DIY Macro Rail - is the thread pitch on this small enough?

[markangeltrueman]

Hi

So i've been looking at the following as a rail for an Arduino driven macro rail

https://www.amazon.com/FUYU-Linear-Actu ... 39&sr=8-43

Electronically I know how to set this kind of thing up (have made timelapse rails in the past)

My main query is if the 2mm pitch is small and accurate enough for extreme macro with microscope objectives.

Accuracy is 0.05mm according to the tech spec. As the included Nema stepper has a 1.8 degree step angle that should give 200 steps per rotation and an 0.01mm step if required.

It *sounds* like it should be accurate enough but wondered if anyone else had experience of DIY rails

Thanks

Mark

[chris_ma]

Hi Mark,

I don't have any experience with extreme macro (I take it we're talking about 5x and up here?) but I'd be very reluctant to start spending significant time on rails like the one you linked.
while with a lot of care and luck it might just about work, more likely it will result in quite a bit of compromises and/or poor results.

for example, while specs on low cost devices like this are usually over optimistic, they mention a max vertical load of only 1kg. so the specs might list 0.05mm step size, but you might get quite a bit of wobble etc.

you're probably better of to look for a quality rail on the used market, if you can stretch your budget a bit the THK ones are fantastic, but I'm sure there's pretty good ones in the sub 100USD range as well.

there's ton of info on DIY rails on this board, try a search on a spare weekend

hope that helps
chris

[markangeltrueman]

Hi Chris

5-10x yeah....

I guess that's my question really, is this rail itself as good as the ones that you get in the "professional" versions. They are, effectively, all the same thing right and its just the accuracy that you are effectively paying for.

I'm happy to (and want to) spend time on the build and programming with Arduino. There's no reason why I can't produce something equally as good, if not better and more customisable for my needs on that side of things that the retail versions

The only variable, in my opinion, is the quality of the rail and motor but want some concrete feedback on this one and maybe pointers to an alternative if it realistically isn't going to be good enough

[ray_parkhurst]

Hi

So i've been looking at the following as a rail for an Arduino driven macro rail

https://www.amazon.com/FUYU-Linear-Actu ... 39&sr=8-43

Electronically I know how to set this kind of thing up (have made timelapse rails in the past)

My main query is if the 2mm pitch is small and accurate enough for extreme macro with microscope objectives.

Accuracy is 0.05mm according to the tech spec. As the included Nema stepper has a 1.8 degree step angle that should give 200 steps per rotation and an 0.01mm step if required.

It *sounds* like it should be accurate enough but wondered if anyone else had experience of DIY rails

Thanks

Mark

The 10um basic step size, with 2.5um quarter steps, hould do fine for 10x, maybe 20x mag. The screw probably has some backlash, so you may need to preload it. The rail carriage might not be preloaded so a cross-preloading may be needed to keep both in check.

If you plan to mount your subject on the stage, it should be fine with the preloading. If you plan to mount a camera, I would recommend adding an idler rail to stabilize things. That single small carriage is not beefy enough IMO to move a camera and lens effectively but the drive system can certainly do it. An idler would strengthen the system nicely.

[markangeltrueman]

Thats great info, thanks Ray.

I'll have to look up what an idler rail is in this context. I assume its a secondary rail that attaches to some kind of modification to the carriage (to make it larger for instance)?

Hi

So i've been looking at the following as a rail for an Arduino driven macro rail

https://www.amazon.com/FUYU-Linear-Actu ... 39&sr=8-43

Electronically I know how to set this kind of thing up (have made timelapse rails in the past)

My main query is if the 2mm pitch is small and accurate enough for extreme macro with microscope objectives.

Accuracy is 0.05mm according to the tech spec. As the included Nema stepper has a 1.8 degree step angle that should give 200 steps per rotation and an 0.01mm step if required.

It *sounds* like it should be accurate enough but wondered if anyone else had experience of DIY rails

Thanks

Mark

The 10um basic step size, with 2.5um quarter steps, hould do fine for 10x, maybe 20x mag. The screw probably has some backlash, so you may need to preload it. The rail carriage might not be preloaded so a cross-preloading may be needed to keep both in check.

If you plan to mount your subject on the stage, it should be fine with the preloading. If you plan to mount a camera, I would recommend adding an idler rail to stabilize things. That single small carriage is not beefy enough IMO to move a camera and lens effectively but the drive system can certainly do it. An idler would strengthen the system nicely.

[Adalbert]

Hi Mark,
I would recommend you the THK KR2001A (full rotation => 1mm step) and NEMA 0.9 degree.
http://www.photomacrography.net/forum/v ... c&start=30
BR, ADi

[ray_parkhurst]

Thats great info, thanks Ray.

I'll have to look up what an idler rail is in this context. I assume its a secondary rail that attaches to some kind of modification to the carriage (to make it larger for instance)?

Yes, the idler is a secondary rail placed either inline or offset from the driving rail, with a platform connecting the carriages. You can see some examples doing a search for "idler".

The small carriage of this rail likely won't support much torque in either pitch or roll. As such it would benefit from an offset idler. I built a similar offset idler for my current Stack and Stitch and it has worked superbly. If you're interested I will see if I can find my design drawings. I use a 2-carriage secondary rail running parallel to the main rail, with the carriages at minimum spacing. The secondary rail is offset by ~55mm from the main rail.

Edited to add: One thing that is not obvious with idlers, especially offset ones, is that since it's almost impossible to line up the rail axes and carriage spacings perfectly, the resulting misalignment effectively creates a preload condition that helps stabilize the combined platform. The screw will still have its inherent backlash though.

[chris_ma]

I'm happy to (and want to) spend time on the build and programming with Arduino. There's no reason why I can't produce something equally as good, if not better and more customisable for my needs on that side of things that the retail versions

sure, if you have a background in coding then indeed it can be fun to try to match or exceed the established solution.

personally I've found that flimsy mechanics can be frustrating. Again if you have a strong background in mechanical engineering (like ray and others here have) then you can most likely make most cheap rails work.
Myself I'm not terribly good at mechanics and find that quality gear is much simpler (and much more fun) to get good results with, and that specific rail looks a bit weakly built.

One option is to simply give it a try, most of the code should be portable in case you need to upgrade. The downside is that the re-sale value of the rail is probably very low, and the money invested in custom adapters (which can get higher then the rail itself) likely wasted.

[markangeltrueman]

Thanks, i'll take a look at those.

Hi Mark,
I would recommend you the THK KR2001A (full rotation => 1mm step) and NEMA 0.9 degree.
http://www.photomacrography.net/forum/v ... c&start=30
BR, ADi

[markangeltrueman]

If you're interested I will see if I can find my design drawings. I use a 2-carriage secondary rail running parallel to the main rail, with the carriages at minimum spacing. The secondary rail is offset by ~55mm from the main rail.

Would be interested to see if it's not too much trouble.

Thanks for the help

[markangeltrueman]

personally I've found that flimsy mechanics can be frustrating. Again if you have a strong background in mechanical engineering (like ray and others here have) then you can most likely make most cheap rails work.

I have done some work with linear guide rails in the past and moved cameras around on them but not to the same precision as required here.

One option is to simply give it a try, most of the code should be portable in case you need to upgrade. The downside is that the re-sale value of the rail is probably very low, and the money invested in custom adapters (which can get higher then the rail itself) likely wasted.

I'm not too bothered about the financial loss on rails. I just like tinkering with engineering and electronics projects. If it works, it works. If it doesnt then the stepper motor and rail should be easily interchangeable with another that might.

[ray_parkhurst]

If you're interested I will see if I can find my design drawings. I use a 2-carriage secondary rail running parallel to the main rail, with the carriages at minimum spacing. The secondary rail is offset by ~55mm from the main rail.

Would be interested to see if it's not too much trouble.

Thanks for the help

Here's what I did for my Stack and Stitch. In my case I used two THK KR15 rails. In your case for a single axis you would omit the upper rail and replace it with a platform to mount the bellows/camera.

[ray_parkhurst]

If you're interested I will see if I can find my design drawings. I use a 2-carriage secondary rail running parallel to the main rail, with the carriages at minimum spacing. The secondary rail is offset by ~55mm from the main rail.

Would be interested to see if it's not too much trouble.

Thanks for the help

I went ahead and modifed the drawing to show what I described above.

I like the FUYU rail a lot. It's small, like the KR15, and with the idler (and backlash compensation) it could be the driver for a solid system.

[ray_parkhurst]

This similar rail also available on Amazon has 1mm pitch:

https://www.amazon.com/Linear-Actuator- ... 14&sr=8-16

Edited to add: the FUYU seller mentions other screw pitches available, but not 1mm. It may be that he can provide the same rail but with 1mm pitch. It's worth asking as it will halve your basic step size. Note that it's not easy to find NEMA 11 in 400-step, so going to 1mm is your easiest way to improve on basic step accuracy.

Edited to add: the second listing states 24V for the stepper motor. The FUYU does not state the voltage but both state the current at ~0.6A. I question the spec of 24V with a current of 0.6A so you might want to delve further into this.

[markangeltrueman]

Thanks for all your help ray, it really is much appreciated. I'll keep you updated with my developments.

This similar rail also available on Amazon has 1mm pitch:

https://www.amazon.com/Linear-Actuator- ... 14&sr=8-16

Edited to add: the FUYU seller mentions other screw pitches available, but not 1mm. It may be that he can provide the same rail but with 1mm pitch. It's worth asking as it will halve your basic step size. Note that it's not easy to find NEMA 11 in 400-step, so going to 1mm is your easiest way to improve on basic step accuracy.