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Thermoforming Polypropylene: Syntactic Foam vs. Solid Polymer

We’ve had a lot of discussions over the years with plastics processors about thermoforming polypropylene (PP) cups. PP is susceptible to scratching, especially with deep draw parts such as drink cups. While syntactic foam has become the preferred plug assist material, the high glass content can cause issues with scratching. Therefore, solid engineered thermoplastics such as polyetheretherketone (PEEK) and polyetherimide (PEI) are sometimes used as plug assists to minimize scratching in transparent PP parts. As we know, several other variables are at play in thermoforming and in the case of PP, sheet temperature can never be overlooked.  Just a few degrees can be the difference between a beautiful, high-clarity part and an imperfect one with scratches.

Digging into the archives, we published a paper showing the results of tests comparing our HYTAC materials with solid polymers. We’re making it available again here via a republished blogpost in case you missed it a few years back.

As always, we’d love to hear your thoughts. Do you have challenges with PP? What steps have you taken to improve the process?

CMT Field Notes: 2013 SPE Thermoforming Conference – Part 1

The 2013 Thermoforming Conference has just ended in Atlanta, GA. While the final numbers are still being tallied, judging from the traffic at CMT’s booth, we would suggest that it was another successful event. In fact, we have so much good stuff to share that we’re going to split it into 2 separate blog posts.

Our GM, Terry Woldorf, played a leading role in Monday’s roll-fed thermoforming seminar dubbed, “Mythcrushers: Separating Black Art from Science”. The goal of the seminar was to bring a new level of scientific understanding to the thermoforming process. Dr. Joseph LeBlanc of Penn College presented information on heating and cooling the plastic sheet and mold, drawing from his knowledge as an aerospace engineer. Ian Strachan discussed the many factors that have led to a perception of thermoforming as a “Black Art” while Mark Strachan of uVu Technologies summed it all up with details relative to tooling and techniques to connect the science to the process.

CMT’s perspective on thermoforming is all about the plug assist materials, but we know that our HYTAC materials do not operate in a vacuum (they operate with vacuum, but that’s a bad joke). Because of the multiple variables involved, we stress that processors should appreciate the interplay of sheet temperature, tool design, friction and associated plug choices such as material and geometry.

Beyond the equations and hard science, however, we have seen how best practices can be standardized to give processors the ability to ramp up more efficiently without as much trial and error. As shown in our machining guidelines, we spent 12 months working with toolmakers and suppliers to develop these metrics. Based on the questions posed to Terry after his presentation, it is clear that many people still want guidance on how to mill, polish and clean HYTAC® plugs. Here is an abbreviated version of the Q + A session:

Q: Is centered turning the only way to make plugs from rods? 

A: No, many people use centerless turning machines or even milling machines with cut pieces of rod. Our online turning and/or machining guides contain complete details for the best types of tools, feed and speeds and depths of cut for all types of equipment and sizes of material.

Q: What material do you use for turning?

A: As with milling, solid carbide inserts with positive rake provide the best results.

Q: Should we mill HYTAC materials dry?

A: Yes. Generally speaking, coolant doesn’t really help. In the case of the thermoplastic materials (B1X, XTL), the coolant will actually roughen and destroy the surface as it is machined. Many times, people run their feed rates too slowly or use dull cutting tools so they see overheating and use coolant.  The use of sharp carbide tools and proper feed rates will result in a tool operating near room temperature. Following these steps will provide the best plug surface results.

Q: What’s the best way to clean the plug?

A: Isopropyl alcohol (pure, not those diluted with water) is typically a good option. A light touch with a very fine scuff pad generally works well.

In the next post, we’ll write about the many heavy-gauge projects we discussed where syntactic foam can provide a competitive edge. In the meantime, check out this post on using HYTAC® as a mold material.

CMT Field Notes: 2013 SPE Thermoforming Conference – Part 2

This is the second in our 2-part summary of the 2013 SPE Thermoforming Conference in Atlanta, GA. As we hinted at the end of our last post, CMT had many engaging conversations with heavy gauge thermoformers. The rapidly growing interest for syntactic foam plug assists in the heavy gauge world seems to stem from the following factors:

  • a steady increase in the price of plastics
  • an increase in quality demands from the market
  • an industry-wide focus on reducing scrap, i.e. eliminating waste
  • many, many companies looking to implement “Lean” or Continuous Improvement projects

Our work with Penn College and a number of processors has shown that HYTAC® can be used with great success in thick-sheet, deep-draw applications.

Because many heavy gauge projects have short runs (from a few dozen to several thousand parts) compared to thin-gauge or roll-fed applications, processors tend to be very cost-conscious when it comes to plug materials. Given that syntactic foam can range from $500-1000/ft3, this is not unreasonable. In many cases, a simple wooden plug can be slapped together and short runs can be achieved with minimal problems.  When one stops to consider the total cost of ownership, however, the calculus changes. While wood offers low costs and easy manufacturability, it has limited temperature resistance which becomes problematic for longer dwell times associated with many heavy gauge projects. Wood also has a tendency to mark-off on the plastic which, if texturing and surface finish are important, can result in rejected parts. When used as a plug material, aluminum offers benefits beyond what you get with wood, but aluminum plugs must be heated and precisely controlled in order to achieve optimally formed parts. This adds a level of cost and complexity to the process.

As a result, syntactic foam is gaining acceptance as an option for large part plug assists. Low heat transfer, durability and minimal mark-off are three key reasons why some heavy gauge thermoformers will use syntactic foam. During the show in Atlanta, we had numerous conversations with processors about their positive results with HYTAC® materials. In some instances, they are using HYTAC® in limited fashion as pushers to eliminate webbing while improving material distribution. In other scenarios, syntactic foam can also be used on the clamp frame to minimize chilling of the sheet.

In July 2012, our senior materials engineer, Kathleen Boivin, published a paper that appeared in Plastics Technology. The following excerpt is taken from that piece as it neatly encapsulates much of what we talk about in heavy gauge thermoforming:

“Production volume is the main consideration when deciding whether to go with a full-size plug or localized pusher. For a 24/7 manufacturing operation, the cost of a full-size syntactic plug can be easily justified by the 15% to 20% cost savings per part. The bulk of this savings is achieved through better material distribution, allowing for down-gauging, which also leads to reduced cycle time and lower energy costs.”

If you weren’t at the show and want to learn more about how syntactic foam can work for you, give us a call at 508.226.3901 or fill out our application form.

CMT Materials Gears Up for K 2013

In just two weeks, the tri-annual K Fair will kick off in Dusseldorf. The venerable global plastics trade show is now its 60th year and we’re sure that the halls of the massive Messe will be crammed full of international visitors. Beyond business meetings in the multi-level booths from polymer giants and plastics multinationals, attendees will be treating themselves to the hearty German fare being served up. Schweinhaxen, anyone?

Given the correspondence in recent weeks, it’s clear that tool designers, processors and machinists from all over the world will be congregating at our booth in Hall 3, Stand B52. We’re planning on serving up plenty of information, tips and guidelines on HYTAC® syntactic foam with an emphasis on new XTL thermoplastic syntactic. We’ll be there with our distribution partners from Europe and Asia to display cutting tools and share best practices from around the world. Here’s a short version of our dance card:

HYTAC® XTL: The Next Generation Thermoplastic Syntactic.  This mauve colored material was developed to improve our popular HYTAC®-B1X line by creating a thermoplastic that was both easy to machine and polish.  HYTAC®-XTL also surpasses B1X in toughness while offering the lowest thermal conductivity and lowest thermal expansion of any thermoplastic syntactic foam.  Developed in 2012 and commercialized in 2013, it is quickly growing in popularity as the “do-it-all” syntactic plug material.  The easily polished surface is ideal for use with transparent plastics and easy sheet release while surviving the most demanding applications.

HYTAC® plug material is being used in multiple show tools for all the major OEMs including IlligKiefelGablerOMGGNWM and it will also be on display for several key thermoform tooling companies including BoschSprangMarbachTermostampiMould & Matic and Techno Tool A/S

So if you’re going to Dusseldorf, be sure to visit us in Hall 3, Stand B52. And if you can’t make it, be sure to check back with us to read our report of the show.

Syntactic Foam and Package Design

It’s very easy to spot a thermoforming professional in the grocery store. The person craning their neck to look at the bottom of a package isn’t your average shopper. Most people don’t stop to admire the latest in packaging innovations, but they certainly shout from the rooftops when they can’t open a sealed clamshell.

We often talk about thermoforming in terms of ‘black art vs. science‘ but when it comes to package design, it’s all about science. There are several key pre-requisites for any thermoformed package across industries, including rigidity and clarity. Features such as impact resistance and ease of de-nesting (the ability to stack, or ‘nest’, one tray on top of another without sticking) are considered. Material selection therefore is of primary importance. Each material type has its own characteristics and film suppliers generally provide the appropriate documentation outlining specific properties including specific gravity, tensile strength and, perhaps most importantly, thermoforming temperature. But it’s not only about the sheet. Our extensive work on the interplay among several variables including sheet, plug and temperatures reveal distinctions that can make a big difference in final part quality.

Syntactic foam plug assists are purpose-engineered for thermoforming and provide unique properties that result in superior packaging. When it comes to package design, form and function must be balanced. Design engineers use state-of-the-art software to create innovative and eye-catching packages while still maintaining the fundamental goal of protecting and displaying the product inside. Syntactic foam plug assists aid in the design process by pre-stretching the sheet into position without removing heat or affecting its formability.  This is critical because the design work is based on material specifications which are based on specific, optimal sheet forming temperatures.  Overheating a sheet is often the cause of loss of plastic orientation, lower strength, loss of clarity, sheet stick to the plug and a wide range of uncontrolled issues, all due to compensation for a plug that chilled the sheet on contact.

So the next time you check the bottom of the package or cup and you’re thinking about the recycling code, stop for a few seconds to consider the amount of upstream design and engineering that went into the plastic shape that is protecting your purchase.

K 2013 Comes to a Close

After a solid 8 days at the Messe Dusseldorf, the CMT team is heading home. The K Fair is a truly global event and with stacks of business cards from thermoformers and toolmakers all over the world, the prospects for syntactic foam plug assists are looking bright.

Many conversations began with, “What is the best material for PET / PP?” With HYTAC plugs in almost every major thermoforming booth, users could see for themselves the benefits of different plug properties and geometries. Whether it was XTL in the Bosch-Sprang booth or B1X in the Illig booth, PET cups were cyrstal clear. GN and Kiefel ran with FLX and FLXT plugs for PP and PET cookie trays and drink cups.

What is also clear is that HYTAC translates quite easily into many languages! German, French, Italian, Spanish, Dutch, Mandarin… our booth was filled with international visitors, partners, distributors and thermoforming experts looking to learn more about XTL, the newest and toughest syntactic foam on the market.

K is a fantastic event, but after this trip, we’re glad it’s only once every 3 years. Tschuss!


How to Cut and Polish HYTAC® Syntactic Foam

The K show taught us a few things about the newest developments in thermoforming machinery and tooling. The application of information technology to the thermoforming process, for example, was one interesting trend that echoes what we see in many other industries where “big data” is the order of the day. Having the ability to meter and monitor data from various sensors, gauges and scanners can help operators dial-in the process to minimize waste and optimize start-up. The ToolVu system and the Illig “Intelligent Control” system were two examples on display. We’re also working to create new parameters related to plug speeds, temperatures and positions that can be fed into these new systems.

For all the advances in technology, however, it was interesting to see how certain fundamentals are not always well-understood. We spent plenty of time talking about how to machine and polish plugs to get the best part possible. From showing people the high-helix geometry of our solid carbide cutting tools to calculating feed rates, it is clear that practical information goes a long way.

Remember that feed rate = spindle speed (RPM) x chip load x # flutes. Too low a feed rate will generate excess heat and reduce tool life. Too high a feed rate will cause poor surface finish or part movement during machining. Proper settings will result in a tool operating at or near room temperature. 

What we have developed in our machining guides needs to be passed along to machine operators and those technicians working most closely with tools and plugs. Small changes can make a big difference in both plug surface and final part clarity. Let us know how we can help.


How to Improve Material Distribution in Thermoformed Parts

Here at CMT Materials, we like to work with partners and end-users to develop practical information that can help you get more from your plugs. We recently received a summary of tooling and plug trials done by a large thermoforming company and we wanted to share it with you.

This mini case-study is only 1 page, but it clearly illustrates why our new XTL syntactic foam is quickly becoming the plug material of choice.


We hope you enjoy it. As always, send us your comments, thoughts or application notes.

CMT Materials Exhibits HYTAC at ProPak Indonesia

The 2013 ProPak tradeshow will be in Jakarta, Indonesia this week. CMT will be there to showcase HYTAC syntactic foam plug assist materials, especially XTL, and to meet toolmakers and thermoformers from around the region. Southeast Asia is a fertile ground for thermoforming as evidenced by strong growth in packaging markets according to Euromonitor International. In fact, at the AMI Thin Wall Packaging Conference earlier this year, Euromonitor reported 6% CAGR in retail unit volume growth from 2007-2012. Asia, and Indonesia in particular, is clearly the fastest growing market for retail plastic packaging of which thermoformed cups and trays play a signifcant part.

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Remarkable Thermoforming in Indonesia

Remarkable Indonesia” is the slogan developed by the Indonesia Investment Trading Board to promote this country of 246 million. After spending several days in Jakarta (pop. 14MM), we can attest to some remarkable facts about the local market for thermoformed packaging.

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