The Santa Fe, New Mexico-based plastics thermoformer has recouped all of its infrared investment within a twelve month period and at a rate of 30% savings on energy. Over this period cycle times have been reduced, energy bills and scrap rates have been lowered as has downtime. Moreover, the retrofit design of new heating system - control design, zone layout and ceramic emitter selection – has been done in modular fashion and has allowed Custom Skylights to use multiple tools and material types within a single thermoforming line.
Custom Skylights owner Jeff Apodaca says ‘we bought a gas oven a year before switching to Infrared technology via Ceramicx and Weco. We put a lot of money into it and it didn’t work: we had hot and cold spots, there was no way to control the temperature, as we needed to continually use it throughout the day. The oven simply kept getting hotter and hotter and we therefore ended up burning a lot of plastic. In addition there was no way to adjust the temperature for heavier gauge acrylic. After a year and day of burn outs, replacement parts and an expired warranty we decided that enough was enough’
Apodaca says that Custom Skylights needed to make a radical change in its heat sourcing. ‘We knew that we needed a new oven and so we decided to attend a thermoforming conference organised by the Society of Plastics Engineers (SPE) and educate ourselves before making another costly decision. At the conference we spoke to several oven manufacturers, and they all leaned towards the IR option for our application. However it was Weco’s ability to test our product samples; provide data analysis and designs that convinced us to buy from them.
Apodaca adds that ‘with this new IR oven we have not had a single day down since it was installed, and it runs 8 hrs a day we can now easily dial in the temperature required and cook different gauges of plastics knowing that our products will come out right the first time, it has cut our production time by 2/3 compared to our old cal rod and gas system, it has greatly reduced the energy consumption and eliminated the plastic loss due to un proper heat distribution.
Weco International Vice President for Technical Sales, Ted Rosingana, points out that incoloy-based heating - eg cal rods, metal sheaths, tubes - are inefficient over their lifetime and provide little directional energy to the material at hand.
‘Emissivity – as opposed to temperature – is the key criteria,’ he notes. ‘An Incoloy-based emitter’s emissivity - ie - the ability of a surface to emit infrared energy compared to that of a black body at the same temperature and with the same area – typically starts its life at 70%. However, after 6-12 months of runtime this reduces down to 35-40%. A Ceramicx brand Hollow Ceramic element, however, begins usage at 96% emissivity - and at end of life remains at over 70%.’
Expressed another way: 100 watts of energy going through a used incoloy emitter produces only 35 watts of energy as infrared directional energy compared to 96 watts from the Ceramicx element. The remaining energy is convection (rising heat energy) and light energy. In the Custom Skylights previous production situation which allowed for top side heating, the material was absorbing little energy from the old incoloy heating system and much of the energy was lost to convection. Directional energy (IR) is especially important when heaters are located above the target. Without moving air it would be impossible to utilize the convection energy of an incoloy-based heater when it is above the target. The convection energy rises and is lost to the surrounding environment. With infrared heating the directional energy is “directed” towards the target and absorbed - thus effectively using the energy the customer is paying for in each electric bill.
In terms of physical size, incoloy heaters are typically long, spanning the width of an oven sometimes in excess of 50 -60 inches. This provides very little zone control. The heaters are typically slow to reach set temperature and the surface temperature will vary significantly across its entire length. A ceramic-based heater has a much smaller surface area and can be individually controlled or grouped to create multiple heat control zones within the oven. At Custom Skylights, the parts required more energy absorption in specific areas to allow the material to form/move without showing defects in the finished product. The 96 x 100 inch thermoforming heating system was designed with 12 individual control zones. The entire oven and control system was pre-tested and shipped to the Custom Skylights. The oven was installed with predetermined mounting locations, power was landed to the control enclosure and the system was running.
Ceramicx founder and director Frank Wilson says that ‘this case study is a far from isolated story - and shows us that infrared technology is on the brink of presenting thermoformers worldwide with the most amazing opportunities for profit gain: Plastics thermoforming is a mature industry that has reached a crossroads in this regard and infrared heating offers a quantum step towards increasing margin and reducing energy cost and carbon footprint. It is in fact fair to say that most thermoformers who run incoloy emitters will continue to run the oven at higher output to achieve the same result. In most cases, the heat work part of these thermoforming systems is running at nearly 100%.
Wilson points out that ‘this way of working actually wastes energy: elements fail faster; more down time is needed to replace them; and convection heat increases the overall temperature in plant, which causes very hot working conditions, and further wear and tear and inefficiencies. The new Ceramicx-based heating that we installed for Custom greatly increased energy input to the plastics sheet material thus reducing cycle times. Less energy was used per part; thus making a sizeable reduction in cost per part.’
The Custom Skylights job also presented Weco and Ceramicx with the challenge of a limited 208V 200 amperage power supply. A standard WECO/Ceramicx oven design of this size would use 600 watt elements and require 400 Amps to power all the heaters. ‘The challenge for us,’ says Wilson, ‘was to design an oven that would still provide enough energy to maintain the customers production quotas and reduce energy costs. A typical oven design of 96” x 100” would normally use 600 watt elements and require over 400 amps to power all the heaters.’
WECO and Ceramicx therefore chose a 300 watt hollow Ceramic emitter mounted in polished aluminized steel reflectors. The aluminized steel reflector provides better strength than aluminum, comparable reflectivity and a higher tolerance to heat than stainless steel. When overheated stainless steel will blacken and without proper maintenance will absorb the IR instead of reflect as originally intended. The overall design provided the best directional energy for Custom Skylights application. The 300 Watt hollow ceramic emitter stayed within the power requirements, the amp draw of the whole system was kept below 200 amps, and the new system provided the maximum directional energy to the material.
Custom Skylights products are designed to allow transmission of visible light. The clear and transparent material can pose difficulty in absorption of energy. Every material absorbs energy at a different wavelength, and Weco and Ceramicx (ceramicx.com) were mindful to best match the IR wavelength to the given materials. Short IR wavelengths in this case were found to provide very little energy absorption and therefore a longer wavelength emitter, the Ceramicx brand Ceramic emitter would provided the maximum absorption for his range of polymer materials.