Stern Thincoat - Dimples & Craters

[c_mario]

I bought a replacement playfield for STTNG from Mirco from Germany and it dimpled as well. I thought it was normal. Metal ball dropping on wooden substrate must cause some damage. Anyone know what specific brand of clear coat is being used by the professionals mentioned in this post. I have done a few myself with Upol brand 2K clear.

[robm]

It appears from martyj pics that it is not happening on the inserts...so maybe the softer timber is the weakest point?

[MartyJ]

I couldn't see any on inserts which I photographed.

I did read a couple of interesting posts on Pinside about the great dimple debate https://pinside.com/pinball/forum/topic/playfield-dimple-reality-check

It shows some photographs of Bally/Wms games with similar issues, albeit different photographs so hard to exactly compare.

I guess it is harder to notice on the older machines, due to use.  I guess for those of us who buy NIB and fold out nearly $10k are picky and closely inspecting every inch of the machine over and over.

I guess if you're concerned, buy a spare playfield, go the ceramic HRP treatment and be happy!

[GORGAR 1]

I think most are happy even without buying a spare PF :) I am and can't wait to play it :)

[andypinboy]

It appears from martyj pics that it is not happening on the inserts...so maybe the softer timber is the weakest point?

+1

I think there is large variance in the Stern playfields. Only an educated guess but Nino's TWD issue seems to be the clear-coat. Big dimples on top of inserts has to rule out the plywood as the primary cause. Not necessarily too thin - but definitely not hard enough (either the product or manufacturing conditions/curing time). Martyj's could well be softish plywood. Some owners seem to have no issues at all (or say they don't). Perhaps it comes down to the playfield & the day it's produced. I would not be happy with Nino's TWD playfield - it seems extreme to me. However, given all the reports of dimpling I'm bracing myself to expect severe dimpling in the 1st new Stern I buy. The big qn is whether to buy an additional playfield as a backup. Is it worth it come resale time?

[Pop Bumper Pete]

Some people on pinside let their NIB stern so for six months before playing them, to give the clear time to cure

The clear is cured when you cannot smell it

[oldskool1969]

Look at the NIPPLES on this play field!


Sorry, sorry you wanted to know about DIMPLES 

[Strangeways]

It appears from martyj pics that it is not happening on the inserts...so maybe the softer timber is the weakest point?

There are some inserts with dimpling, however, not deep depressions or craters as on timber areas. Another anomaly we found today was serious "orange peel" in the top RH corner where the rollover are located - further proof that this playfield's clear is way too thin.

I spent some time testing the clearcoat theory - "Pinball Mythbusters" ? I took the exact ball out of TWD LE and I dropped it on several playfields in my factory.

To ensure the testing was fair, I placed a flipper bat on four other playfields - all clearcoated - in an area that is not really seen and has no prior wear or damage. I placed TWD LE ball on the top of the bat, and allowed it to drop on the playfields. Here are the results ;

Genie - Ball drop under apron area - Nothing. Perfect - Admittedly - this is a very thick clear. Tried several times. Can't get any reaction.
T2 - Ball drop under apron area - Tiny dimple after 2 -3 ball drops.
Sopranos - Ball drop under apron area - Tiny dimple after 2 -3 ball drops.
Stern Playboy - Ball drop under apron area - Tiny dimple after 2 -3 ball drops.

Drumroll .. .. .. .. .. .. .. ..

TWD LE - Ball drop under RHS flipper - left a massive crater in the clear.

So it would be considered to be normal to have small dimples in a clearcoated playfield = Yes.
Metal ball against clear over timber - over a long period of time.
The issue with TWD LE is simply a case of VERY poor coverage of the clear, and way to thin for a $11,000 pinball machine.

I'm hoping that the problem is isolated to this one playfield. I will be contacting Stern for a replacement playfield. Thanks to the guys that have popped into have a look at the issue.

[Strangeways]

It appears from martyj pics that it is not happening on the inserts...so maybe the softer timber is the weakest point?

+1

I think there is large variance in the Stern playfields. Only an educated guess but Nino's TWD issue seems to be the clear-coat. Big dimples on top of inserts has to rule out the plywood as the primary cause. Not necessarily too thin - but definitely not hard enough (either the product or manufacturing conditions/curing time). Martyj's could well be softish plywood. Some owners seem to have no issues at all (or say they don't). Perhaps it comes down to the playfield & the day it's produced. I would not be happy with Nino's TWD playfield - it seems extreme to me. However, given all the reports of dimpling I'm bracing myself to expect severe dimpling in the 1st new Stern I buy. The big qn is whether to buy an additional playfield as a backup. Is it worth it come resale time?

Marty took the photos of TWD LE at my place = same machine.

No one should have to fork out extra $ for a second playfield because the factory playfield in modern pinball machine worth $11,000 is sub standard. But I can see this being the reality. It would certainly prevent me buying another Stern.

[Strangeways]

Some people on pinside let their NIB stern so for six months before playing them, to give the clear time to cure

The clear is cured when you cannot smell it

That's overkill. I've installed playfields after 2 months and they were rock hard. When my KISS LE arrives, I'll be playing it within the first 5 minutes 

[Brunswick Brawler]

Some people on pinside let their NIB stern so for six months before playing them, to give the clear time to cure

The clear is cured when you cannot smell it

That's overkill. I've installed playfields after 2 months and they were rock hard. When my KISS LE arrives, I'll be playing it within the first 5 minutes 

If TWD LE Nino is has got dimpled today, the machine was built 6 months ago.  So the issue is nothing to do with curing time.

I wonder if it may relate to drying speed time.  'Crystalline' materials cooled quickly from their liquid state become dull but flexible (annealed), and when cooled quickly become shiny but hard & brittle.  I thought 'orange peel' was caused by slow cooling - which would also relate to dull but flexible.  (I'm unsure of the orange peel cause).

...could it be that the reason the we are getting inconsistent report is that Stern's clear coater isn't controlling the cooling process.  The dimpled ones were simply made in summer so naturally cooled slowly, and the shiny 'flakey' ones were made in winter so were naturally 'snap frozen' in Chicago.


Question to Platinum: Am i correct to say that your process is to take the playfields out of the oven quickly?  And the reason you clear coat doesn't crack, is that they get strength from being thick.

[Strangeways]

Some people on pinside let their NIB stern so for six months before playing them, to give the clear time to cure

The clear is cured when you cannot smell it

That's overkill. I've installed playfields after 2 months and they were rock hard. When my KISS LE arrives, I'll be playing it within the first 5 minutes 

If TWD LE Nino is has got dimpled today, the machine was built 6 months ago.  So the issue is nothing to do with curing time.

I wonder if it may relate to drying speed time.  'Crystalline' materials cooled quickly from their liquid state become dull but flexible (annealed), and when cooled quickly become shiny but hard & brittle.  I thought 'orange peel' was caused by slow cooling - which would also relate to dull but flexible.  (I'm unsure of the orange peel cause).

...could it be that the reason the we are getting inconsistent report is that Stern's clear coater isn't controlling the cooling process.  The dimpled ones were simply made in summer so naturally cooled slowly, and the shiny 'flakey' ones were made in winter so were naturally 'snap frozen' in Chicago.


Question to Platinum: Am i correct to say that your process is to take the playfields out of the oven quickly?  And the reason you clear coat doesn't crack, is that they get strength from being thick.

The game was played from the day the kit arrived from Stern to Address the bicycle girl fix. It's 100 games were from December to Early February. It had only a handful of games since Greg's passing on the 18th Feb. 99% of the games on this game were December - Early Feb. I took the game out earlier this week for a quick clean and I was looking at updating the code. I checked the playfield as there were numerous issues that I needed to look at and the dimpling issue really became apparent.

I don't think it is curing time. It is very clear to all that have seen the issue, that it is a very poor quality clearcoat, and way too thin for a professional finish. In fact, it looks like the top right hand corner had it's "mist coat" and that was it !

I firmly believe it is a "factory defect". I can drop a ball on other playfields and struggle to see a dimple until the second or third drop. This playfield under the same test leaves a crater.

[pinnies4me]

That's great analysis work Nino, thanks for taking the time to do that. Can't blame people for wanting a little more longevity for the amount of coin being asked.

[Freiherr]

Taking a closer look at Marty's photos I can see a lot or arc ruts left by the ball. I have never seen them on any of my playfields. That clear coat is definitely defective and very soft.

Chech the arcing near the arrow insert. Looks like an ice scating ring after a busy day.

[swinks]

nice testing Nino, and as you noted that it appears to have a mist coat in the corner suggesting the CC should of been at a much higher quality, but BB made a interesting point on the initial cooling as when cooling metal after heating can affect the molecule structure so it may play a factor as well with CC and I still believe that the ply is also a factor but the only way to determine that is by doing a Brinell / Janka Hardness Test. Quite often many quality plys are made with what is considered a clear timber = meaning no knots in the visual layers but who knows if there are some in the middle layers though I am sure if people had a poke around we would see those in any through holes in a playfield so pretty sure they are using select clear timber on all layers. The other is is slow growth (original trees) and fast growth (plantation trees) timber with fast being softer in strength due to the growing conditions and gone are the years where the timber is dried properly like the old days. Even on the CPR page they have removed the plywood info as they are looking at a new supplier. They state they prefer 7 ply over the cheaper 5 ply as 5ply fails quicker and some of the older quality playfields used 9 ply which is your bees knees timber probably from long growth forests not plantation forests. Lastly another factor is the type and quality of the glue used to bind each layer adds to the strength.

So unless someone takes a new playfield, a 10 years old one and 20 year old playfield and do a slice and dice of each one and run tests like Janka on a section with a mild clear, a thick stern clear, a HRP clear, a ceramic clear it is hard to determine the real failing point as to what is really happening:
- ply layers
- ply grade (old growth / plantation growth)
- glue used
- clear coat (mist & mild, thick, automotive and ceramic)
- curing conditions

In relation to clears, since I don't know anything I tried googling some info and say with the products at this link, various products have mixing recommendations, drying recommendations and all state various levels of being gloss, durable and flexible to a degree but are they truely designed for a pinball environment for impacts hence the CC generally holds up to the steel ball racing around a playfield, bouncing etc but feel the surface below is what is giving way to the impact of the steel ball. If the ply is softer and the CC flexible the CC adjusts in shape with the surface below (timber) denting.

http://www.hichem.com.au/hicheminfo/System%20Books/2%20PACK%20booklet.pdf


it would be a great test to do the above of a number of playfields and clears etc to cancel out some of the theories but pointless as their are alot of unknowns and doubt certain companies would ever share a study like this if even they have considered the various components (which I doubt), so the best we can do is at least ensure a decent CC is applied and then just enjoy playing the game and if you can afford it buy a spare playfield if you know a game is going to be your grail / keeper pin.