Handheld Sewing Machine Teardown Project
PROJECT SUMMARY
In my Materials and Manufacturing class, my team of four students was tasked with tearing down a hand-held sewing machine, analyzing its function, writing a presentation on the results, and creating a full CAD model in SolidWorks.
My main responsibilities were to CAD nearly every part from the complex shell to the gearbox, and then to create the 50+ part assembly. My goals were to clearly understand the function of each part in the assembly and to create an accurate and detailed CAD model of the machine. I used digital calipers and precise images to model every part (besides the motor); the large gallery of pictures I took during the teardown process, combined with my careful observation, helped me successfully recreate the entire assembly.
Not only does the final CAD model include every functional feature of the machine, but I used gear and cylindrical mates so that the motion of the motor and/or turning wheel drives the motion of the needle arm assembly!
My main responsibilities were to CAD nearly every part from the complex shell to the gearbox, and then to create the 50+ part assembly. My goals were to clearly understand the function of each part in the assembly and to create an accurate and detailed CAD model of the machine. I used digital calipers and precise images to model every part (besides the motor); the large gallery of pictures I took during the teardown process, combined with my careful observation, helped me successfully recreate the entire assembly.
Not only does the final CAD model include every functional feature of the machine, but I used gear and cylindrical mates so that the motion of the motor and/or turning wheel drives the motion of the needle arm assembly!
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TIME SPENT CADDING (H)
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DIFFERENT PARTS
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GRADE RECEIVED (%)
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DISASSEMBLY & INDIVIDUAL PARTSI started by carefully disassembling the sewing machine removing one individual piece at a time, and taking a picture after each step to help with re-assembly in the CAD. For certain core parts that used rivets or welding, the disassembly process was irreversible, but I made an effort to preserve the original dimensions and geometry wherever possible. My team and I then characterized each part by name, function, and manufacturing method.
I photographed the very small or geometrically complicated components directly from above to minimize distortion, then used that image to model the part. I scaled these parts using a single dimension measured with calipers. |
Case half #1, with all features painstakingly modeled in
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Motor and gearbox subassembly
Needle arm subassembly
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PART SUBASSEMBLIESAfter modeling every single individual part, I built the gearbox and motor arm subassemblies. The purpose of these was to simplify the modeling process for the final assembly and to match the design of the sewing machine. Wherever possible, I used width mates or concentric mates to account for tolerancing and slight measurement inaccuracies, but if this was not possible for some reason, I adjusted dimensions at the component level. My top priority was creating a model that fit together the way the original sewing machine did, while maintaining dimensional accuracy.
I made heavy use of the sheet medal modeling tools for the parts within the needle arm subassembly. This subassembly proved particularly challenging because some of the parts had been slightly deformed during the teardown process, and it was difficult to get as accurate measurements as before. Nineteen parts, including the batteries, were either mounted directly to the case or in such a way that did not warrant a separate subassembly. |
FINAL ASSEMBLY
The final assembly is based on the #1 case half, and includes the subassemblies and all other assorted parts. I carefully build and mated the subassemblies together such that changing or adjusting individual parts would not require the updating of the entire assembly. Where possible, I used mates that allowed for the motion of components within the ranges they saw in the original real-life part. Although the motion in CAD did not fully capture the motion of the real part, it came quite close, as can be seen in the brief video below.
