DIY Linear Actuator design

Admin..I don't know if this constitutes as a new thread. If so please move it. Thanks in advance.

I've been following several DIY threads on building actuators and have noticed that most are using the SFU1605 500mm ball screws in the free end configuration. Looking at the Critical Lap Speed chart on page 21 of https://www.linearmodul.dk/Filer/PDF-Kataloger/PDF-Katalog Ballscrews.pdf I see that this is close to the upper rpm limit of 3000 rpm. They also recommend using 80% or less of the critical lap speed as rotation speed. Has anyone noticed any thread degradation of the ball screw? Also, are you lubricating the ball screw with 4 grams of proper non-moly non-graphite lubricant (page 28 of above pdf)? Are there any thoughts of a need to go to the next size up SFU2005 ball screws? Thanks.

There's been some sort of argument about it in my thread. There is no clear winner or looser, just position and arguments about it. You can find most of it around those posts:

6 DOF from scratch

I would say that at least 2 6dof (Seattime and SilentChill) that are running at full speed for more that a year, and I have not seen any post from them about some special lubrification for their actuator. But I may have missed that last part.

I been running mine now for a long time I just use grease dunno what type it is tbh and everything seems sweet still no issues at all

you'd definitely want to grease them. Interesting because i was going to use LMM grease, as that's what you use on your input shaft and splines on your car but that has Moly in it.. damn, In which case i think just a medium grade grease would be best suited.

https://www.machinedesign.com/mechanical-drives/selecting-lubricant-ball-screws

This article may help.

fitting 2 nuts to the ballscrew would reduce the load on them by half - but probably not an issue if it is specced correctly

I think a separate thread would be nice for this kind of discussion as it is a important part in the design. I have the same kind of questions. It has been some discussion i https://www.xsimulator.net/community/threads/which-ballscrew-pitch-dia-length.12615/

i just finished reading through this thread.

wow. you guys need to write a book! it was amazing to hear about the struggles you went through to go 6DoF.

i am both inspired and overwhelmed.

wow. thank you for sharing the specs, designs and experiences. i only hope i can build something in the near future that will live up to your work.

thank you. please keep sharing.. i watch silent chill's channel.. good stuff

Hi @luky_90 i have my limit switches set at points on the actuator that allow for some leadscrew/ballnut overrun but not allow mechanical Clash if they are tripped .. These actuators are very powerful but inertia sometimes cause over travel, even after a limit switch cuts motor power,.

My New setup has the limit switches connected to a latching relay circuit so once tripped they prevent power going to motor until its reset by the operator . i came across the circuit here somewhere and it will be a major damage prevention Aid with these actuators..

What i noticed was due to the Inertia at speed the Actuator would trip the switch which was fine , but then due to this inertia the actuator Traveled beyond the Switch and so reactivated the Motor .../.... ( BANG not good)

Fitting the switches is a Compromise as you loose maximum actiatior travel to ensure hard contact is not made in the after switches are tripped, i also added some stiff rubber pads to both ends of leadscrew , which have some Give as it were to dampen the actually mechanical clash if the speed was high during switch activation event .

If need be i can post a picture of the Latching circuit ( which works well ,,but not tested on full System yet) all limit switches are connected in series so any one activated will cause all motors to stop ..

hope the info is of some use , if you already knew this, then Sorry for rambling on

your ramblings are gold mine for us...

what games do you play, or do you even use your project?

or have you moved on to bigger and better things...

Hi @luky_90 lol cheers. I'm still around just too many fingers in different pies lol.. i have just rewired 2 sets of controller systems for smc flypt hex pod and sabertooth 2 x 60 set up the other one for Amc128usb with optical encoders and sabertooth 2x32 it's stuff I bought over the years so now need to put it to work. Once testing is done I'll decide which one to fit to motion platform. It' still assembled so just to controller required . As for siMs I have not used any of them for long enough to pick a fave too much tinkering with platform and paragliding lol .. but progress now being made so soon will have some updates around the forum thanks

hey @wannabeaflyer2

may i ask if your current power setup is still , 2 12V@57Amp Server PSU's in parallel / 12Vdc Car Battery as mentioned in your post # 125?
i try to follow this thread, not sure if you are using server power supplies in series or parallel... and your are still on 12V PM90L motors?

i see you are using sabertooth 2x32... you had connected resistors to the 2x32..
i was going to go sabertooth 2x60 doesnt have the power output terminals P1 & P2 which the 2x32 has... how can i apply the resistors to the 2x60 ?

You can't use resistors on a 2x60. If necessary only option is to add a battery.

ok, no problem. im kinda new at the battery implementation.. or at least trying to understand it...
from @wannabeaflyer2 's diagram, his 6DoF runs off (2x) 12V batteries in parallel... is the server power supplies on for recharging? or do you leave it off during motion platform usage?

i did a quick search:
https://www.xsimulator.net/community/threads/sabertooth-2x32-2x60-batteries-alternative.10317/

before i went into @wannabeaflyer2 's diagram.. at first i thought i would be connecting (3x) power supplies to (3x) sabertooth 2x60..
so basically, the ideal setup is (2x) 12 batteries, and (3x) LED power supplies, all in parallel?
or is (2x) power supplies enough for the sake of charging? if charging that means the power supplies have to be tweaked higher?

lol omg, if trying to find 4 gauge barrier terminal blocks wasnt hard enough...
most appreciate the reply @BlazinH <3

Sorry for the previous post I could not paste the links of amazon, here I leave the specifications of it
Specifications
Peak power point: 175N at 4 mm / s
Peak efficiency point: 75N to 7 mm / s
Maximum force (lifted): 200N
Recoil force: 102N
Mass: 56 g
Positional accuracy: 0.3 mm
Maximum lateral load (extended): 40N
Feedback potentiometer: 9kΩ ± 30%
Input voltage: 5-7.4V
Draft current: 650mA

I use 2 batteries in parallele to get the 24V and I connect the 3 led power supply in parallele to them (24v, 12.5A). They recharge the batteries during the use of the rig. I know that SilentChill is using something similar, but for 12V.

most helpful!thank you! going to come up with my own diagram based off everything i have come to know..would be great to have your critique!

did you have to tweak your 24V power supplies higher in order to get them to charge your two series connected batteries? and how many amp Hour rating is your batteries? @Pierre Lalancette

@hannibal You should start your own thread as we are hijacking wannabe thread. I have done nothing to the power, just plugged it to the batteries and I went my way. They are deep charging boat batteries. It's only been a few months, so I don't know about long terms, but all seem fine so far.

i did start my own thread, i just had questions about wannabe's build.
but after just now seeing sixdegreesoffreedom's thread with a focus on how to wire a sabertooth 2x60.. i was even blown more out of the water lolol

i will keep deep charging boat batteries in mind... thank yoU!

so what games do you enjoy most on your 6dof @Pierre Lalancette ?