Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
The plans for the preliminary detailed design phase were to focus on developing models & drawings and to evaluate feasibility & test plans so that a preliminary design can be proposed. The goal of this phase and review is to have a design and plan that is proven to be a valid and appropriate solution that can be used as the guidelines for the final detailed design review.
In the preliminary detailed design phase our created models and drawings for the proposed product solution, contacted partners for design input and plans for production, and evaluated the engineering requirements, test plans, risks, and costs of the designed systems. We also began to determine what the largest challenges of the design will be, how successful designs and subsystems will be evaluated, and identifying sources and triggers for risk mitigation.
The full status of the action plans for this phase is:
- Update/Verify prototype: 0%, decided to focus on producing more fully designed prototype, abandoned original, basic prototype
- Model joints & bones: 100%
- Consider options/model joints attachments: 100%
- Prototype Joints, places of movement: 50%, were unable to print in this phase, but did create models & drawings for future prototype
- Begin planning possible verifying tests/procedures: 100%
- Update flow diagrams: 100%
- Drawings of design plans, prototype: Drawings & plans (100%), no second prototype developed in this period due to modeling being primary focus (25%)
- Update risk factors: 100%
- Identify required factors/ ideal conditions for successful use: 100%
- Plan risk responses & solutions: 100%
- Order toughest problems moving forward: 100%
- Outline resources or methods for solutions: 100%
- Run pre-lim. test on prototype/ Test independent systems if possible: 0%, no systems to test in this phase
- Verification of data acquisition
- Contact with printing resources
- Revision of Engineering Requirements
- Research of joint options
- Update of action items status
- Update of project schedule
- Team vision
- Creation of test plans and required materials
- Created models of 2 bones as well as the assembly
- Did some preliminary research on molded materials.
- Assisted in researching joint options
- Some preliminary strengths testing
- Modeled the radius bone in Solidworks
- Met with RIT trainers to discuss the joint connections and feasibility of proposed prototype
- Researched joint options with RIT trainers
- Created the Bill of Materials
- Analyzed the theoretical force expected on each muscle
- Updated Benchmarking
- Updated the Functional Decomposition
- Communicated with The Construct and determined path for prototyping
- Worked on feasibility analysis of the new model.
- Obtained feedback from SME on 3D printing and casting possibilities for the model.
- Worked on presentation for Preliminary Detailed Design.
- Participated in creating a physiologically accurate model and selection of joint types.
Prototyping, Engineering Analysis, Simulation
A model of the system will be 3D printed using PLA filament to assess proper functionality.
- First joints will be printed to make sure they work well together
- Complete bones will be printed to create a full working model
Manufacturing Plans - Molding
Once a prototype is completed we will cast the models to create molds, which we can then use to create as many models as needed.
Time, cost, and material choice.
- 3D Printing 1 model will take ~20 hours of printing time and cost ~$50 – $60 dollars.
- Vacuum molding is ~$5 - $10 per piece and only has to be done once.
- Silicone Casting is ~$100 per piece, but only has to be done once.
- D Printing only allows for PLA filament to be used. Casting allows for a wide variety of choices.
Feasibility: Prototyping, Analysis, Simulation
- Anatomy of models looks correct and joints selected should work well.
- Begin with printing of only joints to make sure they work as desired to reduce prototyping cost.
- Once we make sure model works well print a full working model.
- Once we have a good model, then we can cast and create other models.
Data acquisition was verified using Capstone.The collection of data from 3 muscles via 3 load cells and the angle data collection from one goniometer is possible. The images below show what students would see when completing a lab and how they'd export their data.
Drawings, Schematics, Flow Charts, Simulations
Bill of Material (BOM)
To be completed by team members to indicate the validity of a prototype or model and show the satisfaction of the engineering requirements for the project.
These test plans are based on and in response to an updated version of the Engineering Requirements.
Materials required for tests:
- 1 device or device prototype.
- 3 PASCO loadcells (assembled with 2 screws each)
- 3 PASCO Sensor Adaptors
- 1 Goniometer
- 3 Velcro Arm straps
- 1 PASCO Pasport
- 1 250kg weight
- 1 500kg weight
- 1 Computer with Capstone software
- 1 ruler
- 1 protractor
- 1 Calipers
- 1 stopwatch/timer
- ER1 – Static Force of Muscle A – Attach load cell to break in muscle A string, hang 250kg mass from hand hook, wait for arm to lower under the weight and settle, then get read out from Capstone. Validity- Force achieved at rest must match accepted anatomical value.
- ER2 – Dynamic Force of Muscle A – Attach load cell to break in muscle A string, hang 250kg mass from hand hook, allow arm to rotate and fall with weight, then get the peak force value through Capstone. Validity- Force achieved at rest must match accepted anatomical value.
- ER3 – Static Force of Muscle B – Attach load cell to break in muscle A string, hang 250kg mass from hand hook, wait for arm to lower under the weight and settle, then get read out from capstone. Validity- Force achieved at rest must match accepted anatomical value.
- ER4 – Dynamic Force of Muscle B – Attach load cell to break in muscle A string, hang 250kg mass from hand hook, allow arm to rotate and fall with weight, then get the peak force value through Capstone. Validity- Force achieved at rest must match accepted anatomical value.
- ER5 – Static Force of Muscle C – Attach load cell to break in muscle A string, hang 250kg mass from hand hook, wait for arm to lower under the weight and settle, then get read out from Capstone. Validity- Force achieved at rest must match accepted anatomical value.
- ER6 – Dynamic Force of Muscle C – Attach load cell to break in muscle A string, hang 250kg mass from hand hook, allow arm to rotate and fall with weight, then get the peak force value through Capstone. Validity- Force achieved at rest must match accepted anatomical value.
- ER7 – With each muscle attached and load cells strung, and the goniometer attached and reading out to Capstone, the arm is bent at the elbow and moved through the available range of motion. Validity- readout must show that the arm can move from approximately 0o and 180o.
- ER8 – Hang a max load of 500kg from the hand hook while holding the lower arm up to the upper arm so that the angle of the elbow is approximately 0¬o. release the lower arm and allow the weight and lower arm to fall. Validity- the arm must be able to fall and stop while still holding the weight, staying upright and stable (no concern of it being easily knocked over), and produce steady force and angel change graphs/tables through capstone. There should be no bending or material failure in a valid case, and the entire base must still be resting on the tabletop.
- ER9- With load cells in place, no weights, and the lower arm resting so that the angle of the elbow is approximately 90o, measure the angles of the muscles with the bones and the distance of the muscle attachment to the bones. Validity – Both values must be within ±5%of the average adult.
- ER10 & ER11- Set the model in each possible position with the 250kg weight. For each position (supinated wrist, pronated wrist, flexed elbow), allow the position to be set and then allow the device to sit, with no contact with a person or extra support from an outside object (excluding tabletop), for 1 minute. Validity – The position set by the user must not deviate by more than ±1cm during the wait period.
- ER12- Begin with an unassembled device. Start a timer and begin assembly, including the addition of base structure (and separate assembly if necessary), strings, load cells, goniometer, and arm straps. Also, include all hardware cables necessary for data acquisition (loadcells, goniometer). Assemble device to match model and plans provided. Validity – The full assembly takes approximately 20 minutes or less to assemble and can support a 250kg weight from the hand hook upon completion.
- ER13- With all loadcells attached to the muscles and the goniometer strapped to track the elbow, use Capstone software to record 30 seconds of data for each sensor by creating 4 graphical readouts of force (N) by time (s) for the loadcell sensor and angle (degrees) by time (s) for the goniometer, and then a table with a column of force readouts (N) or angle (degree) for each sensor and a column of time (s). Record the data results as a 250kg weight is hung from the hook hand of the device and the elbow extends. Validity – each graph or table column can be produced, clearly shows the impact of the weight on the device, and can be saved and exported as a .txt, .m, or .xls file.
- ER14- Measure the dimensions of the final model, upright, holding no weight and the elbow in such a way that the elbow is flexed and the lower arm does not extend past the base of the model. Strings may be loosened or untied to best minimize size of model. No loadcells or goniometer should be attached. Validity – The base of the device must be within 2ft by 2 ft.
Design and Flowcharts
- The Running risk assessment can be found in this document_Updated Risk Assessment Document P17082
Concerns and Issues:
- Frictional losses of the string through the bones
- Use of molding versus 3-D printing parts (product strength)
- Anatomically accurately modeling the joint connections
Design Review MaterialsPreliminary Design Review Power Point Presentation
Plans for next phaseThe full schedule and list of action items for the next design phase can be found here.
The main focus will be on preparations for printing, casting, prototyping. Mainly addressing remaining modeling and design needs, and ensuring models will function and are printable.