Potential stack and stitch rig

[kaleun96]

May I ask what's an idler in this case? I've seen them for V-Slot rails where it's used with a timing belt but I can't see references to one for a generic linear actuator with a ball screw.

Looks like an interesting rig though, a very useful platform to improve upon. Looking forward to seeing how it turns out!

[ray_parkhurst]

May I ask what's an idler in this case? I've seen them for V-Slot rails where it's used with a timing belt but I can't see references to one for a generic linear actuator with a ball screw.

Looks like an interesting rig though, a very useful platform to improve upon. Looking forward to seeing how it turns out!

The way I'm using the term, an idler rail is a secondary rail which acts to stabilize the primary rail against unwanted movement. The idler concept is most useful for rails which have minimal spacing between bearings, such as the various commercial rails like StackShot/WeMacro/mjkzz, or even the single-carriage THK/Misumi/etc rails. You can see an example of this concept used on a WeMacro system here:

https://www.photomacrography.net/forum/ ... ight=idler

I originally proposed using these idlers in response to Lou Jost, who had purchased some very heavy lenses which were expected to strain the rail systems he woudl use them on. The idler arrangement greatly reduces torque on the main bearings, distributing the weight on-axis, where the rails have the most load capacity. You can see this post here:

https://www.photomacrography.net/forum/ ... ight=idler

In that post I proposed two idlers: one for the rail, and one for the lens.

[kaleun96]

May I ask what's an idler in this case? I've seen them for V-Slot rails where it's used with a timing belt but I can't see references to one for a generic linear actuator with a ball screw.

Looks like an interesting rig though, a very useful platform to improve upon. Looking forward to seeing how it turns out!

The way I'm using the term, an idler rail is a secondary rail which acts to stabilize the primary rail against unwanted movement. The idler concept is most useful for rails which have minimal spacing between bearings, such as the various commercial rails like StackShot/WeMacro/mjkzz, or even the single-carriage THK/Misumi/etc rails. You can see an example of this concept used on a WeMacro system here:

https://www.photomacrography.net/forum/ ... ight=idler

I originally proposed using these idlers in response to Lou Jost, who had purchased some very heavy lenses which were expected to strain the rail systems he woudl use them on. The idler arrangement greatly reduces torque on the main bearings, distributing the weight on-axis, where the rails have the most load capacity. You can see this post here:

https://www.photomacrography.net/forum/ ... ight=idler

In that post I proposed two idlers: one for the rail, and one for the lens.

Thanks for the explanation! I've had to use a spring to provide some off-axial loading to counter the jerks to the left/right I get when changing direction, perhaps this would help as well. I'll post my setup at some point and look forward to some feedback on how to boost rigidity.


On your note about the knurled knobs, I have a very similar one but am also unsure where it was sourced from as it doesn't appear to have come from the rail manufacturer. But instead of a dual-shaft design, it's a laterally-mounted motor with the knob attached to the end of the ball screw shaft, after the pulley wheel needed for the timing belt. It's perhaps an older model of the one in the link, since this one doesn't expose the ball screw shaft at the timing belt assembly.

[ray_parkhurst]

May I ask what's an idler in this case? I've seen them for V-Slot rails where it's used with a timing belt but I can't see references to one for a generic linear actuator with a ball screw.

Looks like an interesting rig though, a very useful platform to improve upon. Looking forward to seeing how it turns out!

The way I'm using the term, an idler rail is a secondary rail which acts to stabilize the primary rail against unwanted movement. The idler concept is most useful for rails which have minimal spacing between bearings, such as the various commercial rails like StackShot/WeMacro/mjkzz, or even the single-carriage THK/Misumi/etc rails. You can see an example of this concept used on a WeMacro system here:

https://www.photomacrography.net/forum/ ... ight=idler

I originally proposed using these idlers in response to Lou Jost, who had purchased some very heavy lenses which were expected to strain the rail systems he woudl use them on. The idler arrangement greatly reduces torque on the main bearings, distributing the weight on-axis, where the rails have the most load capacity. You can see this post here:

https://www.photomacrography.net/forum/ ... ight=idler

In that post I proposed two idlers: one for the rail, and one for the lens.

Thanks for the explanation! I've had to use a spring to provide some off-axial loading to counter the jerks to the left/right I get when changing direction, perhaps this would help as well. I'll post my setup at some point and look forward to some feedback on how to boost rigidity.


On your note about the knurled knobs, I have a very similar one but am also unsure where it was sourced from as it doesn't appear to have come from the rail manufacturer. But instead of a dual-shaft design, it's a laterally-mounted motor with the knob attached to the end of the ball screw shaft, after the pulley wheel needed for the timing belt. It's perhaps an older model of the one in the link, since this one doesn't expose the ball screw shaft at the timing belt assembly.

Thanks for the link. I did not know of this mfr before. Always good to see things folks make in our area of interest, especially if someone is using their stuff.

Post a pic of your setup and I'll comment on any stability issues or potential improvements I see.

[ChrisR]

I'll see how it goes.
This is quite a big rig, usable up to maybe 30cm x 30cm subjects, it's not machined to tight tolerances. I think it may be unreasonable to aim for microscope-stage precision. Look at how the vertical extrusion is held to the horizontal. I expect I'll put a diagonal strut "behind" on each side, but I don't have a great way to measure the 90º.

If I use a light mirrorless camera & lens it would ease the problem. Even so, if I put the camera on the horizontal, I daresay the 8mm diameter rails will bend. I could replace them with thicker rods; deflection ∝ diameter^-2 , or replace with this stuff

But if I'm going to change everything I may as well start from scratch!

[elf]

Look at how the vertical extrusion is held to the horizontal. I expect I'll put a diagonal strut "behind" on each side, but I don't have a great way to measure the 90º.

With a part like this, you don't need to measure 90 degrees. Once installed you can use the camera and Zerene Stacker to precisely align the Z axis.