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I would look at a linear actuator, they are very common items and come in all motor type flavours.
A DC motor with a simple SCR control and limit switches to control the forward and reverse extents.
e.g. ebay 380392334380
Al.
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I was wondering if perhaps you could give me a suggestion on a mechanism. I
have been asked to design/machine a somewhat automated spray paint system. A conveyor would carry sheets of product (plate glass, polycarbonate sheets) and I would need to adapt an arm to traverse back and forth dispensing the liquid spray. I need to devise a simple means of reciprocal motion with a stroke of roughly 18" or so. I need to keep it somewhat simple, as it will be manned by individuals who might not have great technical experience. That rules out a CNC based design, or a PLC system. Oh, it also needs to be adjustable in it's speed......
Any ideas?
I would look at a linear actuator, they are very common items and come in all motor type flavours.
A DC motor with a simple SCR control and limit switches to control the forward and reverse extents.
e.g. ebay 380392334380
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
While that would definately get me the result I need, I'm concerned that the overall size of the assembly might be too bulky. I'll keep that as a "last resort" setup, but I'd like to find something more compact. I'm thinking timing belts, pulleys, gears....
The business that is looking for this setup is rather limited on floor space.
Double acting air cylinder?
Dick Z
DZASTR
I would have though you could not get much more compact than a linear actuator?Originally Posted by gearsoup
Especially when compared to belts gears etc??
If you go with a double acting cylinder as Dick suggests, I would look at air over oil for a more smoother control.
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Al,
Isn't a linear actuator one in-line setup? Meaning, if there is 18" of stroke, the entire work envelope is 36"? 18" for the actuator itself, then another to allow 18" of travel?
Look up "scotch yoke" or the drive mechanism used on shapers. The second one will allow you to have different speeds for your "application" stroke and the "return" stroke.
It is somewhat difficult to suggest a design with only knowing a few scant details.
If you are constrained for space then all requirements have to be known in order to recommend a design?
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Al,
Lol, true. Here is the deal: Floor space is at a premium, so I'd like to keep the unit rougly inside the same footprint of the conveyor, which happens to be 2 ft wide. The conveyor length has not been determined, probably in the area of 3-4 feet. There will be a backdraft vent system in place to remove fumes and waste product.
Traverse speed of the arm is rougly 2-4 inches a second, however it would need to be adjustable outside those speeds, to allow for fine tuning.
The arm will be moving a spray gun, dispensing a liquid "paint" onto glass. The conveyor will be variable speed as well. I would set up an optical eye so the gun would only be firing when there were glass in the vicinity.
The weight of the entire arm wouldn't be that severe, as there are no cutting pressures involved, such as with a CNC router.
One note: Floor space is at a premium, but vertical is rather open. Perhaps that could be used to my advantage.........The conveyor needs to stay flat, otherwise the paint would run...
I could see paint over-spray a problem with both mechanism and using optical sensors?
The Scotch Yoke idea maybe an option worth looking at as Matt suggested if space is a premium?
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Well, I think I've come up with a rather clever way of obtaining what I need. I'll share more as I fully develop the idea. However, I need now to find a means of powering a motor (that one is simple) stopping rotation, reversing it, stopping it, reversing it....etc. etc. Any idea on what electronics would be involved? Starting off with a DC motor, I would assume using a rheostat of some sort to control speed, then a relay switch of some sort to switch polarity, then limit switches to determine end of stroke and time to reverese direction of rotation.
I would suggest a bicycle chain and 2 small sprockets, and any simple rail and slider.
For a reversing DC motor (which sounds like a good idea) you can buy a "variable DC power supply" or "variable DC bench supply" from ebay, which will let you adjust motor speed.
You can get DC motor with worm gearbox from an auto wreckers, they are common for car windscreen wiper motors.
For reversing you need a "12 volt DPDT relay" which simply reverses the 2 motor wires to reverse the direction of the DC motor. Limit switches you can gen anywhere. The variable bench supply will help a lot to reduce motor speed and power and makes it a lot safer switching the motor from forward to reverse.
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