Gluing Plexiglas to Stainless Steel

Can you not use screws or some other fastener?

The stainless steel plate is only 1/32" thick and is reciprocating on a fixed bed. There is not clearance for a screw head or enough thickness to tap.

Well it sounds like you need JB Weld.

At some point in time, this piece of Plex will have to be replaced... It's gonna break, the guidelines will need to be different... something will necessitate replacement.

Our Op has told us this is a piece made in-house, not a factory-correct OEM part.

If we successfully suggest something that is, indeed, a good solution to this problem are we simply making a bigger, better problem for the future?

The JB Weld can be removed with a butane torch, which gets as hot as 2600F. The JB Weld needs 600F for removal.

Without seeing the machine, maybe this is feasible.

I would be reluctant to put a torch to my $5 thousand dollar Juki walking foot machine.

"You want something that does not cure to be rock hardness."

I'll agree. In a vibration environment, a hard cure will be brittle and likely to fail quickly. My first thought would be a silicone adhesive like an aquarium sealant. Those are made for smooth surfaces.

Next suggestion would be to try to drill and tap a hole in the SS and fasten the acrylic with a machine screw.

Good post.

He should clean all parts using alcohol (meths or denatured depending on where you live!) and use clean throwaway thin rubber gloves when handling the components.

Clean the gloves with the alcohol first....

Fingerprints will ruin many good glues.....

Make sure that the "mating" surfaces are both flat to each other....smallest gap is important with superglue to assist the bonding by excluding air.....

To achieve this lightly sand the gluing area of the acrylic on a find sandpaper laid on a flat surface. LIGHTLY!!

Hopefully the metal part is already flat.... though fine sandpaper on the gluing area will assist bonding. Try without first.....

Treat the job like an operation, totally hygienic.....

Agree about the hardness of the adhesive. Superglues are generally very brittle and with the CTE mismatch between the acrylic and CRES, it won't last. A few thermal cycles and it's done.

I would put in a call to the Master Bond people as they have much more experience with what works and what doesn't. They can tailor epoxies for almost any kind of application.

I have used their high-compliance epoxies for demanding CTE-mismatch applications with very good success.

If it's available in your area, Goop adhesive works very well.

Goop has excellent adhesion whilst remaining pliable. Just be careful not to get it on parts of the plastic where it doesn't belong, as the solvent used will craze certain plastics. I suspect that alignment guide is probably not made of cast acrylic (Plexiglas), but styrene. Styrene will craze with most solvents. If it is critical that you do not mar the plastic I would recommend that you first mask off the areas to be protected with painters' tape prior to applying the adhesive, and then remove the tape before the adhesive sets (else risk gluing bits of tape to the part). If you mess up and need to re-do it, or eventually need to replace the part, Goop is much easier remove than other, more permanent adhesives such as epoxy.

I laugh at your recommendation as folly.

Solvents based adhesives don't adhere too well to SS.

This Plexiglas (are you sure?) piece... is this a wear or rub plate on the machine?

If adhered, how do you replace when a groove is worn in the Plex?

It is used to align fabric prior to sewing. It has steps on the underside that the operator uses to align three pieces and is Plexiglas so that the operator can see whether the pieces are fully engaged into the guide.

Unless this part was machined in-house for this application, it is unlikely that it is made of Plexiglas. Thin Plexiglas, especially, is extremely brittle and very likely would not be used for a standard part. If shipped as part of the machine, for more likely that it is transparent styrene or similar.

The Plexiglas is 7/32" thick and has been machined (by me) on the back with three steps for alignment guides.

Ah. In either case I would still recommend using Goop for reasons I mentioned in my earlier post.

I've tried cyanoacrelate (superglue)

Cannot recommend that for this application at all as in my experience with stainless steel these adhesives have no give and cannot handle flex and vibration.

What other adhesives have you tried?

Superglue is what our maintenance manager suggested. I haven't tried anything else yet and was hoping to find the voice of reason to avoid a trial and error process. We have two more machine to set up using the same materials and I would like to start them in the right direction.

Superglue, the new Olde Standby when chewing gum & baling wire are unavailable.

I was skeptical, too, when our maintenance guy (he knows just about everything there is to know about sewing machines) suggested it to me the first time. It seems that my skepticism was justified in this case but most of the time he is spot-on.

Nobody's perfect. The materials to bond are right but the application is not.

As alternative have you considered industrial (not the stuff you get for homes) double sided tape? We use this in certain situations.

Just something to keep in the back of your mind.

Lightly sand both surfaces where they will be in contact to provide more surface area for the adhesion and to ensure they are clean. Wipe the surfaces with rubbing alcohol, dry them, then use an RTV material to bond them together. RTV will have a bit of resilience allowing it to absorb the vibration without delaminating.

(edit) Just noticed Lyn had a similar reply.

Try a pressure sensitive acrylic film (PSA). 3M has a variety of types with and without an internal scrim that would be compatible with your materials. They are like a double sided tape.

Well you have a lot of good advice so I'll try another direction that might work....You could solder a piece of slotted stainless L shaped plate instead of the plexiglas...now short of bending a spatula to fit, I don't know where you would get this....

....otherwise JB weld is hard to beat.....or you could get technical with Loctite or 3M...

http://www.henkel.com/com/content_data/140353_productcatalogue.pdf

If I could weld a spatula on this machine and make this problem go away I certainly would. Unfortunately the underside of the piece has to remain relatively clear so that the operator can see through it. Maybe they could look through the holes on the spatula...

How thick is the plexiglass?

I would consider using a 2-56 undercut flat head machine screw.

The head height is specified as .036", which means you would need to counterbore into the plexiglass about .010" maximum and thread the rest of the material.

You can buy these fasteners as small as 1/8" long from McMaster-Carr. Plexiglass is relatively easy to tap with soapy water as the cutting fluid. Buy a good brand name tap like Greenlee.

The stainless can be countersunk easily enough on a drill press.

Drill out the hole in the plexiglass with a #50 drill. You can use a few drops of soapy water to prevent melting the plexiglass. I would spot drill that with an 1/8" center drill like this one and use it to provide the small counterbore you need. Then tap the holes.

Some form of LocTite would keep the screws from backing out.

You can also add some double sided sticky tape like a polyester or polyethylene tape. They make that as thin as 0.003" thick and that with the screws would probably do very well in a vibration environment.

That's how I would do it.

If you are suggesting drilling and countersinking a tapered hole for the head of the screw into acrylic, I think this is ill advised.

It will crack when the screw is torqued, even if OP is handy enough to accomplish this feat.

I think some two sided acrylic tape is worth a look. (Easy to repair)

I hate it when I complicate these threads.

The alternative is a PEM nut in the plastic or even the SS.

Press fit nut or stud in the St.Steel to attach the Plexiglas?

Yes, a flush PEM nut would work well.

This....if it is available in your geographical locale. Sikaflex 291.

http://www.supercheapauto.com.au/online-store/products/Sikaflex-Marine-Adhesive-291-310ml.aspx?pid=122707#Cross

There are superglues and then there are superglues. Not all are equal and the stuff you buy in the 99 cent store is not much good.

Go to someone like http://www.cyberbond1.com/adhesive-solutions/plexiglass-adhesives.aspx or Loctite and ask them what to use. Loctite also has a clear epoxy that I guarantee will not let go. It is used to fasten NASCAR driveshafts together (carbon fiber and steel). We use it to make radiators for small engines.

Superglues come in all types of viscosity and speed of cure. You can also use a spray accelerant or just plain old baking soda to speed their cure. However, accelerating the cure generates a lot of heat and it might melt the plexiglass.

I have read everyone's comments, and am most surprised to note that no-one has mentioned silicon sealant. Dow Corning clear is probably the best. I believe it will ignore your vibrations, and stick like crazy. I once mounted a hardwood strip to a concrete wall in this way, and hung more than 20lbs worth of hammers on it for 5 years, no problem.

You need to let it cure properly before use though...suggest at least overnight.

No one has mentioned urethane adhesives which seem to work better than silicone. I haven't tried them on ss to Plexiglas, but it seems to adhere well to things you don't want it on.

Off the shelf, clear silicone caulk should work. You would just have to take the part out of service until it was completely cured, (24 hours).

It's used on all types of plastic, as well as sealing SS sinks, etc. I'd put a nice 1/8" bead between the two surfaces rather than trying to use it as a thin layer "glue". It will be able to flex, as well as absorb the vibration.

Use the same sanding and cleaning methods from above.

Sikaflex 295. It will adhere to both and will absorb some vibration easily. Be sure to clean the plastic and the ss thoroughly and not to corrupt the clean surfaces before bonding.

A good VHB tape will do the job.

3M have many type of VHB tape and it's works well.

Clean before gluing with isopropyl alcohol and wait 72 hours for full cure bond.

As Pops7 says, VHB tape. 3M makes some that they call permanent that work exceptionally well.

Note, however, generally you only get one shot to get the placement correct!

You might try Loctite Black Max. I use it to glue glass/plastic to ss or aluminum. It dries tough rather than hard.

Thank you all for your help. I've tried two things so far: contact cement (seems to be working fine); and epoxy (the jury is still out). Oh, and thank you, Lyn, for not asking if this was a test or interview question!

HA! I just KNEW this was a homework question.

Lyn, you owe me a quarter.

Doorman not withstanding, I don't think anybody could make that up.

Yeah... you're right. Too mission specific for a typical homework Q.

I owe you another quarter.

loctite 37438, 3M 08752, permatex 81844. The adhesive they use to adhere the bracket for the rear view mirror on to the windshield? That bracket takes a good bit of punishment as the mirror bounces up and down on it. The bracket is SS and Plexiglas has similar surface properties as glass.

I would also recommend using PETG plastic. I have found it more durable the acrylic.

Epoxy is definitely the way to go. I had to replace one of the pieces I had epoxied on yesterday and the piece broke before it all came off.

What I thought was long lost was ply o bond and I just found BARGE CEMENT that

is what looks to me as the same thing. It is a rubber cement that works on almost everything. I found it at a shoe repair place and it works great on shoe sole and

metal things I have used it on. I have also found it on Ebay.

Ply 0 bond if I spell it right was made by GC and I think it has been 15 years or so since they made it so I am happy to find BARAGE that is the same as far as I can tell.

Hi John,

My favorite contact cement has always been 3M Scotch Weld 1300.

It is chloroprene (neoprene) rubber with fast dry solvents. The only drawback is it is bright yellow, but it sticks like crazy.

Apply to both surfaces, let dry, put together. Done.

Welcome to the zoo.