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I'm wishing for a miracle -- Advice on my senior design project please...

  1. Feb 2, 2016 #1

    Hey guys, as shown in above link, I've explained my almost no engineering knowledge and no experience in design project, which put into an intense anxiety attack. I really do not want to trouble my 2 team members so I decided to suck it up and made a decision to make contribution

    So for the senior design project, we're making a tension tester using 3d printed parts. We're planning to use off the shelf and easily fabricated parts and use stepper motors coupled to lead screws to generate enough force required to break the specimen (3d printed parts). The load applied by the machine will be measured using load cells mounted between the jaws that hold the specimen and the frame of the machine. Arduino will be used to read the data from load cell and possibly a second Arduino will control the motion of the stepper motors using a stepper motor driver. The overall frame of the machine will be built from extruded aluminum sections with slots for t-nuts.

    My questions are

    1. I'm not really sure what he meant by use stepper motors coupled to lead screws to exert the force? I know that stepper motor generate mechanical energy to make rotation but when he said coupled to lead screws did he simply just meant connecting it to the main body?

    2. I really want to make a contribution and not feel like a worthless human being. Please provide advice on how I can prepare myself to take part in making this? (I tried researching how tension tester is made and all I get is video of pre-made one being used for experiments). In other words, I would like a proper guide to learn the creating process.

    3. Should I tell the group that I really have no experience in this field and that I'm gonna have to do lot of extensive research to make contribution and might take longer than others?
  2. jcsd
  3. Feb 3, 2016 #2


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    well, i think it is good to be honest with your group and come out with a solution. I think up to the semester you have been, you should more or less have some knowledge in you eventhough you said you dont know much (you would have fail all the subjects if you have 0 idea on everything). Just be honest with your group and emphasize that you want to contribute as well and you guys will find a solution/compromise. Maybe you can do the less complex work like preparation and thereotical research, simplex calculation and data documentations.
  4. Feb 3, 2016 #3

    Simon Bridge

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    ... that hardly seems fair. I think your lack of experience will be quickly apparent to them and soon, so you are better to fess up.

    1. a connection can be anything that will have the motor turn the screws ... the screw does not need to be attached directly to the shaft of the motor (though you do see this configuration in, say, electric model trains.)

    2. You should be honest with your teammates - you are betraying them by hiding your inexperience and anxiety... IRL this is worse than worthless: it's a menace, and potentially dangerous.

    3. Yes. It is likely the others will step up (or confess their own ignorance: how did you get on this team?) and probably find a way for you to contribute within your abilities. Not everyone can be an expert. There is no shame in ignorance - but there is lots in hiding your ignorance from people who are expecting, and maybe relying on, you to be expert. If you skim through these boards you find lots of times quite senior members, with research backgrounds and degrees up the armpits confess "I don't know" or "I am not the expert on this"...
  5. Feb 3, 2016 #4


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    What?!?! No!!!

    Christy, your senior design project is the first real project any of you have attempted. You aren't supposed to know how to do it. You are supposed to use your bag of mental tools to learn new skills and figure things out and your resourcefulness to find answers and methods for things you have never done before. That's what engineering is!

    Not only do you do you not owe them a pre-emptive heads up that you probably won't be of much help, you owe them better than that! See, if you tell them in advance, what you are really doing is lowering expectations to let yourself off the hook for a poor effort/performance.

    What you actually owe them is your best effort. If you give your best effort, you will make a positive contribution.

    Also, a more specific tip: there are a lot of tasks to complete and not all of them are purely technical or complex. There is a lot of other work on an engineering project, like creating/making presentations and writing proposals and reports. Make yourself useful by tackling some of that.
  6. Feb 3, 2016 #5
    I agree with what everyone has said here already.. say you want to make a contribution but you're not sure how to go about it because you don't feel comfortable with your knowledge. Myself, I lack a little bit of the book-study side of engineering, but I grew up on a farm with a pile of scrap metal, and got really good at mentally designing stuff with what I had... Since then I've learned autocad and that has been a great help in making things look prettier and avoiding pitfalls. 'nough of that.

    On point 1....
    There's lot of options for driving the lead screw from the stepper motor...
    Perhaps start with a cogged belt and some pulleys.. Here's a good place to start

    Then look at lead screws

    And stepper motors, some with the controllers already... I chose a fairly large one since you'll probably need to apply a fair bit of force.. you can gear down a smaller one too though

    And finally, some linear bearings for things to slide on nicely.. some mounts are there too.. all ready to bolt to your T slot frame

    All that's left for you to do is chose the right parts, do some (pretty simple) math to come up with gear ratios needed to supply the necessary force, and put it together

    Good luck with it, take courage and give it your best shot
  7. Feb 3, 2016 #6
    thank you very much for the response. I'll be sending emails to my members right now to tell them that I'll probably end up doing extensive research when making contribution to project as I do not have any design experience. I honestly I have no idea how all those parts you listed contribute to building the tension testers (yes, this is how bad I am) so I'm also thinking about asking the member (who came up with idea of tension tester for 3d printed parts) how the structure/design will be for this.

    When creating tension tester, in terms of making the machine do specific motion, is stepper motor really all you need? Is there anything else needed?

    So stepper motors will be used to add force to tension when trying to break the specimen but is this the adequate size for fragile ones like 3d print parts? Just out of curiosity, how much bigger stepper motor is needed to break a usual specimen which has stronger resistance?

    I apologize for asking too many questions.

    thank you
  8. Feb 3, 2016 #7
    Perhaps you should ask your team members for some basic parameters for the project...

    What will the biggest part be? What is the maximum pull required?

    It's impossible to start designing something (and purchasing parts) before you have the basic guidelines... 3D printed parts could be something as small or as big as you can imagine... and the required strength to break it will be proportional to it.

    You will probably only be testing one axis, so yes, one stepper motor and 1 or maybe 2 screws should be sufficient... if you're testing small parts you can use smaller components.. The stepper motors data sheet will list the torque they can produce at a given speed, you can calculate how much torque you need to apply to the lead screw to produce a given amount of pull, and from that you can calculate the necessary gear ratio between the motor and lead screw... in some cases you may be able to directly couple the lead screw to the motor.. but without some project guidelines, I can't speculate on how big anything needs to be.
  9. Feb 3, 2016 #8
    thank you very much for fast replies! Regarding the "start designing something", yes I do agree with you. I tried to find online on how tension tester is generally built in detail because if I understood the fundamental function and structure, I would be able to take part in discussing with the group of how to design one; for some reason, I could only find information about testing it rather than building process... sigh.

    If it's not too much trouble, would it be fine if I private message whenever I have question when working on my part assigned by the group?

    thank you
    Last edited: Feb 3, 2016
  10. Feb 3, 2016 #9
    Sure, you can PM me.. I'm not going to do the work for you, but I will give you guidelines on how you can go about making it, and can help out with the concepts.

    basically, you have 1 end mounted solidly to your frame, you attach the load cell to that, as well as one end of each linear shaft.. you have a table that can slide on your linear shaft anchored to the end by the load cell.. you attach one side of the part you're testing to this table. On the other end of the frame, you mount the other end of your linear shafting, your motor, belts, etc... some bearings for the lead screw(s), and another sliding table that is driven by the lead screw(s).
  11. Feb 3, 2016 #10


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    First I'd agree with whoever said, find out exactly what this project is and what the parameters are. In my experience (of projects at high school level) most groups start their projects with a very hazy idea of what they're trying to do. Usually the project ends up being defined by what they did rather than by what anyone wanted to do. (At your level, you probably won't get away with that!) If you know clearly what you've got to do, provided it is a realistic target (I think your supervisor ought to be able to warn you if it's not,) getting it done becomes a much less haphazard process.

    Absolutely! I'd suggest one role, that you'd be particularly useful for, is asking questions.
    See, you're already doing it. Whatever suggestions come up, make sure YOU understand them. "Well how will that work?" and get them to explain in it. Use a XXX, "why a XXX? Will it be &&& enough?". Etc., etc. If someone can make you understand what they want to do, then there's a fair chance they actually understand it themselves, which is often not the case with many of the ideas that crop up. Questions and finding the answers enables your project to progress: hazy ideas and questions not even thought about, can lead you up blind alleys and waste a lot of time.
    Research?. So when answers are lacking, you get googling - not "how do I design and build a tension tester?" but specific points, like what motors can you buy, get their data sheets, aluminium section suppliers, get available sizes, strength data, what material is used to make the 3d parts, how strong is it, etc.?
    I expect I'm teaching my grandmother to suck eggs (or the reverse, since I'm probably old enough to be your grandmother!) but finding info on the web is a bit of an art.
    Yes, I didn't find a lot using "tension tester", but then I'd never heard this machine called by that name. So I described it differently and found more. Then I realised the most interesting results were coming about the machine's use, so I changed to searching on that. And found lots. (You are not going to test steel bolts or hawsers. What are you going to test? What else similar are people likely to be testing already?) And as I said above, you don't have to find the complete solution laid out for you. Look at leadscrews until you do know what they are, how they work, what people use them for. Stepper motors, ditto. You won't need to know all that, but I'd be surprised if you didn't learn something useful in the process.
    Maybe you don't even have to search on the web. I guess you have books on engineering. With a project like this, maybe you're even a mechanical engineer or similar. Somewhere in one of your textbooks I'd be surprised if there wasn't something about doing tests like this. Maybe even a diagram of a machine. At least you might find out what the right jargon is to use in your web searches.
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