MODULE 17 / PRINTING & ASSEMBLY
Turn geometry into an assembly
Connect CAD geometry to a manufacturing method, mating surfaces, fasteners and loads. Prepare one subassembly thoroughly before committing to a full build.
By the end, you can…
- Build a part/interface worksheet
- Explain clearance and tolerance
- Reconcile construction with the simulation model
CAD inspection and export
Forces and actuators
An assembly is a collection of interfaces
For each component, ask what locates it, what holds it, what touches it, what moves past it and how it can be removed. A motor mount can fit in CAD while leaving no room for a screwdriver or cable connector. Assembly order and service access are design properties.
BDX-R’s geometry contains structural parts, covers and purchased-component representations. A motor-shaped STL is not a motor to print. Establish identity and manufacturing category before counting parts. Keep source revision, material, quantity, mating parts and questions in one worksheet.
Nominal dimensions do not guarantee fit
A nominal dimension is the design target. A tolerance describes allowed variation. Clearance is the deliberate gap between mating parts. A 5 mm shaft and nominal 5 mm hole do not automatically slide together: actual size, roundness, finish and manufacturing process matter. A sliding fit and a press fit are different requirements.
Printed geometry depends on orientation, supports, shrinkage and the actual machine/material process. Make a small coupon containing an uncertain interface before a large part. Measure it and record its orientation and process settings. One good sample supports that specific process; it does not validate every orientation or material.
Specify a complete fastening joint
“M3 screw” is incomplete. Record diameter and pitch, length convention, head/drive, material or strength grade, and receiving feature. A clearance hole lets a screw pass; a thread or insert holds it. Count washers, nuts, spacers and inserts separately when required. Check engagement, bottoming and interference with moving parts.
Follow the exact insert maker’s hole and installation guidance. There is no universal diameter or temperature. A washer spreads load and an insert may improve serviceability, but neither repairs a poor load path or thin wall. Tightening torque depends on the actual fastener, receiving material and joint; an arbitrary value can strip plastic or damage a motor.
Respect the reinforced build and its mass
Kayden’s video describes printed hip-roll connectors breaking and later being replaced by aluminum, plus an aluminum head base plate. That establishes a construction change, not a full machining drawing or material-grade specification. Identifying those parts and matching their revision remains explicit build work.
After fabrication, record assembly masses and component positions. Metal replacements, battery placement, cables and covers affect balance and inertia. A simulation can look accurate while using the wrong mass distribution. A cosmetic accessory can become control-relevant when it is heavy or far from the torso.
WORDS YOU NOW KNOW
- Tolerance
- Allowed variation in a dimension or property.
- Clearance
- A deliberate gap between mating components.
- Load path
- The sequence of parts and interfaces carrying force.
YOUR CALL
Finished with this module?
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Primary references for this module. Use the version and hardware revision named in the lesson.
BDX-R CADKayden’s build videoDesign for printed manufacture