Posted on September 15, 2022
Completed - 11 months leftAssist 2 Develop Challenge: CAD Mechanism
ROTATIONAL PASSIVE LOCK WITH 90-DEGREE INCREMENTS
Assist 2 Develop Challenge: CAD Mechanism Video
You have a minimum of two components, A & B, that rotate relative to each other.
You need to design a mechanism that makes it possible for component A (red) to passively lock into place relative to component B (gray) when rotated in 90 deg increments (i.e. passively locks in four equally spaced rotational positions). The passive lock should be easily overcome (rotated) by a human operator. Tip: You don’t have to reinvent the wheel; you may use products around you or the internet as inspiration. Reverse engineering is allowed. You may use different colors and geometries in your solution, you do not have to use the same exact red and gray disks above, they’re simply used to illustrate the challenge.
The CAD design can be composed of parts designed from scratch and/or downloaded hardware from a website like McMaster-Carr.
Goals:
Determine if the participant can translate written requirements into a working mechanism on CAD with motion.
In addition to submitting a CAD file, kindly explain how your mechanism is a viable solution. Concisely explain your thought process/logic in less than 2 paragraphs. You may use 1-3 images.
Estimated time to solve: 2-4 hours.
The top three participants to receive cash prizes:
1st place: $350
2nd place: $100
3rd place: $50
Top submissions will also have the chance to interview with top employers.
This design proposal consists of a 3 piece assembly of low-cost injection molded plastic components. The design consists of a CAP_TOP and a CAP_BOTTOM. The CAP_BOTTOM is a sub-assembly of the CAP_BOTTOM and CAP_INNER components. This sub-assembly is designed to easily snap together to minimize costs. The CAP_INNER component is also keyed to ensure there is only one assembly orientation (not important for this design, but may future-proof additional product iterations). The CAP_TOP also snaps together with the CAP_BOTTOM allowing for rotation. A touch of pre-load on the plastic snap fits provides a secure fit for the rotating components.
The design is able to index into 4x unique positions situated 90 degrees from each other. This indexing is accomplished through 4x flexible plastic arms on the CAP_INNER that click into detents on the “CAP_TOP”. Generous lead-ins in both rotational directions allow the two CAP halves to work in either direction and be easy to rotate out of the 4x fixed locations. The flexible plastic arms have been made as long as possible to ensure an adequate number of cycles and the plastic does not permanently deform over time.
The design of these components has been optimized for injection molding. The CAP_INNER component has been separated from the CAP_BOTTOM to minimize the number of undercuts if the two parts were combined. The CAP_BOTTOM has 4x snap hooks that engage with the CAP_INNER. These details currently require lifters, but could also be shut-off molded, however, this would introduce holes on the outside of the part. The CAP_TOP also has 4x snap hooks allowing it to be assembled to the CAP_BOTTOM. These details are also formed with lifters, but could also be revised to a shut-0ff style design.
This design presents a low-cost solution to the brief that could scale into extremely high volumes if so desired (and tooling costs were accounted for). Alternatively, the design is sound for many forms of additive manufacturing. This design is not well suited for machining in its current form.
The choice of injection molding and developing the mechanism with geometry, as compared to off-the-shelf components gives the utmost flexibility to define the feel of the rotation, the feel of the snaps, and the exact amount of force required to actuate the mechanism. With an open-ended brief such as the one provided, it is always desirable to build flexibility into the design so that product features can be precisely dialed in.
13 year(s) experience
0 challenge(s) worked
Mechanism consists of 2 parts, snap fit together, with a ratcheting system to enable rotation passively locking every 90 degrees.
8 year(s) experience
0 challenge(s) worked
My submission attempts to use as few parts as possible, and those parts should be readily available or easy to manufacture. In terms of readily available parts, I used a set screw and a flanged button head screw from McMaster Carr that are inexpensive and available in large quantities. The screws will need helicoils (I haven’t included them in the CAD) so as not to damage the threads of the plastic parts. I’ve used a small spring for my locking mechanism which should be easily procurable. There are three parts that need to be manufactured, and I made sure to use simple shapes (rectangles and circles) to simplify the manufacturing process. The most complicated shape I have is the groove in which the hook locks, which is filleted and angled to allow for the hook to move into and out of it quickly. In this sense, I believe that my design will be easy to build.
The mechanism is relatively simple. There are four grooves in component B at 90-degree angles. The grooves are for the hook, which is pushed into the groove by the spring above it. The spring’s strength can be adjusted by the set screw. When rotating the part, the hook will slide along the filleted sides of the groove and easily pop out of the slot. What’s more, this mechanism can turn both clockwise and counterclockwise. Hence, I believe that this mechanism can be easy to use and adjust.
I will include the videos and files in the zip folder. Thank you.
1 year(s) experience
0 challenge(s) worked
Hi I’m Prasoon,
Here I submit a simple proposal which uses a wedge mechanism & spring lock.
Hope this will suffice all the requirements.
Regards,
Prasoon
4 year(s) experience
0 challenge(s) worked
The simplest method for this mechanism is to use a spring loaded wedge or simply using a ball plunger. Ball plungers are available in almost any size we want, so this model is also scalable to any disc size we want. I have developed two models in which I have used a spring loaded wedge on one, and a ball plunger on the other. The working mechanism is very simple- the spring loaded part ( wedge or the ball) gets trapped in the groove provided on second disc, and escapes the groove when rotated , with the spring compression. Both models are designed considering the factors- scalability, and easy manufacturing and assembly. I have included both my design models and the explanation in the zip file I am attaching here.
1 year(s) experience
0 challenge(s) worked
The button has 4 positions in which it can be locked.
Turning involves pressing the button, which interacts with the spring, then turning it to one of the 4 positions(in 90 degree increments).
Releasing the button, the spring pushes back the knob which locks its position through the shaped sockets.
The second option for turning is to use more force to turn it. Thanks to the shape of the sockets, by using more force, the button itself can compress the spring and this will allow the knob to turn.
Translated with www.DeepL.com/Translator (free version)
4 year(s) experience
0 challenge(s) worked
For this project, some assumptions were made as they were not spelled out in the project constraints:
1) The grey part of the mechanism would be stationary, possibly part of the panel of some machine, and the knob is used to make a selection setting on the machine.
2) The stationary part of the mechanism need not be round as the project constraints state that the geometries can be changed. I assumed the grey, stationary part would be metal.
I made the rotary knob plastic (probably ABS), and is designed to be injection molded or 3D printed, and is approximately 2 inches in diameter to make it easy and comfortable to grab. Indexing marks are molded into the knob and cut into the stationary grey metal part B for the operator to reference during use. The knob has molded knurling in the outer edge for grip. It is drafted relative to parting line and has no undercuts relative to parting line simplifying the mold needed to make this knob, making the mold less expensive. It is hollowed out as per best practices for injection molded plastic parts.
For the passive locking mechanism that occurs at every 90°, inexpensive and easy to obtain spring loaded ball nose plunger (McMaster PN 2191A261) is used along with molded in spherical detents on the back side of the red, molded knob. I used 2 plungers, each at 180° from each other to balance out the forces, as using a single plunger would result in asymmetric forces causing the knob to be crooked and/or the center hole would wear abnormally over time.
I designed all the parts of this assembly to be easy to manufacture. For example, the ball spring plungers are mounted parallel to the center axis instead of being mounted radially. In Part B, the single hole and the detent spherical holes can all be machined from a single setup on the CNC. If I had arranged the spring plungers radially, it would make machining the holes much more difficult, and would require additional setups, a 4th axis or special fixturing.
The advantage of using the spring plungers is that they can be adjusted to provide more or less “holding force”. This means the force required to rotate the knob can be adjusted. It can also be adjusted to account for wear.
An inexpensive, $3.00 thrust bearing is used along with the shoulder screw, to keep the knob rotary friction consistent over time, preventing wear.
Because the knob is plastic and is retained by the shoulder screw, and threads tend to easily tear out of plastic, a metal threaded insert (McMaster PN 94180A353) is molded in place (or heat staked after the knob is molded or 3D printed).
14 year(s) experience
0 challenge(s) worked
I enjoyed a lot solving this challenge. I have uploaded my solution for the challenge in this zip file.
Hoping for many more such challenges in upcoming days.
2 year(s) experience
0 challenge(s) worked
Thank you for this oppurtunity,
The description for my design is as follows,
The spherical ball end parts travel through the groove (in Part B ) and lock in place every 90 degrees. The locking mechanism
can be overcome with little force by rotating it.
The design of the groove is such that it does not allow for the back wards movement.
the pin and slot sliding mechanism is has been used for ease in assembly of the product as well as for allowing linear movement in a confined and precise manner in the slot
the ball bearing and the spring is downloaded from traceparts.
These parts can be made using 3D printing.
Furthermore, we optimise the design by providing drafts and material flow analysis in the mold for injection molding process.
2 year(s) experience
0 challenge(s) worked
Hello. First of all THANK YOU for the challenge. as a part of it i learned few things. i am going to introduce a simple concept which include two parts . through out the process keeping the requirement in mind my one of the main objective where make the concept as simple as possible.
1 year(s) experience
0 challenge(s) worked
The locking mechanism used here is a simple one which involves
a container (A) and a cover (B). The container has a lock plug that is
flexible enough to bend a little when the cover is connected. Turning
the cover clockwise or anti-clockwise should make the locking socket
locate the plug immediately.
This design is made such a way that the plug is filleted well to ensure
smooth sliding in and out of the socket. Therefore, with increments of 90
degrees, both parts meet in a locking position.
5 year(s) experience
0 challenge(s) worked
Hello! This is Krishna Prasanth pursuing Bachelor’s in Mechatronics Engineering. I have been worked on many events from SAE e-Baja to Mega ATV Championship. The area where I was working gave me more exposure to the mechanisms and how they actually work. Currently, I’m working as a Project Associate at Rane (Madras) Ltd. for implementing automation design at the plant which produces steering systems for automotive companies.
The mechanism I have tried is capable of being able to manufacture easily. And the cylinders are also able to rotate in both clockwise and counterclockwise.
3 year(s) experience
0 challenge(s) worked
Hello there! I´m Martin. First of all thanks for this opportunity, I hope you like the mechanism I’ve been working on.
Initially I started taking a piece of paper and a black pen, my first goal was to sketch at least a viable and working solution. However, I wasn’t satisfied with the results of the first couple of ideas. So suddenly the functional principle of a ratchet wrench came to my mind out of the blue, then this drove me to think of a third and chosen idea.
The way this system works, it’s pretty simple. It consists of four main parts: piece A, piece B, a little ball, and a spring. The first piece contains the string and the tiny ball, while the second one has four slots sized for the ball. When the piece A is rotated, the spring retracts, unlocking the mechanism so both pieces can be swung around 90 degrees in both directions, till the other locking position is met.
3 year(s) experience
0 challenge(s) worked
Hello,
this is my simple proposed mechanism, a sliding ball pushed by the string assembled in a cylindric hole in part B, the sliding is locked in one direction and the sliding ball is locked every 90° but still easy to overcome by just rotating,
Thank you for this opportunity 🙂
4 year(s) experience
0 challenge(s) worked
Press release button with turn function and return spring
90 degree as wished , when released locked in 0/90/180/270 position
when engaged and turned then in non the above and via versia.
year(s) experience
0 challenge(s) worked
Hi!
So my solution is it to parts have an annular snap fir joint which facilitates a rotational joint. As for the 90 Degree snap motion, I have worked to design a simple 4-lobbed male and female part with spacing to facilitate locking points, and if force is applied the lobes interfere with each other as opposing torque is applied to the two parts. Once 90 Degrees turn is complete, the interference zone ends, and the parts snap into the free space. The parts are designed to be 3D printed, in my Prusa, so that is the manufacturing process kept in mind when designing the parts. A little lubricant like petroleum jelly can help a slide when the lobes interact.
7 year(s) experience
0 challenge(s) worked
Greetings,
I’m KOUSHIK, experienced and certified professional in mechanical design with AutoCAD, Solid work & Catia. Expertise in Product design, Sheet Metal Design, Custom Enclosures, Drafting, Product Documentation and Reverse Engineering.
Thanks for the opportunity.
I have attached all the related files required.
year(s) experience
0 challenge(s) worked
Sou do Brasil (mas não tem a opção do meu país para selecionar)
O conjunto proposto é do tipo “macho” e “fêmea”.
O mecanismo adotado é composto por um duplo encaixe semicircular, que após as peças apoiadas uma sobre a outra, faz-se o giro de 90 graus da peça vermelha (macho), que executa o travamento através de elementos cônicos de ajuste preciso.
Proponho peças plásticas obtidas por impressora 3D.
Assim pode-se experimentar a melhor composição química e alcançar boa precisão de medidas para garantir o ajuste (travamento), além de viabilizar uma produção em série
15 year(s) experience
0 challenge(s) worked
Hello
I Modeled the Lock Mechanism System in Solidworks 2018 in the challenge you have given a couple of Drawing Sheets. I used that sheet as a reference and for the dimensions, I have drawn some basic Freehand drawings for a self-help Purpose.
Also, I learn lots of new things in this challenge so thanks for Organising this challenge
Regards,
Krunal Dhaygude.
0 year(s) experience
0 challenge(s) worked
Greetings,
Thanks for providing me this opportunity, My name is Ashish Palankar pursuing Aeronautical Engineering with excellent problem-solving skills and ability to perform well in team. Passionate about designing and enjoy learning new things. Proficient in Autodesk Fusion 360, AutoCAD, Ansys Fluent etc. Designed and Developed many CAD models, worked with many projects and also participated in many competition.
I have designed this to improve my Innovative skills in design because “Every Innovation starts with a Design”.
3 year(s) experience
0 challenge(s) worked
Mehtab Alam
Mechanical design engineer
Linkdin: https://www.linkedin.com/in/mehtab-alam-b7395113a/
mail: amehtaba160@gmail.com
about project:
Hye i made two disk and these insert into each other and then rotated. the have a bulge which snaps into the cut when rotated. once it snaps it cant move unless some rotational force is applied in opposite direction.
the video explains the whole mechanism.
the files can be downloaded from here
the link contains videos, files, step files, solidworks files and assembly
https://drive.google.com/file/d/1hXZZqs1uly6MMFnMSpXvb070gqbJNTsm/view?usp=sharing
4 year(s) experience
0 challenge(s) worked