The problem
Battery packs often carry dozens of brackets, fasteners and harness clips that add cost, assembly time and failure points. Many packs are also hard to service. DFMA methods give a structured way to question every part, and they are widely used in automotive industry design reviews. Applying them with CAD tools shows how a pack can be cheaper and faster to build without losing strength or safety.
Objectives
- Model a baseline pack with modules, trays, brackets, busbars, BMS and fasteners.
- Score assembly efficiency with a DFA method and identify candidate parts for elimination.
- Check manufacturability of key parts with DFMXpress and process rules.
- Redesign to reduce part count, fastener types and assembly directions.
- Compare baseline and redesign for part count, estimated assembly time, mass and stiffness.
What you need
Tools and toolboxes
- SOLIDWORKS Assembly — Baseline and redesigned packs, with configurations and exploded views for assembly sequence.
- DFMXpress — Rule checks for machined, sheet metal, injection moulded and turned parts, such as hole depth, corner radii and wall thickness.
- Interference Detection and Hole Alignment — Confirm that consolidated parts and reduced fasteners still fit and align.
- SOLIDWORKS Simulation (Static, Frequency) — Check that consolidated trays and brackets keep stiffness and natural frequency under example loads.
- Excel — DFA worksheets, assembly time estimates and comparison tables.
Software
- SOLIDWORKS 2023 or later
- SOLIDWORKS Simulation
- Excel
Extra parts and data
None beyond the software above.
Key concepts
- DFA index
- A measure comparing the theoretical minimum assembly time for a design with its estimated actual time. A higher index means a more efficient design.
- Minimum part criteria
- A part is essential only if it moves relative to others, must be a different material, or must be separate for assembly or service. Others are candidates for combining.
- Assembly directions
- Parts that all go in from one direction, usually from above, avoid reorienting the pack and reduce time and errors.
- Design for service
- Modules and the BMS should be removable without dismantling the whole pack, which matters for warranty repair and second life.
Step-by-step guide
- 1
Build the baseline pack
Model an example pack for a small car or three-wheeler: four modules on a welded tray, a separate set of module brackets, a lid with a gasket, a BMS board on standoffs, busbars, a service disconnect, a main connector and harness clips. Use Toolbox fasteners. This baseline should look like a reasonable first design with deliberately separate brackets and mixed fastener sizes, so there is real scope for improvement.
Checkpoint: A fully mated baseline assembly with a BOM listing every part and fastener.
- 2
Map the assembly sequence
Create an exploded view in the order parts would be fitted, and write a process sheet: each operation, the parts, the tool and the direction of insertion. Count reorientations of the tray and fastener types. Note which operations need a second person or a lifting aid. This sequence is the input for the DFA scoring and makes hidden complexity visible.
Checkpoint: A process sheet with operation count, fastener count, fastener types and insertion directions.
- 3
Score the baseline with DFA
For each part, apply the minimum part criteria: does it move, need a different material, or need to be separate for assembly or service? Estimate handling and insertion time with a published DFA table approach, or with a consistent simplified scoring scheme you define and state. Compute a DFA index. Mark parts that fail the criteria as candidates for elimination or combining.
Checkpoint: A DFA worksheet with time per part, theoretical minimum part count and a baseline index.
- 4
Run DFMXpress on key parts
Run DFMXpress on the tray, brackets, busbars and lid, choosing the correct process (mill/drill, sheet metal or injection moulding) and material. Review flags such as deep small holes, sharp internal corners, holes too close to edges or bends, and walls that are too thin. Record each flag and whether you will fix it now or in the redesign. Save the DFMXpress report for each part so the redesign can be re-checked against the same rules later.
Checkpoint: A list of DFMXpress findings per part with an action for each.
- 5
Generate redesign concepts
Develop at least two concepts. For example: integrate module brackets into a stamped or extruded tray, replace mixed fasteners with one size, use snap-in harness clips moulded into the module covers, and make all fixings top-loaded. Consider whether busbars can be laminated as one part. Sketch each concept and estimate its part count and DFA index before modelling in detail.
Checkpoint: Concept sketches with estimated part count and DFA index, and a chosen concept with reasons.
- 6
Model the redesign
Model the chosen concept as a new configuration or a copied assembly using Pack and Go with a suffix. Use Hole Wizard with one fastener type, add locating features such as dowels or tabs so parts self-locate, and add lead-in chamfers. Keep the service disconnect and BMS accessible from the top. Run Interference Detection and Hole Alignment checks on the new assembly.
Checkpoint: The redesign passes interference and hole alignment checks, and all parts insert from one main direction.
- 7
Check strength and stiffness
Run a static study on the redesigned tray with an example vertical shock load of a few g on the module masses, using remote masses for modules and bolt connectors where fasteners are kept. Run a frequency study to check the first natural frequency stays above an example target, so it does not couple with road input. Compare with the same studies on the baseline.
Checkpoint: Redesigned tray meets the factor of safety and natural frequency targets, with values within a stated band of the baseline.
- 8
Re-score and compare
Repeat the DFA scoring on the redesign. Build a comparison table: part count, fastener count and types, reorientations, estimated assembly time, DFA index, mass and the structural results. Check that safety features such as gasket sealing, high-voltage barriers and isolation from the tray have not been compromised. Flag any trade-off, such as a tray that is cheaper to assemble but harder to repair.
Checkpoint: A side-by-side table showing the redesign improves the DFA index while meeting structural and safety checks.
- 9
Review service and end of life
Walk through removing one faulty module in both designs: count the operations and parts disturbed. If the redesign made service harder, adjust it, for example by splitting one integrated bracket. Note fixings that would help later disassembly for recycling. Record the final process sheet with the new sequence and operation count. Use the exploded view in reverse to animate the service sequence, and count how many fasteners of each type must be removed and refitted in each design.
Checkpoint: A service walk-through showing module removal operations for both designs, with the redesign no worse than the baseline.
- 10
Document and report
Produce exploded drawings and BOMs for both designs, the DFA and DFMXpress worksheets, structural results and the comparison table. Explain that DFA time estimates are approximations and need confirming with a timed trial build, for example of a scaled or printed mock-up. Discuss how the method would be used in a real design review. List every assumption behind the time estimates, such as operator skill and tool availability, so a reviewer can judge how far the comparison can be trusted.
Checkpoint: A report with both designs documented and a plan for a timed physical trial.
Testing & validation
- Baseline and redesign both pass interference checks.
- DFA scoring uses a consistent, stated method for both designs.
- Structural and frequency checks meet stated targets, with mesh convergence on the peak stress.
- Safety features such as sealing and high-voltage barriers are retained.
- A timed mock-up build is proposed or carried out to check time estimates.
Expected results
A baseline and a DFMA-improved battery pack with DFA and DFMXpress worksheets, structural checks, a service walk-through and a comparison showing reduced part count and assembly operations.
Research angle for your M.Tech thesis
Study how DFA-driven part consolidation in battery packs trades off against serviceability and recyclability. A useful study defines metrics for all three, applies them to several pack architectures and checks DFA time predictions against timed mock-up builds.
Take it further
- Add SOLIDWORKS Costing to compare part costs between the designs.
- Simulate the assembly line with the process sheet in a spreadsheet takt-time model.
- Run a timed build of a 3D-printed scale model with classmates.
Viva and review questions
How did you decide a part could be eliminated?
By the minimum part criteria: if it does not move relative to its neighbours, does not need a different material and is not needed separately for assembly or service, it can in principle be combined.
What does DFMXpress check and what does it miss?
It checks rule-based issues like hole depth, corner radius and wall thickness for a selected process. It does not judge cost, tooling or assembly, so it must be combined with DFA and engineering judgement.
Did consolidation hurt anything?
Integrating brackets into the tray made one repair step longer, so I split one bracket back out to keep module removal no worse than the baseline.
Learn it at DIYguru
These DIYguru courses and programmes teach what this project needs.