Go Back   IceInSpace > Equipment > ATM and DIY Projects

Reply
 
Thread Tools Rate Thread
  #121  
Old 30-06-2018, 04:12 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
I'm having issues with 12micron - it is EXTREMELY sticky, like, hard to move! What is the issue here?!
Reply With Quote
  #122  
Old 30-06-2018, 05:28 PM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
Quote:
Originally Posted by Lognic04 View Post
I'm having issues with 12micron - it is EXTREMELY sticky, like, hard to move! What is the issue here?!
It sounds like you are adding too much grit and not enough water. It should be quite runny, the consistency of water. Try mixing it up in a squeeze bottle - eg old shampoo bottle and add a dash of detergent. Squirt it on the mirror and then lightly run your clean fingers through it to check for sharp bits.

If you look at the start of this video, you'll see how runny it is:

https://m.youtube.com/watch?v=noBWSeozpkI

A fine grinding wet should last 5 minutes or more.

Rod
Reply With Quote
  #123  
Old 30-06-2018, 05:51 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
Thanks Rod, that fixed it!
However, it still loves to hug one particular edge region. Any ideas as to why this occurs?
Reply With Quote
  #124  
Old 30-06-2018, 06:30 PM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
It may be drying out in that area. Add a little more of the mixture and see if that helps. Don’t force it when grinding. Be gentle.

Rod
Reply With Quote
  #125  
Old 30-06-2018, 06:36 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
It is like that from the start however?
Reply With Quote
  #126  
Old 30-06-2018, 06:43 PM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
Maybe do a sharpie test just to make sure the tool and mirror are well matched. Use a felt tip pen.
Reply With Quote
  #127  
Old 30-06-2018, 06:50 PM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
Also try adding a little more grit to the mixture
Reply With Quote
  #128  
Old 01-07-2018, 11:02 AM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
I feel it might be best to skip directly to polishing at this stage as I am having sticking issues. I will use polishing pads so the time spent will be marginally different from 12 to 5 micron. Should I skip?
Reply With Quote
  #129  
Old 01-07-2018, 02:05 PM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
Hi Logan

I don't like the idea of jumping to polishing before we know what's going on. You will be polishing for a long time, even with pads and if you have a problem where the mirror and tool are not spherical it just wastes time. I would prefer to at least finish with 9 micron and preferably 5.

I would really like to be sure your mirror and tool are properly mated. That's why I suggest the sharpie test as described on the stellafane site.

My other theory is that you may have now added too little aluminium oxide to the water. That would cause it to grab. Make the mixture a little richer and see if that changes things.

Perhaps you could post a video of what you are doing somewhere. That might make it easier to spot the problem.

Rod.
Reply With Quote
  #130  
Old 01-07-2018, 02:11 PM
Billyboy78 (Bill)
Registered User

Billyboy78 is offline
 
Join Date: May 2018
Location: CRESTMEAD Brisbane
Posts: 103
If you have sufficient lube, as in watery grit, then the only reason they will stick is that the discs aren't matched up perfectly from rough grinding. Possibly they match up COC and thus you get a good sharpie test, but trying to move off centre air can't get in as they mis-match and a vacuum is formed locking everything up.

You have 3 options, go back to 25 micron and grind slowly and carefully aiming for 100% match, persevere with 12 micron, it will eventually come good, or put a flash polish on the mirror and do a KE test to see where you're at.
Reply With Quote
  #131  
Old 01-07-2018, 02:16 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
Maybe I could try channelling the tool? It has absolutely no gaps so that could be a problem. I will also add grit, see if this continues and if it does post a video
Reply With Quote
  #132  
Old 01-07-2018, 03:29 PM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
Hi Logan

Don't try channeling the tool at this point. It's only going to invite scratches. Plenty of people make telescope mirrors with a glass blank as the tool - no channels.

Remember to try the easiest solutions first. Vary the mix a bit as discussed. See if that helps. Try a sharpie test. It's easy to do.

When you have done the above report back and then we can discuss what to do or try next.

Rod
Reply With Quote
  #133  
Old 05-07-2018, 03:35 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
About to shellac and begin polishing! Yes only after 12u, as Mark (from ASV) said that it would be best. By the way, the sticking is pretty much gone after letting it sit for a few days and i presume thermally equalise.
Reply With Quote
  #134  
Old 05-07-2018, 07:10 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
Polishing pads on! And so begins the 3rd and final part of mirror making!
Reply With Quote
  #135  
Old 07-07-2018, 02:32 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
Polishing is going well!
Reply With Quote
  #136  
Old 19-07-2018, 12:52 PM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
Forgot Stefan was watching this!!!
Did polishing with the pads for 6 or so hours and I realised fine grinding wasn't done, so I went back to 12,9,5 and then begin polishing again, by the way, I am 2hr 20 mins in and have already a beautiful shine across the entire mirror and the edge is near invisible! If I am not pouring the lap at the asv i will be finishing Polishing on the awesome spinny machine
Reply With Quote
  #137  
Old 20-07-2018, 08:35 AM
Stefan Buda
Registered User

Stefan Buda is offline
 
Join Date: Jul 2013
Location: Melbourne, VIC
Posts: 823
I give you another 6 weeks before I re-join the race.


You may not realize that you are only about half way trough this job. By far the hardest part is still ahead of you.
Reply With Quote
  #138  
Old 30-07-2018, 07:04 AM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
29 jul
begin figuring
1hr COC to reduce ring

1hr blending, ring nearly gone, bad tde

diagnosis tot short strokes

20min tde tot edge improved, slightly oblate
diagnosis mot tde strokes

Just chucking my log here.
Reply With Quote
  #139  
Old 20-08-2018, 06:22 AM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
HA! I beat you Stefan!
I just finished my mirror at 1/10 wave p-v, 0.98 strehl!
Attached Thumbnails
Click for full-size image (IMG_20180819_210415_008.jpg)
171.2 KB72 views
Reply With Quote
  #140  
Old 20-08-2018, 06:22 AM
Lognic04's Avatar
Lognic04 (Logan)
Registered User

Lognic04 is offline
 
Join Date: Mar 2016
Location: Melbourne, VIC
Posts: 889
Thanks for all your help everyone! What a fun journey!
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 07:54 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement