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How can I bond ABS (plastic) to NRL (rubber)?

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Neil Lickfold21/01/2022 09:17:20
835 forum posts
166 photos

Can you use another material instead of the ABS? ABS is terrible stuff to try and glue to, especially when a peel strength is required.

Steve Skelton 121/01/2022 09:37:34
140 forum posts
6 photos

"I am using strip of rubber to create a hinge between two plates of ABS."

Why not redesign it using polypropylene so that you use one piece of material - PP make perfect natural hinge material? May be easy to 3D print it? Would be a much more elegant solution.

https://www.protolabs.com/resources/blog/living-hinge-basics-for-injection-molding/

Howi21/01/2022 09:46:12
avatar
351 forum posts
19 photos

Simple Evostick contact adhesive will do the job wiuthout anything fancy.

John Smith 4721/01/2022 18:58:57
393 forum posts
12 photos
Posted by Dave S on 21/01/2022 08:22:37:

When hunting a Unicorn it is usually best to start with the Unicorn breeders

Henkel, Sika both have very helpful technical teams

Good suggestion. However long story short, I have basically drawn a blank from both of them. :^(

3M have been super-slow to reply but are also now chewing on the problem. 

UPDATE:
I have now bought and done careful test on all 4 of the above adhesives that I listed above. For the hell of it, I even also tested Zap 30min Epoxy and Collall general purpose glue.

Sadly all of the glues were complete FAILS.  i.e. None of them were able to resist even pretty weak peeling forces and they have basically failed to bond well enough.



Clearly the designs of my prototypes will need to be improved so as to avoid peeling vulnerability, but for now it's too late as the prototypes have been 3D printed in high res and are well advanced.


I have now spent multiple hours on this exact question (googling/emailing/phoning...) but I am broadly none the wiser, except I have a strong sense that a primer is required(!). Also I am told that silicone sealants are likely to work best with silicone rubber, even though silicone rubber is generally hard to bond to.

I was offered some Wacker G718 primer to go with my Elastosil E41 sample, however at c. £300/bottle and no way to get a smaller sample, I'm afraid I didn't go for that.

More or less out of desperation I have order some Sikaflex EBT+, but I remain unsure what primer it really needs to bond to plastics like ABS. Also out of desperation, I have also ordered some Dowsil 1200 OS Primer to go with my Dowsil 732 silicone sealant, even though there was little evidence that it worked on plastics.

If all else fails I could try superglue again, but it's it instantly screws up the NRL rubber's finish. And so small accidents would be irrecoverable as unlike most glues they are not be able to be cleaned up (e.g. using Isopropanol)...

Hey-ho.

Edited By John Smith 47 on 21/01/2022 19:07:05

Nicholas Wheeler 121/01/2022 19:04:22
906 forum posts
86 photos

How about using a wider rubber strip that's attached further into the case, rather than along the edge? Then it won't be as susceptible to peeling off.

Dave S21/01/2022 19:08:55
361 forum posts
90 photos

If the adhesive technical team don’t have a suggestion that is a good clue that you have the wrong materials (or design - but since the design is secret I’ll go with materials).

If you have to use ABS because you already made those parts then find a flexible alternative that you can stick.

Peel is a problem for glues. Most adhesive structures avoid it, or use mechanical fixings to prevent the peeling starting.

Assumkng you 3D printed in ABS the it’s only cost to get 3D prints in a more suitable plastic. Sometime you have to let go of the money already spent to actually make progress toward the end goal. (Easy for me to say, I have no financial or emotional investment in your thingy)

John Smith 4721/01/2022 20:22:41
393 forum posts
12 photos

Posted by Nicholas Wheeler 1 on 21/01/2022 19:04:22:

How about using a wider rubber strip that's attached further into the case, rather than along the edge? Then it won't be as susceptible to peeling off.

Sorry I don't quite understand your point.

The whole problem peeling is that rather than the whole area taking all of the forces - i.e. tension/compression/sheer etc forces - at the same time, depending on what is being done to the lid in any one moment, all of the tension is felt at the very each of where the soft material is bonded.

e.g. In my image, if a force was being applied vertically DOWN

The result would be that only a very thin strip of material - i.e. a strip that is nearest to the hinge - absorbs all over force.

This is ultimately because one material - the rubber in this case - is SO much more flexible that the rest of the structure. And exactly because of this flexibility of the soft rubber, it doesn't any significant difference how far away from the hinge the rubber extends.

Sorry hard to put into words, but I don't think I'm trying to say anything non-obvious.

@Dave - you just have to trust me when I say that it's too late to change the design. If you really want to know, the 3D parts were 3D printed at a best-in-class high resolution and then vac-formed into a strong, high quality ABS. It is specialist work that (obviously) I outsourced and it cost a LOT of money. Well into 4 figs. There is certainly no budget to re do it.
To get clear, this is primarily just a proof of principle prototype/model, and the ultimate product would almost certainly be completely re-designed by licensees, presumably using an over-moulded rubber design. The idea isn't to solve ALL of the manufacturing problems. At this point we need something that says "there is a hinge HERE... and it behaves roughly like THIS..."

For the real injection-moulded/over-moulded product there will be many and various workarounds, but for this prototype I just need... a good strong bond between the rubber and the ABS!

From everything I have heard, I am quite certain a very much better bond than we are currently getting is technically possible. But its a deeply technical subject and getting access to the correct experts has been proving tricky.

SillyOldDuffer21/01/2022 20:48:22
Moderator
8469 forum posts
1885 photos
Posted by John Smith 47 on 21/01/2022 18:58:57:
Posted by Dave S on 21/01/2022 08:22:37:
...
...


Sadly all of the glues were complete FAILS. i.e. None of them were able to resist even pretty weak peeling forces and they have basically failed to bond well enough.

...

If all else fails I could try superglue again, but it's it instantly screws up the NRL rubber's finish. And so small accidents would be irrecoverable....

Thing is Superglue is your best bet because it sticks ABS and NRL.

Objections seem to be personal as much as technical:

to be honest I've always rather hated CA, because:
- the fumes rather sting the eyes,
- it requires a good fit (i.e. not good at filling in any gaps) and
- it's such a nightmare to clean up any spillage - particularly if it gets on the your skin!

These can all be fixed with proper technique:

  • fumes - improve ventilation and wear goggles
  • fit & spillage - ensure there are no gaps or spillage by holding the parts securely in a folding jig. Or, accept hand-methods won't be perfect in a prototype. Note it's very common in engineering to hide messy details behind some sort of cosmetic facade. If you can't make it, fake it!

Peeling can be prevented by adding mechanical support such as staples.

Is this endeavour solving a prototype or a production problem? A prototype only needs to work well enough to prove the concept. And does a hinge really require this level of attention? Details are usually best left to the Production Engineer. He'll do them cheaper and better. Unlikely there's any need here for the Inventor to get lost in a maze of glues, materials, primers and solvents.

Dave

Edited By SillyOldDuffer on 21/01/2022 20:52:23

John Smith 4722/01/2022 01:43:12
393 forum posts
12 photos

I seem to have lost my previous reply.

Dave, you may well be right...

However suffice-it to say, no I am not going to use superglue/CA, not just yet at least. There are multiple reasons for this, not least of which is that I have to accept that too much skill is required! And TBH, my parts are too valuable for me to work on with such an unforgiving material. My product designer who is extremely experience with CA found it extremely difficult to get a strong, absolutely dead-flat bond when applying the stuff in our configuration.

So I am going to try various other more forgiving adhesives first... Some of which are now on order... and most of which also allow any small spillages to be wiped clean (e.g. using Isopropanol) without damaging the rubber surface, as well as allowing small amounts of repositioning to get the rubber into exactly the right places, and the judicious use of small rollers to help level out the adhesive and create a dead-flat top surface to the rubber. 

I am also waiting to hear back from the likes of 3M who were talking about better primers & adhesive delivery via transfer tapes.

> Is this endeavour solving a prototype or a production problem?
Both. Albeit primarily the former for sure, it is also de-risking some of the key production issues.

> Does a hinge really require this level of attention?
Yes. The ergonomic nuances are of central importance.

We are very nearly there with this prototype round. We just need what is primarily a proof of principle and broad feasibilities. You are of course correct that in many ways the exact materials that we model with don't matter in the slightest, but we need to prove roughly what could be done, with roughly what materials and for roughly what price. And for example the exact behaviour of the hinge is critical!


SILICONE RUBBER
If all else fails, I shall do some out-right fakery with hidden mechanical stuff (e.g. I have my eye on some ultra-fine nylon threads favoured by the best magicians!)... but first I am also going to experiment with silicone rubber instead of NRL, as some suppliers were adamant that some of the adhesives in question, being made from silicone rubbers, would bond "very much" more strongly to silicone rubber than to NRL.

My slight problem with going silicone is that I have been unable to find anyone who can supply black, silicone rubber that is 40° shore or less, that is also 0.8mm thick. I have some 1.0mm stuff from Silex...

https://silex.co.uk/shop/sheeting/solid-sheet/general-purpose-sheet-40-shore/

...but at 1.0mm thick it is a bit too rigid for us... and also sticks out too much, creating some unwanted ridges that one can definitely feel albeit not really see.

Can anyone recommend an suitable alternative supplier of rubber latex sheet?

J

 

Edited By John Smith 47 on 22/01/2022 01:51:12

Michael Gilligan22/01/2022 07:19:48
avatar
20057 forum posts
1040 photos

John,

I don’t mean to pry; but feel obliged to ask a serious question :

Given that this new product appears to be intended for handling …

Are you sure that Latex is an appropriate material to use ?

Latex Allergy is unpleasant and can be life-threatening.

[ Hopefully you have already considered the risks, ]

MichaelG

Ebenezer Good22/01/2022 08:17:19
18 forum posts
2 photos

Have you tried CT1? It sticks just about anything to anything!

I've forgotten how to upload photos on here but a Google search will soon find it, it says it sticks ABS in the blurb...

AdrianR22/01/2022 09:28:22
571 forum posts
36 photos

Depending on your materials you may be able to use UV setting glue.

Have you looked at hot melt adhesive film? Maybe there is one that will bond ABS and Rubber.

Maybe it would be worth designing a jig for assembly so you don't need the assembly time.

Perhaps if the front side of the hinge joint rubber was pressed tightly to the ABS with a knife-edge, it would create a seal. Then the CA could be applied from the rear.

Howi22/01/2022 09:57:44
avatar
351 forum posts
19 photos

Why are we trying to solve someones commercial product problems.

Having spent a lot (?) of money so far, why go cheap skate now, talk to adhesive manufacturers and get the right product for the job.

Don't you just hate it when someone comes on here for advice, only to Poo Poo (Black adder 4) every idea thrown at them.

This post is not the only one recently.

Gordon Tarling22/01/2022 10:44:24
181 forum posts
4 photos

Give this a try - if it doesn't work, I don't know what will!

G.

noel shelley22/01/2022 11:24:59
1278 forum posts
21 photos

CT 1 ! It comes in many colours ! Noel.

John Doe 223/01/2022 15:06:21
avatar
75 forum posts
6 photos

Aha ! With his photo of the hinge on this thread, we now know why John 47 is asking on another thread how to make those very thin metal strips with an angle on one edge ! One can be seen here as part of a hinge seating mechanism or somesuch.

Edited By John Doe 2 on 23/01/2022 15:08:39

John Smith 4723/01/2022 15:30:54
393 forum posts
12 photos
Posted by Michael Gilligan on 22/01/2022 07:19:48:

John,

I don’t mean to pry; but feel obliged to ask a serious question :

Given that this new product appears to be intended for handling …

Are you sure that Latex is an appropriate material to use ?

Latex Allergy is unpleasant and can be life-threatening.

[ Hopefully you have already considered the risks, ]

MichaelG

 

Fair question. No, it is emphatically NOT the material we would use for a product, because the life expectancy isn't long enough. This is purely for proof of principle.

For the real product the plan would probably be to use a silicone rubber. But ironically I was put off modelling with it because everyone said it was harder to glue!

Yes I have been talking to manufacturers of the leading brands of glue (see above)

@John Doe 2 - I wish I could tell you folks all about my designs but it would me a public disclosure and everything would not longer be patentable.

J

PS  'All Purpose Welder Contact Adhesive' ordered - thanks!

Edited By John Smith 47 on 23/01/2022 15:33:02

John Smith 4723/01/2022 23:06:51
393 forum posts
12 photos
Posted by noel shelley on 22/01/2022 11:24:59:

CT 1 ! It comes in many colours ! Noel.

Which type of CT1? There seem to be many completely different types of adhesive...

**LINK**

https://www.ct1.com/our-products/

Robert Butler23/01/2022 23:27:01
382 forum posts
6 photos

Of relevance, there only appears to be Superfast in 20 or 50ml packs but I am happy to stand corrected!

Robert Butler

Pete White24/01/2022 09:46:03
162 forum posts
16 photos
Posted by Howi on 22/01/2022 09:57:44:

Why are we trying to solve someones commercial product problems.

Having spent a lot (?) of money so far, why go cheap skate now, talk to adhesive manufacturers and get the right product for the job.

Don't you just hate it when someone comes on here for advice, only to Poo Poo (Black adder 4) every idea thrown at them.

This post is not the only one recently.

I did wonder this myself, but I suppose its because everyone on here is always keen to help wherever they can.

I am not really sure about how I could recommend a bonding agent without knowledge of the intended use though?

Sorry about the joined quote and reply system is having a bad day, was getting a red outline on the reply page ?

Edited By Pete White on 24/01/2022 09:53:09

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