The dreaded dimples

[ChaddingtonBear]

Hello,
I’ve recently started working at a new pressing plant in the UK.

I’m currently having issues with dimples on the records after pressing.

I’ve read a few related topics on here and understand that it’s a common issue.
Could it be from the way i’m currently cleaning the stamper/moulds that is causing this??

The most baffling part is, there is nothing visible on the moulds before I put the stamper on..I’ll press a few off and there they are!
I’ll take the stamper off to clean it all again and visibly notice ‘bits’ on the moulds.

Could anybody share some tips and give some insight on this that I may be overlooking

Cheers
Matt

[Ketaman]

Could be worth cleaning the back of the stamper with a scotch brite pad to remove any nubs if there are any. Check that the moulds are smooth, no damage or rusty spots. Otherwise its most likely dust between the stamper and the the mould. You need to be a bit more vigilant with cleaning, perhaps use a bright light at an angle to look across the moulds and stampers before you put them together. A microfibre cloth wet with acetone works well to clean the moulds and stampers...

[ChaddingtonBear]

I’d say I’m pretty vigilant when it comes to cleaning the moulds and stampers (I’m already doing everything you mentioned!)

I read a post that mentioned about using an air gun and silicone towels, have you ever tried this method?
Also Is there any benefit to using alcohol instead of acetone?

Thanks

[bluesprocket]

Our guys have gone through a few different variations to reduce pockmarks. We ended up getting small vacuums that the crew uses to go over the molds before mounting the stampers. The natural static charge generated by the vacuum also helps to pull small dust particles out of the press. Give it a shot, and see if it helps.

-Chris

[Aussie0zborn]

You have foreign particles between the mould and the stamper and these will leave an impression on the disc or you have "nickel knobs" on the back of the stamper which were not polished out when the stamper was back sanded.

Nothing new about using compressed air but it must be filtered close to the point of use. Say 0.3µm filter.
Clean the mould and the back of the stamper with a solvent so that it evaporates.
Blow any muck off with compressed air. Put the stamper on the mould quickly before any dust can settle back onto the mould.
Keep the press around the mould area super clean.

Always leave a stamper on the mould until its time for a stamper change. If the press is not used for two days, the stamper still stays there. The mould is never left exposed to free air.

Dimples in the pressing are a red flag and a bad look for the record pressing plant. And if you have the word "vinyl" in your business name or you offer "vinyl pressing" rather than "record pressing", then it just proves my point that its a newbie business and still needs time to find its feet so its best avoided.

[llary]

Are you 100% sure there is no contamination in the extruder/hopper? If stampers are scrupulously cleaned and you are getting pockmarks on both sides that get worse the more you press it's probably contamination of the extrusion.

[Aitchy]

Acetone wipe the mold and back of stamper, then wipe the mold once with a tack cloth. Then wipe back of stamper with tack cloth and finally hit the mold with tack cloth once again before immediately putting on the stamper.

I find it useful to use a light to illuminate the molds so you can see any fine pieces of dust. Also if you look along the surface of the mold at eye level it’s easier to spot dust.

It kinda sounds maybe like you need to clean out the centrepin area.. sometimes at our plant we can have stockmarks appear mid run after a perfect application. This is usually due to pvc and other crud displacing from around the centre pin area and getting under the stamper.