A bolt is basically a cylindrical rod with thread cutting on it and a nut is likewise a threaded
hole and if you put them together and turn the helix angle of the screw will create a linear
movement. In this video we'll make a linear actuator that works on this simple principle.
Actually this project is not new in this channel i made a linear actuator about a year ago but
there are some important missing in the design. So i'm going to make a new one okay now let's start
with this bearing block that's where we'll fix the traded rod and first i put the inserts into these
holes. The inserts are M3 and as you can see teeths are crossed as double helical gears not
straight. I was actually worried to use these inserts but after watching a few videos i was
absolutely sure and i suppose these cross-threaded inserts last up against to 180 kilogram tensile
load this is really really good. By the way i didn't use any inserts in the previous
version instead i fixed with bolts. But these inserts look definitely better and really solid.
In this version i fixed threaded rod with these locknuts.
I fixed with those circlips in the previous one and i think it wasn't good idea for high forces.
So this time i use locknuts. This is a very important spacer
because i'm going to fix the block gears motor everything onto it. First i fixed
the motor with M4 bolts and then i'll fix the bearing block i prepared with M3 bolts.
An important shortcoming of the previous version was, there was no end stops.
In this time i use the end stops to limit the piston. Now let's move on to the gearbox but
before, we need a lid to cover the gearbox we are going to make and i want it to be transparent.
For this i used PCBWAY cnc machining service... First of all i go PCBWAY and i quickly prepare
my order. It's really easy to order, just upload the module and choose the material.
If you want add something here are the options and soon at your door. Here is the lid,
just as i designed looks perfect. By the way i had ordered steel sheet from pcb way before and it was
really great. If you want to build something but can't because don't have the right tools,
pcbway do it for you and they have many services besides cnc machining, you can use 3d printing,
sheet metal fabrication, injection molding and pcb production services with comfortable.
This is my second order from pcbway and they have done great job on both,
highly recommend. So i've added the link below and i'm sure you'll find something you needed.
I attach the output gear and install a M2 cutter pin to lock it in place.
This pink one is the middle gear and with that the gear ratio will be 9:1 In before
was 6:1 so this version has one and a half times higher torque. By the way i have used helical
gears before and their exial movement was bit of a problem and as you can see the gear is worn out.
So this time i used herringbone gears to cancel the axial movement and this is the gearbox cover.
I put the inserts...
...and drill a hole from here to take these wires out.
Finally i place an eight millimeter ball bearing(608zz) for the output shaft
and now it's time for the feedback mechanism.
i'm going to use this 10 turns potentiometer uc to get the feedback.
I'm putting that to the cover and taking out the wires.
Then i screw it tight.
Before forget i solder these right away.
Now i'll add the gears in order to transfer the position of this output shaft to the
potentiometer. In here we can choose the modules of these gears very small,
they don't need to be solid they just need a torque to overcome the friction that
occurs when turning the potentiometer and as you know that's such an easy.
The reduction ratio here will be 8 and that means the output gear will turn
8 times less and to calculate this ratio we need to go back to threaded rod. The pitch of this M8
threaded rod is 1.25 millimeter and also the stroke of the actuator will be 100 millimeter.
So in order for the piston to complete its stroke, the threaded rod needs to rotate 80 turns
and if i attach the potentiometer to the output shaft directly
in this case the potentiometer also needs to rotate 80 turns.
But it can rotate maximum 10 turns. That's why i am adding an 8 gear ratio gearbox.
So simple.
So when the threaded rotates 80 turns for a full stroke the potentiometer will turn
80 over 8 equals to 10 turns and which is also is literally what we want.
now let's see how it works.
It looks really nice actually.
and the next job is the end stops.
i fixed the end stops to the holes on this sled and i designed these
holes with 3 millimeter spacing. So we can operate the piston in the stroke we want.
(lithium grease)
Now the stroke is exactly 100 millimeter and i am taking back
the piston into zero position. I am also setting the potentiometer to zero
and now let's see how much the potentiometer will turn when the piston reaches the endstop.
In the pistons full stroke the potentiometer rotated exactly 10 turns. Actually i thought
there would be some loss in the gearbox and the potentiometer wouldn't rotate a full 10 turns
but it didn't. So to protect the potentiometer i take the end stop back one hole just in case
and now the stroke is 97 millimeter. So when the piston goes the full stroke the
potentiometer will not rotate exactly 10 turns, it'll less.
And now for the rest first i place the inserts into these
holes and then lubricate the piston slide.
I screw the cover and ready.
By the way the bottom of this pink here is a bit crooked and i guess
it's somehow causing wear. So i replaced it with a new one
Then i screwed this cover tight to its place.
Now the last job is to put an acrylic lid on the top side.
I use the lid that Pcbway sent for this.
I almost screwed up here but luckily nothing happened, it's all good.
After a while i finally put on the inserts with my new awesome soldering iron.
Then i guess i pushed my luck too hard and my precious soldering iron...
...exploded.
and it's done!
I uploaded a simple code and it works as we want.
By the way with the motor i use at 3000 rpm and reduction ratio of 9 here
the traded rod rotates at 330 rpm.
With these values the piston can make a full stroke in 14 seconds.
That was really good.
i'm so surprised right now. It lifted almost 100 kilogram and not even any scratches.
Gears inserts are all perfect.
Piston hole is a little crushed but that's fine
and i think the most damaged thing here was the chassis.
I can't believe these tiny balls and inserts here lift up 100 kilogram. This thing is a monster.
By the way i don't know what to make with that i'm wondering your most interesting ideas.
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