New linear actuator design

I got the bushings for the rotating ball-nuts and the bearings.

So I think I should have all parts, now, to assemble two prototypes. Unfortunatelly, my 3D-printer broke down. The Hot-end doesn't heat up anymore. The heating resistor seems OK (~10ohm) so I think it's a broken ribbon cable.

Yay, the 3D printer is working, again.

As I suspected, one of the ribbon cables and an FPC connector was broken. But I later found out the idler of the extruder also was. I normally don't like ordering at Amazon, but when it comes to urgent spare parts their prime shipping saves the day.

Unfortunatelly, my own (cheap chinese) lathe is not precise enough to make the bushings. So I asked a friend to make it for me. But I forgot to tel him the tolerances for max. runout and, of course according to Murphy's law, it went wrong. The bushings from post #21 had 0.25mm asymetric runout which would lead to the ball screws staggering 1.8mm at the end. So we decided to make new ones.

I'll check them nbext weekend and hopefully can finally assemble one or two actuators.

This time the bushing fitted perfect with a runout below 0.01mm. The spindle runs smooth and without staggering.

Now, I need to weld the aluminium tubes and buy the timing belts.

(BTW: the irritating timing belt noise in the background is my Pick&Place machine)

My friend Ingo helped me welding the aluminium tubes. It went much better than we first expected.


I'm not really happy with the 3D printed spacer block, though. It shows some warping at the corners so if I tighten the screws too much the ball bearings get too stiff. I think I mechine them from solid metal, next time. And I miscalculated the distance of the motor axis to the spindle. AT5 timing belts are available with 340mm length but HTD5M only come in 330 or 350mm length.I have to make a new motor mounting plate. But that's why we make prototypes...

Pulleys added

Today I ran the first test with the servo motor attached

Stroke, noise and speed are OK but I'm not really happy with the big pulley. I machined the bore hole with my own lathe but the runout is quite bad. Next time I order the pulleys from a manufacturer who can customize the bore hole.

Mass production started...

Some more pulleys have arrived.

Unfortunatelly, at the end of the year the workload increases and there is less time left for fun stuff...
But at least there is some progress. Mass production continues:

It feels like the smallest parts take the longest time.
https://youtube.com/shorts/MTj3qAzNOPA

Sven was also diligent:

Some more holes drilled and de-burred

For 12 actuators, 6 for me and 6 for Sven, I need 24 U-joints each of which have 4 bearings. So I need a total of 96 of those bearing holders.

I asked JLC the famous PCB house that also offers CNC services, recently. They quoted a single part for an incredible $18. Wow, I'd take $18 for writing an invoice doing nothing at all.
But unfortunatelly, I don't get much discount if I order 100. They'd charge $1200, so I decided to machine them on my own mill. It's around 3 hours machine time plus one hour for manual countersink and thread cutting and maybe another 2 hours for deburring.

all my push rods are full steel diameter 12mm and all on balls bearing. It s not empty alluminium.
Cover plates and middle plate are alluminium. 5mm top. 1 cm after. 6mm the slider. 3 cm bottom.
Bottom for electrical motor is 6 mm full steel.