Polycarb Tube Fabrication — Mentor's Guide

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Who This Handout Is For

Adult mentors and parent volunteers supervising students through the polycarbonate-tube fabrication for the V1.5 hero bot's intake mechanism. Use this guide before, during, and after the fabrication session.

This document was written assuming the mentor is a technically capable adult (engineer, shop teacher, or experienced parent), but is not necessarily a polycarbonate-thermoforming expert. It assumes nothing beyond basic shop skills (drill press, hand tools, calipers) and gives you everything you need to safely supervise a 60–90 minute fabrication session.

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The students do the work. Per G4 in the game manual, all robot work must represent the students. Mentors demonstrate technique on a scrap piece, then hand the heat gun to a student and coach from the side. The handout is structured around this division of labor.

When to use which version

PDF: primary distribution copy. Print and bind; keep at the bench. Same content on every device that opens it. Use this for the actual fabrication session.
DOCX: editable copy for the team's records. Customize mentor names, dates, location, and team-specific notes. Re-export to PDF after edits if printing.

CONTENTS

What's Inside the 21 Pages

Section-by-section overview. Page numbers in the right column match the printed PDF.

Table of Contents

Cover — document metadata, time/risk/skill summary, mentor-role callout p. 1
How to Use This Handout — reading order for first session vs. subsequent p. 2
Bill of Materials — sheet stock vendors, equipment list with model recommendations, consumables, PPE p. 3
Workspace Setup & Safety Briefing — ventilation, hazard table, read-aloud safety briefing p. 4
Step 1 — Pre-flight Checks (5 min) — bench, sheet, and personnel checklists p. 5
Step 2 — Cut the Flat Pattern (10 min) — cutting and edge prep p. 6
Step 3 — Drill the String Holes (10 min) — drill-press setup, deburring p. 7
Step 4 — Pre-dry the Sheet (30 min, optional) — preventing moisture bubbles p. 8
Step 5 — Heat to Forming Temperature (5 min active) — the highest-attention step p. 9
Step 6 — Wrap and Clamp (3 min active) — mandrel forming, time-critical p. 10
Step 7 — Cool Under Clamp (5–10 min) — springback prevention p. 11
Step 8 — Release and Verify (5 min) — ID/length measurement p. 12
Step 9 — Anneal the Tube (30 min, recommended for competition) — stress relief p. 13
Quality Verification Checklist — eighteen items the student completes and the mentor signs p. 14–15
Failure Modes & Fixes Reference — twelve common failures with diagnosis and fix p. 17
Engineering Notebook Documentation — nine required photos, R24 compliance template p. 18
Session Sign-Off — date/location/student/mentor blanks, outcomes, improvement notes p. 20–21

EXCERPT

Critical Safety Notes

If you only read three things from the handout before your first session, read these. Full safety briefing is on page 4 of the PDF.

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Heat gun reaches 1000°F. Long sleeves, heat-resistant gloves rated to 500°F (welding gloves work; nitrile does not), and safety glasses on everyone within 6 feet. Set the gun in a stand when not in use — never on the bench surface.

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Ventilation matters. Polycarbonate at forming temperature (280–310°F) releases trace bisphenol-A vapor. Open garage with a fan, well-ventilated workshop, or fume hood. Don't work in a closed bedroom or unventilated basement.

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Anyone can call “stop.” The pre-work safety briefing on page 4 is meant to be read aloud to students before any heat is applied. The most important sentence: “If something feels wrong — too hot, too smoky, smell off — say stop and we stop. Anyone can call stop, no consequences.”

The yellow-tint failure mode

The single most common way this fabrication goes wrong: a student holds the heat gun in one spot too long, the polycarb yellows, and the tube is structurally compromised but visually still mostly clear. This is permanent — the molecular damage from overheating doesn't reverse. The handout's STEP 5 OVER-HEATED — STOP callout (red box) drills this in. Discard yellowed parts immediately, no exceptions.

EXCERPT

Bill of Materials — At-a-Glance

Full BOM with vendor links, model numbers, and pricing on page 3 of the PDF. Order at least a week before the planned fabrication session.

Category	Item	Cost
Sheet stock	0.060 in polycarbonate, 4×8 in, 4 sheets (Robosource or Tap Plastics)	$32–60
Heat source	Variable-temperature heat gun with digital readout (Steinel HG2310 or equivalent)	$80–150
Measurement	IR thermometer, digital calipers	$40–80
Forming tools	2.4 in aluminum mandrel, 2× C-clamps with rubber pads	$37–52
Drilling	Drill press access, 1/16 in twist bits, deburring tool	$20–40 (consumables)
Consumables	Cotton cloth strips, 220/400 grit sandpaper, silicone work mat	$15–25
PPE (per person)	Safety glasses, heat-resistant gloves rated 500°F	$20–35

Total first-time investment: ~$250 in equipment that lasts several seasons, plus ~$50 in sheet stock and consumables per fabrication run.

Companion Pages

This handout pairs with the design study and the rule reference. If you arrived here without context, start with the design study to understand why we're making this part before walking the team through how.

spartan-hero-polycarb-tube-intake — Design study covering the mechanism's geometry, gear ratio, cylinder mounting, and decision matrix for chain-bar vs. swing-bar pairing. Read this first if you don't know what the tube is for.
polycarb-tube-onshape-guide — OnShape CAD guide for the tube. Complete dimension reference, parametric variable setup, step-by-step modeling. Useful if students are documenting the part in the engineering notebook before fabrication.
spartan-hero-chainbar-lift — The lift the tube mounts on. Covers tower placement, three-goal scoring scenarios, rule compliance.
VRC Override Game Manual — Rule R24 (custom plastic)↗ is the binding constraint for this fabrication. Section 4 of the handout itself has the relevant rule excerpts; this link is for the full manual.
clawbot-mentor-handout.pdf — Sister handout for the Clawbot training curriculum. Same format, different topic.

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Feedback or correction? The DOCX is editable — if your team identifies a fix or a missing step during a fabrication session, mark it up in the DOCX and send the changes to Coach T. Version 1.1 will incorporate field corrections after the first round of teams uses it.