplicate parts. Additionally, the use of paper patterns as a substitute for wood patterns for sand castings is gaining popularity. One reason for this is the notable decline of skilled craftsman who make the wood patterns. A number of patterns for castings were on display (Figs. Kira.1-9).

Tooling

One of Kira's target goals that Mr. Inui noted is the making of molds. Accuracy is the most critical factor for this application. Paper patterns are being used as master parts for molds. Inui noted conversion has been accomplished of a master paper part to a silicone pattern and then to an epoxy material for use in mold making. He also acknowledged that Kira customers are doing a fair amount of lab testing.

Medical

Mr. Inui said he was not aware of any medical applications.

CAD STANDARDS, INFRASTRUCTURE AND PART SHAPE ACQUISITIONS

The only CAD interface to the Kira Solid Center is through the STL file format. Additionally, the system can only build separate STL files and cannot merge them into a one-build assembly.

MISCELLANEOUS OBSERVATIONS

• Although the computer generates the slice data relative to the actual part height, the greatest technical challenge is height control to maintain accuracy in the Z direction. A 2-3% increase in size is attributed to humidity. A 1.5-2% compensation in the Z direction is necessary.

• Of the 18 machines sold, Mr. Inui noted that 40% were purchased for service bureaus, 25% for electronic and automotive industries, 25% for universities and local educational offices (polytech centers, after-school trade and vocational high schools), and 10% for wood pattern construction.

Fig. Kira.1. The Kira Solid Center KSC-50 with Inui and Prinz.

Fig. Kira.2. A view inside the machine showing the pen plotter with the cutting knife.

Fig. Kira.3. A view inside the machine showing the hot press in operation.
Note the position of the cutting knife on the right side.

Fig. Kira.4. A view inside the machine showing operation of cutting knife (out of view due to movement).

Fig. Kira.5. The swivel cutting knife, approximately 5/8 in. diameter, 3 in. long.

Fig. Kira.6. A sample of models showing shoe forms, animals, etc.

Fig. Kira.7. Sample of models for automotive and electronic applications.

Fig. Kira.8. A sample pattern to replace a wood pattern.

Fig. Kira.9. A mold for a cellular phone housing.

REFERENCES

Inui, N., S. Morita, K. Sugiyama, and N. Kawaguchi. 1994. SAHP -- A Plain Paper 3D Printer/plotter Process.