Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Glass pulling away from frame

Fri Jun 18, 2021 1:21 pm

We use the Rpi official 7 inch touchscreen and case in out product. so I've assembled hundreds of these with no problems. However, on the latest batch I received, the glass pulls away from the frame after a couple hours. These are assembled using a Rpi 3A and a custom hat inside an official 7 inch case.

Packaging:

All previous batches were packed using the pink foam. This latest batch was different, they were packed using a bubble wrap envelop

I believe there are two causes to this:

1) there is a slight difference in the mounting tab depth (the distance between the front of the glass and the metal mount tab) This may pull the metal frame away from the glass when the four cases screws are tightened.

There seemed to be a 0.2mm difference between older versions and newer versions. We'd need to get more samples of these measurements
8.35 for new, 8.55 for old

2) There seems to be a slight misalignment of the plugs and their corresponding holes in the case.

This was observed on the 5 displays that we assembled from the new batch. We stopped work after all 5 failed.

Thinking it might be a case problem, we assembled a couple new screens in our test case. (white case). This particular case has had dozens of Rpis assembled in it over the past year where they may operate for a few days or weeks while we perform software / hardware tests. There has never been a glass separation from the older screens mounted in this white case..

I have several more photos, but it will only let me upload three....
Attachments
Screen_Fail_3_600.jpg
Screen_Fail_3_600.jpg (32.47 KiB) Viewed 1086 times
Screen_Fail_2_600.jpg
Screen_Fail_2_600.jpg (51.74 KiB) Viewed 1086 times
Screen_Fail_1_600.jpg
Screen_Fail_1_600.jpg (49.69 KiB) Viewed 1086 times

ejolson
Posts: 7597
Joined: Tue Mar 18, 2014 11:47 am

Re: Glass pulling away from frame

Fri Jun 18, 2021 3:14 pm

Waiter21 wrote:
Fri Jun 18, 2021 1:21 pm
There seemed to be a 0.2mm difference between older versions and newer versions. We'd need to get more samples of these measurements
8.35 for new, 8.55 for old
Yikes. That's a pretty big difference. How many of the new screens do you have?

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 29039
Joined: Sat Jul 30, 2011 7:41 pm

Re: Glass pulling away from frame

Fri Jun 18, 2021 3:32 pm

I have passed this on.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Working in the Application's Team.

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 29039
Joined: Sat Jul 30, 2011 7:41 pm

Re: Glass pulling away from frame

Fri Jun 18, 2021 4:21 pm

Hi, we would like to get some of these back for examination. Can you email info@raspberrypi.com FAO James Hughes with your details, and someone will get in touch.

Thanks.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Working in the Application's Team.

Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Re: Glass pulling away from frame

Sat Jun 19, 2021 11:30 am

I just sent you the info.

The touchscreen and case are wonderful products, very robust, and my customers haven't been able to destroy them, yet. :D Whatever I can do to help resolve this...

I did order another batch from a different vendor and received the pink foam version, all were assembled with no problems..

John Mc

Arnaud_Pi
Posts: 2
Joined: Wed May 05, 2021 6:57 am

Re: Glass pulling away from frame

Thu Jun 24, 2021 11:05 am

Hi,

see my post here.

viewtopic.php?f=108&t=309768&sid=5f0e4a ... 986ba2bcd2

which version will be followed, which one will be discontinued;
edit : -> seems it is answered :
2021-06-24 13_29_32-Daughter Board, Raspberry Pi 7__ Touch Screen Display, 10 Finger Capacitive Touc.png
farnell discontinued
2021-06-24 13_29_32-Daughter Board, Raspberry Pi 7__ Touch Screen Display, 10 Finger Capacitive Touc.png (142.4 KiB) Viewed 808 times
pity that no information about sizes changes were published

arnaud

Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Re: Glass pulling away from frame

Fri Jun 25, 2021 11:19 pm

WELL CRAP....

I've made three orders from Newark in the past couple weeks. The first two batches were the pink foam style.

This last batch I just received is the bubble wrap. The very first one I put together, the glass separated after about 20 minutes.

I need to get this resolved as this is a key component to the product I sell. no touchscreen, no sales.

www.waiterecc.com

CONSIDERATIONS.. I'm thinking about a shim that I can place between the touchscreen and the case. I'll 3d print something and try it.
Attachments
Rpi_ScreenPulled awayBW_800.jpg
Rpi_ScreenPulled awayBW_800.jpg (74.83 KiB) Viewed 754 times

Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Re: Glass pulling away from frame

Fri Jun 25, 2021 11:57 pm

Possible shim between new screen and case.

I reviewed the post that Arnaud_Pi linked to. I took measurements between the old and new screens.

Taking into account the glass is thicker on the new screen. The distance between the mount tab and the inside surface of the glass is critical. The old screen this distance was about 7.8mm. The new screen its 7.1mm. The glass touches the case before the screw tab touches. when the screw is tightened, it pulls the metal frame back and the glass separates from the frame.

I'm going to 3d print a couple .7 - .8mm shims and place between the mount tab and the case.

I believe if this works, I'll find some thin washers and scotch tape them to the mount tabs. AN960-4 or AN960-6 are 0.032 inches thick, thats 0.81mm, might be perfect..

John Mc

Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Re: Glass pulling away from frame

Sat Jun 26, 2021 12:31 pm

Forgive the crud drawing, but it shows the problem, the distance between the inside surface of the glass and the mount tabs changed significantly, 0.7mm.

Note that the glass thickness changed, its now thicker. Old glass thickness > 0.8mm. New glass thickness > 1.2mm.

This may be aggravating the problem as the glass doesn't flex as easily, so the glass isn't able to flex (bend) to absorb the difference in mount dimensions.

Also - viewed from the front of the display. The recessed area of the case allows the glass to recess a little from the front lip of the case. with a thicker glass, the front of the glass will not be recessed as deeply, and may be even with the front of the case.

I made a shim and taped it to the inside of the case and assembled a new display. This helped, the display has been sitting on the bench all night and no problems. The dimensions of my 3d printed shim aren't easily repeatable and consistent. I'm going to swing by the airport and get some AN960-4 and AN960-6 washers. These are consistent in their thickness (0.032 inches = 0.8mm). I'll tape these to the mount tab on the display and see if these mitigate the issue.
Attachments
Rpi_Glass_Issue_10_800.jpg
Rpi_Glass_Issue_10_800.jpg (109.75 KiB) Viewed 688 times
Rpi_Glass_Issue_11_800.jpg
Rpi_Glass_Issue_11_800.jpg (85.78 KiB) Viewed 688 times
Rpi_Glass_Issue_12_800.jpg
Rpi_Glass_Issue_12_800.jpg (28.33 KiB) Viewed 688 times

ejolson
Posts: 7597
Joined: Tue Mar 18, 2014 11:47 am

Re: Glass pulling away from frame

Sat Jun 26, 2021 1:43 pm

Waiter21 wrote:
Sat Jun 26, 2021 12:31 pm
I made a shim and taped it to the inside of the case and assembled a new display. This helped, the display has been sitting on the bench all night and no problems. The dimensions of my 3d printed shim aren't easily repeatable and consistent. I'm going to swing by the airport and get some AN960-4 and AN960-6 washers. These are consistent in their thickness (0.032 inches = 0.8mm). I'll tape these to the mount tab on the display and see if these mitigate the issue.
Does the tape hold things in place only during assembly or is the washer a small metal part that's likely to come untaped and short out the circuit board?

In either case, adding washers with tape sounds like it would increase assembly time to me. While that's not a problem for a one of a kind hobby item, could it be a problem for commercial use?

Maybe a new release of the housing will follow the change in physical form factor of the LCD screen. I find it surprising these things weren't synchronised. At any rate, it looks like one needs a temporary solution just to continue.

Hopefully the washers just work.

By the way, your Pi-based product looks interesting enough to me that it could make a good story for the blog. Good luck with getting this resolved.

Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Re: Glass pulling away from frame

Sat Jun 26, 2021 8:02 pm

The tape would hold the washers in place during assembly, and any subsequent disassembly. The shim (washer) would be permanent (either taped to the tab or maybe double sticky tape). Unfortunately it adds a step to the assembly process, but until a solution is implemented and works its way through the current inventory, its either this, or stop production.

I'll probably make a sticker and plaec it inside the case to give anyone a heads up that the washers must be in place.

IMPORTANT - The 4 shim washer MUST be in place when assembling the case.

Waiter21
Posts: 7
Joined: Sun Oct 13, 2019 9:09 pm

Re: Glass pulling away from frame

Fri Jul 02, 2021 6:06 pm

I've installed about 10 of these modified cases so far without any problems. The only issue (not really an issue) is the glass is thicker. In the old unit, the glass was kind of recessed a little in a lip on the case. With the thicker glass, when its mounted in the case, it doesn't recess in the lip, its kind of even with the lip. Not a real big problem.

As for using the cases, I taped a 0.8mm shim washer to the inside of the case. I also placed a reminder sticker on the inside of the case and the display. I used AN960-6 washers as these will be consistent 0.8mm thick, regardless of when or where they are purchased from (0.02 cents each at Aircraft Spruce)

We're shipping these units to customers. I added a special designation code to their touchscreen unit so I can keep track of what customers got the displays with the shims.

If the foundation releases a updated case, we'll stop using the shims.

THOUGHTS - I would lower the recessed surface (the surface the glass rests on) by 0.8mm, When the display is then mounted, the glass would once again be recessed in from the lip, AND, it would effectively move the metal frame and screw tabs aft by about 0.8mm. This will be an issue with configuration control of existing inventory, but thats the way it is.

NOTE - Has anyone seen if this issue also effects the Rpi4 case?
Attachments
SpacerInstall_3_800.jpg
SpacerInstall_3_800.jpg (75.16 KiB) Viewed 444 times
SpacerInstall_2_800.jpg
SpacerInstall_2_800.jpg (130.62 KiB) Viewed 444 times
SpacerInstall_1_800.jpg
SpacerInstall_1_800.jpg (60.34 KiB) Viewed 444 times

Return to “Official Foundation Display”