Hello All,
I am new to arduino. I am building a 2-axes spinning machine. I plan to power the 2 shafts with 2 DC motors (24V). The max speed would be about 1000rpm. I would prefer to control the speeds using a software. I am not sure if there is any free s/w that can do this.
I need help in selecting the type of motor (if not DC) and also controller board for this project.
Please let me know a good approach and BOM for this project
What is a "2-axes spinning machine"?
http://imgur.com/aX9mwTH (Sorry, the photo is not showing up)
You will have to do a lot more work than a pencil and paper drawing before you can hope for advice on choice of motors.
The dimensions of the device, the materials from which it is constructed, the bearing arrangement and the masses and moments of inertia of the rotating segments must all be known.
Yes. I am working on the design on Solidworks. That is why I am choosing the BOM now. But I felt I needed to know the type of motor I am going to use. This is basically a device to spin and spool thread/yarn.
I know this is not easy. But I would be 3D Printing a Prototype to see the working (structural components). Eventually I would be printing the structural frame with Fiber-reinforced 3D printed parts (Mark One). They are very rigid.
To answer few of the known factors:
I would be using mounted bearings for the main shaft (25mm) and regular stainless steel bearing for the smaller one.
The shafts will be driven by a belt and pulley arrangement
the Y-shaped bracket has a distance of about 120 mm between the fork to give a rough idea. width is 50 mm. length is about 180mm
I cannot calculate the moment of inertia now without balancing the mass (mech n electrical components).
Please let me know if you need more information
warankarp:
The shafts will be driven by a belt and pulley arrangement
How would you do that for the smaller axle without the belt becoming twisted around the larger axle?
Or are you going to mount the motor for it on the Y piece with all the complications of supplying power to a motor that's not fixed in place?
I suggest that your main shaft is made hollow with an inner shaft to drive the smaller spinning axle via a crown gear and pinion. http://curriculum.vexrobotics.com/sites/default/files/8.7.1%20Crown%20Gears.png That way, you'll not have a motor flying in circles. In fact, if you chose your gearing correctly, fixing the inner shaft so that it doesn't rotate will mean that the small axle will rotate when the main shaft does, without any motor (but then you won't be able to adjust the relative speeds of rotation).
Adafruit (and others) sell a nice slipring that will allow you to put a motor onto a rotating device. That would be my preference instead of crown gears.
Henry,
Thanks for the suggestion. I was thinking of something on that line. Please see the drawing. Motor is on the center. I dont think the belt and pulley will slip. The spinning speed not exceed 500rpm actually.
Hollow shaft sounds like a great idea and adding what Morgan said about using a Slipring for the DC motor seems great.
Let me know how this looks.
Looks fairly good, but I would move the smaller motor to the other end of the main shaft and fit its shaft inside the main one. That way, it can be fixed in place and no slip rings will be needed.
If you have only a two line slipring you can use Pulsed DC to communicate with the controller inside.
Henry_Best:
I would move the smaller motor to the other end of the main shaft and fit its shaft inside the main one.
I didnt quite get that. I understand that your suggestion will keep the small motor stationary. But how will the smaller motors shaft drive the angular gear drive, might need another coupling shaft.
KeithRB:
If you have only a two line slipring you can use Pulsed DC to communicate with the controller inside.
All the standard sliprings come with 3 wires, I believe we can just cut one off. correct me if I am wrong.
Also, what kind of controller do I need. Is there any commercially available ? which I can hook up to a computer and control maybe.
To precisely control speed, you need either a stepper motor OR some kind of feedback from a sensor on the shaft. A stepper requires a minimum of 4 wires. A brushed DC motor with a hall-effect or optical sensor needs 4-5 wires. A 3-wire brushless motor can work without sensors but that imposes other limitations on RPM.
The controller chosen depends on what you want to do. Do you need the motors accurately synchronised? Then you'll probably need to make your own controller with an Arduino.
warankarp:
I didnt quite get that. I understand that your suggestion will keep the small motor stationary. But how will the smaller motors shaft drive the angular gear drive, might need another coupling shaft.
A long shaft through the main shaft and concentric with it, to drive the bevel gear that you've shown attached to the motor on your diagram. The shaft can be directly coupled to the now moved motor. You'll either need that inner shaft to be a snug fit inside the main shaft (like a sleeve bearing) or fit bearings (between it and the inside of the main shaft) where it enters and leaves the main shaft. All depends on the materials and sizes you're using for the shafts and your preferences. A thin inner shaft in bearings at each end may vibrate in the middle like a piano string. It won't in a sleeve bearing or if it is wider.
MorganS:
The controller chosen depends on what you want to do. Do you need the motors accurately synchronised? Then you'll probably need to make your own controller with an Arduino.
I dont want accurate speed control, at least for now. I just want the motors to be independently controlled with a fairly good accuracy. The mechanical part is more critical. I should be able to spool threads. But I will keep this in mind for future upgrades maybe.
Henry_Best:
A long shaft through the main shaft and concentric with it, to drive the bevel gear that you've shown attached to the motor on your diagram. The shaft can be directly coupled to the now moved motor. You'll either need that inner shaft to be a snug fit inside the main shaft (like a sleeve bearing) or fit bearings (between it and the inside of the main shaft) where it enters and leaves the main shaft. All depends on the materials and sizes you're using for the shafts and your preferences. A thin inner shaft in bearings at each end may vibrate in the middle like a piano string. It won't in a sleeve bearing or if it is wider.
Ok, I get it now. I am concerned about the sleeve bearings. Have not really used one before. Are the sleeve bearings designed for high speed and wear and tear ?
Also the shaft length is going to be roughly 150mm. I am just wondering if I could get a sleeve bearing of that length. Also, shaft coupling could be an issue from a design and assembly stand point, everything needs to be perfectly aligned for a long shaft to spin without any offset
Define "fairly good accuracy". Do the two movements have to be synchronized?
Sleeve bearings can go to more than 100,000 rpm, so no problem there.
By sync, if you mean to ask whether the motors run at the same time, yes they do!
They need to run individually and also simultaneously, The thread will be twisted (main motor) and wound (small motor) at the same time. But the speed control needs to be independent of each other.
I was referring to accuracy more like efficiency, deviation from the set speed. No need for complex feedback control. Hope that answers your question
Think of the hands on a clock. They are synchronized so that when the hour hand is pointing at an hour, the minute hand is always pointing at the zero.
For your system, if you choose some speed ratio, do you require that ratio to be exact and stay in sync for long periods (seconds)? If you paint a dot on the inner rotor then does that have to be on top every time the outer rotor is at 12 o'clock?
If synchronisation is not required then two DC power supplies can be used to run the motors very simply.
warankarp:
Ok, I get it now. I am concerned about the sleeve bearings. Have not really used one before. Are the sleeve bearings designed for high speed and wear and tear ?
They are used in the cooling fans in your PC. High enough speed and longevity for you?
But you don't need sleeve bearings if the hole in your outer shaft is cut to fit the diameter of the inner shaft.
If you make your shafts from PTFE, you should have no need for lubrication.
I sort of designed the entire set up and was trying to see what difference it is going to make by keeping the shaft on the other end. The power transmitted from the motor is being delivered in more than 4 stages.
I was wondering if it would be much simpler if the motor is placed right at the Yoke junction like this, where the motor is hidden inside the cylindrical area.
Also we might need a slipring at the end of the shaft in either case, so that the motor terminal ends dont keep spinning
