Cost of linear actuators

I have an application where I have to move a 3 lb object in a 3 ft cubic space. I am not looking at high performance or high accuracy.
It can take as much as 30 seconds to traverse the 3 ft distance and the accuracy could be no better than 0.020 or 0.050 inch (possibly the spec could be even looser).
Linear actuators would appear to be the best solution, but I am finding that they are hundreds or even thousands of dollars. The product I want to build will have to cost no more than $2,000 for a 3 axis device with controller, overhead and profit.
What is it in a linear actuator that costs so much that you could not build a low cost version using a threaded rod, servo or stepper motor and an extruded frame for a lot less?
Does anyone know of a linear actuator that can provide the kind of performance I am looking for for a couple hundred dollars?
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Yes, people commonly (even normally) build linear actuators from things like threaded rod. Here is one source for the components. www.mcmaster.com Search for the phrase "Acme Threaded Rods". They have an extraordinarily well done web site. There is a link on the right to show the actual catalog page, which is easier to view when you are looking to find the cheapest product. Also if you search for "linear actuator" you can get to a catalog page with a list of various types of linear actuators.
However, if you are not used to specifiying the components for something like this, it might be better to find a complete package.
Also, here is a link to a web site www.cnczone.com that has a forum on a do-it-yourself cnc router (mostly gantry types). http://www.cnczone.com/forums/forumdisplay.php?fH
Joe Dunfee
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On Nov 3, 9:46 am, snipped-for-privacy@yahoo.com wrote:

Joe,
Thanks for reminding me of McMaster-Carr. I am looking at some possibilities there. They are my heros anyway. Best website and service on the planet for buying parts of all kinds!!
I would like to be a little more specific about what I am trying to do. 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. 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 on a computer screen and be able to return to that position (by storing the X-Y-Z coordinates).
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I don't think you are going to do it in your price range. Here is a commercial unit which I think represents the closest you are going to get to your goals. It set a new price point when it was introduced.
www.shopbottools.com
Joe Dunfee
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eganders wrote:

You have precisely described a common three-axis CNC mill or router. Do a Google search and you should find a lot of commercial and homebrew examples you can learn from.
-- Gordon
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You can easily make what you described yourself with what you described. I do it just about every day. With a little experimenting you can too.
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wrote:

Hey castvee8, got any links we take a look at with examples ? I'm always interested in good ways to do that. Thanks ! JCD http://www.AmazingRobotics.com
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You will find your solution at www.technoautomation.com

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eganders wrote:

<snip>
You've gotten some pretty good responses so far, but you should take note of something: the three foot travel is going to either cost you money, accuracy, or both. Even at 0.050". Remember that to get a *workable* 3 foot space you probably need a 4 foot (or so) linear actuator. Ordinary low-end X-Y tables aren't designed for this size, and the length causes all kinds of dimensional problems due to shear and other stresses. You'll probably need to go to a roller-type gantry system. Check out the X-Y table systems sold at robots.com for ideas.
Also keep in mind that if it's a cutting tool you're moving, and it makes mechanical contact with the material it's cutting, you'll be moving more than three pounds. You have to calculate bases on the load on the tool. Obviously a laser, paint head, or water jet don't make physical contact, but a router does.
I would definitely check out CNCzone.com so you don't end up reinventing the CNC machine, at it were.
-- Gordon
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wrote:

I made an error in describing the space I need to traverse. I only need to cover a little over 12 inches on a side or about a 1 cu ft space, not 3. Maybe that will help. The 3 lb load is all I have to concern myself with. I will not have an additional force to apply except for a short, light cord that I will have to drag around which should only amount to a few ounces.
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eganders wrote:

That shouldn't be quite as expensive to implement, but as noted, there are lots and lots and lots of CNC rigs and plans available on the Web. A Google search will turn up how other people have done what you're trying to do, which is a CNC router. There are already commercial products in the $2K price point you mentioned earlier with specifications of the type you mention, so take note of that if you're wanting to get into the market.
-- Gordon
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