www.photomacrography.net :: View topic - Sr-90 P MJkzz not worth it
www.photomacrography.net Forum Index
An online community dedicated to the practices of photomacrography, close-up and macro photography, and photomicrography.
Photomacrography Front Page Amateurmicrography Front Page
Old Forums/Galleries
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Sr-90 P MJkzz not worth it
Goto page Previous  1, 2
 
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> General Discussion Forum and Community Announcements
View previous topic :: View next topic  
Author Message
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 19327
Location: Richland, Washington State, USA

PostPosted: Sat Jul 21, 2018 3:03 pm    Post subject: Reply with quote

Speaking as the only Admin currently online, I am choosing to let this thread remain open for further posting.

However, I strongly advise all participants to take a deep breath, perhaps a long walk, and think carefully before posting.

Postings written while upset seldom end up looking good in the long run.

--Rik
Back to top
View user's profile Send private message Visit poster's website
ray_parkhurst



Joined: 20 Nov 2010
Posts: 1700
Location: Santa Clara, CA, USA

PostPosted: Sat Jul 21, 2018 3:15 pm    Post subject: Reply with quote

I'm hoping the moderators will simply delete this thread for the good of the community.

Edited to add...Hmm, saw Rik's post AFTER I posted this.
Back to top
View user's profile Send private message Visit poster's website
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 19327
Location: Richland, Washington State, USA

PostPosted: Sat Jul 21, 2018 5:52 pm    Post subject: Reply with quote

ray_parkhurst wrote:
Hmm, saw Rik's post AFTER I posted this.

Yeah, bummer about the posting count, putting mine on the top of the second page where it was easy to miss. I thought about editing the last post on the first page, to include a warning to read to the end of the thread before posting. But then on second thought I figured the thread might be more interesting if I left it easy to not do that. That part seems to be working fine. Wink

As for the rest of the thread, this does not strike me as a situation that requires sudden and unilateral action. It's clear that there's some contention, but equally clear that people are still taking the time to read what other people wrote, and to respond with more reason than emotion. Atypical as this thread is for photomacrography.net, it's still notably more collegial than the comments section of pretty much any current news article.

--Rik
Back to top
View user's profile Send private message Visit poster's website
Nestor



Joined: 18 Jun 2018
Posts: 7

PostPosted: Sun Jul 22, 2018 11:25 am    Post subject: Reply with quote

I would like to comment that I have not told my experience here to argue with Peter. Comment also that the order came at the time without breaks or bumps of the package as seen in the photo I send.

https://farm2.staticflickr.com/1769/42667613465_ffc1f149cd_k.jpg20180608_143611 by Nestor yanes, en Flickr
 I'm not really interested in losing more time than I've already lost.
As Mike says, I want my experience to serve someone in addition to transmitting the solution that I finally found, which has helped me to make the SR-90 P moderately operational, at least until stacks do not exceed 12 x. Beyond those magnifications I think it is not operational. I just had to try replacing the skate and rail of recognized brand such as Hiwin. Anyway, I do not know if I'm interested in continuing to modify the SR-90 P since I have a SKK 20 from THK. Perhaps the best thing would be to abandon the SR 90 P and invest in the SKR 20.
This is the store where I bought the skate and the rail:

https://www.aliexpress.com/item/MR9-9mm-linear-rail-guide-1pcs-MGN9-L-400mm-with-mini-1pcs-MGN9H-linear-block-miniature/32665279486.html?spm= a219c.10010108.1000016.1.20773926VgdFcr & isOrigTitle = true

The only recommendation is to loosen the screw nut slightly so that the assembly moves smoothly.

regards
Nestor
_________________
Tenerife ( CANARY ISLAND-SPAIN)
Back to top
View user's profile Send private message
ray_parkhurst



Joined: 20 Nov 2010
Posts: 1700
Location: Santa Clara, CA, USA

PostPosted: Sun Jul 22, 2018 3:04 pm    Post subject: Reply with quote

Well, since this thread still continues on, I decided to view the videos. The amount of movement I see is utterly unprecendented. I have never seen a linear bearing have anywhere near that much movement...actually, never seen one with any movement at all. And similar movement in the screw carriage is doubly-perplexing. Only way I can see this much movement could occur is if the ball bearings in the linear bearing, and the acme nut in the carriage, had been removed.
Back to top
View user's profile Send private message Visit poster's website
mawyatt



Joined: 22 Aug 2013
Posts: 1626
Location: Clearwater

PostPosted: Sun Jul 22, 2018 4:15 pm    Post subject: Reply with quote

Nestor,

The shipping packing looks OK, except could use a little more packing on the ends of the black aluminum extrusions. The rail looks very well protected, and everything seems to have arrived intact.

Maybe you could post a video of the rail now that you've replaced the components in question, so a comparison can be made.

Ray,

I quickly checked by just twisting by hand all my rails. With the Stackshot, Wemacro and SR-90 and I do feel some slight movement, but nothing like what the video shows.

So maybe a rogue skate on the rail, that somehow got by Quality Inspection??

Best,
_________________
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike
Back to top
View user's profile Send private message
ray_parkhurst



Joined: 20 Nov 2010
Posts: 1700
Location: Santa Clara, CA, USA

PostPosted: Sun Jul 22, 2018 4:43 pm    Post subject: Reply with quote

mawyatt wrote:
Nestor,

The shipping packing looks OK, except could use a little more packing on the ends of the black aluminum extrusions. The rail looks very well protected, and everything seems to have arrived intact.

Maybe you could post a video of the rail now that you've replaced the components in question, so a comparison can be made.

Ray,

I quickly checked by just twisting by hand all my rails. With the Stackshot, Wemacro and SR-90 and I do feel some slight movement, but nothing like what the video shows.

So maybe a rogue skate on the rail, that somehow got by Quality Inspection??

Best,


I think the Stackshot and WeMacro use similar principle of dual-rail with bushings. There is a natural (though small) amount of movement due to the lack of preloading in this type of bearing. I was not familiar with the SR90 before this thread, but it appears it uses a ball bearing linear rail, which is essentially a smaller version of that used on a THK KR rail. The distance between the ball bearing surfaces is of course much smaller than the THK type, but in principle a properly-working rail like this will give almost zero movement within its torque rating due to the preloading in the assembly. So either there is something wrong with the rail, or the torque rating is being exceeded.

This does not address the carriage movement, which in my mind is not possible if the construction is as I imagine, unless something is loose or missing.
Back to top
View user's profile Send private message Visit poster's website
Nestor



Joined: 18 Jun 2018
Posts: 7

PostPosted: Mon Jul 23, 2018 6:58 am    Post subject: Reply with quote

ray_parkhurst wrote:
mawyatt wrote:
Nestor,

The shipping packing looks OK, except could use a little more packing on the ends of the black aluminum extrusions. The rail looks very well protected, and everything seems to have arrived intact.

Maybe you could post a video of the rail now that you've replaced the components in question, so a comparison can be made.

Ray,

I quickly checked by just twisting by hand all my rails. With the Stackshot, Wemacro and SR-90 and I do feel some slight movement, but nothing like what the video shows.

So maybe a rogue skate on the rail, that somehow got by Quality Inspection??

Best,


I think the Stackshot and WeMacro use similar principle of dual-rail with bushings. There is a natural (though small) amount of movement due to the lack of preloading in this type of bearing. I was not familiar with the SR90 before this thread, but it appears it uses a ball bearing linear rail, which is essentially a smaller version of that used on a THK KR rail. The distance between the ball bearing surfaces is of course much smaller than the THK type, but in principle a properly-working rail like this will give almost zero movement within its torque rating due to the preloading in the assembly. So either there is something wrong with the rail, or the torque rating is being exceeded.

This does not address the carriage movement, which in my mind is not possible if the construction is as I imagine, unless something is loose or missing.


Hi Ray,

As you can see in the pictures, the MGN skate has nothing to do with the SK 20, 26 ... The first ones have a single row of balls on each side and the second ones have two rows of balls on each side.
In addition to the above the spindle nut is simply a nut machined with the same thread pitch on the screw and that of the SR 20, 26, ... takes balls inside.
descarga by Nestor yanes, en Flickr

images by Nestor yanes, en Flickr

sr 20 by Nestor yanes, en Flickr




regards

Néstor
_________________
Tenerife ( CANARY ISLAND-SPAIN)
Back to top
View user's profile Send private message
ray_parkhurst



Joined: 20 Nov 2010
Posts: 1700
Location: Santa Clara, CA, USA

PostPosted: Mon Jul 23, 2018 7:34 am    Post subject: Reply with quote

Nestor wrote:


Hi Ray,

As you can see in the pictures, the MGN skate has nothing to do with the SK 20, 26 ... The first ones have a single row of balls on each side and the second ones have two rows of balls on each side.
In addition to the above the spindle nut is simply a nut machined with the same thread pitch on the screw and that of the SR 20, 26, ... takes balls inside.

Néstor


Actually, it has everything to do with it. On their skates, both use dual-row, preloaded, infinite loop ball bearings on each side to eliminate the "play". The amount of play seen in the video could not happen if the ball bearings were in place and making proper contact.

The carriage on the KR series also uses ball screws, while I believe all 3 of the WeMacro, StackShot, and SR-90 use acme screws. The ball screws give a more precision (preloaded) contact, with essentially zero backlash, while the small amount of play in the acme screw allows a bit of backlash depending on the quality of the machining. However, an acme screw won't allow the amount of movement shown in your video, so the most likely explanation is the acme nut was not properly bolted down within the carriage assembly.
Back to top
View user's profile Send private message Visit poster's website
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 19327
Location: Richland, Washington State, USA

PostPosted: Mon Jul 23, 2018 8:49 am    Post subject: Reply with quote

Just thought I'd mention that Admin is continuing to watch this thread.

The addition of constructive content, as in the last few posts, is very welcome.

Our current thinking is to restructure the material at some later time, to separate various aspects in whatever way seems to produce the most useful record.

Until then, please continue the discussion. Thanks for your thoughtful participation!

--Rik
Back to top
View user's profile Send private message Visit poster's website
mawyatt



Joined: 22 Aug 2013
Posts: 1626
Location: Clearwater

PostPosted: Mon Jul 23, 2018 9:01 am    Post subject: Reply with quote

Ray,

The preloaded ball bearing skates and nut certainly explains why the THK rails have almost no apparent backlash nor wobble.

I knew they were good from experience (not speculation), but didn't know exactly why, so thanks for pointing this out Very Happy

Best,
_________________
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> General Discussion Forum and Community Announcements All times are GMT - 7 Hours
Goto page Previous  1, 2
Page 2 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group