Re: A survey about teaching RPM for college students

From: Jan Helge Bohn (
Date: Sat Jun 06 1998 - 20:01:55 EEST

This is in regard to the survey by Jack Feng, May 29, 1998:

I have been teaching the course ME 4644 Introduction to Rapid Prototyping
here at Virginia Tech since 1995. This is a senior technical elective
approved for graduate credit. Typical enrollment is 35-45 students each
spring semester (90% are from Mechanical Engineering, 75% are seniors).

This is a 3-credit semester course (15 weeks, two 1.5-hour lectures per
week). Students must complete extensive CAD, CNC, and FDM out-of-class
self-scheduled assignments (2-person teams). Students reverse engineer
medical CT scan data into a solid model and then CNC machine it (sculptured
surfaces, two setups). Students design, fabricate, peer review, redesign,
and refabricate the housing for an electrical razor; they design for UL
standards (94, 746A-D, 1128), injection molding, and human factors.
Texbook used: Automated Fabrication, by M. Burns (1993).

The syllabus for the course is available online at:
Additional detail on this course is described in:
J.H. Bohn, "Integrating rapid Prototyping into the Engineering Curriculum -
A Case Study," Rapid Prototyping Journal, vol. 3, no. 1, 1997, pp. 32-37.

The students design using SDRC I-DEAS Master Series. CNC machining is
performed on one MAXNC-10 CNC 3-axis mill. The electric razor housing is
fabricated on one FDM 1600.


1. One CNC mill is more than sufficient for 20 teams. Each team typically
machines for 3-4 hours.

2. One FDM 1600 is just sufficient to provide each of 20 teams with two
20-hour sessions (Monday through Friday). Maintain a service contract to
keep downtime to less than 24 hours. The FDM 1600 typically goes down
twice during the semester. Weekends and one non-vacation idle week in the
middle are used for catch-ups.

3. Have students research topics prior to class; submit typed summaries and
questions for discussion. Discuss topics in class instead of lecturing.

4. Have students research design requirements imposed by material
selection, UL standards and injection molding during the first few weeks of
class. Discuss and share findings in class.

Dr. Jan Helge Bohn
Assistant Professor of Mechanical Engineering
Virginia Tech, Blacksburg, VA 24061-0238
Phone: +1-540-231-3276, Fax: +1-540-231-9100
PGP public key:

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