Ethernet for PC-based machine control blow-molding retrofit

Silvercom Solutions retrofit increases blow-molding machine throughput by 20% and reduces raw materials use by over 5% for plastic parts manufacturer. PC-based controls and an Ethernet protocol provided needed functionality. See photos.


Blow-molding applications are arguably some of the most cost-sensitive in manufacturing. Considering manufacturers’ end products, such as plastic items, that must sell from a few cents to no more than a couple of dollars, knowing whether to retrofit an old blow-molding machine or purchase a new one can mean the difference between boom and bust. Silvercom Solutions, a technical solutions provider located in San Antonio, Texas, offers consulting experience to determine if older machines for blow molding, CNC, specialty machines, and other applications should be rebuilt. 

“Conducting a machine retrofit is naturally a cost-effective alternative to buying a new machine,” Patrick Grissom, president, Silvercom Solutions, advised. “The potential to flexibly select unique controls that are tailored exactly to the customer’s need is much greater via retrofit.”

Silvercom Solutions helps customers with complete or partial machinery retrofits to ensure manufacturing sustainability. The company can conduct partial retrofits at customer sites during planned downtime in the evening or on weekends, minimizing the production impact.

Retrofit to the future

While recently implementing a retrofit for Tejas Plastics, also based in San Antonio, Silvercom selected PC-based automation technology to handle parison programming (to control blow-molding plastic thickness), heaters, timers, press control, and hydraulic and pneumatic control on two machines. Tim Williams, production manager at Tejas Plastics, initiated the retrofit project with Silvercom to revamp the blow-molding machines with new controls technology to improve product quality and reduce raw materials use. Originally built in the 1960s and fitted with different controllers since then, the blow-molding machines used by Tejas Plastics make a wide variety of plastic products. These include storage containers, parts for schoolbuses, playground equipment pieces, audio speaker components, animal feeder barrels and funnels, several types of “dummies” for athletic training, and roping for rodeo cowboy training. 

Despite prior controls retrofits, machines used by Tejas Plastics were equipped with an outdated control system.

“We were having difficulty finding spare parts for the previous control system and often had to go through eBay to find replacement parts,” Williams recalled. “In addition, the previous parison programmer was limiting because it provided a mere 20 points of control.” The new control system manages up to 200 points of control, Williams said. A parison programmer with more points of control augments machine precision for determining weight distribution in parts and reduces the amount of plastic used, while creating higher quality products.

Cost was another consideration. Most Silvercom customers already use Microsoft Windows-based systems, Grissom said.

“Industrial PCs (IPCs) capably and inexpensively integrate into existing IT infrastructures, which is a clear benefit.” Because Silvercom has been a long-term proponent of Microsoft Windows Embedded operating systems, most customers recognize that the chosen PC-based control architecture is exceptionally stable. Customers also can use “standard Microsoft software tools—a cost-effective way to boost machine functionality.” 


After the specification was finalized, the Tejas Plastics machine retrofits by Silvercom incorporated a PC-based control system: a cabinet-mounted industrial-grade panel with a 1 GHz Intel Celeron M CPU for the automation controller and HMI. The 12-in. display computer runs PLC software and Microsoft Windows Embedded CE.

The PC-based blow-molding software has more flexible programming for the parison programmer and part weight controller, which “helps us complete retrofits faster,” Grissom explained. The blow-molding software has features unavailable in other parison programmers, including advanced temperature controls, counters, and timers, and provides faster and more accurate diagnostics, saving time, he said. It supports IEC 61131-3 programming languages standardized by PLCopen (Structured Text, Ladder Diagram, Function Block Diagram, Instruction List, and Sequential Function Chart). The solution offers “the most advanced hardware and software available” and expertly covers industry-specific functions, said Nick Kamas, sales manager, Silvercom Solutions. This PC-based system allows “considerably more customization and parison precision... than with PLC-based alternatives. Of course, customization means everything for retrofit projects.”

Flexibility of distributed I/O terminals adds functionality and customization options. To this end, the Tejas Plastics retrofit uses EtherCAT I/O terminals connected via a coupler, integrating high-precision measurement, safety, condition monitoring, motor control, and other capabilities. The Ethernet protocol also delivers the ability to communicate to 1,000 distributed I/O in 30 µs (microseconds), providing “all the Ethernet-based functionality we need,” Grissom said.

It seamlessly connects to the customer’s current network and the EtherCAT communication protocol “is extremely reliable; its speed is vital for machine safety, and it ensures the highest possible performance of the parison programmer on the retrofit.” The 10-fold increase in parison programming points enables Tejas Plastics to achieve higher quality resin distribution and lighter end products, which reduce use of raw materials and increases end product quality. The parison programmer on the Tejas Plastics retrofit can run at 2 ms and 5 ms. The system also permitted inclusion of a special “Stop Blow” feature on one of the Tejas Plastics machines.

“An alternate, plastics-industry-only black box solution we evaluated simply couldn’t provide the functionality unique to the Tejas machine that was required to stop the bottle blowing process,” Grissom said. “There are not many machines on the market that require this particular feature, so finding a controller that can fulfill it was difficult until we started working with this system.”

Automation sustainability: Retrofits

The retrofit of the two blow-molding machines was completed in December 2010 and is considered a success by Tejas Plastics and Silvercom. Tejas would have needed to spend an estimated $100,000 to $800,000 to purchase a new machine; the retrofit cost a fraction of that.

Building on this success, Silvercom Solutions is developing an off-the-shelf, 400-point parison programmer for retrofits designed with PC-based hardware to be as cost-effective as possible. The panel PC “reduces hardware infrastructure compared to other solutions, where you may have one monitor and one CPU to run one parison programmer and another monitor and CPU to run the machine,” Grissom explained.

“With this architecture we’re lowering the customer’s control hardware costs by as much as 50% and the customer can incrementally upgrade their machine to spread the downtime over the course of weeks or months rather than all at once,” Grissom said. Williams said, “For our first contract handled by one of the Silvercom retrofit machines, we increased throughput 20% for a 6-ft landscape timber (made of plastic) from 15 parts per hour at 14.75 lb to 18 parts per hour at 14 lb, reducing raw materials use by 5.3%. With another machine at Tejas, we increased throughput 20% from 15 parts per hour to 18 and decreased part weight 5.5% from 9.5 lb down to 9 lb. As an example of additional savings, the amount of required overtime for our employees to complete the project was also reduced.” Over the course of a year, these raw materials savings will substantially help Tejas Plastics increase profitability.

“In addition, our end products have a much higher quality appearance due to the increased accuracy of the machines because the plastic is more evenly distributed,” Williams stated. “Our end-customer for these parts is also quite pleased with the results.” While many sectors are improving, numerous financial pressures that characterized the economic downturn are here to stay. With this reality in mind, Silvercom Solutions can successfully serve budget-conscious manufacturers with older machinery that, due to budget constraints, needs to be modernized to operate for years to come.

“As proven with Tejas Plastics, our customers can greatly reduce their costs by using older machines with modern, PC-based controls,” Kamas added. “Even if a manufacturer can afford a new machine, they should consider that a Silvercom Solutions style retrofit can modernize an older machine with 2011 technology and inexpensively go head-to-head with brand new machines.”

Besides the cost savings that can be achieved via retrofits, resin and production costs are, of course, a critical factor. “As Silvercom Solutions has demonstrated, reducing raw materials usage is a key area to improve operations—especially as volatility and instability in the Middle East can quickly spike the cost of oil for plastics production globally,” Grissom said.

With the PC-based controls chosen, “Silvercom Solutions can help achieve these cost saving goals via machine retrofits,” he concluded.

Technology notes: Tejas Plastics, Silvercom Solutions machine control retrofit technologies

Silvercom selected PC-based automation technology from Beckhoff Automation to handle parison programming, heaters, timers, press control, as well as the hydraulic and pneumatic control on two machines.

Beckhoff cabinet-mounted CP6201 Panel PC with a 1 GHz Intel Celeron M CPU functions as the all-in-one automation controller and HMI. It has a 12-in. display and runs TwinCAT PLC software alongside Microsoft Windows Embedded CE.

TwinCAT Blow Molding Framework has a parison programmer and part weight controller. The Blow Molding Framework has features not available in other parison programmers, including advanced temperature controls, counters, and timers.

TwinCAT provides faster and more accurate diagnostics, saves time, and supports IEC 61131-3 programming languages.

EtherCAT I/O Terminals from Beckhoff are connected via an EK1100 EtherCAT Coupler.

Partnering with Beckhoff Automation on the controls side helped make Silvercom Solutions achieve its cost saving goals via machine retrofits, the companies noted.

- Shane Novacek is marketing communications manager, Beckhoff Automation LLC. Edited by Mark T. Hoske, CFE Media, Control Engineering, 

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