How to Choose the Right Plug-Assist Material

A question that we get asked a lot is, “What type of syntactic plug material should I use for my application?” Like most things in thermoforming, the answer is, “It depends.” However, we recognize that thermoformers and toolmakers want some degree of certainty when choosing plug materials. That’s why we have created a selector guide to help processors make an informed choice.

Each material is optimized for performance with different types of plastic sheet, temperature use, machining conditions, surface finish, durability and even pricing.  While every HYTAC® product is suitable for a wide variety of applications, making the “best” choice reduces machining costs, improves material distribution, enhances clarity, reduces plastic residue sticking to the plug and maximizes plug life.

Though some materials may initially cost more as a percentage of the overall tool price, it is important to understand the total cost of ownership. In other words, the savings generated over the life of a particular project should all be taken into consideration, from time in the machining center to set-up time, from production of initial parts to perfection of consistent parts, not to mention the cost of replacing any damaged plugs due to a production mishap.

Please refer to our CMT Material Selector Guide for more information. Of course, you can always contact us at any time and we’ll be happy to discuss your application with you.

Best Practices for Machining HYTAC® Plug-Assist Materials

Machining syntactic foam is not like machining other materials such as wood, aluminum or plastic. That’s why we have created guides to help toolmakers and thermoformers select the right tools and the right geometry for machining and cutting HYTAC® syntactic foams from CMT.

Properly machined, HYTAC® materials generally require minimal extra polish or surface preparation.  Following our guidelines will improve surface quality of the finished plug and aid consistency of plug performance.

Tools must be sharp to obtain a satisfactory surface finish when machining HYTAC® products. High helix geometry with a special point for upward chip flow, smooth sidewall and improved bottom finish is recommended. Dull cutters or incorrect geometries will result in poor surface conditions. High speed steel cutters are quickly dulled and are not suitable for use with syntactic foams. Solid carbide cutters are preferred due to the sharp edge and long life that may be obtained. Diamond coated tools may last longer, but are not required and have not been found to provide additional benefit in machining.

Once the tool is selected, dialing in an optimal feed rate on any CNC milling machine is done using the formula “Feed Rate = Chip Load x Spindle RPM x # of flutes.”  Chip load is the measure of thickness removed by each cutting edge (flute) in a single rotation.  The intended chip load for milling tools should be available from your tool supplier.  Optimal speeds, feeds and depth of cut when turning are listed on our turning guide.

If you have a new  job or just some questions about plug machining or polishing, contact us today

Best Practice: Polishing HYTAC® Materials

HYTAC® materials may be polished to a smooth surface finish condition. A properly polished plug will reduce scratching and aid in plug life/reduce sheet stick to the plug.

Syntactic foams are a variety of combinations of epoxy, plastic and hollow glass microspheres.  The same properties that make these foams the top choice for plug assist can create challenges in polishing.  The goal of sanding is to smooth microscopic peaks to eliminate potential scratching, prepare the plug for use and to modify surface area for different frictional performance.

Thermoset Epoxy Syntactic foams (HYTAC-W, WF, WFT, FLX, FLXT and C1R) may be wet or dry sanded using random motion. When following CMT machining/turning guidelines, most users find 220 grit sandpaper provides the appropriate roughness as a starting point. Finer and finer grits may be used for finish rubs until desired the desired surface finish is achieved.

Thermoplastic Syntactic foams (B1X and XTL) may also be polished, but a good starting surface is critical. A surface that has been damaged in the machining process cannot be fixed by sanding. After following CMT machining/turning guidelines, most users find 400 or 600 grit sandpaper provides the appropriate starting point, though many move up to 1200 and 1500 for an ultra-smooth finish. HYTAC® B1X should always be dry sanded. Download our polishing guide for details.

CMT continues to work with our partners in industry and academia to develop new techniques for polishing HYTAC®. If you have a tip to share, please let us know!

Best Practice: Threading HYTAC® Plugs

HYTAC®-B1X and XTL are thermoplastic-based syntactic foams. Due to the thermoplastic base, both B1X and XTL are extremely tough and durable. Unlike traditional syntactic foams which require inserts, B1X and XTL can be direct threaded. For all other HYTAC® materials, CMT recommends use of slotted inserts bonded into the base of the plug. We have worked with machine shops and toolmakers to develop a series of best practices for both direct threading and insert installation. Our insert installation guide offers complete details.

For direct threading, we developed a tensile test and used our in-house material testing equipment to record the results in pounds force. B1X and XTL were tested. For inserts, what we have found is that direct scored aluminum inserts work very well. Some of the key success factors for this simple process include the elimination of coolant during cutting (for proper adhesive bonding) and face milling the bottom of the plug after insert installation (to ensure a flush mating surface for the plug to the base is created).  We typically recommend Loctite 495 for bonding and our pull-out test results were based on this adhesive.

Field Notes: AMI Thin Wall Packaging Conference

CMT participated in the 2nd annual AMI Thin Wall Packaging Conference this week in Wheeling, IL. This was the first time that we attended this seminar and based on what we heard and who we met, it is likely that we will return next year.

AMI is a global market research firm and they brought together some major players from the world of plastics packaging. For companies like CMT that operate in the B2B space working with toolmakers and thermoformers, it is always valuable to expand the frame of reference beyond the engineering challenges of our daily work. Not only did we hear from upstream resin suppliers such as Milliken Chemical (who debuted an interesting new app), major brands such as General Mills, Danone and Kraft Foods provided insight into the importance of customer acceptance of new package design. We had the opportunity to talk about the critical role that our syntactic foam plug-assist materials play in overall package design and finished part quality. Thermoformers, toolmakers, sheet suppliers and major converters as well as some injection molding suppliers were all present at the table-top exhibition. Barrier film technology, in-mold labeling and retort packaging were just a few of the topics presented.

Down-gauging and light-weighting were two key topics and ones that are central to our value proposition. The ability to reduce the starting thickness of thermoforming sheet (source reduction) while maintaining the integrity of package and the contents within provide clearly documented financial and environmental benefits. In addition, lower weight parts also contribute to improved end-of-life processes (waste reduction).

We frequently talk to our partners about the interplay of plug material, plug design, material selection and sheet temperature. During the AMI show, we were glad to hear about some new projects where people were talking not only about down-gauging, but also reducing sheet temperature. The topic of sheet temperature vs. oven temperature can be addressed in its own blog, but we were very pleased to hear that some people recognize the importance of running at the sheet’s optimal temperature.

In addition to technical presentations, we also heard interesting talks on market trends, including some statistics on M+A activity in the packaging space. There were 112 deals in the past 6 years, 60% of which were thermoforming-related. Of those deals, approximately 60% were done by strategic buyers and 40% were done by financial buyers. The speaker, John Hart from PMCF, sketched out 3 categories of deal types (low, mid, high) and provided EBIDTA multiple ranges for each: 5-6x for low; 6-7x for mid; 7-8.5x for high.

AMI are hosting the 8th annual European Thin Wall Event in Cologne this December and we are planning to attend.

Field Notes: National Hands-On Heavy Gauge Thermoforming Workshop

by Kathleen Boivin, Sr. Materials Engineer, CMT Materials

Last week, CMT participated in the 4th annual National Hands-On Heavy Gauge Thermoforming Workshop at Pennsylvania College of Technology (Penn College) in Williamsport, PA.  CMT has participated in this workshop since its inception.  The first year, we attended the workshop as participants.  The last three years, we have supported the workshop with presentations on syntactic foam plug assist materials.

Penn College is a national leader in applied technology and prides itself on degrees that work.  It is only one of five institutions in the country that provide an accredited plastics engineering technology program.  The workshop was sponsored by the college’s Plastics Innovation & Resource Center (PIRC) and drew participants from six different companies in NY, MA, and PA.  The participants included machine operators, technicians, engineers, and purchasing managers.

Like the college, the workshop focused on hands-on learning by combining technical presentations with numerous labs.  The workshop was coordinated by Christopher Gagliano, Program Manager of the Thermoforming Center of Excellence (part of the PIRC) at Penn College.  Thermoforming expert, Jay Waddell of Plastic Concepts & Innovations, was the workshop leader.  Jay presented key information on heating the sheet, controlling vacuum, optimizing mold cooling and trouble-shooting.  Numerous guest speakers supported the workshop with presentations on their areas of expertise:

Roger Kipp of SPE: “Tooling Performance: The Little Things Mean a Lot”

Eric Short of PMC:  “Choosing the Right Material for the Job”

Dr. Joseph LeBlanc of Penn College:  “Heating & Cooling the Sheet”

Kathleen Boivin of CMT Materials:  “Optimizing the Cut Sheet Thermoforming Process with Syntactic Foam”

Sam Hacman of uVu Technologies – ToolVu: “Thermoforming Quality Control and Process Monitoring”

Bill Noderer of Raytek: “Explanation of Thermal Imaging Scanner Use & Benefits”

Our presentation focused on the fact that syntactic foam can be used anywhere that chilling of the sheet is an issue.  Often, heavy gauge formers do not use full-size syntactic foam plugs due to low volumes.  However, syntactic foam can be used as localized pushers, as mold inserts, on the clamp frame, and for prototype/low volume tooling.  Compared to other common assist materials such as wood and felt, syntactic foam offers the benefits of no bond lines, improved durability, minimal mark off, improved material distribution and part cost reduction (through down-gauging).

Participants acquired hands-on learning with labs in thermoforming, physical property testing, and extrusion.  In addition, a demonstration of CMT’s HYVAC vacuum fixture material was provided.

In the thermoforming lab, participants marked the sheet with gridlines so that they could visually see the material distribution.  They got to adjust machine parameters and see first-hand the impact of those changes.  The extrusion lab allowed participants to run the extruder, thread up the line and understand how hard it is to make good sheet.  The testing lab gave participants a better understanding of why sheet physical properties are important.  They got to see the effect of temperature on properties by testing the impact resistance of both room temperature and “frozen” sheet.

During the HYVAC demonstration, the benefit of being able to make a trim fixture quickly without machining was discussed.  The participants were given tips on fixture design and instructed on how to work with the material.  The participants got to work first-hand with the material and make several fixtures.

The participants enjoyed the workshop and found the information extremely valuable.  They especially appreciated the fact that about half of the workshop time was spent in the labs.  Penn College will be hosting the National Hands-On Thin Gauge Workshop on June 25 through 27.  Industry expert, Mark Strachan, of Global Thermoforming Technologies, will lead the workshop.

Field Notes: National Hands-On Thin Gauge Thermoforming Workshop

By Terry Woldorf, General Manager, CMT Materials

“Highly interactive.”   “Informative.”  “Surprising.”  “Great combination of lab, lecture and science and fun.”  These are just a sampling of comments overheard at the 4th annual National Hands-On Thin Gauge Thermoforming Workshop.

CMT Materials, Inc. again was invited to present in the lectures and participate in the lab.  The three day course equally balances classroom instruction time with hands-on lab time. The workshop covers a wide range of planned topics but also intentionally allows for flexibility to cover unplanned topics raised by participants.

The workshop takes place each year at Penn College of Technology campus in Williamsport, PA and is part of their Workforce Development and Continuing Education program in the Plastics Innovation and Resource Center (PIRC).  Attendees from as far away as Wisconsin, Florida, Texas and Michigan mixed with others from nearby states to fill the roster to its cutoff capacity of 30 people.  Keeping the group small ensures instructors and guest speakers are able to interact and fully explore topics, effects as well as the inevitable surprises from process-related matters in the extrusion, thermoforming or testing labs.

Hosted by Chris Gagliano, PIRC Program Manager –Thermoforming, and instructed by Mark Strachan, President of uVu Technologies, lectures included:

Dr. Kirk Cantor (Penn College):                   “Raw Material & Sheet Extrusion for Thermoforming”

Mark Strachan (uVu Technologies):          “Fundamentals of Thermoforming, Advanced Thermoforming Techniques, Trimming and Stacking”

Robert Wandelt (uVu Technologies):        “Thermoforming Quality Control and Process Monitoring”

Julie Griswold (WR Sharples Co.):              “Structural Design Considerations When Building Steel Rule Trim Dies”

Terry Woldorf (CMT Materials):                  “Plug-assist Material Selection, Geometry, Processing Methods and ROI Calculations”

Robert Borse (Angle Tool Works):                “Tool Design”

Dr. Joseph LeBlanc (Penn College):             “The Physics of Heating and Cooling the Sheet”

Bill Norderer (Raytek):                                     “Thermal Imaging Tools and Techniques”

These topics combined with multiple break-out group lab sessions where participants ran equipment, tested new and old procedures, interacted with each other, students and full-time PIRC employees. Participants generally tried to prove/disprove a wide variety of theories and traditional “best-practice” approaches to the thermoforming process.

If you missed out on this year’s event, be sure to contact the school to sign up next year.

Field Notes: Kiefel USA Thin Gauge Thermoforming Workshop

By Conor Carlin, International Sales Manager

On June 27-28, CMT participated in an impressive thin gauge thermoforming workshop hosted by Kiefel Technologies USA at their facility in Portsmouth, NH. The event was a highly technical affair with presentations from a variety of experts as well as a demonstration of a KMD85 inline thermoforming system. Attendees and participants came from both sides of the Atlantic including Germany and the Netherlands, New England, Canada, Ohio, Michigan, Wisconsin, California and Florida.

If any single theme emerged from the two-day event, it was that new technology has most certainly impacted the thermoforming process. The increased adoption of fast-cycling, tilt mold machinery means that tooling, including the plug assist, must be exceptionally precise and engineered to very tight tolerances. The use of air-save technology is just one of the new innovations in thermoform tooling. On the topic of air consumption, Kiefel explained how new high-volume, dual circuit pressure forming valves allow air to flow in and out of the mold cavities for faster cycle speeds and a significant reduction in air consumption and, by extension, operating costs.

The application of information technology to thermoforming is proving to be a rich vein of conversation in the industry. As demonstrated by Sam Hacman of uVu Technologies, real-time visualization of data from multiple monitored points (strain gauges, temperature sensors, plug drive sensors, vacuum/pressure transducers) can now allow operators to truly understand the variables in the forming process, further removing the moniker of ‘black art’ from thermoforming.

Here is the list of speakers and topics:

Julie Griswold – Sharples: “Structural Design Considerations for Steel Rule Die Applications”

Conor Carlin – CMT Materials:  “Best Practices for Using Syntactic Foam Plug Assists in Thermoforming”

Frank Karai – ODC Tooling:  “Tooling and Challenging Applications”

Michael Walper – Hekuma:  “T-IML Automation: Technology Ready for the Market”

Martijn Haex – Bosch Sprang: “Advanced Tooling Technology for In-Mold Cutting”

Jeff Nigro – Klockner: “New Product Innovation”

Markuz Zlotosch – Kiefel Technologies: “Advantages of a Speedformer”

Todd Morgan – Ametek LAND: “Scanners for Thermoforming Applications”

Brian Golden – Kiefel Technologies: “Beyond Conventional Wisdom”

Sam Hacman – uVu Technologies/ToolVu: “Thermoforming Quality Control and Process Monitoring”

Thomas Huber – Kiefel Technologies: “CAT System Presentation on Kiefel KMD85B”

Our presentation on plug assists began with a live poll of the audience to determine the percentage of tools that were manufactured with plugs. A second question explored the different types of materials used for plug assist. From the responses, it appears that syntactic foam is the leading choice of thermoformers and toolmakers. We dug further into why it is important to understand the interplay of the plug material, plug geometry, tool design and sheet temperature, and not just to look at each element in isolation. While the choice of plug assist material directly impacts the plug life, machinability and ease of processing, it is also directly tied to material distribution, cycle time, start-up time and process cost.

In addition to bringing together industry experts and processors for a great seminar, the Kiefel team also proved to be generous and thoughtful hosts. We were treated to a tour of The Redhook Ale Brewery and a traditional New England lobster bake for dinner! Here’s hoping they make this an annual event….

How Syntactic Foam Plug Assists Improve Your ROI

Understanding the interaction and balance among plastic sheet, plug material choice, plug design, mold design, plug speed, vacuum, form air and numerous other factors often separates true artists from lucky amateurs.  At CMT, we like to talk about the interplay of all of these factors as the plug meets the plastic: the point where the action is most immediate in the thermoforming process.

While there is often no single choice to be made, making the “best” choice reduces machining costs, improves material distribution, enhances clarity, reduces plastic residue sticking to the plug and maximizes plug life.  Introducing science to the process allows even unlucky amateurs to become thermoforming artists.

Many machine operators know the stress of trying to meet production goals while maintaining quality standards. Running large machinery with precise tooling means that you’re in charge of some serious operational assets. You don’t always have the time to stop and appreciate how ROI is calculated or what you can do to improve it. However, stopping to think about the role that the plug plays in your process can save some serious time while you’re reflecting on machinery, tooling and material.

The following comments came from a thermoformer who participated in one of the recent workshops where CMT was invited to speak. We think it provides excellent insight into the daily challenges faced by operators and how a small change can have an outsized impact.

“I took what was learned in your class concerning material flow over the plug assist and applied that to the design of our mold. I started with 1/8” offset from the cavity, applied blends in strategic areas based upon my new understanding, and had the tool maker polish the HYTAC FLX plugs to a 1500 grit. These three things together resulted in a wall thickness that was more than double what we had seen in the part’s troubled areas.  

I’ve only been involved with this project for a relatively short time (8 months or so), however, I know that over the years (several years, in fact) at least two engineers and a host of operators and tooling people have all tried their hand at carving assist plugs, adding on to the mold length, and various other forms of ‘black art’ in the attempt to thicken up those troublesome thin walls. In short, the training we received from you proved that there is more of a science to thermoforming than most people recognize.”

CMT will be co-leading a thin-gauge thermoforming seminar at the upcoming SPE Thermoforming Conference in Atlanta, GA on September 9-12. Titled, “Mythcrushers”, we set out to separate myths from facts in thermoforming. We’re looking forward to an interactive and dynamic conversation.

“Which Syntactic Foam Should I Use?”

We are often asked to provide recommendations on plug materials based on a specific project. Usually the processor will ask us, “Which material should we run with PP/PS/ PET, etc.” And while we are happy to engage with toolmakers and thermoformers, there are many elements beyond our scope that need to be taken into consideration. However, we strongly believe that using the right material under the right conditions can make a dramatic difference in the end product.

The following is our response to a typical customer inquiry. We are writing about in our blog today because it is a universally relevant response. As always, we would love to hear from other processors who have different experiences. (All names are changed or removed to protect the innocent!)

“In this [PP cup] case, I think the answer is simply to have your customer reduce the temperature and fine tune the process.  PP has a very narrow window for forming temperatures and the range your customer is at is very high.  This is common when the customer has past experience with DELRIN due to the high thermal conductivity of DELRIN, which takes heat out of the sheet very quickly so the PP must be run at higher temperatures. (The thermal conductivity of DELRIN is over 2000% higher than XTL!)

While FLX and XTL will provide suitable performance, XTL will hold up better to abuse in the process.

Several factors that may help in the comparison of materials:

  • XTL, FLX and DELRIN all have the same service temperature of 350F/176C.
  • Thermal conductivity for each material (which controls how fast the material absorbs heat from the sheet ):
    • XTL: 0.17 W/m0K  (0.10 BTU/hr-ft-0F)
    • FLX: 0.11 W/m0K   (0.065 BTU/hr-ft-°F)
    • DELRIN: 4.32 W/m0K  (2.497 BTU/hr-ft-°F)
  • Thermal expansion for each material (which controls how much the plug expands as it is heated):
    • XTL: 58 x 10-6 m/m/0C (0.000058 m/m/°C)   (32 x 10-6 in/in/°F)
    • FLX: 42 x 10-6 m/m/0C (0.000042 m/m/°C)   (23 x 10-6 in/in/°F)
    • DELRIN: 85 x 10-6 m/m/0C (0.000085 m/m/°C)  (47 x 10-6 in/in/°F)

The true meaning to the application of the numbers above comes from realizing that thermal conductivity has a double impact.  First, the higher the number, the faster heat is absorbed from the sheet.  (This results in the need to run the material hotter than is recommended and results in “chill marks” that show where the plug contacts the sheet. It also means the process typically must run slower to allow time for the sheet to form.) Second, the higher number means the plug itself will absorb heat faster, which means it will expand more quickly. (This results in the need to run more pieces at startup to allow the plug to stabilize in temperature and size.)

For thermal expansion, the higher the number the more the plug will expand as it is heated.  This means the user must start with a plug that is smaller at room temperature than is needed for best material distribution.  Many pieces must be run to stabilize the plug as it expands over time.

If you focus strictly on the numbers though, it would indicate FLX is the best choice.  FLX does work very, very well with PP and we often recommend it.  In the case of your customer though, you can see from looking at the plugs that there is much material buildup.  This generally results from running the sheet at too high a temperature creating a buildup of melted plastic on the plug. The scratch marks and chipped- out sections indicate the material has been scraped or chiseled away from the plug and damaged the plug surface.  In this case, we would suggest XTL is the better alternative because it is so much tougher and more resistant to chips and dings.

If the customer turns down the temperature (even a drop of 5 degrees will help) the parts will run better, they will likely be stronger in crush strength and the material will not stick to the plugs.”

Needless to say, our email exchanges can be very in-depth, but we wouldn’t have it any other way. Got any questions on your own application? Let us know by filling out our basic form here.