Threaded Fastener Joint Design & Torque Control

Bolted joints into plastic: preload, self-loosening, creep-driven preload loss, boss and insert design, torque control strategy — the mechanical fastening discipline assembly methods surveys can't fit.

Private cohorts & on-site
Format: 2-day (8:30 a.m.–4:30 p.m.)
Level: Intermediate-Advanced
Location: Scheduled on demand · on-site at your facility or a regional venue
Date(s): Not yet scheduled for open enrollment. Get notified when it is, or book it privately for your team.
Includes: Certificate of Completion · printed slide binder · take-home reference text

Get notified when this course is scheduled

One email when dates are set. Or skip the wait: run it as a private cohort, on-site at your plant.

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Faculty

Faculty details for this seminar will be announced with the full schedule.

Fees

Early: $1,895 (payment 4+ weeks ahead)
Standard: $2,095 (check/ACH) · $2,165 (card)

Group discount: $200 off per attendee for 3+ from the same organization.

Also Available

  • Corporate on-site delivery at your facility
  • Private cohort sessions
  • Digital curriculum licensing

Seminar Overview

The screw is still the most common joint in plastic assemblies, and the most commonly mis-designed: bosses split from overtightening, preload vanishes to creep within weeks, self-tapping screws relax at temperature, and the joint that tested fine at room temperature hums loose at 85°C. This seminar teaches the bolted joint into plastic as a first-class engineering discipline: preload and the joint diagram, self-loosening mechanics (the Junker test), creep-driven preload loss, boss and insert design, and torque-control strategy that reflects what a plastic boss can actually deliver.

Boss design gets dedicated hours: boss OD/ID vs. screw size, fillet rules, gusset discipline, self-tapping vs. molded-in vs. heat-staked vs. ultrasonic inserts, and the pull-out/push-through calculations per screw type. The torque-control half covers torque-to-yield thinking adapted to plastics, torque-angle strategies, and what a torque wrench can and cannot guarantee on a viscoelastic substrate.

Case history runs throughout — the split bosses, the loose screws, the creep-loosened ground straps — drawn from ETS's failure corpus, ending with a design-limit checklist for the Monday-morning drawing.

Ideal Learner

  • Design engineers specifying screwed plastic assemblies
  • Mechanical engineers responsible for joint integrity
  • Quality engineers diagnosing field loosening and boss failures
  • Assembly process engineers setting torque specs

Learning Objectives

  • Draw the joint diagram for a plastic-boss screw joint and defend the preload target
  • Design bosses: proportions, fillets, gussets, and the self-tapping vs. insert decision
  • Predict creep-driven preload loss and design against it
  • Apply self-loosening mechanics and anti-loosening strategy honestly
  • Set torque specs and control strategy that survive viscoelastic reality

Consulting Sessions

Seminar attendees can sign up for individual consulting sessions with the instructor. Sessions are free for registered attendees, first-come first-served — sign up when registering by calling 248-539-0473 or during the seminar.

Seminar Outline

  • Preload and the joint diagram, plastic substrate edition
  • Thread shear and pull-out calculations per screw type
  • Self-tapping screw mechanics: thread-forming vs. thread-cutting
  • Boss proportions: OD/ID/wall per screw size with data
  • Fillet and gusset rules that prevent splitting
  • Molded-in inserts vs. heat-staked vs. ultrasonic vs. self-tapping
  • Push-through and pull-through failure modes
  • Creep relaxation: the weeks-long preload decay curve
  • Temperature cycling and differential CTE preload changes
  • Self-loosening: transverse vibration and the Junker test
  • Anti-loosening features: what works on plastic, what doesn't
  • Torque-preload scatter on plastic: why 30% is normal
  • Torque-angle and yield-control strategies adapted to bosses
  • Assembly-line torque audit strategy
  • Re-torque myth and service-ability design
  • Case files: split bosses, loosened grounds, rattling fairings
  • The relaxation math you keep
  • Design-limit checklist for screwed plastic assemblies
  • Workshop: design and defend a bolted boss at 85°C

More in Track C — Design, Molding & Tooling

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