Onshape

Kickoff: 

• Build Onshape Document Folder

  • Separate Document for each subsystem with standard naming convention

  • Create templates for: field element sketches, drivetrain and dimension sketches

• Build Krayon CAD simple concepts to visualize and facilitate discussions

Prototype/Concept Week:

• Start Layout Sketches and Hi Fidelity Block CAD in the same part studio

• Create folders

  • Master Sketch at the top

  • All individual sketches at beginning of subsystem folder

  • Group block CAD features by subsystem

• Create Master Sketches

  • Design Lead and/or mentor (depends on student experience)

• Create Block CAD

  • Design team and/or mentor (depends on student experience)

• Assign CAD Teams

  • By subsystems

  • Each subsystem assigned by parts

  • Work in parallel

  • Do not deviate from Master sketches/Block CAD

  • Identify issues and communicate

  • Adjust Block CAD as needed when issues arise

Reference: Prototyping 101

Prototyping is not for just proof of concept. It's to give the designers specific information. 

Know what questions to answer before starting:

• How far off the ground should the intake wheel be to engage the flare?

• How much wheel compression is enough to intake the flare with being to obstructive that could result in the flare getting pushed away?

• Should the top and bottom rollers/wheels be aligned?

• How does the flare behave when intaking, to being lifted vertically, to when being released onto ALL poles?

• Be as thorough and inquisitive as possible. You may discover more questions that need answers

• Don't prototype something that would never be used

  • Holding the intake by hand and saying that it works is not as effective as attaching it to a rigid structure. 

Don't limit the prototype design based on the restriction that wouldn't be designed

• Example: attaching a prototype to an existing drivebase is a great idea, but saying that it can't go lower because the bumper is in the way is a restriction that wouldn't be in the design. so take the bumper off or change the prototype mechanism.

• Prove it! Show videos in different stages. document in the EN your lessons learned

If it is critical to guarantee proper functionality, then PROTOTYPE it --- do NOT say it "SHOULD" work

Prototyping should be rapid that allows fine tuning the spacing of critical components. 

• Need to adjust the height quickly to find the precise perfect position for example

• Laser cutting MDF, using wood, or Protopipe/PVC can be quicker than using 2x1/brackets/bolts and assembling/reassembling

• You can build several mounting options into a single laser cut MDF or piece of wood

• or you can use Protopipe that allows a loosened 3dp connector to slide along the PVC pipe for quick adjustment

Announcing KrayonCAD: A Robot Planning Library for Onshape - Technical / CAD - Chief Delphi 

Demo Video (link)

KrayonCAD allows easy brainstorming of basic design concepts

How to create: 

• Create New Onshape Document

• Go to Assemblies Folder

• Select Insert>Other Document

• Search for KrayonCAD

  • Look for Green Logo KrayonCAD with version number

  • Ignore the many copies of KrayonCAD others have created

  • Avoid making copies of the KrayonCAD; Insert into your own document instead

• Configure inserted parts

MKCAD also has KrayonCAD versions of parts you can use to make an assembly

• Each field element sketch on both sides of robot

• Drivetrain and extension limits

• Each subsystem (sometimes combined with out systems if a lot of interdependencies)

• ALWAYS constrain geometry (lines should be BLACK)

• Sketch in multiple positions (keep sizes consistent using equal constraint)

• Define Vehicle Coordinate System: 

  • Define origin cube on the floor with robot facing correct direction

  • Make origin cube defined on this point for all subsystems for later assembly

• DO NOT sketch in fillets

  • Changes can cause fillet errors

  • Add fillets as last CAD step of design

• Add Origin Cube to the center of the drivebase

  • Top surface of the cube should be fastened to orign to represent the ground and also not to interfere with the robot structure

Overview:

• Made from Master Sketches

• Communicates design intent early on and saves CAD'rs from wasting time figuring it out

• Identifies interference issues early on

• Saves time with design changes during CAD process (1 hour versus multiple hours)

• Enables less experienced CAD'rs to contribute without having design experience

• Provides team wide understanding early on of design direction and enables electrical wiring plan early

• Provides kinematic analysis before going into full detailed CAD

• Figure out drivebase earlier which is essential for programmers to get started much sooner (Goal: Drivebase done in 1 week)

STAY ON PURPOSE: Show geometry/build space, "how to build", design intent, critical locations and interferences

Part Studio started with the Block CAD (sketches are not used in PS)

Draw robot in starting position

Add sketches to aid construction

Avoid extruding/revolving layout sketch geometry - Create new sketches for Block CAD features

Make parts monolithical (Critical!)

• Derive parts in the subsystems

• May have to add filler or connecting geometry

Name the parts

Color each subsystem

Tubes are rectangular blocks -- no need for most brackets

Gears and Motors can be cylinders of correct length and diameter

Hex shafts as round cylinders or spacer OD

model belts as wide as pulleys

Model bearing flanges as sticking out

Use rounded perimeters of parts to show shaft/pivot locations without needing to model them

Block CAD Assembly:

• In same document as layout sketches and block CAD

• Add mate connectors

• Use limits on mates to create real range of motion

• Use configurations

• Use Named Positions tab

Include bumpers, electronics and battery

Add details to subsystem interfaces like at moving joints and tightly packaged areas where critical geometry needs to be communicated

Skip details that are far away  from joints and subsystem interferences

• Leave out brackets/gussets unless space is tight

• Spacers, shafts and small components that are already implied by the other block components

• if in any doubt about interference, then add the detail, otherwise skip it

ALWAYS manage versions after every change to the CAD

Link: 3005 RoboChargers - High Fidelity Block CAD - FIRST / General Forum - Chief Delphi 

Attach to derived parts where possible

• Allows updates to Block CAD to migrate to detailed CAD automatically

Do not extend beyond Hi Fi Block CAD to prevent interference issues

Extrude up to the face

• Blind extrusions will NOT update when the block CAD is updated

Use End Conditions

• Up to Face, Up to Next, Through All -- instead of using blind (typing in a distance) -- this allows you to communicate design intent

Use Lightening featurescript as final part of design, not part of sketch

• Lightening algorithms can break if the design is changed and it's part of the sketch

Add in fillets as a feature, not as part of a sketch for the same reason as above regarding lightening

Mirrors and patterns should be used as features instead of parts of sketches

• Eg. You could include holes as part of the sketch and mirror which would cause issues with design changes, or even better, you can include them after the sketch using the hole feature that will not break when the sketch design is changed

Use hole feature after the sketch to choose the proper hole type (ie. clearance vs tapped), instead of looking up tables to sketch proper diameter hole

Fix broken references in feature tree as soon as you detect them

Double click faces to update dimensions

Learn and use shortcut keys -- it will cut your CAD time to a fraction of the time

Use interference detection to allow Onshape to show you interferences of parts that you cannot easily see with your own eye

• Featurescripts are time savers -- Here are some great ones:

  • Featurescripts | FRCDesign.org 

  • Spectrum's D3.6 FeatureScripts - Google Slides 

• Belt Featurescripts are useful if used correctly

  • Know what number of tooth belts there are and ensure the featurescript gives correct pulley and C-C distances using realistic belt sizes

  • Back up the featurescript with a belt calculator from AMBcalc.com if unsure

FRC 3005 RoboChargers Onshape CAD Class | Onshape4FRC 

FRC Design & Modeling - YouTube Channel 

[MKCAD] 2024 Support Thread - Technical / Onshape - Chief Delphi 

Onshape best practices for FRC Video / Slides

Using Assembly Configurations

Purposeful and Efficient CAD