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Linear Servo Actuators

by potentprintables Oct 28, 2018
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Hi Potentprintables!
Thanks for this thing!
I ran into some trouble making some customized rods. The STLs seem to be not entirely "clean", so both FreeCAD and OpenSCAD refused to do e.g. boolean operations on it. Would you mind sharing the source file?
Thanks again!
Best regards

Hi- no problem, glad they are useful to you. STEP files are in a zip file in the download section. Hope this helps.

I missed that! Thanks for the hint!

Another question. I printed everything out but the gear shaft hardly fits in the groove. Do I need to print out in higher quality? Sand it down? Any suggestions would be appreciated. I’ll try printing from a different axis so that there is no excess filament raft or supports there.

It is intended to be a close fit, but I didn't have to do any sanding. It should move back and forth smoothly. If yours doesn't do this, I would recommend a little sanding and then add a little silicone (plumbers) grease to reduce friction.

What size would the servo motor be for the large print? if it's available can you please send a servo model number i can use to purchase. Thanks!

Links to both types of motors are in the video description, so check there.

Could you design the whole thing to be more precise? I would like the round part dedicated for the small servo to have for example 8 teeth instead of 16, so the one revolution would result in half of the current travel.

What are the best printer settings for the pusher rods? I could see printer failures happening if it were standing. Is the best way to just leave it laying down and let it print supports along the entire pusher? I'm using a CR-10
Thanks for any advice!

Hi- yes, I printed the pusher rods laying down (with long axis of the part parallel to the printer bed) and used supports. Hope this helps!

Just curious how you arrived at your jb weld approach versus modeling into the pinion gear an inlet space for the blade(s) (might require a little trimming of length) that come with most of the little servos. Some of the robotics projects take that approach. I was thinking to do a remix and try that approach, but not if you already did and found it to be unfavorable for some reason.

Hello, I need a 250mm pusher, how can I achieve that?

Hi, I've printed this great model 5 times, but the gear in the motor holder doesn't go into the slot. Where can I be making a mistake? I'm using my 3D printer model Anet A8 PLA.

Did you try to [slightly] scale down the "male" part..?

Thanks for the response. I reduced the male part. But there was deformity. I redesigned the female section and solved the problem.

thanks for sharing.
How do you detect end of course in both direction?

No problem, hope it is useful to you. The motion is all time based, using delays in the Arduino code. So there is no sensing of the ends of travel. I talk more about the details of this in the video if you are interested.

Hi. This looks great to drive a H0 scaled railroad crossing gate, with the servo enclosure and "gearbox" mounted under the rails. Connection to the gate could be made from thin steel wire as extension to the black part in the picture, as there is minimal load on that type of application, and the drive must be flexible. Is it possible for the electronic components to have a soft start/stop of the servo used? Real gates do not crash up or down to the end with full speed. They slow down before... To understand better what I am after, check this video from 0:50 for about 10 sec. The gate hammers to closed and open - it is just an electric magnet in the base. It can't stay close for more than 15 secs, it starts smelling and getting hot.

Perhaps since you are talking about pulling a line, instead of the gear and shaft, you could wrap the line around a lopsided reel. Such that at the beginning of the movement a rotation doesn't translate into much linear motion, in the middle of the motion it translates into more and towards the end it is back to a small amount.

You can adjust the speed for the full move of the actuator. Meaning you could slow it down quite a bit, so it isn't crashing down.

But I don't think you can have a soft start/stop as part of one continuous move; the electronics and servo are just to crude for this type of control.

Nice simple design. On the larger version of the actuator, once the gear is glued to the wheel, it is no longer removable. I would suggest adding a hole to the gear to allow access to the screw below.

For sure. I was thinking the same thing.


Nice design... Any chance of adding additional lengths up to 400mm?

(Even longer could be very useful but 400mm is approximately the max that could be printed diagonally on a 300mmx300mm bed, which is fairly common nowadays...ie: CR-10, etc)

Thanks. I wasn’t planning on adding anymore lengths. I put a drawing in with the STL files that has the dovetail and gear teeth dimensions, if people want to make their own versions of the pusher.

Keep in mind as the pusher gets longer, it deflects and wanders more when it encounters a load.

Thanks, I saw the PDF in the files, so that is perfect and all I need.

Also, I totally agree that longer lengths (even the 150mm) may need additional guiding sliders/axles to prevent the geared actuator from flexing. Again, an issue easily solved by the inclusion of the PDF with the dimensions... I wish everybody did that, it is very useful when scaling or enhancing a design to fit a particular purpose.

Great job!

Glad it is useful- I figured it would be especially helpful for a very generic design like this one.

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can you use this with out the Arduino boards, like just in and out with a couple of buttons.

Do you mean without the Adafruit Motor Shield? If that is what you mean, then yes, you can drive the servo using just a base Arduino board, like the Uno I show in the video. The Motor Shield just makes wiring and controlling multiple servos + other motor types easier.

And you could certainly set it up to be triggered by a couple of buttons.

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Hello, Sorry I'm new in 3D world and maybe is a stupid question, but If I try to print this when I arrive at the "servo support" layers my printer start to print in the air.
Do you have any tip ?

Thanks you

Hi- unfortunately this sounds like a printer specific or STL slicing problem, so I probably can't help very much. Maybe your printer manufacturer offers some technical support and you can contact them?

I resolved by cutting the rear part and print it from another angle.
thanks you very much but just to understand your printer will add some support to print the parts that don't touch the ground or you can print "in the air "? I mean for the part where the servo has to be screwed up this two little arm.

Thanks you

I did use support material for the "Motor_Bracket" parts (that the servo screws into).

On the "Thing Details" page I put the printer settings and part orientations I used (all the way at the bottom of that page, under "Print Settings").

Thanks you very much

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For what servo models are these?

Full parts list (including servo models) are in a .pdf that is in "Thing files".

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Nice designs! Any idea why you needed to run the motor + to VIN?

Thanks. Not sure about why I needed to connect to Vin. I didn't need it for the "mini" size, but definitely needed it for the larger size. Looking around online, people mention using a pull down resistor on the signal line, so I would probably try that next [when trying to get rid of also connecting to Vin].

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