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Thread: Blocking cool down time

  1. #1
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    Blocking cool down time

    Hi,

    Can anyone shed some light on their experiences with cooling down lenses after blocking (with alloy)?
    There is some disparity in the answers from every tradesperson I ask. From 5 minutes to 40 minutes is the answers I get.
    I wanted to know if there are any best practices out there.

    Thanks.

  2. #2
    ATO Member HarryChiling's Avatar
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    I lean towards 10min. no ryme or reason, when I worked with alloy this was often how long it took for me to block up a few jobs, so when I finished blocking the first blocked was the first generated so thy all would go about 10min.
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    Quote Originally Posted by HarryChiling View Post
    I lean towards 10min. no ryme or reason, when I worked with alloy this was often how long it took for me to block up a few jobs, so when I finished blocking the first blocked was the first generated so thy all would go about 10min.
    Was there or is there any noticeable discrepancies between the various types of material or blank thickness? Would you say 10 minutes for all lens types (in general)?

    Thanks.

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    ATO Member HarryChiling's Avatar
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    It has been a while, but I do remember that the hi index lenses required a little longer, I would let them sit for aybe 15min. or dunk them in cool water and let them sit for 10 min.
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    Thanks for the reply Harry. Would there be any issues relating to stress withing the lenses if they went from hot to cold?

    It seems that 10 minutes is the norm, but I was wondering if anyone had experimented with anything quicker yet?
    If not, I will do some testing on my side. If anyone is interested in the results they can let me know and I can give them the info.

    Thanks

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    ATO Member HarryChiling's Avatar
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    Quote Originally Posted by Websta View Post
    Thanks for the reply Harry. Would there be any issues relating to stress withing the lenses if they went from hot to cold?

    It seems that 10 minutes is the norm, but I was wondering if anyone had experimented with anything quicker yet?
    If not, I will do some testing on my side. If anyone is interested in the results they can let me know and I can give them the info.

    Thanks
    I remember we did that to help with some of the waves that would be present if we generated before the lens was cool. I don't hink we dunked straight after blocking, but that was almost 5-6 years ago, I'll ask my brother in law as he still works in that lab and let you know.
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    Quote Originally Posted by Websta View Post
    Thanks for the reply Harry. Would there be any issues relating to stress withing the lenses if they went from hot to cold?

    It seems that 10 minutes is the norm, but I was wondering if anyone had experimented with anything quicker yet?
    If not, I will do some testing on my side. If anyone is interested in the results they can let me know and I can give them the info.

    Thanks
    The fastest way to make lenses is to get them correct the first time. Cool 15 minutes. Do not try to distinguish between different powers and materials. If you allow such arbitrary judgments to be made, it is just another place where errors can be made. Play it safe. Train all your folks to wait 15 minutes. Develop a procedure for this.

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    Hi Gemstone,

    Thanks for the reply. What I am trying to do is get a average, and just as you said, I do not want to start making arbitrary judgements which would make it too complex.

    All I wanted to know was whether there have been any experiments with this and what is the norm. We make many types of lenses so I would like to use just one set time for all.

    Cheers

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    Exclamation

    I t is always best, subject to using an efficient cooling plate to wait 15 mins for all materials before generating. This is also based on using a low melting alloy of 117.

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    ATO Member HarryChiling's Avatar
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    We use wax and the wait is 13 minutes, the time for cooling is built into the process. Morning the lenses get blocked and while they are cooling the rest of the equipment is turned on and calibrated/cleaned. Then the first blocked is the first generated.

    It sounds to me like you are trying to get a good feel for how long the average is so that you can adjust your process accordingly. I would agree if it is going to be built into your process 15min or 10min or 30sec in the course of the amount of work done in the day isn't going to mean much in terms of how many more jobs you process, unless you have the same guy running the jobs or you block a number of jos then move to the next step.

    If your lab is larger wait the full 15, if it is smaller with limited staff, you may want to experiment with times, but it would be more headache than it's worth and at most you would shave off 2-3 minutes per job.
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    Many moons ago...

    For 8 years I used alloy with a Semi-Tech Dual Center blocker. We waited a whopping 45 seconds for our alloy to harden (in the chill ring) and the they went right into the 108 (dry cut). It was a decent retail operation and we surfaced around 40 pair per day. No waves, no problems of any kind.
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    The cooler the better.... but I would think 15mins would be more than enough.

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