Polishing Challenges on Cr.39 LENS

[readyslinks]

Hello Guys,
Please i need someone to bail me out.
I am having issues with a cylinder machine.It tears off the polishing pad very easily even when the pressure is correcly set.How can i wriggle out of this.I am counting on the gurus to save me.
Does Cr.39 Lens need high speed polishing?
Furthermore,without using a baume hyddrometer,how will i know when the polishing solution is weak? On the average,how long does a gallon of polishing solution last.
Thank you guys in advance.
Regards
Okafor

[Jeff Trail]

Are you running a gripper system? or is the pads directly applied to the laps? and dumb question, but I have seen it, you are not putting the polish pad stacked on top of the roughing pad are you, or I saw an office that was "cleaning" the laps and put WD40 on them?? Never know until you ask ... since it is only on the polish side and everything checks out, pins speed and pressure, first thing I would look at is if you got a bad batch of pads, not enough adhesive .... check another roll and make sure it is not the same lot number and try those... in the last few years I see this more and more...

Being able to read your Baume' is a must, I would go ahead and invest in it, in the long run you are going to come out way ahead.. either through saving un-necessary breakage or dumping good polish because you are not sure.. how long it last depends more on use than "age" ..since volume changing constantly?.. well you see my point.

Jeff "been around WAY to long" Trail

[readyslinks]

Hello Jeff,
Thanks for the attempt.I run a gripper system.I also put the polishing pads stacked on top of the roughing pad.
This is the sequence i amploy. I will clean the laps with a similar solution as WD40 (Acetone) to remove the residue of smoothing pad prior to application of smoothing pad.Thereafter,i will wipe the smoothing pad free of any liquid,before stacking the polishing pad directly on the smoothing pad.
I once tried sticking the pad directly on the lap and it still came-off.I am inclined to believe that the adhesive was not properly applied.
Please can i get contact details of a Baume Hydrometer dealer?
Regards

[Jeff Trail]

I do not know how other people are doing it, but I NEVER ever wipe anything down with acetone before application of pad..if you have any residual acetone it will eat up any adhesive on the applied pad.. and WD40 is oil and it is about as far as you can get from acetone (paint thinner)

If you are saturating those grippers with acetone you are going to have a huge mess..those first fine pads should not leave enough adhesive on a gripper to change the curve of the tool, grippers should be changed out when you get rips or parts missing .. I would change my cleaning methods and see if that removes the problem... if you were applying pad directly to lap before and it was slipping sounds like a "process issue" more than a defect, more so if you tried some multiple lots of pads ....
Another issue that maybe worth checking is when you bounced back and forth from gripper to non gripper did you adjust your cutting to allow for compensation?

you can contact about and surface manufactering company (LOH/GerberCoburn etc., etc.) and get a baume' kit..

Jeff "grind'em til the yell" Trail

[albednar]

This feels a bit confusing to me. First and foremost, if you are using a "base pad system", you should be on one of the newer generation vinyl materials. If you are still on the older grit style drive pad, this can cause some contamination issues with the particles breaking loose. As you initially stated, if the polish pad is tearing off, is this during the polishing process or after during standard removal?

I would never apply a polish pad on top of the smoothing (fining pad). By doing so, you will be flattening the radius of curvature resulting in minus lenses that are weak and plus lenses that are strong. Always apply the polish pad directly on top of the "base pad". If they are slipping off, can you verify that the pads you are using are designed for a base pad system or for bare lap tools?

The rule of thumb for polish life is between 350 to 400 lenses per gallon. Baume is a great indicator of solids suspended in the slurry, but somtimes this reading will also be affected by pad nap etc.

Al Bednar