Laboratories

Rapid Prototyping Laboratory

Ing. Pavel Růžička, Ph.D.

Head:

Workers:

Description:

Fused Deposition Modeling technology

Rapid Prototyping and 3D Printing technologies, under which Fused Deposition Modeling is categorized, enable a physical prototype model to be produced much more rapidly than with classical technologies on the basis of computer data. The computer data can be provided by CAD software packages, 3D scanners, scientific and technical computations or medical imaging systems. The prototype model is created layer by layer, so it is possible to make models of practically any complex geometry. However, the limited range of modeling materials is a major disadvantage.

The Laboratory of Biomechanics is equipped with Fused Deposition Modeling (FDM) technology developed and provided by Stratasys, U.S.A. The Laboratory has a Prodigy Plus machine, see fig. 1, and Stratasys Insight software for production process preparation and control code generation.

Fig. 1: Stratasys Prodigy Plus

Akrylonitril-butadien-styren (ABS) thermoplastic is used as the modeling material. ABS has material properties, tensile strength 22 MPa and tensile modulus of elasticity 1.627 GPa that allow the use of prototype models as functional prototypes. Prototype models made of ABS can be machined or glued, model surfaces can be finished, polished, painted or vacuum metal plated. Stratasys WaterWorks material is used as the supporting material. It is a soluble material, and the support structures can therefore be dissolved.

The FDM model production process can be briefly described as follows. Modeling and support materials (ABS and WaterWorks soluble) in the fiber form are fed to the extrusion tips, heated up to 280°C, and applied layer by layer. The selectable layer thicknesses are 0.178 mm, 0.254 mm or 0.330 mm. Prodigy Plus is able to build a model up to 203 x 203 x 305 mm in size. Larger models can be made in parts and then glued together.

In the laboratory, the FDM technology is used to support research and development projects in the field of biomedical engineering, but it is in fact general-purpose RP technology. The Laboratory of Biomechanics offers cooperation in rapid prototyped model production.

An example of the RP technology application in the design of a total knee endoprosthesis

As an example we can demonstrate the production procedure for a prototyped model of a knee joint replacement femoral component. First, a computer model is created by means of Unigraphics - the CAD software package (Fig. 2). The model is fully parametric; therefore it is possible to work with the model geometry in order to optimize the model and fulfill new requirements.

Fig. 2: CAD model of the knee replacement femoral component

Next, the CAD model is exported as STL data. The STL file format is the standard data format for RP technologies; a spatial object surface is represented by a network of triangles. The RP model is prepared by means of Insight software, which was provided with Prodigy Plus. The STL model is sliced into horizontal layers. Then the support structures and extrusion head trajectories are generated. The user can control all preparatory steps, check or modify and create slice curves and support structures, and influence the model building strategy (Fig. 3).

Fig. 3: RP model preparation by Insight software

As a result of working with Insight software, a file containing the control code for Prodigy Plus is obtained. Then Prodigy Plus, following through the control code, builds the RP model without any operator intervention (Fig. 4).

Fig. 4: RP model of a total knee replacement

The RP model of the total knee replacement femoral component is employed in prototype production of the ceramic femoral component of the knee endoprosthesis (Fig. 5). The RP model made of ABS thermoplastic is molded into silicon rubber and the tool obtained in this way is used to produce ceramic semi products by the cold isostatic pressing method.

Fig. 5: Knee replacement femoral component made of zirconia ceramics

Benefits of applying RP technology in the medical field and in biomedical engineering

RP technologies contribute to the design process of implants, prostheses, splints or fixtures and medical equipment. The relationship of RP technologies with computer-aided design and the rapidity of the model production enable the design of individual replacements. Several technologies can be used for producing functional prototypes, e.g., FDM technology, and technologies for directly manufacturing individual implants are under development.

RP technologies can also be employed in surgery planning. At the present time medical imaging appliances are available to analyze the situation inside the patient?s body noninvasively. Image data can be acquired by computer tomography (CT) and micro tomography, magnetic resonance imaging and ultrasound. Each method has its advantages and limitations. Data, that supports the physician?s decision, is not limited to 2D images. Modern software instruments are able to analyze the acquired images mathematically, build and display 3D virtual models. There is only one step between a virtual 3D model and a physical RP model. The RP model facilitates surgery planning and communication between physicians. There are materials available that can be made aseptic by UV rays. RP models can be utilized in education, seminars and meetings, or as an instrument for communication with the patient.

More examples of RP models

An image of one slice through a human cervical vertebra acquired by computer tomography (CT) scanning

3D computer model of a human cervical vertebra created by the process of 3D reconstruction of CT scans

RP model, a copy of a human cervical vertebra

Fig. 6: An image of one slice through a human cervical vertebra acquired by computer tomography (CT) scanning

Fig. 7: 3D computer model of a human cervical vertebra created by the process of 3D reconstruction of CT scans

Fig. 8: RP model, a copy of a human cervical vertebra

CAD model of the experimental set-up component for experimental analyses of the acoustic field inside a human vocal tract

RP model of the human vocal tract produced for experimental purposes

Fig. 9: CAD model (Unigraphics NX) of the experimental set-up component for experimental analyses of the acoustic field inside a human vocal tract; the computer model of the acoustic cavity was created by 3D reconstruction of magnetic resonance (MR) images, and other construction features have been added.

Fig. 10: RP model of the human vocal tract produced for experimental purposes

Fig. 11: A handle of a forearm crutch, RP model on a scale 1:1, assembled of three parts

RP modely tibie a tibiální komponenty náhrady kolenního kloubu

Fig. 12: A skull model, an example of anatomy model based on medical image data acquired by means of a computer tomograph

Fig. 13: A model of a skull with extensive resection of bone afflicted with tumor, and models of designed implants, on the left the implant made of UHMWPE

Fig. 14: RP models of a tibia and tibial komponent of a total knee prosthesis were used for verification of the individual implant replacing missing tibia tissue


Fig. 15 and 16: Two examples of individual mandibular implants, bone models in white color and implants in red or metal

Modely odlitku těhlice přední nápravy formulového vozu

Fig. 17: Concept of a truck, the RP model intended for measurements of aerodynamic forces in a wind tunnel

Fig. 18: Models of hub carriers of a racing car front axle were used for sand casting mold manufacturing

Fig. 19: A calibration plate positioning device makes calibration process of 3D digital image correlation system easier. The device has been manufactured directly by FDM technology out of gray color ABS thermoplastics

Obr. 20: A prototype of Gottmark's telemark ski binding

Stratasys Prodigy Plus - technical specifications

Modeling material: ABS

Support material: WaterWorks soluble

Model build envelope: 203 x 203 x 305 mm

Layer thickness: 0.178 mm, 0.245 mm, 0.330 mm

Input data file format: STL, Parasolid, Unigraphics PRT, STEP, IGES, DXF, ...

Cooperation: