CNC macro rail

I know that macro digitizing stool is not completed yet but let open my second small project in the very beginning phase.

Target:

- precise (about 1 to 10 μm) and solid / rigid construction of CNC moving for DSLR body (w or w/o lens ... possible lens on bellows)

- start with 1 axis ... afterwards possible 3 axis movements of DSLR body

- the shortest possible lag between requests and start of motor stepping (app on client side directly communicate with something like Raspberry Pi 2 and controller app for drivers of stepper motors)

- possible usage in nature (not only in "studio")

The beginning, here are 16 mm rods and couple of other parts of linear technology:

The following steps:

- absolute measurement of position via something like this:

http://www.renishaw.com/en/linace-absolute-inaxis-linear-shaft-encoders--17800

- moving via stepper motor with something from HIWIN:

http://www.hiwin.com/ballscrews.html

Thanks for the reply. This thema may by one man show but other suggestions are welcome too.

The rectangle guideway i am using for the digitizing stool. But for this purpose i was thinking to try use something other.

On the first photo there are two round rails which will be mounted together with ball screw. On one side of the rails and ball screw will be stepper motor (holder). On the other end of round rails will be holder of DSLR. Two ball cabins will be connected together on some platform for mounting to tripod or for mounting to next axis.

This first photo is my own ... so this things are already at my hands so they will be used certainly.

I expect to use something like 12mm from this ball screw line:
http://www.cncshop.cz/fsi-din-matice-sroub

With micron measure device from first post.

It should be used with MP-E lens, so 1:1 to 5:1. But maybe with other lenses too. (Not only under the 5:1 mag. But over 1:1 too ...)

F.e. later with some macro lens for middle/large format.

I would like to do it as precise as i am able. So no budget is set for it. But together it means longer time to the finish.

A lot of things i buy on our local store http://cncshop.cz there is most of the necessary things.

And CNC thing has to be on my own. Hope that i will able to solve it. Because i would like to push my skills forward together with the hobby. Later i would like to build my own "hobby" 12x20" camera with complete "remote touch screen control" with possibilities of technical camera. So this will be the step forward before the biggest project from my own hands...

(only small targets... )

One new small step:

http://12in.cz/fotografie/velka/30

Depending on your load, you may need to stiffen up your shaft along the radial direction. Something like this: http://www.pbclinear.com/Linear-Shafting-Support-Rails

If your load starts bending your shaft, it will bind on your linear bearing.

A recommendation for a simplistic linear motor instead of using a home made ball screw assembly is this: http://www.robotshop.com/en/firgelli-technologies-l12-30-210-12-p.html

They come in all different lengths and have built in potentiometers (pretty easy to measure in comparison to encoders).

Hope that used guide rods not to bend on load. The length is 500 mm and diameter is 16 mm, induction hardened (62HRC). It is not lightweight construction. It is more like a tank. But small weight is far to the top of important parameters this time. The most important parameter in this my "DIY CNC rail project" is ultimate precision. Precision goes together with nonbending/robust solution after load by attaching camera and other parts.

Now i tried to load it by my weight (about 85 kg) and it was still moving without trouble.

No way to bend it via more than twenty times lighter real equipment.

http://www.robotshop.com/media/files/pdf/l12_datasheet.pdf

The second hyperlink looks good but two parameters miss the target:

- Datasheet say 100mm max stroke. It is four times less than this axes needs

- Positional accuracy about 0.1 mm - my expectations are with precision at least ten times better.

If ultimate precision is what your after, then with 500mm stroke and 85kg combination, you should think about stiffening that shaft as 16mm is quite small.  You will definitely have significant bending to the point where your linear renishaw encoder will have alignment issues.  I've used those encoder's in my workplace, and tbh, they are very sensitive to alignment issues, which mostlikely will be your worst problem if precision is your ultimate goal.

I expect that there will be some troubles but 85 kg was only extreme test when i was writing the answer. One end will be with stepper motor, driver, etc. (about 2 kg max) other side with camera, lens, etc. (about 2 kg max too). Ends of the rails will be loaded about 5 kg max when it is sumarized from point of SMAL double closed linearset which will be attached to a tripod or other axes.

Third small step, attached Manfrotto 625:

Luisifer wrote:

Third small step, attached Manfrotto 625:

Sorry if I am going off-topic, but how do you get such nice backgrounds for the pictures. Is it added in PP, or some cloth?

It is background from black colored paper (no real black on used light, but dark gray) with small tonal differences. In PP are those differences via curves "narrowed".

Luisifer wrote:

It is background from black colored paper (no real black on used light, but dark gray) with small tonal differences. In PP are those differences via curves "narrowed".

Thanks for answering.

Really nice shots. You are a pro.

And good luck with the build.

Only amateur.

And thanks. Hope that i find some budget for next step...

You can buy complete linear rail assemblies including the stepper motor for probably little more than the cost of the components. Here's an inexpensive one that uses a trapezoidal screw and brass nut. This supplier has a number of types and lengths including ball screw driven units for not much more. Have a look in Store Categories on the left of the page:

http://www.aliexpress.com/store/product/ST-200mm-Linear-Guide-Moving-Table-T-screw-slide-Slip-way-1Pcs-42-Stepper-Motor/1986599_32647250431.html

Fourth step will be attaching ball screw etc.

http://12in.cz/fotografie/velka/71_Linearni-technika-IV

Looking very good but I suspect there might be issues having the tripod plate right at one end.  With the camera all the way to the far end from the tripod mount you'll be rather prone to vibrations...

A  rigid board/sheet linking both the lower mounts with the tripod fixing central would seem a better bet to me.