Page 34 - 3D Metal Printing Winter 2018

3D AM for the OR
Fig. 2—Optical images of the cross-section of surgical graspers show that printed samples are near full density.
Table 1—Density of the graspers with three different teeth patterns
Grasper type
Cubical
Lofted
Hemispherical
Density
> 98.7%
> 98.3%
> 99%
Table 2—Dimensional measurement of the lofted and cubical teeth patterns
Teeth Length/ Diameter μm
Teeth Width/ Diameter μm
Base Length μm
Base Width μm
Lofted Bottom
372±25
377±30
594.31 ± 25
631.72 ± 32
Lofted Top
385±17
366±17
572±10
622±40
Cubical Bottom
255±19
275±21
404±14
N/A
Cubical Top
240±17
273±18
423±31
N/A
Fig. 3—Representative optical image of the surgical grasper.
time and a composition of stainless steel requiring less energy for manufacturing. The team L-PBF printed surgical graspers using 17-4 PH steel as part of a collaboration with Concept Laser, Inc., Grapevine, TX. The following shows the steps taken to ensure dimensional accu- racy and density, and for verifying that these instruments can be printed accu- rately and precisely, with little deviation, from drawings made using SolidWorks CAD products by Dassault Systèmes,
Waltham, MA.
CAD Model
The laparoscopic graspers were designed and simulated with three teeth patterns— lofted, cubic and hemispherical (Fig. 1c)— for gripping tissue, blood vessels and fat during surgery. The CAD assembly design is shown in Fig. 1d. The grasper measures 26.23 mm long and 4.38 mm wide, and the microscopic teeth vary from 250 to 1000 μm. The grasper design facilitates
multi-planer gripping to reduce stress on the tissue. It also provides chamfered grip yielding, meaning that after a certain force is reached, no additional force will be applied.
Results
Concept Laser printed 54 surgical graspers using the same processing parameters. All were found to be near full density, with no significant difference
observed in relative density, irrespective of micro features (Fig. 2 and Table 1). The cut and polished surfaces exhibited few pores, and those measured only a few microns at the most.
The team measured dimensions for the lofted, cubical and hemispherical grippers, and also collected data for the teeth length, teeth width, base length, base width, vertical teeth diameter, horizontal teeth diameter, base diameter and the
Table 3—Dimensional measurement of the hemispherical teeth pattern
Vertical Upper Teeth Diameter μm
Horizontal Upper Teeth Diameter μm
Base Diameter μm
Closest Distance between Two Teeth
μm
Hemispherical Bottom
442±45
438±44
1017 ± 17
96±15
Hemispherical Top
497±57
501±52
1024 ± 12
85±12
32 | 3D METAL PRINTING • WINTER 2018
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