Open Focus Stacking Rail (OpenBuilds & RatRig)

[mjkzz]

I think I am going to shoot myself in the feet (ouch ), but I think this is going to benefit the whole community, so here it is . . .

Before I went on to a long vacation (9/22nd to 10/15th 2018), I happened upon a video and the so called C-Beam rail by OpenBuilds in the US and it seems there is another company selling this rail in Europe, RatRig in Portugal. I bought it right after I came back and it turns out to be an excellent rail for stacking. Here are some benefits:

anti-backlash screw nuts, so little backlash
delrin nuts so it is silent and self lubricate
long travel distance (even the shortest version has 150mm travel)
super precise and WOBBLE FREE, I tried 50x and it works great.

How it looks (motor might be different from OpenBuilds or RatRig)


Leas screw and Delrin nut


Did this 31x using this rail.


I did not like the fact, INITIALLY, it uses two poles to hook up the motor, but it turns out that is not an issue at all -- the lead screw is being positioned and held by two ends, the flexible coupler provide power transmission.

Another POSSIBLE difficult part for DIY'er is its LONG pitch, 8mm to exact. So a controller with fine micro stepping capability is needed. Or alternatively, replace the lead screw.

The only thing I am a little concerned is its capability of holding weight, its "elasticity" of the delrin nuts for finer step size (less than 1 micron). But I think this is more than most people would need, if people need even better solution, I think those industrial rail are only choices.

Here is a blog I wrote about it if you are interested in details.

[mjkzz]

In spirit of openness, I will finish that Arduino based controller, so ideas as how to operate that are welcome.

And also, for those who want to learn, they do not have to buy my controller and open it up then copy ideas. It will be open

[JohnyM]

I've ordered bunch of those C beams and V-Slot profiles and gantry plates for my WIP horizontal S&S rig. Wheels and rails are coming together pretty nicely, but i've decided to put 2x THK KR 15 and 1x Wemacro rails inside. Less microstepping, but very nice and rigid. Additionally, i've spring loaded all the rails to (hopefully) eliminate backlash.

My weakspot is programming and electronics. Can the controller you offer in your shop be connected to Wemacro and thk rails? Im nearly finished with mechanics and promised XYZ from Wemacro is still unheard of, so good time to start looking for replacement.

[mawyatt]

In spirit of openness, I will finish that Arduino based controller, so ideas as how to operate that are welcome.

And also, for those who want to learn, they do not have to buy my controller and open it up then copy ideas. It will be open

Peter,

This rail certainly looks interesting and your results show it can perform. I would be a little concerned with quality as you mentioned, but maybe this is just a one off event!!

The 8mm screw thread seems coarse since most are using 1mm or 2mm thread pitches. I've done quite a bit of experimenting with various stepper controllers/drivers & motors and reported some findings on here. Micro-stepping is not as good a solution as a finer pitch screw thread and motor, but given you are stuck with a coarse pitch thread then micro stepping is probably the only option after a finer pitch motor. As mentioned the Ti DRV8825 seems to have issues with precision micro-stepping, and maybe some of the other Ti parts do as well, this is why I went with another controller/driver (Tic-500 based on MPS6500) from Pololu.

Pololu in LV is a great resource for controllers and drivers for DIYers, they have extremely sophisticated stepper motor control algorithms and features in their controllers. This should be no surprise since they originated from the MIT Robotics group I believe.

I'm working with the Raspberry Pi for my Precision Stack and Stitch system, I chose this over the Arduino simply because it seemed easier to work with and I'm not a programmer, so easy was important for a noob!! The code I'm developing in Python allows defining the rail zero state for all 3 axis, center for X and Y axis, as well as the start, end and step size for each axis. The Y and X axis are for the subject and the Z axis is for the camera/lens in vertical orientation. The Z axis has a separate start, end and step size for each Y & X position if desired, so one can tailor a session and not waste a lot of time stacking out of focus space for a subject that is tilted.

All the axis motor and rail details are all programmable, including rail pitch, rail range, motor step angle, motor peak & holding currents, start velocity, max velocity, acceleration profile, deceleration profile and so on for each axis, X,Y and Z. All the data is of course stored in user specified files stored to micro SD card, so one doesn't have to reenter anything if desired and can start a session with just a couple keystrokes from a previous session, or a default session (or even a trashed session).

The camera and strobe timing are programmable and available to allow use of EFCS with flash/strobe, as well as all the usual timing for rail settling and such. Outputs are optically isolated with LED indicators to show when the camera and strobe are triggered.

All Z axis stacking points and image data collection are done from only one direction, so backlash effects are reduced.

I have VNC working now, so the complete setup can be controlled remotely over the WiFi network, and no monitor, keyboard nor mouse is required with the Raspberry and setup.

I'll be posting some more on this Precision Stack and Stitch setup soon.

Having tackled this effort I have the utmost appreciation for all that are involved with developing, supplying and building these rail system and controllers. This was, is, and will be a lot for work for me and I really appreciate the wonderful products available to us macro photographers; hardware, software and the combination.

So my hat's off to all the folks behind all the great products, and information provided here on this site

Best,

[mjkzz]

JohnyM, I do not know if my controllers will work for you. Mike, good luck with your adventure.

This C-Beam thing is making focus stacking equipment a commodity product, it is stable, backlash free, wobble free. People can start doing PRECISION, high magnification focus stacking for under 350USD even with a LIFE time license of Zerene. This is something to be reckoned with.

Now I just found out that there are arduino base solutions for focus stacking, already, though not sure if they are suitable for this rail, it would not be hard to make it happen, so I might not have to make one

[mawyatt]

I've ordered bunch of those C beams and V-Slot profiles and gantry plates for my WIP horizontal S&S rig. Wheels and rails are coming together pretty nicely, but i've decided to put 2x THK KR 15 and 1x Wemacro rails inside. Less microstepping, but very nice and rigid. Additionally, i've spring loaded all the rails to (hopefully) eliminate backlash.

My weakspot is programming and electronics. Can the controller you offer in your shop be connected to Wemacro and thk rails? Im nearly finished with mechanics and promised XYZ from Wemacro is still unheard of, so good time to start looking for replacement.

Johny,

I can confirm that the MJKZZ Stand Alone controller will operate the Wemacro rail with the proper cable assembly, as well as KR20 rails with 1~2 ohm motors. However I would caution the use with the THK KR15 that are part of the US Automation surplus rails. The NEMA 11 motors in these have a high internal resistance of 5.6 ohms and get quite hot if the current limit isn't set/controlled well below 1 amp, I'm using ~625ma. The Pololu Tic-500 I'm using in the development of the Precision Stack and Stitch System works very nicely with these high resistance motors, and allows the motor current limit to be programmed. Since the motor characteristics are fully programmable, you can use just about any typical stepper motor we normally use with the Tic-500, with an added benefit of motor current energy recovery which significantly reduces the supply current requirements. Of course getting this controller integrated with a full Stack and Stitch setup is quite an undertaking though.

For the same reason I would caution using any other controller with the USA KR-15 where you can't directly control the peak motor current. If you decide to try a controller be sure to monitor the motor temperature constantly to make sure it doesn't overheat. The Stackshot controller allows motor current control, so this might be an alternative to consider, although I haven't tried such.

Hope this helps,

Best,

[ray_parkhurst]

The mjkzz XYZR/SNS works well with the THK KR15 with USA and MachMotion motors. Only issue I had was OS compatibility, but I am using the XYZR/SNS on Win10 and it works fine. Motor current (both idle and peak) can be controlled so no overheating.

The C-beam is very interesting. I assume it has two delrin nuts, on in the main part and one in the narrow part, and that the screw adjustment is used to remove the "play" in the system? I'd worry that small variations in the acme screw would cause "tightness" of the system to vary quite a bit over the length of the screw. Would be interesting to test these out though. Do they come in tighter pitches, like a more standard 2mm pitch / 8mm diameter type? I suppose the tighter pitch may give the system more problems. Wider pitch is probably a lot more forgiving.

[elf]

You can find the TR8 leadscrews on Aliexpress in 1,2,4, and 8mm pitches. I have a 500mm long TR8-1mm for another project. The quality appears to be excellent. You will need to be able to machine the ends in order to make it fit the rail.

[mawyatt]

JohnyM, I do not know if my controllers will work for you. Mike, good luck with your adventure.

This C-Beam thing is making focus stacking equipment a commodity product, it is stable, backlash free, wobble free. People can start doing PRECISION, high magnification focus stacking for under 350USD even with a LIFE time license of Zerene. This is something to be reckoned with.

Now I just found out that there are arduino base solutions for focus stacking, already, though not sure if they are suitable for this rail, it would not be hard to make it happen, so I might not have to make one

Peter,

It's been a fun but trying adventure developing this Precision Stack and Stitch system so far

Working quite well now, and the orchestrated movement of the motors and rails, with all the flashing LEDS (3 USB, 3 motor activation, 3 command, camera trigger, & strobe trigger) and strobes is fascinating to watch

I've tried to mess up the system by changing motor direction commands while the motors are moving during initial parameter setup defining start, end and step, and the system keeps precise track of all the motor positions in spite of my attempts to mess things up!! I've even pulled the motor power plug during sessions in the middle of all the motors moving, or course everything stopped!! When I restarted the session the motors returned to the staring positions with only a small error!! This is because the motor supply voltage is monitored on all 3 axises, and when it falls below a limit the step commands are halted, thus not accumulating a large position error. I'm still working on some of the error routines and may expand these even more.

As my programming skills improve I'm able to accomplish more which is encouraging to me at least.

Best,

[mawyatt]

The mjkzz XYZR/SNS works well with the THK KR15 with USA and MachMotion motors. Only issue I had was OS compatibility, but I am using the XYZR/SNS on Win10 and it works fine. Motor current (both idle and peak) can be controlled so no overheating.

The C-beam is very interesting. I assume it has two delrin nuts, on in the main part and one in the narrow part, and that the screw adjustment is used to remove the "play" in the system? I'd worry that small variations in the acme screw would cause "tightness" of the system to vary quite a bit over the length of the screw. Would be interesting to test these out though. Do they come in tighter pitches, like a more standard 2mm pitch / 8mm diameter type? I suppose the tighter pitch may give the system more problems. Wider pitch is probably a lot more forgiving.

Ray,

The MJKZZ Stand Alone Controller doesn't have a current limit set point, at least it's not available on the display, so the one you mention must be the USB version, which Peter indicated does have current limit control. Do you know what stepper driver chip is used in the USB version?

Best,

[ray_parkhurst]

You can find the TR8 leadscrews on Aliexpress in 1,2,4, and 8mm pitches. I have a 500mm long TR8-1mm for another project. The quality appears to be excellent. You will need to be able to machine the ends in order to make it fit the rail.

The leadscrews are no problem to find, but I'm wondering if the C-Beam nuts are available in these tight pitches...

Found one seller on aliexpress selling 2mm pitch c-beams:

https://www.aliexpress.com/item/2pcs-TR ... 6512CWiotB

These are brilliant looking! Single pieces of machined delrin with play-reduction tightening mechanism. When did these become available, and who invented them. Pure genius. With a good quality acme screw this is a super solution for low-load applications.

[ray_parkhurst]

The MJKZZ Stand Alone Controller doesn't have a current limit set point, at least it's not available on the display, so the one you mention must be the USB version, which Peter indicated does have current limit control. Do you know what stepper driver chip is used in the USB version?

I do use the USB version, but I have not opened up the controller to check which driver chip Peter uses. I am sure he'll have no issue letting us know.

[mjkzz]

The mjkzz XYZR/SNS works well with the THK KR15 with USA and MachMotion motors. Only issue I had was OS compatibility, but I am using the XYZR/SNS on Win10 and it works fine. Motor current (both idle and peak) can be controlled so no overheating.

The C-beam is very interesting. I assume it has two delrin nuts, on in the main part and one in the narrow part, and that the screw adjustment is used to remove the "play" in the system? I'd worry that small variations in the acme screw would cause "tightness" of the system to vary quite a bit over the length of the screw. Would be interesting to test these out though. Do they come in tighter pitches, like a more standard 2mm pitch / 8mm diameter type? I suppose the tighter pitch may give the system more problems. Wider pitch is probably a lot more forgiving.

Ray,

The MJKZZ Stand Alone Controller doesn't have a current limit set point, at least it's not available on the display, so the one you mention must be the USB version, which Peter indicated does have current limit control. Do you know what stepper driver chip is used in the USB version?

Best,

Mike, all of my controllers have current limiting capabilities. For the stand alone one, it is on the second page, press PM to see i.

[mjkzz]

The MJKZZ Stand Alone Controller doesn't have a current limit set point, at least it's not available on the display, so the one you mention must be the USB version, which Peter indicated does have current limit control. Do you know what stepper driver chip is used in the USB version?

I do use the USB version, but I have not opened up the controller to check which driver chip Peter uses. I am sure he'll have no issue letting us know.

I do not even know which chip my controller uses :-) I never check it, I only experiment with it.

[mjkzz]

You can find the TR8 leadscrews on Aliexpress in 1,2,4, and 8mm pitches. I have a 500mm long TR8-1mm for another project. The quality appears to be excellent. You will need to be able to machine the ends in order to make it fit the rail.

The leadscrews are no problem to find, but I'm wondering if the C-Beam nuts are available in these tight pitches...

Found one seller on aliexpress selling 2mm pitch c-beams:

https://www.aliexpress.com/item/2pcs-TR ... 6512CWiotB

These are brilliant looking! Single pieces of machined delrin with play-reduction tightening mechanism. When did these become available, and who invented them. Pure genius. With a good quality acme screw this is a super solution for low-load applications.

I wrote in my blog, you can replace the lead screw, but that means you have to buy it separately. I do not see any issues with micro stepping, even at 50x.