cost of linear actuators

You used to be able to buy 1 - 2 foot actuators cheap. They were used to position the big K band satellite dishes. Don't know if they are still available.

Well, each day the "ego" and "I wanna be a millionaire by tommarrow" taxes go up. They actually have a college course that preaches to its students that they have a god given right to make as much money as they can and do as little work as possible.... I think its called ethics and morality or something like that. Its a big hit with the medical and law students. The engineering students are doing well in it.

That's useful...

I can't see exactly who it is you are attempting to slam with that drivel. What do you mean by "Its a big hit with the medical and law students. The engineering students are doing well in it."

Try

who have lots of cheap(ish) actuators. They are used in furniture and aids for the disabled.

If you are in the US they may have an agent or there will be US suppliers serving the same market.

Michael Kellett

Stepper motor/belt drive? Tear in to a couple of old ink jet printers and see what they do, then multiply the belt size to a length that meets your needs. You should get the accuracy you need. As to the weight of the object, you will either need gearing or a large stepper motor, 3 lb is heavier than a print head...

Linear actuators that are sold into industry are designed to work in anything, bear overload, be easy to engineer around, last forever, and look good while they're doing it. So of course they're expensive.

If you're going to be building in volume (even modest volume like

100/year) and it's not an aerospace application or a work-anywhere industrial application then you may do better building your own, or looking in some of the places others have suggested.

You may also want to look in the Granger's catalog under "jackscrews". With the right controller and position sensor, these may do what you want. You may also want to consider hydraulics or pneumatics to get the job done

-- once again you'll have a challenge to find economical parts, but you'll reduce your motor requirements to one and your actuators will get smaller.

Sounds like a fun project.

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Steel cable loop drive.?

fine Acme threaded traverse screw ?

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You certainly can build a "lead screw and follower" actuator for a lot less than thousands - motor and couple of limit switches?

Or motor with a disk and offset pin like a crankshaft to translate rotary into linear motion.

Don't overlook air cylinders. 3 feet is expensive for a cylinder but if you can get by with a shorter cylinder with mechanical advantage they have lots of advantages.

My OM put a satellite dish actuators on his drive way gates. Lot of hassle running 120 out there and weather proof and in code. All kinds of problems when something kept the gate from closing or opening completely (like snow, ice, leaves, debris) and there was the overkill necessary to make it work. A few air cylinders fixed it with no hassle - 1/4" OD tubing, the actuators can stay stalled all day long with nothing to burn out, speed is easy to adjust with a valve, pressure is also easy to adjust. The only hard part was finding a pressure switch that would work with the 30 PSI diaphragm pump we had

- the rest of it was hardware store parts.

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I understand that I could design the components myself. Ultimately I expect to be building low production quantities of these and was hoping that a linear actuator/controller combination might exist in the marketplace so I don't have to redesign the wheel. It will be required to work in an office environment. I have designed high-speed line printers and automotive sensors in my career, so I could build one of these. However, I don't want to find (as I have in the past) that a simple, low cost solution exists that I could use out-of-the- box and that is already being built in production quantities. Ideally, I would like to have 3 linear actuators, 2 of which would be on an X-Y base and the 3rd that would travel vertically from this X-Y base (call this the Z axis). I would need to control the three with a controller that would be programmed from a computer program I would write for the specific application I have in mind. (I can't divulge the purpose of this device at this time in case there are patent issues). I need to be able to represent the position by an icon or representation of the position using a diagram on the computer screen. I would have be able to return to previous position (by storing the X-Y-Z coordinates).

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And the problem with a satellite dish leg is...?

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Many years ago there was a demonstration robot that could do that, although probably couldn't swing three pounds around in its gripper.

It came with a keyboard and you programmed it by laboriously slewing to the coordinate you wanted one axis at a time, storing that position then on to the next one. When you played it back the robot would move in all axis at the same time to get to the coordinate that you put in memory (one axis at a time). It could also pause for a predetermined time. It and had an RS232 connector. Forget what it was called. It was something like $300+ back in the age of DOS.

I only came across it at work and had it do things like dial my phone and throw switches. No idea why the company bought it. The precision was excellent - geared stepper motors moving push pull braided steel cables.

I'm not aware of any ready made, inexpensive, linear positioners that meet your specs. Maybe some of the robotic or radio control groups?

Lots of hobby interest in modifying the mechanics of scanners to become X - Y tables - but not 3 foot swings.

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Do they have feedback or just go to one of two positions and stop?

I bought a surplus one. It is incredibly strong. Has limit switches, a 24 VDC motor - but no position feedback. Total range of motion is

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You just pointed out an error I made in my original post. I meant to say the cube was one (1) cubic foot (possibly slightly over that). That would be just over 1 foot in each of the X, Y and Z directions. Unfortunately I led everyone to think 3 times what I really needed. Sorry...

Eganders

I guess I see the problem. A quick search of CNC / XYZ positioners yields tons of web sites - all seeming to have incredible load capacities and impressive positioning accuracies - which has to cost. And since many of them don't give representative prices leads me to believe they are expensive.

Maybe one technique would be to determine your needs and anticipated quantities and start phoning or emailing around.

Try posting to a forum - these folks are building that stuff

Lot of pictures showing how others have done it (but you have to register to get past the thumbnails)

Another search term might be Cartesian robot or gantry robot for a DIY site. Place I worked at had a laboratory (Cartesian) robot would do exactly what you want (for about $5K+ but that did include the computer and software and table)

3 pounds is probably more than any normal scanner positioner can support directly. They do put Dremel tools on scanners for table top CNC machines but a Dremel probably only weighs a pound or so.

Satellite dish positioners are probably overkill even if you find one with feedback. Mine can easily lift 150 pounds takes ~30 seconds to fully extend/retract - very heavy construction.

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C band:

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Michael A. Terrell
Central Florida

Think about it: Who would buy cheap, consumer-grade actuators for mass-produced items when they can be made even cheaper and better suited to the task by integrating them into the product itself, like scanners and copiers?

There simply is no market, so all you can get is heavy-duty, industrial-grade stuff.

robert