TrueBlend® blenders from The Conair Group now can be equipped with a compressed air self-cleaning system making it possible to change colors almost instantly, with no manual cleaning required. With as many as twelve ingredient bins on a single blender, molders can stage multiple colors and change from one to another “on the fly” under what amounts to “lights-out” manufacturing conditions. A compressed-air clean-out system purges each color before the next run begins.
“We’ve been building blenders with nine, ten or even twelve material hoppers in response to two important trends, explains Jeff Bickel, Product Engineer, Blenders and Feeders. “First, many processors are actually running materials that require many individual ingredients and they need that blending capability; and second, processors are using the blender to prepare colors and additives to facilitate quick product changeover. That was the case with the nine-position we developed for a producer of automotive components who makes frequent color changes. To be really effective, the system had to be essentially self-cleaning and so we’ve incorporated that feature as well.”
With the Conair system, the color changes are programmed into the easy-to-use touch-screen control. As the end of a particular color run nears, the flow of material from that bin is shut off. Successive blasts of compressed air sweep any remaining pellets first out of the blender weigh bin, then the mixing chamber, then the surge bin below the mixer and the pocket conveying valve beneath the surge bin. Finally the conveying lines and material receiver on the molding machine are blown clean before a new color is blended with natural and conveyed to the press.
FAST-RESPONSE CONTROL SYSTEM
In combination with the latest Conair software, the TrueBlend control ensures the highest level of blend accuracy. An improved algorithm intelligently analyzes dozens of weight readings in a matter of milliseconds, filtering out electronic noise and the effects of vibration. A diagnostic screen displays target setpoint percentage and actual percentage dispensed, as well as dynamically displaying start and finish weights for each material per batch.
The Conair blenders also include a material-use reporting capability that can be a powerful competitive tool for plastics processors. The system weighs every ingredient dispensed to ensure that each blended batch is accurate to within a fraction of a percent. That data can be used to generate reports, identify just-in-time purchase requirements, analyze and validate product material usage estimates, or calculate process yield versus waste. For ISO certified companies, data collected by the reporting software offers proof of compliance with quality, safety and recycling requirements.
The self-cleaning option is available on the entire TrueBlend family, which includes blenders that range in size from the TB45, with throughputs 10 to 175 lb/hr (4.5 to 79 kg/hr), to the TB3500 Series blenders, which can process up to 12,000 lbs/hr (5443 kg/hr).
The TrueBlend blenders from Conair are designed for the best possible accuracy. When the full-length access door is closed, all pellets are contained. With all ingredients contained and accounted for, the Conair blenders can be accurate to within ±0.5% of setpoint on colorant and additive weights. The standard microprocessor control adjusts after every dispense cycle, compensating automatically on the next weighed batch for any minor variations in dispensing, as well as for changes in resin bulk density and particle geometry. For a very critical low-volume additive, where variations of a pellet or two can affect the accuracy of the blend, the ultra-simple control system can be set to the precision additive mode, which gives priority to the weight of that minor component. Then, dispense weights of natural resin and all other ingredients are adjusted accordingly to achieve the best possible accuracy.
