-
Failing Flat Cut Lettering
Back in January I fitted a sign consisting of flat cut lettering at my local high school.
The lettering was made from dibond and I noted at the time that my supplier had glued a thin sheet of plastic (Acrylic I think?) to the back of the dibond prior to routing out all the letters, and glued the locators to the plastic rather than directly to the dibond. (I assume this was done because the glue was better suited to attaching the locator’s to the plastic than directly to aluminium composite). This was the finished job:-
Today I received a call from the school to tell me one of the letters had fallen off.
When I called in this afternoon to see what the problem was I discovered that the letter had detached itself from the plastic. Worse still, looking closely at all the other lettering I could see that quite a few other letters were also in danger of falling off!!
On closer examination, I could see that the plastic backing has warped which is what caused it to seperate from the dibond.
My problem is how to re-attach the letter and ensure that the same problem doesn’t happen to all of the other letters.
I’m hoping that the collective genius that is the UKSB will provide a solution.
Worst case is I will have to remove all of the letters and start again but this will leave holes in all the wrong places and I am hoping for an easier solution to the problem
-
22 Replies
-
Differential expansion due to different materials and changes in temperature? I’d bet they will all fail over time 🙁
I’d be tempted to strip the letters and leave the letter fixing cups in place. Plug each cup with a new stud and top it with VHB tape.
Have a new set of letters cut in acrylic and stick them onto the VHB.
In practice I think I would replace one at a time to make it easier to keep the original alignment.
-
If it is your suppliers fault then I would be looking at them to come up with a solution as it is their work that has failed. If they have sold this to you then they would have also have sold to others which will also fail.
(:) -
Thanks for the suggestion Neil, I agree the problem is likely to be caused by expansion and contraction of the different materials at different rates.
I agree 100% Mike – and I will be speaking with them tomorrow to see what solution they can come up with, and to point out that this is likely to be an ongoing problem for others provided with the same system.
Meanwhile – regardless of who is to blame, this reflects badly on my business and I am determined to come up with the best solution that I can regardless of what my supplier may suggest. They may well have an answer – but someone else on UKSB may have a better solution
-
That’s terrible that should happen. I have never seen a seperate layer glued on the back of Dibond letters, why should they have to do that.
almost sounds like they glued the locators on over the protective covering sheet.
The only solution I can see is as Neil says.. a very time consuming process on your part.
-
Is a good looking bit of work as well, bet you were happy with the first time you fitted.
I’d be well pi£$ed!
Redoing it I would think would be the least hassle in the long run though.
Do the suppliers keep copies of locator’s templates?
I’m trying to imagine the process of how they make these letters up?
Can they not just repeat the order?
James
-
http://www.google.co.uk/#q=tigerseal&hl … 80&bih=799
Take each face off and put a dab of this behind it and they’ll stay for good,
Problem is down to contraction as already said, I dont trust VHB nowadays as "every tape" is now VHB if you know what i mean.
We use high PU on all sustrates and it will not fail. -
the reason they have doubled up the plastic to the dibond is because they have probably discovered their current adhesive used to glue the locator to the dibond heats up very hot while curing. however, this heating process doesn’t agree with dibond or any composite for that matter and creates large dimples on the face of the composite.
-
Martin – You may have a point and I will check this out tomorrow when I return to take some pictures of the affected lettering and examine it more closely now that I have had time to reflect upon the problem
James – each letter has the locators glued on by hand and these will be in a different place every time a new letter is made. Thus a new template has to be created everytime a new set of lettering is made up – even if the lettering is the same the template won’t be.
Thanks Rob – your explanation makes sense and explains why they would have have produced the lettering this way.
Ian – if the Tiger Seal is as good as you say then this may be the answer. I’ll speak to my suppliers tomorrow and see what they suggest.
-
Ian, does the tiger seal cure quickly mate?
Only asking because fixing on-site on the wall may allow movement while curing. i guess it could be taped in place etc but just wondering how difficult due to the formation of those letters being anything but easy. 😕might be worth getting some in myself as we only use the 3M 2-part adhesives for locators and the like. but even that creates dimples on composite. we learned the hard way! 😕
-
i’d go with the different expansion rates too! in the van I have a load of moulded / cut sample letters on locators with a magnet on each locator, I kept them stored on the inside of the van roof and blamed the kids when the first fell off…. turned out as one by one they fell off, the magnet obviously contracted in the frosty nights while the perspex didn’t, the glue broke and left the magnets on the roof!
-
quote Phill Fenton:Martin – You may have a point and I will check this out tomorrow when I return to take some pictures of the affected lettering and examine it more closely now that I have had time to reflect upon the problem
James – each letter has the locators glued on by hand and these will be in a different place every time a new letter is made. Thus a new template has to be created everytime a new set of lettering is made up – even if the lettering is the same the template won’t be.
Thanks Rob – your explanation makes sense and explains why they would have have produced the lettering this way.
Ian – if the Tiger Seal is as good as you say then this may be the answer. I’ll speak to my suppliers tomorrow and see what they suggest.
Ian, I haven’t used Tiger Seal myself so can’t comment, but I have no doubt if you’re recommending it then it will be good. However I don’t think I would (re)laminate them at all. Even if the Tiger Seal holds up they will probably still bend and buckle. I’d go to the heart of the problem and get rid of the laminating all together. Do the job once and regain your cred Phill. Costs involved are a separate matter and no doubt will be resolved between yourself and your supplier in due course. In the mean time rescuing the job successfully, and your professional reputation are top priority.
-
I would try and get as much information from your supplier as to exactly how they were made Phil.
What glue was used?
Was the Dibond laminated to the acrylic before the letters were routed or were they routed separately and then glued?……If it was the latter maybe they have been too sparing with the glue so it didn’t seep out over the edges?
Are the letters placed directly over a radiator or other heat source?
Does it have to be a Dibond face, could you not just use acrylic letters?……It’s difficult to tell from the picture what colour the letters are but even if it butler finish you could still cover acrylic letters in a brushed vinyl to get the same effect
-
Same as Ian, but I would use this stuff instead
http://www.uksealants.co.uk/product.asp?idproduct=189
They use it to stick car panels on, so it’s pretty sticky – just wear gloves FFS or you’ll be picking it off your hands for weeks! :lol1:
One tube would do all those letters, as you only need a bit.
ETA a better link.
-
Having been back to the school, taken photos, and discussed this with my supplier I now think we have identified the cause.
I no longer think it was due to heat causing the acrylic to warp. I now think it is a result of the cups that the pegs plug into being incorrectly aligned putting tension into the plastic and trying to bend it out of shape resulting in the delamination. The following photo shows some of the other letters affected in the same way, and I have drawn a diagram which I think demonstrates the effect of miss aligned pegs.
I think the answer is to realign the cups on the affected lettering before re-gluing the plastic to the dibond. With correctly aligned pegs there should no longer be any tention causing the failure. This at least is a more satisfactory explanation as only the letters that have miss-aligned pegs should exhibit delamination (which seems to be the case). It also means that there is now no reason to believe that all the lettering will eventually fail, only the miss-aligned ones. Once these have been rectified the problem should be resolved.
Does that make sense?
Attachments:
-
I see what you mean, but I wouldn’t expect a product to delaminate under such a strain. The one in the foreground seems to have a very shiny surface on the ‘glued’ surface. Makes me wonder what type of adhesive would leave that surface if it had initially been properly stuck.
I’d like to think that would fix it Phill but I think time is the only way to tell.
-
Interesting Phill, it does make sense.
That is the trouble with locator work….trying to get them aligned correctly, but I agree with Neil and don’t think they should have given way.
Iv’e still never seen a backing sheet applied as you have there.
I guess it’s good news in a way…. how many letters do you think are affected?
-
Thinking more about this and your illustration/photo I really wouldn’t expect the locators to be the cause. In fact it’s possible that the expansion/contraction of the material has pushed/pulled them into that position. As you know these locators are very easily bent and wiggled around and therefore I would expect them to easily absorb movement of this kind without affecting the letter at all.
-
forgive me if you already do this but on fixing the cups do you tighten the screw right down or do you leave a little play (ie head of screw not tight on bottom of the cup) – I’ve always been tought to fix this type of lettering in this way for exactly the reason you are experiencing as the cup can then move to take up any drilling slippage. (again sorry if I’m stating the obvious)
-
Thanks Craig – you’re not stating the obvious, I do tend to fully tighten the cup in position and I appreciate your advice to leave some free play.
-
I’m more inclined to think that the adhesive has failed between the acrylic and the composite.
The reason that they haven’t stuck the acrylic locators directly to the dibond is because it is problematic so to stick an acrylic backing to the letters will hold the same problems albeit with a larger gluing surface
As Neil has already said…it’s best to leave the cups with a bit of play….The letter stiffens up the cups when plugged into the sockets
-
I think it could be a combination of factors, if the acrylic has expanded since fitting then it would be the same as Phils drawing with the locators being pushed out. Contributing to the failing bond to the composite.
-
quote Robert Lambie:Ian, does the tiger seal cure quickly mate?
Only asking because fixing on-site on the wall may allow movement while curing. i guess it could be taped in place etc but just wondering how difficult due to the formation of those letters being anything but easy. 😕might be worth getting some in myself as we only use the 3M 2-part adhesives for locators and the like. but even that creates dimples on composite. we learned the hard way! 😕
Tiger seal is just a brand of High PU, there are other as well , truflex, tigerseal, ubond etc
essentially they are for the same purpose. bonding panels to cars etc, been used for years and just doesn’t fail
it has a high initial grab, infact it’s a bugger to squeeze out of a tube.
it will part cure in about 20 minutes, takes about 24 hrs to fully cure. it doesnt heat during curing, and also if flexable enough to not cause dimpling during contracting expansions.
good things in life cant be rushed , this is one of them.nothing annoys me more than looking at fret cut panels with acrylic backing having failed due to people not using the correct adhesive.
A lesson learnt to me years ago, is double fix where possible. it’s the oldest saying around "dont carry all your eggs in one basket"
We use a mix of VHB for initial grab and around areas where you don’t want sealant to escape then High PU on the rest.Some day i’ll get round to doing a demo for this site
😀 😮
Log in to reply.