Glowforge lens with spots - how to get through a project before you MUST replace the lens

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OMG it does get worse, yes the logo on the top is used for focussing - no that has nothing to do with it not cutting on one side (which is almost certainly a dirty len - clean it with a Zeiss wipe)

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NO NO NO NONO NO!!!! The surface that is being cleaned with the abrasive is actually an optical coating - all you are doing is abrading this coating. Just bloody clean the thing with a Zeiss wipe and clean it often (every few hours of cutting)

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OK, this is probably one of the most misguided and misleading glowforge videos I have ever seen.