THK KR15 cheap on eBay

[JohnyM]

Those rails are really tiny, not much larger than cigarettes pack. I want to use them as microscope stage.

[viktor j nilsson]

Amazing! To be honest I did not expect it to be THAT tiny. Our house, and my work place, is also very small, so I guess it will fit right in.

[viktor j nilsson]

Ok, I'm going to express my ignorance here, wasn't really planning to get a rail so I definitely haven't done my homework. Is it correct that the only thing I need to do to control this rail is to:

1) buy a Mjkzz wireless controller + appropriate camera cable.
2) remove the controller board from the stepper motor.
3) attach the cable from the Mjkzz's controller to the cables from the stepper motor as shown in Ray's picture. These connector will match right out of the box?

Edit: realized that the wiring wasn't quite as easy as I first thought. It's probably pretty easy, just not obvious to me. When I look at the wiring at http://www.usautomation.com/Accuriss28.aspx I can't even figure out what 4 pins I'm supposed to use. What pins are supposed to line up with Mjkzz's controller cable?



In Ray's picture it's the black, yellow, orange and red cables. But I just can't believe that those colors match the color coding in the table above.

[ray_parkhurst]

Ok, I'm going to express my ignorance here, wasn't really planning to get a rail so I definitely haven't done my homework. Is it correct that the only thing I need to do to control this rail is to:

1) buy a Mjkzz wireless controller + appropriate camera cable.
2) remove the controller board from the stepper motor.
3) attach the cable from the Mjkzz's controller to the cables from the stepper motor as shown in Ray's picture. These connector will match right out of the box?

To show how the cable colors work with mjkzz controller I simply pushed the bare wires into the connector, but you should plan to cut the wires, twist and solder, and individually wrap or shrinkwrap the 4 wires to make a permanent and insulated connection. Make sure when you buy the controller that you get a motor control cable like I have shown. The one shown came from Peter so he should be able to send one with the controller. The other end of the cable plugs into the mjkzz controller.

In addition to the above, you will need to mechanically interface the camera/bellows to the rail. The rails come with a small aluminum block that has the limit switch actuator attached. This block is nice to have since you can use it as a template for the screw pattern for your interface block. The interface block design depends on what you plan to mount to it. How do you plan to mount your camera / bellows? You could make a direct mount, or use an arca clamp, or short arca rail, or some other method. You'll need to plan the design of the interface block to properly match with your camera mounting hardware.

The rail needs to be mounted rigidly. It has 4 screw holes to mount to a surface or adapter. One thing to note is the screws used to mount the rail must be low profile. They can't stick up above the bottom of the rail or they interfere with the carriage movement.

Another thing to note is the motor underhangs the bottom of the rail, so you need to compensate for this when mounting the rail. I like to make 1/4" aluminum interface plates that the motors mount to, then the plates mount to the table or platform or granite block or whatever. 1/4" is enough to clear the motor so you can then mount the rail on a large surface without interference. I almost always do this with double-stick tape, which gives a rigid yet relatively easily removed / repositioned attachment.

Finally, I am still not sure how well the KR15 will handle the stress of moving the camera/bellows/lens around without an idler. If anyone wants to implement an idler, I will draw up a plan for it and post. Let me know.

[ray_parkhurst]

Edit: realized that the wiring wasn't quite as easy as I first thought. It's probably pretty easy, just not obvious to me. When I look at the wiring at http://www.usautomation.com/Accuriss28.aspx I can't even figure out what 4 pins I'm supposed to use. What pins are supposed to line up with Mjkzz's controller cable?

Pic removed

In Ray's picture it's the black, yellow, orange and red cables. But I just can't believe that those colors match the color coding in the table above.

You should completely ignore that table. It refers to the wiring connections for the controller, which you will remove. Once you remove the controller, you'll find 4 motor wires soldered to it. These are the 4 wires I show in my picture, and they are not shown in the table because they are not normally available to the user.

[viktor j nilsson]

Many thanks, Ray, that really cleared up my confusion. That'll help me sleep better (it's 1:40am here).

Your thoughts on how to mount it will no doubt be valuable when that time comes. My current rig is constructed using a combination of arca compatible clamps and plates and DIY aluminum adapter plates that I've drilled and tapped. I have quite a bit of flat aluminum stock of different thickness that I'll be able to use.

Time to sleep.

[mawyatt]

Viktor,

Ray's advice and information is very useful.

The KR15 is very tiny and probably not an ideal choice for mounting the massive camera and lenses we normally use, but better used for moving the tiny subjects as mentioned. The stepper motors are small NEMA 11 types on these KR15 rails, and probably don't have much torque. When using micro-stepping the torque falls off quickly (38% at 1/4), so this will be even more troublesome.

The KR20 or KR26 are larger rails, and use larger motors with better torque and stability. For vertical work even the KR20 is questionable with a heavy bellows/tubes, full frame cameras and heavy lens like the Nikkor PN105mm f2.8, the KR26 is better suited to handle these very heavy loads IMO.

Anyway, these just my thoughts on using the KR15.

Best,

[ray_parkhurst]

The KR15 is very tiny and probably not an ideal choice for mounting the massive camera and lenses we normally use, but better used for moving the tiny subjects as mentioned. The stepper motors are small NEMA 11 types on these KR15 rails, and probably don't have much torque. When using micro-stepping the torque falls off quickly (38% at 1/4), so this will be even more troublesome.

I agree that for vertical use, the KR15 on its own shouldn't be used for camera mounting, but my concern is not the load capability, nor the torque capability of the motor. I'm concerned with the dynamic moments and effect on the carriage bearings. This is why I recommend the idler, as it greatly reduces the moments. For horizontal use, I have a little less concern, but it still may be marginal from dynamic moment perspective. The idler fixes this, but whether it is needed will depend on how the rail is loaded. If the camera system is balanced on the carriage, and the rail is moved only slowly, it probably won't develop too much torque on the carriage. To be safe, the idler would fix the problem.

I just checked an example of this rail, using the mjkzz controller, with 625mA drive current, on slowest mode (which I believe is 32 microsteps), I could not cause the rail to stall with perhaps 30lbs of axial force. So most likely there should be no loading or motor torque problem, just still a concern about dynamics and associated carriage torques.

Edited to add: checked the data sheet, and the dynamic load of the KR1501 is 340N (!)

Further Edit to add drawing of KR1501 rail, base plate, idler rail, and carriage plate supporting an Arca rail:



Edit 3: The 1/16" spacer over the idler carriage is an estimate based on published specs. When the carriage plate is installed, it's important to ensure the tops of the carriages are perfectly planar to avoid any residual torques on the two carriages. Add shims or pieces of paper or card stock as needed to bring the surfaces to planar.

[houstontx]

thanks to all of you for this helpful information. the idler rail graphic really helps ray! Planning to use this for a canon 600d with microscope objective. hopefully its light enough. I have a couple massively heavy 12"+ rails, maybe I can use what I learn on this smaller system to get one of them running. thanks

[ray_parkhurst]

thanks to all of you for this helpful information. the idler rail graphic really helps ray! Planning to use this for a canon 600d with microscope objective. hopefully its light enough. I have a couple massively heavy 12"+ rails, maybe I can use what I learn on this smaller system to get one of them running. thanks

With the idler, I'd expect the system to handle well in excess of 20lbs, so should not be an issue.

[viktor j nilsson]

Ray, I really liked your idea for the idler rail so I've ordered a 100mm mgn12h. Thanks for all your helpful suggestions.

[ray_parkhurst]

Well, I went ahead and built a proof of concept of my drawing. I made a few changes:

1) used an 80mm long THK SRS9GM instead of the 100mm long 12mm rail. This forced me to make a 5mm shim instead of a 2mm one. I made a simple square-ish shim that fits between the mounting screws.

2) used 3/8" for the bottom plate instead of 1/4". This was because I had a 3/8" x 1.5" x 12" piece of bar stock available, and it was convenient to cut it into 7" and 5" sections for the bottom and top.

I have a 200mm Arca rail on order and will install when it arrives. For now I hope this encourages folks more than just a drawing.

Ray

[viktor j nilsson]

Looking very good, Ray. Do tell me, what "Arca rail" were you thinking of putting on top? I was thinking a long QR plate, and then a two-sided QR clamp on top. But if you have a nicer solution in mind, I'd love to know.

[ray_parkhurst]

Looking very good, Ray. Do tell me, what "Arca rail" were you thinking of putting on top? I was thinking a long QR plate, and then a two-sided QR clamp on top. But if you have a nicer solution in mind, I'd love to know.

I bought this 200mm rail (I guess it's called a "plate"):

https://www.ebay.com/itm/200MM-Lens-Pla ... 2749.l2649

It will mount rubber damper side down toward the KR15.

I figured a 1-sided clamp on top of this and then the camera/tripod/bellows.

[lothman]

Well, I went ahead and built a proof of concept of my drawing. I made a few changes:

1) used an 80mm long THK SRS9GM instead of the 100mm long 12mm rail. This forced me to make a 5mm shim instead of a 2mm one. I made a simple square-ish shim that fits between the mounting screws.

Why don't you use a THK rail with two ballbeared sledges like the KR2602B (the "B" is for the two sledge model) . OK this version has 2mm pitch but is much stiffer than the smaller versions. So you don't have to bother about alignment but on the other hand loose some of the stroke, since there is an additional sledge in the rail.


Ebay auction for two new KR2602B