ONSHAPE
Strategic Design and CAD'g are two different things. This section covers the development of the robot CAD using Onshape to meet the strategic design intent from the design team.
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Strategic Design and CAD'g are two different things. This section covers the development of the robot CAD using Onshape to meet the strategic design intent from the design team.
Goto https://onshape4frc.com/getting-started and follow instructions:
Create an Education Account
Setup MKCAD Library (allows quick import of common FRC parts)
Add Featurescripts
Download OnShape App for your phone
Watch optional setup video (link)
RoboChargers CAD Training Module 1: Covers most basic elements for our needs
KrayonCAD: Simple Block CAD essential to develop and communicate design concepts
Announcing KrayonCAD: A Robot Planning Library for Onshape - Technical / CAD - Chief Delphi
FRC254 KrayonCAD demo (video)
To Use, Option 1:
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
To Use, Option 2:
Select KrayonCAD tab in MKCAD (if installed, see above)
Select parts and configure
Additional training resources
Additional key concepts:
In FRC ALL > CAD Library folder, create Game Elements document:
Import game element CAD (game pieces and field elements)
Create game element sketches for use in brainstorming, prototyping and design
In 1 - Drivebase + Master Sketches document, create drivebase, starting configuration and extension limit sketches
Keep documents organized in following naming standard using numbers and title (dependent on subsystems used):
0 - Top Level Assembly
1 - Drivebase + Master Sketches
2 - Intake
3 - Shooter/Arm
4 - Climb
Create folders extra file organization outside of the main robot design - some examples:
Concept Development: where all brainstorming and concept development files should reside
Game Specific CAD Imports: store all imports here for later insertion into main robot document
Minimize importing files directly into main robot CAD documents for better render performance
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Create multiple parts that are geometrically and spatially related to each other into one parts studio
Create each unique part only once to avoid creating multiple instances of the same part
Affects Bill of Material (BOM) feature if not done
Limit unique part number to 10 and features to 250
Use origin cubes
Rename sketches, extrusions, mates and parts as you go for easy reference
Add material and appearances to parts when completed
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Group newly inserted parts with origin cube mated at the origin
Duplicate then fasten any repeated parts
Organize parts into folders (tubes, swerve, spacers, etc)
Subsystems with no degrees of freedom is one assembly
Subsystems with multiple moving parts should be separated into rigid assemblies
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Belt Calculator: ReCalc - Belt Calculator
Best practice is to use a single type simplify supply requirements
HTD (5mm pitch):
Our typical go-to for most applications, especially high torque applications
GT2 (3mm pitch -- Smaller pitch than HTD):
Typically for lower load applications
Smaller pitch allows higher reductions in tighter spaces
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Use Lexan or SRPP if material flex is allowable
Use lightening and pocketing patterns in aluminum or lexan
3" Joint Comparisons (in order of weight):
Rev 1/2 x 1/2: 0.03 lb
Rev 3/8" nut bar: 0.04 lb
Note: eliminates need for nylock nuts at 0.005 lb each
Rev angled aluminum: 0.05 lb
Rev Ion 1 x 1: 0.06 lb
Rev/WCP 1/8" 1 x 1: 0.07 lb
Rev 1" Extrusion: 0.11 lb
Rev/WCP 1/16" 1 x 1: 0.12 lb
3" Shaft Comparisons (in order of weight):
Churo: 0.04 lb
Rounded Hex Shaft: 0.06 lb
Nuts and Bolts:
Use standoffs with short bolts instead of spacers with long bolts and nut
Use nylon bolts for low load fasteners like camera mounting
3/8" 0.25" Grip Length Rivet: 0.001 lb
Low Profile 10-32 Nyloc nuts: 0.005 lb
Full Profile 10-32 Nyloc nuts: 0.006 lb
0.75" 10-32 Button Head Alloy Steel Bolt: 0.008 lb
Add structure to bumpers, like sponsor plates, if rules still allow
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5B - Onshape Best Practices - NE Mentor Conference 2024 - Bennett.pdf - Google Drive
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
Hole feature also adds important details in the fabrication drawings easily (hole size, type, etc)
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
Onshape Learning Center: Become the Onshape master and complete learning modules and get certified in Onshape
[MKCAD] 2024 Support Thread - Technical / Onshape - Chief Delphi
5B - Onshape Best Practices - NE Mentor Conference 2024 - Bennett.pdf - Google Drive