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Need help selecting a small motor for moving a small rig back and forth left-to-right only about 1 inch. Answered

I have never worked with motors before, and I am starting to realize that there are dozens if not hundreds of different types of motors.

Imagine two 6" long, 1/2" dia. aluminum rods suspended between two pieces or trapezoidal shaped plywood that are secured to a base and braced to make this whole structure rigid. on these two aluminum rods "rides" a small carriage that is literally just a small 2" x 2" platform made from... whatever... 1/4" plywood. This carriage can slide left and right on these two aluminum rods.

I need a motor that can somehow move this little platform left and right, back and forth, only between 1/8" to 1".

I need to be able to control the speed (rate) at which is travels this small distance.
I also need to be able to control the starting point and the end (return) point.

Basically, I and transferring string from one spool to another. So the platform will have a spool of thread on it, and it will be going left-to-right while another spool is turning. The left-to-right movement will be coordinated with the speed that the second spool is wrapping (turning) so that the thread windes as close to "perfectly" in layers. And each spool will be between 1/8 - 1/4 - up to 1" wide. This is why I need to be able to set the starting point, and the end point where it will stop and reverse direction.

I will be controlling this with a project board like an Arduino. I just need to know what kind of motor to look for, and any other suggestions

Thanks guys!

Discussions

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randofo

4 weeks ago

On second though, reading through the comments here again, have you considered building a reciprocating mechanism like this one?
https://www.amazon.com/DC-Reciprocating-Adjustable...

You would basically get a 12V 30RPM geared motor and set the bar 1/2" off center from the rotating motor shaft. This would move the platform 1" back and forth for every rotation. In other words, this would be 1" of travel in 1 second. No need to mess with steppers or threaded rods. Just power the motor on with 12V and it goes back and forth.

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Omniventrandofo

Reply 26 days ago

Hi,
.
Unfortunately it will be impossible to synch to the take-up spool.
Even if successful in getting it to go at the perfect rate, it will build up an error that makes it go haywire in a short time.
To get a level wind all the way from empty to full, the mechanism doing it must be synchronized to the take-up spool, which is exactly what a level wind mechanism is all about.
.
Have a nice day :)

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Omnivent

4 weeks ago

Hi,
.
It sounds like you're trying to reinvent the wheel, or at least a Level Wind mechanism?
Plenty exists, from thread winding on e-spinners over some types of fishing reels to huge ones for seriously heavy steel wire cables.
The mechanism is easily made with a diamond shaft (name refers to the diamond shaped grooves it has got) and a runner that traverses back and forth between the ends, driven from the main rotation with an amount of gear reduction dictated by thread diameter.
Other means exists, but you will be better able to select a method, knowing the right words and googling a bit.
https://www.google.com/search?q=level+wind+mechani...
.
Have a nice day :)

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rickharris

5 weeks ago

It depends on how fast you need the platform to move. If relatively slowly then a DC motor driving a length of threaded rod with a nut on it attached to the platform will do the trick and is easy to speed control with PWM( Pulse width modulation).
Faster movement then i would go to a Toothed belt and a stepper motor, this is going to need some research on your part to understand how to drive it , but there is a LOT of information on the web.
You might get away with a dc motor and step down gear box, say from a cordless electric drill or screw driver. This can drive a toothed belt.

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Dolmetscher007rickharris

Reply 5 weeks ago

Hi @rickharris... thanks for your response. I really appreciate it. I need to platform to traverse 1 inch per second, then come back the other way 1 inch in 1 second. So, in 60 seconds it will have come back-and-forth 30 times. To me, that seems pretty fast. I feel like threaded rod would have to haul ass to spin enough to move a carriage 1 inch in 1 second, and then stop on a dime, and go back the other way.

I'm not familiar with a "toothed belt". Would that be like a pully is attached to the spindle of the motor, and another pully is attached to the pully would have grooves cut in it to accept "teeth" on a belt, and the belt would be pulled to and fro by the motor, which would in-turn advance the carriage left-and-right?

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rickharrisDolmetscher007

Reply 5 weeks ago

OK a length of 6 mm all thread rod has a 1 mm pitch, that is for each turn of the rod the nut travels 1 mm, so 25mm in an inch.

You need to get 25 Rev per sec = 1500 RPM
A lot of small DC motors will do 3000 RPM or more, the load will be very light.

This should work for you.

Yes the toothed belt is as you say - see image.

Amazon have a choice because of people making 3D printers.

Of course you can size your pully to give you higher or lower RPM at the rod.

You can click on the images to see it bigger.

Check out Linear actuators. both DIY and commercial.

To drive the motor both ways you will need an H bridge. If your using an Arduino

https://www.instructables.com/id/DC-Motors-Part-1-...
https://www.instructables.com/id/H-Bridge-for-Dumm...

Or a DPDT switch if you want to try it manually initially

Have fun

Toothed belt 2.jpgtoothed belt.jpgplatform.jpg
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rickharrisrickharris

Reply 5 weeks ago

I missed out a picture of this done directly with a belt.

You would need to find or make a motor run at a suitable speed

platform 2.jpg
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rickharrisrickharris

Reply 5 weeks ago

Whilst we are discussing this you will find it hard to get the platform to stop abruptly at the ends of travel. Unless you allow a distance to getup to speed and slow down you may not get the 1 inch of constant speed you need.

The commercial way to do this is to implement a PID loop (look it up - You tube has some videos.) so that as the platform nears the end it starts to ramp down the speed coming to a stop exactly on the mark every time.
this may or may not be an issue for you but I suf=ggest you will need as a minimum an end limit switch and probably some kind of soft buffer if you don't use a PID loop.

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Dolmetscher007rickharris

Reply 5 weeks ago

@rickharris... Base on your post, I was able to find the exact motor I'd use (Nema 17), the exact rod stock, ball screw (or acme screw), and exactly how I would attach the stage to the rods. And then... after 2 hours of researching parts and looking at CNC machines for ideas, it happened...

I am a software developer, and at least once a month, someone on my team (usually a total newbie) suggests a new feature, or even a whole new application where the pitch goes something like this...

NEW DEVELOPER: So, this would allow users to connect their debit card or bank account to a merchant account, and then they can send money to and request money from their friends to exchange small transactions for things like when you owe your buddy $15 for lunch that one time. You know... rather than having to actual go get cash.

EVERYONE ELSE: (in unison) You mean like Venmo and/or Square Cash?!

Here I am asking extremely detailed question, and getting amazing help from you guys, and then I found out that what I am asking for help on how to build, literally, verbatim already exists and is inexpensive and in the perfect size. Check out the pic. I've attached. It's a 100mm long (perfect) linear stage actuator. It can advance the stage a max of 1.9 inches in 1 second, which is actually almost twice as fast as I'd need. And it is already perfectly constructed so that I would just need to turn my attention to the code and board (arduino/Rspb Pi) And it only costs $54. After totalling up all the parts I had already researched, this thing is almost just as cheap as if I built it all myself.

I really appreciate your help man!

Screen Shot 2018-11-10 at 7.58.00 AM.png
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rickharrisDolmetscher007

Reply 5 weeks ago

Glad to be a help.

"Check out linear actuators" as I said - 90 % of the problem is knowing where to look.

Good luck with the development

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Toga_Dan

5 weeks ago

Sounds like a CD player carriage. If you have a way to control it, it's ready made.

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loneoak

5 weeks ago

It sounds like to me you need a stepping motor, a small Dc motor that can move in small increments. I would look at putting a screw drive of some type to move you sled left and right. Look here to maybe find a motor and drive, they have plenty, https://www.mcmaster.com/

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Dolmetscher007loneoak

Reply 5 weeks ago

Hi @loneoak, I went to the mcmaster.com website, and there do not seem to have any motors labeled specifically "stepper motors" I found some that seemed like they might be stepper motors, but they were like $65-$450. And then you still needed to buy something called a "Driver" and some other thing. So that can't be it. I've seen people build CNC's online with motors that they said were only a few dollars each.

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Downunder35m

5 weeks ago

Just look up "arduino coil winder" ;)
Plenty of projects to give you an idea and code.
Stepper motors are the way to go and liniear rails, as a bundle often available for under $50 on online shops.
You can salvage though if you have old printers, floppy drives or similar to find stepper motors and rails.

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randofo

5 weeks ago

It sounds like you might find the mechanism you need in an old floppy drive mechanism. They are driven by a stepper motor, which can be controlled by an Arduino using a 2-channel motor controller. A stepper will give you precise positioning because you can count the number of 'steps' that the motor takes forwards and backwards.

Alternately, you can use a linear actuator:
https://www.amazon.com/SOViK-Actuator-Maximum-Trac...

You wouldn't be able to do precise positioning with the actuator itself, but you can attach the sliding platform to a sliding potentiometer (especially if it is traveling less than an inch):
https://www.amazon.com/Bourns-PTA6043-2015DPB103-P...

You would then measure the resistance to determine where the platform is.