A new vacuum resin dryer enables more molding and extrusion processors to obtain the substantial advantages of vacuum dryers over conventional desiccant systems, including lower operating cost, increased efficiency and greater control over the drying process, according to the vacuum dryer’s maker Maguire Products.
The VBD 300 vacuum dryer from Maguire (Aston, Pa.) achieves throughputs of up to 300 lb. (136 kg) per hour, which is double the capacity of the company’s VBD 150 model. While the VBD 150 is sized for the throughputs of many injection molding machines and of small extrusion lines like those for medical tubing, the new VBD 300 model opens the benefits of vacuum resin drying to a broader range of applications. Maguire also offers the VBD 1000 dryer for high-volume operations.
In comparison with desiccant dryers, the VBD vacuum dryer consumes 60% less energy, dries resin in one-sixth the time, and substantially reduces the heat history to which polymer is exposed. The speed with which the VBD system removes moisture makes properly dried polymer available for production only 35 minutes after a cold start.
Like other VBD models, the VBD 300 dryer is a gravimetric system that employs load cells that precisely monitor the weight of material at 2 critical points, making possible precise control over material consumption and documentation of process conditions for certification to customers. Use of load cells also enhances control over the drying process, according to Frank Kavanagh, vice president of sales and marketing for Maguire Products.
“Load cell control makes it possible to precisely match the drying rate to the processing rate of the molding machine or extruder, which is particularly important for proper drying of technical polymers like nylon,” Kavanagh said. “And because load cell control ensures that no material is left in the dryer when production stops, the next production run can start immediately.”
VBD vacuum dryers use gravity to move material through three vertically arranged stages of the drying process, with the discharge of material from one stage to the next controlled by high-speed slide-gate valves with an accuracy per dispense of +/– 4 g. The vessels for the 3 stages are, from top to bottom: a heating hopper that brings resin to a target temperature; a vacuum vessel in which vacuum reduces the boiling point of water, causing moisture within the pellets to volatilize and be forced out of the pellet into the low-pressure environment surrounding it; and a pressurized retention/take-away hopper that is continually purged by a membrane air dryer to maintain the target level of dryness until the material is discharged. The vacuum vessel and retention hopper are mounted on load cells.
The VBD 300 dryer has an intuitive, easy to use touchscreen controller that allows operators to manage all drying parameters from just one screen. Like all Maguire equipment, the new dryer comes with a 5-year warranty.