Friday, April 24, 2009

Plexiglass Glass Cup Display

This is something fun made from Plexiglass sheet. We had a customer come to us with this giant wooden toothbrush and ask us to make a matching glass for an advertising display.

There is this whole world called the "ad specialty" industry that put people's logos on... well, anything.

What makes plastic so fun (keep in mind that the word PLASTIC means: Capable of being shaped or formed: plastic material such as clay. See Synonyms at malleable.) is that with a little heat, imagination, time, and the proper forms - you can make anything.

It's certainly tricky to take go from a flat sheet to a compound curve, bond the joint, and then mate the bottom. But then, that's the magic in plastic fabrication

Thursday, April 23, 2009

Plastic Glue and Adhesive

I thought I would blog a little about plastic glue (plastic adhesives) to help sort out the mystery of using adhesives and plastics. There's really some basic element to cover first. That's whether the plastic material you want to glue or bond CAN be solvent glued.

So let's take a test and see if the plastic can be glued. There a large group of plastics that CANNOT be solvent glued. They included polyethylene, polypropylene, teflon, acetal (Delrin), and Nylon (and some other exotic plastics).
A quick test is to take a solvent like acetone (nail polish remover) or MEK (hazardous stuff) and put a little dab on the material. If it gets tacky, you can glue it. If it does nothing, you need to use mechanical fastening or adhesive tape. There is a special treatment for Teflon to allow epoxy glues to adhere (called "etched teflon").

Water jugs, plastic gas tanks, plastic water tanks (RV's) are mostly HDPE (high density polyethylene) and can only be hot air welded. They are generally white in color. They are "waxy" and slick on the surface. Your 1 gallon milk container is HDPE. The bottome of your snowboard or ski is UHMW and cannot be solvent glued. Soda bottles are made of PETG which is difficult to solvent bond.

PVC (normally gray in color) CAN be solvent glued. PVC is used in sprinkler pipes (along with ABS). And PVC comes in CLEAR - think vinyl windows, think synthetic leather and upholstery.

Here's a list of adhesives by material type to explain further about the plastics that CAN be solvent glued... keep in mind that a "water thin" solvent adhesive needs the pieces to fit together perfectly and has a short working time - whereas a "bodied" adhesive allows some gaps to be filled and has a longer working time. ALL ADHESIVES REQUIRE 24 HOURS TO CURE AND ARE STRONGER IN 48 HOURS. Some adhesives have a 20-30 minute setting time and seem strong enough to move. They are not. I always tell people to wait overnight before testing the bond. The first 24 hours usually cures to about 85% of ultimate bond strength. The next 24 hours goes to about 90% with a couple more days to full strength. Just thought you might want to know.

Repairing a Crack in Plexiglass? Click on this link - I wrote about that elsewhere in this blog. (Repairing Plexiglass acrylic sheet and Lexan Polycarbonate sheet are similar issues)

Plastic Adhesive and Glue Cross-Reference Guide (thanks to IPS for this chart)

Plexiglass Glue - Plexiglas is an acrylic based sheet - the actual solvent for Plexiglass is Acetone, but is not a good glue as it evaporates too quickly. The proper glues are either based on a Methylene Chloride solvent formula (WeldOn 3, 4, and 16) or have PMMA monomer in the mix (WeldOn 40). I have seen people mix in other chemicals such as Acetic Acid to "enhance" it. My recommendation is learn to use what's in the can as adding other chemicals that are pretty nasty, and potentially cancerous, isn't the wise course of action. When building a display case you would use Weld-On #4 - that gives you the clear bonded edges. When building a large aquarium of 3/4" thick plexiglas you would use Weld On #40. #40 requires experience as it is a 2-part adhesive and 30 minute working time. It is almost as strong as the sheet itself.

ABS Plastic Glue - ABS is a styrene based plastic - very widely used in automotive and electronics industries. Could have a textured finish or not. Test with acetone to see if it gets tacky. ABS is a high impact material but can still crack and break. There are water thin solvents and milky bodied adhesives. Since ABS is always a solid color, it's easy to work with.

PVC Vinyl Glue
- PVC could be a medium gray color or clear. It can be rigid or flexible. It could even be a foam sheet (hard or soft). Confused? Hmmm. The gray is easy. The clear is easy. But foam? Yes - sign makers use a foamed PVC sheet (called Sintra, Celtec, Komatex, etc) that is widely available and comes in white, black and a rainbow of colors. Backpackers use a soft PVC foam sheet to sleep on. Sign Banners are typically PVC based material. Convertible windows, air matresses, inflatable pool toys are mostly flexible PVC based. There are water thin and bodied glues. As in other materials, the water thin are great for matching parts. For everything else, a bodied adhesive is required.

Multipurpose Glue - I call this group of adhesives the "sticky" ones - they tend to STICK the plastics together rather than chemically solvent weld. A contact adhesive like IPS 1829 will stick 2 flat faces of materials together rather well. A "structural" adhesive like IPS WeldOn #10 is a 2 part mix - and the adhesive itself becomes structure. It's white so it's usually used behind the material where it's hidden. WeldOn #40 is also a structural adhesive and is CLEAR. It seamlessly bonds Plexiglass and is great for bonding different plastics together. #40 requires some patience learning how to mix and apply. As always, try a test part before going forward with the real deal.

Lexan Polycarbonate Glue - Polycarbonate is a bit more sensitive to solvent adhesives, so a fast drying glue like Weld On #3 is a great choice. There is a new specialty adhesive, IPS #55, that requires a special application gun. For industrial users, this baby delivers a high strength liquid that is superior to all the other glues available.

Styrene Glue - styrenes are very sensitive to solvent adhesives. Most of the styrene product that is being solvent glued is a solid color (not clear) and either is a quick shot for tight fitting parts, or you need the bodied adhesive for filling gaps (or extra working time).

Polyethylene Adhesives & Glue - The fact is that the group of olefins (polyethylene based plastics), which include LDPE, HDPE, and UHMW, are so chemical resistant that modern science has not invented a solvent glue to bond these plastics. Of course, such properties are why these plastics exist and perform their job so well. You might even note that the solvent applicators and most chemical containers are made from polyethylenes.

All is not lost - You do have some choices!

1. Mechanical fasteners - screws, nuts and bolts and the like - you may have to recess the hole or deeper countersink based on the application.

2. Pressure Sensitive Adhesive applied to 1 surface. For the thinner sheets of UHMW - called "Slick Strips" - you can peel and stick a variety of thicknesses and widths from .010" to .125" thick,

3. Contact Adhesives - IPS Weld On adhesive #1829 - it STICKS but the bond is limited as it would be with ALL solvent based contact adhesives. There are a wide variety of solvent based contact adhesives available nationwide.

4. Double Sided Tape - OK, I know you didn't want to hear this, but for some of you, laying down a few strips may do the job. There are 2 kinds of tape. Double Sided Foam Tape is a permanent adhesive good for non-smooth surfaces. "Killer Red Tape" is a thin 0.015" thick acrylic adhesive transfer tape perfect for SMOOTH surface applications. Thicker tape is available such as the line of 3M VHB tape.

5. Hot Air Welding - the way LDPE and HDPE tanks and trays are built is by hot air welding the pieces together. Similar to metal welding, but at lower temperatures, a welding rod is melted into the sheet joint to make a strong bond. The materials must be the same - you cannot effectively join dis-similar materials.

Whew. Ok - I will probably have to keep expanding this post - it's a BIG subject area.

Tuesday, April 14, 2009

Another Day in Plastics Fabrication at the Shop

I was walking around the shop today and saw some incredibly different tasks going on. I guess it's what makes it fun every day for me, as well as for our team. Don't forget to click on the pictures to see larger versions!

Starting at the Shipping Department, it looks like a lot of display frames are ready to ship to a regional bank. Still needs some pallet wrap and protection.

Waiting for pickup from a local museum in San Diego, I found a stack of 24" x 24" x 24" acrylic vitrines - these are made from Optix brand acrylic sheet from Plaskolite.

Over in the CNC area they are cutting out some interesting shapes for a new customer. These parts will be "line-bent" into a new shape - a lot like oragami - that will have 3-D structure. Can't tell what it is. Heck - I don't know what it is anyway. (Have to check the work order tomorrow.....)

Over in the plexiglass thermo-forming department, Jason is working on a prototype for a couple of pedestals and windows. The soft felt-like material allows him to handle the plexiglass while it is still hot (275F) without transferring any mark-off to the sheet surface.

So this base is 3" thick clear CAST Plexiglass sheet about 18" x 24". It will become a base for some art object - each object has a different shape at the base and will require tailoring of the recessed holes to make them fit. We haven't polished out the holes completely as this is a work in progress.

Check out this photo. You are looking THROUGH the center of the plexi. That's a nickel on the other side, and the bottom of this base acts like a mirror - you are seeing a reflection of the machine and ceiling!

That's crazy.

Hope you enjoyed these pix.

Thursday, April 2, 2009

Architectural Resin Panels

I am sure you have noticed that in many restaurants, bars, and offices there has appeared a new kind of plastic decorative sheeting - filled with patterns and organic materials as well as solid colors. Some of these materials are made with PETG (pop bottle material) both pre and post-consumer based material (virgin and recycled resins). Some others are made from acrylics (Plexiglas). The variety and the applications seem to be endless.

We have been working with theses manufacturers for several years and do a lot of cutting, machining, and forming of these panels to help the interior designers and architects visions become reality.

At the "W" Hotel here in San Diego, we had a chance to create 1" thick panels of 3-Form Chroma material 48"x96" and then engineer the mounting holes and specialized slots for the surfboard fins that are mounted on the panels. The material was given an "aged" look - which we all thought was funny because Plexiglas does NOT yellow - but it looks cool on the wall as you can see in the picture.

Some clients use the materials as Donor Recognition boards - and we CNC cut out the boards to fit the particular look and feel of the installation.

Something new on the market are Architectural Resin Panels from Chrysalis HD - made here in California (hooray) and bringing a new set of patterns and standards to the market. The team behind this product are very creative and driven with backgrounds in design and architecture. The price is substantially less than other similar materials on the market (hooray hooray) which makes it very attractive considering the economic times. Lower price - better product is always welcome.

One of the things we like about the Chrysalis HD line is the formability of the product as most of the interior materials will allow forming (unlike many of the organic materials found in the other manufacturer's sheets). Lead time on getting this material is quick. Distributors should have stock but if they don't, sheets can be manufactured quickly. At my company we offer a "cut sheet" program to allow for designers to achieve their dreams without having to buy the whole sheet.

These are just a few of the 50+ patterns available. Cool!

Wednesday, April 1, 2009

Plastic Ice - Plexiglass acrylic Ice sheet

Plastic Ice. Fake Ice. Faux Ice. Artificial Ice. It is funny how there are so many things that we make that are fake. Really! I mean in Japan you walk down the street and every lunch restaurant has a set of fake portions set out to tempt you in. Even the mannequins in the department stores are looking more realistic.

Seems like everyone wants fake ice. The bigger the better. We have all kinds of fake ice in our store, but the largest block is about 9"x9". Not big enough for some people.

Today one of our suppliers came in with a sheet of fake ice. Really good fake ice. Check it out - it's crystal clear and we can cut shapes from it, or build it into pedestals or big blocks or cubes.

This sheet comes in any thickness - but I want to have sheets of 1/2" and 1" thick for some amazing possibilities.