Idea for Testing

[TomyOne]

Hello,

I would like to ask about best solution for my project.

I need to do a reliability test of some electric conductive adhesives on flexible substrate with 32um cuprum.
I have flexible PCB it is made of poliimid on which is coated Cu of 23um. And I am going to attach on it resistor matrix, thesee resistors will be adhere by three different adhesives.
And I need to Create some mechanical bending of that flexible foil with resistors and than measure resistance of every resistor and get results how much mechanical stress it can take.

I get some idea to Create some linear mechanical movement machine, where will be stepper motor. Drive by MCU, I have available MSP430 launchpad and some Stepper motor drive IC. Do you have any ideas where to find scheme how to connect it ?

Or how to make that mechanical connection of that device which will do linear movement ?

Thanks

 

[MrAl]

Hello there,

To start off if you do a search for Stepper Motor Driver IC chips you should run into a number of driver chips which will have data sheets on the web too. Looking for those data sheets you'll find several schematics of how to connect the steppers and what is involved. Some driver chip sets actually do much of the work for you in generating the pattern, you simply supply the step clock and direction control inputs. But there are lots of variation too and the pattern isnt too hard to generate yourself if you dont mind going through that work too. Then you can use just the driver chip itself to actually run the motor.
The driver chips are typically just transistor H bridges. The control chips typically contain logic that puts out the right pattern to drive the driver chips, and also usually have a feedback input for current feedback so the current in the bridge and/or stepper motor is limited (via PWM).

 

[TomyOne]

Hi, thank you MrAl, Yeah I think I have now little clear how this stepper motor should be drive.

Now, I need to design machine for bending tests of flexible board,
Somethig similar to this at page 9
http://www.project-cosmic.eu/docs/autumnschool2012/Erwin Yacoub-George_Presentation Reliability tests on flexible printed circuit foils and laminates.pdf

I am not so good at mechanical engineering, So I have no idea where to start. What should be the good program where should I draw it ? And I think I need to find/buy thesee mechanical parts.

And One thing do you have any papers or anything how should I choose stepper motor which will be suitable for moving these mechanical parts?

I need to make it somehow to bend test specimen which is just 10x6 cm big.

 

[MrAl]

Hi,

I dont have a good program for drawing mechanical stuff either, mainly just electrical. There are some free programs on the web but i never found one i liked enough.

The stepper motor is chosen based on the load it has to drive. It might be difficult to choose one with such an unusual load such as this one though. The stepper motor will have spec's of current and torque, and the torque translates into the linear mechanical motion under the assumed load, but again the load for something like this would be somewhat harder to estimate unless you had experience with that very type of load. You'd have to build up the mechanical part of the machine without the motor and then do some tests with perhaps a spring scale and with the assumed load connected, then order a motor that was oversized to make sure it works. If you only have to build one of these that's not a bad idea, and if you have to build more you could try lower power motors and do some tests.

I dont have any papers on this but you could look on the web i would think there should be plenty of pages that explains torque and how it translates to linear motion. The nice thing about doing it one step at a time is that you dont have to assume too much, you only have to assume that eventually you will get it to work once you have the right motor. You can look up motors to find out what the general size is so you make sure you have enough room to mount it, but that's probably not a huge problem.

 

[ikalogic]

I am not so good at mechanical engineering, So I have no idea where to start. What should be the good program where should I draw it ?

We use google sketchup at work.. it's not as powerful as solidworks, but it's good enough, free, and very very simply to use and get started with!

 

[jpanhalt]

And, if you use Sketchup, don't forget to look for some user enhancements. The most useful one for me helps do matings of two surfaces.

John