Hi,

I am doing surface quality studies an want to seal a cnc milled cavity (surface roughness approx Ra 0.8µm) on a new/unused Sika M960 board (1,2g/cm3 density) with S120 sealer.
The laminates shall be of very high surface quality.

1) For this purpose: How many S120 applications do you reccomend? My plan is 4-5. Enough?
2) Referring to "De-Nibbing" a tool making professional explained to me, that he sands tooling boards after every sealer application with gradually decreasing grits from 400 to 1200: Do you reccomend this as well? How long do I have to wait until i can sand a S120 layer? 20min @RT enough? Or better 20min @60°C - The data sheet is a bit unclear here, unfortunately.

Many Thanks
Holger

The number of layers is hard to predict exactly but that does not sound unreasonable. I would follow the process in our recent video on making a pattern which included board sealing.  In essence, we only stopped applying layers once we were happy with the improvement in surface finish and gloss. There is no problem with de-nibbing where necessary.

You can watch the video here: Precision Patterns and Moulds from 3D CAD


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Why do you want to do 4 sanding steps? It's quite unnecessary, you only need to flat it down once and then the wipe on applications go on very nicely.

In my experience, tool sealers get to a point where they stop improving the surface finish, and all you are doing with each additional coat is risking a bit of dust getting in there or accidentally overapplying and causing smears. It can also start to crack if it is applied too heavy, so you really want to do the minimum amount of applications to get the gloss you are after.

I also think that whilst tool sealers are an amazing product - they dont work QUITE as well as you might be hoping. I've used them a lot, spent hours applying and sanding - and while the finish is pretty good, it still isnt at the level of a 10 minute paint job with a good 2k clear coat. 

As hanaldo says, I don't see the need for all the sanding?  You could elevated temperature cure but it might not help the surface finish initially if you don't allow it to touch dry first.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi,

thanks for all the valuable advises. I will then follow your experience and sand only the pre-final coat to de-nib as shown in the video.
Many thanks, Holger

Most dealers need a de nib but not all the grades
Spray application is by far the best way
Marcacote sealer is the best out there at the moment for hand finishing.
With that each coat can be cooked at 60 for 20 mins and onto the next coat
After about 6/8 any block should be fully sealed,bake that then de nib with 1200 an put a nice wet coat on and let it dry naturally,don't force it.
Each sealer is different to give you some idea the chemlease sealer will probably take 10/12 coats before it's ready to de nib an that then will need 3/4 coats to get the final Finnish onto it