Støping av robotgriper med compliant mekanisme
Bachelor thesis
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https://hdl.handle.net/11250/3004145Utgivelsesdato
2022Metadata
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Sammendrag
Hensikten med å lage robotgriper med compliant mekanisme er å redusere kostnader, bedre vedlikehold og mindre deler ved sammenstilling. Compliant mekanisme består av en del som er maskinert og designet slik at den mekanisk bruker sine egne påkjenninger for å oppnå avbøyning i en retning. Målet er å produsere en prototype av en compliant mekanisk robotgriper i en aluminiumlegering.
Metoden går som følger, først lages det håndskisse av modell, som deretter blir modellert i et 3D Computer-Aided Design (CAD). Videre blir enkle utregninger gjort for å finne estimerte spenninger, og modellen blir optimalisert med bruk av statisk- og utmattelseanalyser gjennom CAD. Etter kalkulasjoner og simulasjoner blir det produsert en sandstøpning konfigurasjon av modellen 3D-printet for bruk som pattern ved sandstøpning. Modellen blir sandstøpt med pattern, og deretter klargjøres den for CNC-maskinering. CNC-maskinen freser den sandstøpte modellen, og vi får en frest robotgriper modell. Modellen blir boret hvor en kompakt sylinder skal festes til, og tilslutt blir det utført deformasjonstester av modellen.
Resultater fra prosjektet viser at det er mulig å gjennomføre en compliant mekanisk robotgriper med grundig optimalisering prosess for å få en fungerende mekanisme. Videre blir modell 3D-printet med parameter egnet for pattern hos sandstøpning. Ved sandstøpning var det viktig med å ha nok materiale for modellen og luftehull for gasser. CNC-maskineringen av sandstøpning-modell måtte modifiseres for å kunne bli maskinert, men pga. CNC-maskinens begrensninger kunne ikke modellen bli frest på en ønsket metode. Viktige resultater gruppen kom fra til var at materiale har stor betydning for en fungerende compliant mekanisme, og ha dimensjoner som er egnet for både sandstøpning og CNC-maskineringen med kalkulasjoner og simulasjoner som egnet for compliant mekanismen. The goal for the group were to make a sand-cast prototype of a robot-gripper in aluminium alloy. This robot-gripper should consist a mechanical function called compatible mechanism, which consist of one part. The group starts out with sketching the model on paper and by inspiration produce different kinds of sketches of the robot-gripper.
Afterwards the group decides which of the sketches are chosen for 3D-modelling in the CAD software Solidworks. There were done simulations on the model in Solidworks simulations to get estimated results that can be compared to the 2D-handcalculations. With these values the group gets somewhat understandable knowledge. The values are somewhat close to the values of the practical test which also will be similar to the results from hand calculations and simulations. With the values there were done 3 optimizations of the model to figure out the best product the group could produce for sand-casting, the compact cylinder and parameters for static- and fatigue analysis. With 3D-printing there were printed two different mould for sand-casting-patterns. Both of these patterns would later on be sand-casted and the result were equally same. Both patterns had similar defects, shrinkage and weight. By CNC-machining there were done preplanning with fastening the product and milling the model. The model was uploaded to the program and a simulation ran to produce a CNC-milling route, but in the end the group decided that the CNC-machining couldn't be done.
For materials there were done analysis with different aluminium alloys. The plan was to first use the Aluminium 6082, which had good characteristic for sand casting and compatible mechanical properties. The group ended up on using the material available in the lab at NTNU-Gjøvik S-building. The group used the material based on aluminium-silicon. This material had good sand-casting properties, but the mechanical properties weren't compatible for the compliant mechanism. During CNC-machining the group couldn't finish the product. The reason were because of the restrictions from the movement in the milling machine and the software, the software couldn't simulate any end product. The model had to be divided up in many sections to perform the milling. Which resulted in correct parameters couldn't be reached with machining, and cause of a lot of alternating movement of the model with re clamping. The group had to conclude it is possible to produce a compliant mechanic robot-gripper. The materials value on durability and mechanical properties fulfilled the groups requirements. It is important to pick a good material and a balance between the deformation, max stresses and a good factor of safety.