DIY Linear Actuator design

Thank you!


A question about the universal joints on the bottom: Do you use high quality ones with bearings that run slack-free, or cheaper ones that have a little slack in them. Do you feel any jolt?

Dirty

Mine cost around $20 each (is that cheap ?). There is a small amount of slack at the joint, but this does not relate to anything that you can feel/hear when in use.

That's good to hear

Simple U-joints w/o bearings will be my plan B then. Plan A (so far) is using these M10 windsurfing powerjoints:


About 15€ each, absolutely slack free, meant to take quite a lot of abuse, bend well over 90° in all directions, some dampening and quite forgiving of minor inaccuracies.

I know, it's a bit of an unorthodox choice. But I'll see how they perform... and can still switch later on.

Dirty

Hello @wannabeaflyer2
Congratulations for your project. I wonder how much space your rig requires at full lateral motion. Would a 4 * 1.68 m room bei big enought? That is 16 cm at each side of the base for lateral motion. Thank you very much for a brief reply.

Hi @Zwodog my sim is still in one piece but not been powered up for a while ( seems like years even LOL ) my sim room is something like 2.4 x 2.8M
but I believe the working footprint of the sim at extremes would be in the order of 1.8 x 1.8M .. not been active here for a long while . got all the gear but sidetracked with other things and work .. hope this helps in some small way , at the last setup I was running 2 x 32 Sabertooths but a lot of guys have moved to the 2 x 60 as they have a bit more overhead current capability wise ... I never really ran my sim in anger so even though the 2x32 seemed to work fine for me ..maybe the guys made the switch due to issues I had not seen yet during my testing phase .. Great Product form Dimension engineering ( some could say Expensive But the fact that they have great service backup and seem to last once fitted means they are worth the extra ) .. I digress LOL the guys know I waffle on so hope the info helps anyways

hi, I read all the post and conjectures for the project completed.
I would like to try to build a linear actuator myself and reading his post I can not figure out where the microswitches are connected and what are they for, could I have more information?
I have a 2 DOF with the SMC3 code, VNH5019 engine boards and I wanted to keep all the electronics because I feel very good.

hi @luky_90 the limit switches are mounted to the side of the actuator and triggered by a lever Connected to the balllnut, when the ballnut has reached a position defined as the maximum safe mechanical travel distance .. i.e set so you loose around 50mm travel at top and bottom of the actuator extension. purely to minimise mechanical contact and also to Cut power to the motor or all motors and in and emergency and in so doing preventing a massive current draw which could fry your controllers .. each actuator design will dictate how far apart the switches can be .. but please be aware that gravity / weight / inertia will conspire to make the ballscrew backdrive on the downward stroke even after power is cut . this usually mean you loose more travel on the downsroke but better this than the potentiall expensive mechanical damage if the motor or position feedback have a runaway or loss of position error .. will try to find my wiring diagram as a possible guide ..

[Quote = "wannabeaflyer2, alberino: 153995, membro: 17577"] hi [USER = 21098] @ luky_90 [/ USER] i finecorsa sono montati sul lato dell'attuatore e attivato da una leva con collegamento balllnut, quando la ballnut ha raggiunto una posizione definita come la distanza corsa massima sicurezza meccanica .. cioè quelle elencate in modo sciolto circa 50 millimetri corsa superiore e inferiore dell'estensione dell'attuatore. puramente per ridurre al minimo il contatto meccanico e anche per tagliare l'alimentazione al motore o tutti i motori e in e di emergenza e così facendo prevenire una massiccia assorbimento di corrente che potrebbe friggere i controller .. ogni disegno attuatore detterà la distanza tra gli switch possono essere .. ma tieni presente che la gravità / peso / inerzia cospirano per rendere il backdrive vite a sfera sulla corsa verso il basso anche dopo che l'alimentazione viene interrotta.

ok, but with the SMC3 setting limits does not have the same function as microswitches?

Softwares sometimes get lost and provide wrong positions. Safety switches are a physical... Safety.
You can run without, but no one recommand it.

@Pierre Lalancette
thanks a lot of the advice, the microswitch must be connected directly to the positive pole of the motor to stop the power supply right?

No! You're going to electrocute yourself if there is a short. They are connected either to a relay that will swith off the power or to the arduino, programmed to turn the power off. The relay solution seams better.

Everyone may implement it differently - I do use 60 amp 12v relays that cut power directly to one side of the motor - don't know why this is not safe? - Edit - FI Limit switches normally cannot handle high currents by themselves so you just use them to drive a high current relay. I also have a momentary limit bypass switch in the sim so I don't have to get out and physically back-wind the actuators, if for some reason they momentary drive too far in normal use - can happen when you are first setting up simtools for each game.

When using VNH5019 drivers you should use high current relays in conjunction with your limit switches as recommended. With Sabertooths though one can use a little creativity and eliminate the need for the relays.

good evening guys,
I started thinking about the design of my pistons and I was thinking of using a 16x10 ball screw, what do you think? I saw that everyone used a 16x5 is there a good reason to use a shorter pitch?

I found this scheme in the forum okay?

1610 ballscrew used here in this thread and it is a 1610 in this post also, im sure there are a few more examples out there.

No, due to the large currents we are normally running - unless those diodes and limit switches are designed to cope.

Where should I connect the microswitches? is there a picture of the links in the forum?

talking about limit switches... once a limit switch is reached... it turns the motor off... and then...?? what... you have to manually move the rig so the motors can work again... or is there a way to allow the motors to got back "automaticlly" to a safe position once the limit switch is activated? (i hope i made my self clear... as you can see english is not working well today.... )

fer