Linear actuators are useful things, moving things in straight lines rather than annoying circles like so many motors. [Retsetman] recently built a linear servo actuator of his own design with accurate positional control.

The design relies on a carriage that moves along a threaded rod, perhaps the most rudimentary design of linear actuator. A large brushed DC motor is used to turn the threaded rod through a 3D-printed 9:1 herringbone geartrain, shifting the actuator back and forth. End stop switches are used to disengage the motor to avoid damage to the mechanism. Feedback is via a ten-turn potentiometer driven off the output geartrain to match the range of the actuator to the rotational range of the pot. Helical Designs Rotary Actuators

The final build has a stroke of approximately 100 mm, and can lift and hold a 15 kg weight with ease. In a pull test, the actuator failed at a load just shy of 100 kg. If you’re looking for something smaller, though, you can try building a linear actuator out of old DVD drive parts instead. Video after the break.

[Thanks to BaldPower for the tip!]

It didn’t FAIL at 100kg, it just maxed out at 100kg, but could still release and work correctly after this. That’s a HUGE success in my opinion.

I would reuse a pipe tube for the long part.

Indeed. Me too. Actually I’m 80% through a design with a 42.4mm precision pipe for the inside and a 50x50x2 steel square tube for the outside, an 1605 ball spindle and a Nema 23 stepper motor with timing belt transmission. Goal here is positioning accuracy over some 900mm. The timing belt is chosen to rotate the motor 180 degree and make it shorter, but also to have an option to easily change the speed to force ratio.

For the first iteration I just rely on the stepper motor for positoning. As a later extension, I plan to add an option for an absolute encoder. This encoder will be partly made from a hobby RC servo, of which I use the gearbox and potentiometer to count full revolutions of the 1605 spindle, And this will be complemented by a rotary HALL sensor directly on the motor (or spindle) shaft.

linear servo actuator,no such thing,this is the humble jack screw renamed,the particular implimentation copyied in this instance has its origins in aviation a very long time ago. and the testing has no relevance whatsoever unless its been repeated many many tens of thousands of times oh and pipe is one product and tube is another,with the worlds supply of “pipe tube” being zero the only interesting part of this project is the electrical control side,which is comendable.jack screws are availible in countless numbers and varieties,wheras control circuits are always proprietary and purpose built and expensive

“and the testing has no relevance whatsoever unless its been repeated many many tens of thousands of times”

You may be exaggerating a bit. Do you expect a hobbyist to run thousands of tests on a device made “for fun”?

This test proves to a good degree of certainty that this design can handle single-digit-kg loads. Maybe not for a very long time (plastics creep), maybe not for a huge number of cycles. But this is not a commercial product.

Better yet, he can print one out and doing actual test “many many tens of thousands of times” will be more useful than making useless comment so that he can ejaculate; less messier and able to prove his point. I guess japanese hentai porn doesn’t do for him anymore. Hence, the alternative?

“linear servo actuator,no such thing”

Servomechanism (def): a powered mechanism producing motion or forces at a higher level of energy than the input level, e.g. in the brakes and steering of large motor vehicles, especially where feedback is employed to make the control automatic. (via google)

This definition, and the literal thousands of commercial linear servo products, and the long history of use, including in the aerospace industry where this type of packaged unit is called a servo (Woodward autopilots use them, for example), tend to lean against your statement.

Also, grammar and punctuation are important to clear written communication… Just sayin’

Not only that, but you can buy similar things (solid metal) for opening gates from surplus stores that are rated a couple hundred kg. I got one from All Electronics for $20 plus shipping. Runs on 12 VDC and easily lifts my own weight.

Not to deprecate Day’s efforts in this project, which I’m sure was fun and interesting. Just if you need such a device, they are cheap and plentiful.

You do realize which website were on though right? It is called hackaday which is a place for makers and DIY people, for the most part. Really interesting thing about that is the fact that the website isn’t called buy-this-aday

You must be loads of fun at parties. Or does anyone even invite you to any anymore?

I was just going to scroll past and ignore this, and actually did for a while. It bothered me enough that I had to come back though.

This is more than ego self-stroking at the expense of someone else. By making this negative and discouraging comments on other peoples projects, you are making it more difficult for people to enjoy the experimentation and discovery of doing things for themselves. You are contributing to the dumbing down of future generations by telling them that they should just buy the hardware instead of trying to learn how to make it.

The iterative process of building and rebuilding the same thing multiple times to improve upon it is how we refine our knowledge and learning of various processes.

I seriously doubt that this particular device is going to be used for anything that would require tens of thousands of performance tests. It is a tool for learning. But who knows? Maybe someday the knowledge gained from doing these build and tests will lead him to building rigorously tested equipment in the future. Or perhaps making a new discovery in the field that nobody else thought of. Don’t be a d!ck that tries to kill that enthusiasm.

You and some of the others that I see in these comments sections are too busy mentally m@sturb@t!ng yourselves in an attempt to make yourself look and feel smarter and better. But absolutely nobody but you cares.

the exact same number of people who give a sh!t about the difference between pipe and tube.

The difference in pipe and tubing is important if you are ordering some!

Pipe is measured internally; tubing is measured externally. So if you don’t know the difference, you have a 50% chance of getting something that doesn’t fit your application.

I think the biggest affront in metalman’s reply was the attitude. We all come here to learn something, not to have it shoved down our throats.

Oooh, I did not notice that relationship, I wonder if its truly universal as I’m sure I’ve seen ID or OD measures used ‘incorrectly’ in the past then – but a quick skim around the web does seem to suggest that relationship is true often enough at least…

I’ve always looked at the mechanical drawings or bought it from somewhere else just to be sure – after all you care about more than just one crucial dimension, wall thickness can be important and the tolerance is very very often important!

It must be really, really hard work being as miserably critical as you are.

All that you have contributed to my life today is to add to my despair that I have wasted time in reading your ridiculously trite and superficial (and badly spelt and ungrammatical) comment. A comment which, incidentally, has added nothing but an unexamined opinion to a gentle debate about a creditable construction.

If you wish to add to a discussion, do please consider writing something of non – trivial content, something which adds structure and information rather than being a wonderful example of pointlessness. And perhaps something which encourages rather than degrades.

I understand people that all we are doing is useless … It’s absolutely true. But doing something for fun is fun and sharing it is also fun. I find this project very fun. And I will download files and print useless parts for fun. My friends asks all the time, “why you are doing it” … you can orders this shai* from china much cheaper … but the point is doing and thinking for fun is fun for itself … I have fun why don’t you? Life will end but next one in line will have some fun filling the (ex-truder)end – of useless 3d printer ;)

Also – just because you can order it from China cheaper now doesn’t mean it will always follow you can just order it – Ship stuck in the Suez again, Economic or political divisions that shut down the border, needing specific characteristics or better quality than the Chinisum producers are doing, and of course the lack of funding can make building something yourself is a winner beyond just being fun and educational (even if it technically ends up more costly if you have x,y,z in your spares bin from other projects, all those short FDM tails you can’t use on a cosmetically important print etc – they are effectively a negative value if you don’t use them, wasted money, and wasting workshop space(for me more important))

Very nicely done project. Also it shows the value of 3D printing for quick prototyping of ideas. Great video too.

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