THK KR15 cheap on eBay

[JohnyM]

Well, my pair will (hopefully) turn into microscope stage
I find 30mm travel too small for anything else than micro (mine starts from 10x)

JohnyM...same question for you...any update? ...Ray

Attempt to adapt them to microscope stage proved to be a disaster. Instead i moved them to XYZ horizontal rig project. WIP ~75% done.

[mawyatt]

Well, my pair will (hopefully) turn into microscope stage
I find 30mm travel too small for anything else than micro (mine starts from 10x)

JohnyM...same question for you...any update? ...Ray

Attempt to adapt them to microscope stage proved to be a disaster. Instead i moved them to XYZ horizontal rig project. WIP ~75% done.

Johny, Victor,

I'm going to use two KR20 rails cross coupled same as KR15, for the longer travel (70mm vs 30mm)mm). These have the same long ARCA clamp on the back of the lower KR20 so you can simply slide out the 30mm travel KR15 cross coupled set and slide in the 70mm travel KR20 cross coupled set. The top KR20 has a plate with the 1/4-20 threaded holes so easy to attach the usual subject fixtures.

I have the KR20 rail range and NEMA 17 motor parameters available (have all my rails & motor parameters available); range, thread pitch, current, step size, resistance, inductance, speed, acceleration and so on, to activate with the Experimental S&S controller. So it's just a matter of selecting the correct rail and motor pair for each axis and start the session.

Would have been nice if these little KR15s had a longer travel than 30mm, but can't complain, wish I had a couple more!! They are so quite I can't tell if they are moving unless I look at the stage, the KR20 are more noisy tho. This might partially be attributed to the NEMA 11 motors, which are a higher quality than the NEMA 17 motors I have on the KR20.

Maybe someone can comment on this noise effects relative to the different stepper motor characteristics, do the higher quality motors produce less noise and have less resonate effects? There's a new controller out that has a "Silent Mode" which is using a clever and patented control algorithm based upon spreading the harmonic distribution of the PWM motor drive signals. The claims are reduced motor noise and less motor/rail resonate effects. This is very much like what we do with "noise spreading" coding for various advanced electronic systems & chips, clever use of these techniques indeed!!

Best,

[ray_parkhurst]

Well, my pair will (hopefully) turn into microscope stage
I find 30mm travel too small for anything else than micro (mine starts from 10x)

JohnyM...same question for you...any update? ...Ray

Attempt to adapt them to microscope stage proved to be a disaster. Instead i moved them to XYZ horizontal rig project. WIP ~75% done.

Johny, Victor,

I'm going to use two KR20 rails cross coupled same as KR15, for the longer travel (70mm vs 30mm)mm). These have the same long ARCA clamp on the back of the lower KR20 so you can simply slide out the 30mm travel KR15 cross coupled set and slide in the 70mm travel KR20 cross coupled set. The top KR20 has a plate with the 1/4-20 threaded holes so easy to attach the usual subject fixtures.

I have the KR20 rail range and NEMA 17 motor parameters available (have all my rails & motor parameters available); range, thread pitch, current, step size, resistance, inductance, speed, acceleration and so on, to activate with the Experimental S&S controller. So it's just a matter of selecting the correct rail and motor pair for each axis and start the session.

Would have been nice if these little KR15s had a longer travel than 30mm, but can't complain, wish I had a couple more!! They are so quite I can't tell if they are moving unless I look at the stage, the KR20 are more noisy tho. This might partially be attributed to the NEMA 11 motors, which are a higher quality than the NEMA 17 motors I have on the KR20.

Maybe someone can comment on this noise effects relative to the different stepper motor characteristics, do the higher quality motors produce less noise and have less resonate effects? There's a new controller out that has a "Silent Mode" which is using a clever and patented control algorithm based upon spreading the harmonic distribution of the PWM motor drive signals. The claims are reduced motor noise and less motor/rail resonate effects. This is very much like what we do with "noise spreading" coding for various advanced electronic systems & chips, clever use of these techniques indeed!!

Best,

From my understanding, by reducing the permanent magnet fraction of the "hybrid" design, things like motor noise and microstep accuracy are improved, while torques are reduced. The noise spreading algos are needed mostly for the high power motors which need such tricks to reduce vibration. Low power motors like the ones coupled with fine-pitch rails like on the KR15's tend toward having improved noise and accuracy.

[mawyatt]

Ray,

The stepper controller I was referencing is the German Trinamic TMC5160, there's a couple videos online showing the features.

Best,

[ray_parkhurst]

Ray,

The stepper controller I was referencing is the German Trinamic TMC5160, there's a couple videos online showing the features.

Best,

Yeah, Trinamic drivers have implemented such features for quite some time. I have a bunch of the drivers and USB-RS232 controllers waiting for me to put them together and get them working. I was heading down that path, using Helicon Remote (which interfaces well with Trinamic), when I changed direction and went with the mjkzz/WeMacro/StackShot controllers. The Trinamics, while beautifully engineered, will probably languish in a box.

[viktor j nilsson]

Looking very good, Ray. I must have missed the thread about your bellows, must check that out. I have one of those huge old Pentacon M42 bellows. In general I'm ok with it, but the front leg protrudes so far forwards that I sometimes bump into my xyz specimen holder. I'll probably change it for something else at some point.

My project is slowly moving forward. Got the controller and complementary motor cable from Mjkzz yesterday (thanks Peter!). The KR15 arrived a week ago. It is indeed very small, but with a very nice, solid feel to it. Still waiting for the linear guide rail from China. But in the meantime I'll try to get the KR15 operational.

Viktor...do you have an update on the KR15 system? Or did you publish in another thread? I'm curious how it turned out...Ray

It's moving forward, but grindingly slow with two kids and little spare time. Over Christmas, I used my father-in-laws' drill press to drill and tap all the holes in the adapter plates. I then realized, however, that my M3 screws had too high heads for the KR15 (as mentioned by mawyatt, so I haven't put it all together yet. I should get the low-profile ones this week however.

Got my low profile screws today, and here's where it's at right now:



Adapter plates works well, the connection is about as straight and flat as I might have hoped. Will countersink the top bolts later. Edit: I'll also try to find a slightly thinner shim than the steel washer that's currently there. As you see, it's tilting a bit.


However... Something bad just happened. When I started running the rail back and forth to make sure the connection with the idler rail was true, I started hearing a scrunching noise every turn of the lead screw. However, only when running it in reverse. At first I just heard it occasionally along the lead screw, but then it started to be audible as soon as I ran it in reverse. Then it suddenly disappeared, but reappeared again. Now it's there as soon as I run it in reverse and I don't want to run it anymore for fear of destroying it.

Before, I could easily turn the stepper motor smoothly with my finger, but now there's district, uneven, gritty resistance.

It's not friction from the idler rail. I disconnected everything and tried with only the KR15, still that schrunch, scrunch, scrunch.

I believe something has gotten into the linear bearing assembly. Possibly a aluminum chip that got stuck on the adapter plate?

I'm freaking out a little. How worried should I be? Should I disassemble and clean?

[mawyatt]

Viktor,

I would try and inspect the rail with a magnifying glass headset and carefully clean it from any debris. You might remove the motor and rotate the shaft by hand to see if you can feel anything without the motor clogs involved.

Taking these apart might be difficult, I've never done that.

Hope it's not something in the bearings, suspect they are quite delicate. Wish I could provide more help, but try cleaning first.

BTW, really nice setup!!!

Good luck and keep us posted.

Best,

[viktor j nilsson]

From "Precautions on Handling LM Guide Actuator Model KR":

- Do not disassemble the product.
- Recommended greases KR15 : THK AFF grease
- Entry of foreign material may cause damage to the ball circulating path or functional loss. Prevent foreign material, such as dust or chips, from
entering the system.
- If foreign material, such as dirt or chips, penetrates the system, replenish the lubricant after cleaning the product. For available types of
cleaning fluid, contact THK

Looking at a diagram of the ball cage, I ain't gonna disassemble it, that's for sure.

Cleaning: any tips on getting a foreign object out of the ball cage? I wonder if the grease might just helps keep it in there. Should I use a cleaning fluid to clean off the grease first?

I've read some people recommend purging KR20 rails with new grease through the grease nippel, but the KR15 doesn't seem to have a grease nippel?

Re-lubricating: THK recommends THK AFF grease, which is a light synthetic lithium grease.

You think I could just use white lithium grease instead? What do others use on theirs?

[viktor j nilsson]

Here's a heretic thought. If something got in there, it's going to be aluminum. Are the ball bearings really that delicate? I'm thinking that sooner or later that little aluminum chip will wear down from contact with the much harder steel lead screw and steel bearings. What if I just kept going? It already feels better after moving it by hand a bit to feel what it feels like.

[viktor j nilsson]

Quick update.

Cleaned the lead screw under the stereo microscope. I actually found a tiny piece of aluminum that was entirely flat, I believe that it was not there at first but came out from the ball bearing cage.

'The crunch' is still there, though.

The crunch is only felt when a certain part of the lead screw is located between the 1 o' clock position and the 12 o' clock position, and only when run in reverse.

The stepper motor easily moves through this area of increased friction when set at 1A power. I tried to decrease the power. Worked fine at 0.625mA. At powers at and below 500mA, however, the increased friction caused the motor to stall.

Disconnecting the controller and moving the screw by hand, it is easy to tell where the crunch is; the screw is no longer easy to move but requires a little bit of force.

I think I'll just keep using it and see how it works out. Since it is only felt in reverse and only over 1/12 of a turn (approx.), I doubt that it will have much if any effect on focus stepping.

I also found a perfect spacer between the top plate and the idler rail plate. An older, Danish 50 Öre coin that I had lying in a drawer. Sorry Ray, no time for coin images right now.

Still appreciate thoughts on lubrication.

[viktor j nilsson]

Would have been nice if these little KR15s had a longer travel than 30mm, but can't complain, wish I had a couple more!! They are so quite I can't tell if they are moving unless I look at the stage, the KR20 are more noisy tho. This might partially be attributed to the NEMA 11 motors, which are a higher quality than the NEMA 17 motors I have on the KR20. Best,

Is your KR15 also this silent when running it continously from end to end? Mine gives out a slightly annoying high-pitched sound when doing so, but I have nothing to compare it since I've never used any other linear rails and stepper motors.

Edit: accidentally attributed this quote to Ray. Corrected now.

[viktor j nilsson]

I'll keep the monologue going...

After cleaning as best I could, I applied some CRC Multi Grease, an all-purpose Lithium grease with a base oil viscosityof 155 mm2/s at 40°C, fairly close to the THK AFF viscosity of 100mm2/s. The biggest difference is that the CRC multi grease is mineral based, vs synthetic for the THK. Don't think it'll make a difference for hobby use. For reference, THK recommends a grease with a viscosity of 25 mm2/s for the KR20. I simply applied it to the lead screw and worked it in. The ball cage ate it all up, which makes me think it was almost empty of grease before.

Long story short: the crunch sound is comptely gone. The rail is moving smoothly. I am happy.

I'm waiting for my Thorlabs breadboard, but soon I'll have this thing up and running!

[pbraub]

Viktor,

thank you for keeping the monologue going. These are the kind of threads I often refer to when planning a project such as yours.

Kind regards
Peter

[mawyatt]

Would have been nice if these little KR15s had a longer travel than 30mm, but can't complain, wish I had a couple more!! They are so quite I can't tell if they are moving unless I look at the stage, the KR20 are more noisy tho. This might partially be attributed to the NEMA 11 motors, which are a higher quality than the NEMA 17 motors I have on the KR20. Best,

Is your KR15 also this silent when running it continously from end to end? Mine gives out a slightly annoying high-pitched sound when doing so, but I have nothing to compare it since I've never used any other linear rails and stepper motors.

Edit: accidentally attributed this quote to Ray. Corrected now.

Viktor,

The high pitch sound might be the controller/motor effects, I've heard this often with my Stackshot & Wemacro rails, but not so much with the THK. The sounds is likely from the controller PWM rate and motor/coil/mount resonances. You can try and change the motor supply voltage, step size and motor current to try and extinguish the sound. If your controller allows, you could change the PWM rate or characteristics.

The KR15s I have are absolutely quite with the Pololu controller, the KR20 are little more noisy though.

Great news on the lube eliminating the binding. I should probably lube the THK rails, since I have no idea on their prior service life. On thing that might be considered is if the mineral based lube might attack the seals, since THK specifies a synthetic lube?

BTW if enough folks are interested maybe we should all get together and develop a controller based upon the Trinamic TMC5160, this controller has a "Stealth Mode" which is effective at reducing resonances and motor noise. It would be prefect for our macro focus rails I believe.

Best,

[ray_parkhurst]

Wow, quite a saga viktor! Luckily the lubrication fixed the problem.

I am concerned about the tilt in the connection between the KR15 and the idler rail. It looks like you just need a bit of extra space above the KR15 mount. I'd suggest the following procedure:

1) remove the screws from the KR15
2) tighten the screws fully on the idler rail
3) note the spacing between aluminum cross bar and KR15 mount
4) slide the idler rail along its full length to ensure a consistent spacing
5) add pieces of card stock until you feel a strong interference fit
6) cut the appropriate pieces of card stock a bit bigger than KR15 mount
7) punch holes in card stock shims to allow for screws
8) install card stock shims and screw system together

If you need more than 4 or 5 pieces of card stock, you will probably need to adjust the thickness of the shim on the idler, but in any event this will fix the problem for short term.

It's really bad for both the KR15 and the idler to run them with significant torques that are being produced by the non-coplanar cross bar.

Edited to add: funny that my number 8 above was interpreted as an emoji.