is part of the Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

A short, simple path to lowering molding machine energy bills

“What the heck is wrong with moving a couple hundred thousand dollars to the bottom line?” says 
Dan Sherrill jokingly, but he’s serious about moving money off the monthly energy bill and into the profit column.

“What the heck is wrong with moving a couple hundred thousand dollars to the bottom line?” says 
Dan Sherrill jokingly, but he’s serious about moving money off the monthly energy bill and into the profit column.

Sobering fact: Much of the technology needed to—for want of a better phrase—save the planet doesn’t exist yet. It’s still in some phase of development, including a lot of the sustainable greener energy technology we read about. Don’t feel discouraged, though. There are many ways to be more energy efficient that are available right now. Hint: Most of them involve cutting consumption and waste—without living in the dark.

Just adding barrel insulation like the green blanketing on this IM’s barrel will instantly reduce the machine’s energy consumption substantially.

For instance, if you start looking for ways to cut your home’s energy costs, you quickly begin hearing a one-word piece of advice: insulate. Install insulation if you don’t have it, or add more to what you already have, and less energy is lost to the atmosphere—instantly. The savings are seen in the next bill from the power company. Insulating an injection machine (IM) works just about the same way.

Of the tasks that electricity performs, making heat is one of the least efficient. As the screw and barrel assembly of an IM changes pellets into melt, a substantial portion of the total energy it takes to do that escapes to the atmosphere as heat. The cost of that energy is irretrievably lost.

Yet stopping or reducing this loss is one of the most straightforward ways to cut costs in a molding shop. It’s neither difficult nor time-consuming. Up-front cost is relatively low. Full payback is most often less than a year. And just like insulating your home, the savings start with your next energy bill.

Energy costs 
get respect
“I’ve been in the business of cutting energy costs in some form since 1978. When times were good, it was tough to get a molder to even think about energy costs. It was small change. Now they call me and say, ‘My power bill is out of control.’” The speaker is Dan Sherrill, president of UniTherm, a supplier of high-temperature insulation, including products specifically made for molding machines. The voices he has been hearing on the other end of the phone, who in recent years are as likely to be a CEO or CFO as a production manager, often sound pretty stressed out.

The reason is simple: Energy costs are going up, and it’s a real stretch to imagine them ever coming down. Energy that is lost as heat radiated into the atmosphere is energy the molder must pay for the following month when the power company bill arrives. Sherrill says the money lost by industry as a whole is likely in the hundreds of millions of dollars per year, and it can easily be hundreds of thousands for a molding business.

That likely would be a medium to large company with many molding machines, but Sherrill points out that the savings and ROI are per machine, so the overall stop-loss and saving are proportional to the number of IMs. He has worked with companies whose monthly energy bill was $300,000, so their annual savings was substantial. But proportionally, saving is saving.

“And it’s hard dollars,” says Sherrill, “No smoke and mirrors—you  stop paying the power company and move the money to your bottom line.” And the savings continue past payback all the way to machine decommissioning. Plus, molders know what the savings will be before installation. In Unitherm’s case, Sherrill or someone else arrives at the machine with a kilowatt meter and calculates how much energy will be saved by insulating. The company can also do infrared studies, which can be very dramatic. With that data and the kWh rate, calculating savings is fairly simple math.

Simple install, multiple benefits
What we’re talking about is high-temperature insulation blankets that wrap around the barrel of the injection machine. If you have an uninsulated barrel, you already know how much heat is coming off it. Installing the insulation consists of removing the barrel shroud, wrapping the blankets, which are supplied in sections that fit the space between thermocouples, securing them with straps fastened with double D-rings, and that’s it. Installation takes 15-30 minutes, at most. As the installation progresses from the back to the front of the barrel, those nearby can feel the heat drop, and well they should. When complete, external barrel temperatures that were about 500°F are closer to 100°F.

Other benefits besides cost savings include:
• safety (see OSHA regulations, below)
• improved process control from consistent plant temperatures
• savings on air conditioning in warm weather
• faster startup by up to 30% after a shutdown
• extended heater element life
• rebates from local energy company in some places.

Why would you not?
What does it cost to insulate a molding machine? Sherrill says that, on average, insulating a 50-ton machine costs about $150-$160; 100 tons, $300-$350; 350 tons, $550-$600; 1000 tons, $2000-$2200. Unitherm recently wrapped a 3000-ton press. The cost was about $3500 and payback was 10 months. Payback is almost always within a year, with the added benefit that your energy consumption drops immediately.

Another factor in a molder’s favor is the rebates or credits many power companies offer for cutting energy consumption. Sherrill says UniTherm recently insulated 80 machines for about $100,000, with payback projected at 12 months. When the molder’s energy supplier picked up half the cost, payback came in six months. Nice.

With these benefits available relatively inexpensively, why might a molder not jump right into this? There can be an issue of insufficient funds, but even that could be handled with payment terms, which are often available. In terms of technical reasons not to insulate, excessive shear heat is one, and an air-cooled barrel is another.

Some also see an issue for custom molders that make frequent mold and material changes. If you run a material at 500°F and change to one that runs at 300°F, the time to cool an insulated barrel could add changeover time. UniTherm addresses that with one of humanity’s great technical breakthroughs: Velcro. Popping open Velcro-fitted Quick-Cool blankets to start a changeover exposes the top of the barrel so heat drops fast. Refasten them and you return to energy conservation mode.

Sherrill says business is pretty good for UniTherm these days, using the word “exciting” to describe it. It seems molders have had a “Eureka!” moment, he says, discovering that decreasing energy costs leads directly to increased profitability. And almost as a kind of bonus, you achieve better corporate sustainability. You are greening the company—profitably.

Insulation increases safety
From OSHA standard requirements:
“Safeguards for personnel protection—1910.335. Protective shields, protective barriers, or insulating materials shall be used to protect each employee from shock, burns, or other electrically related injuries while that employee is working near exposed energized parts which might be accidentally contacted or where dangerous electric heating or arcing might occur. When normally enclosed live parts are exposed for maintenance or repair, they shall be guarded to protect unqualified persons from contact with the live parts.”

Typical savings and payback from barrel insulation

Machine: Arburg 70 ton
kWh study               Uninsulated         Insulated
test environment     energy usage     energy usage

60 minutes                  1.72 kWh           1.09 kWh
16 hr/day                  27.52 kWh           17.44 kWh
0.15 kWh rate          $4.13 cost/day       $2.62 cost/day 
6 days/week            $24.77 cost/wk      $15.70 cost/wk
4.3 weeks/month     $106.50 cost/mon  $67.49 cost/mo
12 months/year       $1278.03 cost/yr    $809.91 cost/yr

Three-year investment/savings
Cost to insulate: $210
Amount saved: $1194
Payback time: 5.38 months

Machine: Cincinnati Milacron 1500 ton
kWh study                Uninsulated         Insulated
test environment     energy usage      energy usage

60 minutes               15.54 kWh          9.25 kWh
24 hr/day                372.96 kWh         222.00 kWh
0.067 kWh rate     $24.99 cost/day      $14.87 cost/day
7 days/week         $174.92 cost/wk     $104.12 cost/wk
4.3 weeks/month  $752.15 cost/mo     $447.71 cost/mo
12 months/year    $9025.78 cost/yr     $5372.49 cost/yr

Three-year investment/savings
Cost to insulate: $1782
Amount saved: $9178
Payback time: 5.85 months

Machine: Husky 550 ton
kWh study               Uninsulated          Insulated
test environment     energy usage      energy usage

60 minutes                  4.92 kWh           3.01 kWh
24 hr/day                118.08 kWh           72.24 kWh
0.075 kWh rate       $8.86 cost/day        $5.42 cost/day
7 days/week           $61.99 cost/wk       $37.93 cost/week
4.3 weeks/month    $266.57 cost/mo     $163.08 cost/month
12 months/year      $3198.79 cost/yr     $1956.98 cost/year

Three-year investment/savings
Cost to insulate: $910
Amount saved: $2815
Payback time: 8.79 months

Rob Neilley

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.