Waterjet cutting offers precision and flexibility to fabricators and manufacturers, but there are aspects of these installations that can be unreliable or inefficient. One machine manufacturer uses a waterjet table to cut carbon and stainless steels and polycarbonate sheets, and maintaining an effective rate of production demands a steady supply of cutting material.
Formerly, this involved 70-lb (32-kg) bags of garnet delivered on pallets to the system, where operators would manually lift and dump six to seven bags into a charging hopper at the start of every 8-hour shift. Manual dumping required about 45 minutes — downtime — and occasionally resulted in spilled garnet, generating dust and exposing workers to potential injury.
In addition, the waterjet system consumed about 60 lbs. (27 kg) of garnet per hour, often depleting the volume of garnet in the pressure pot prior to the end of a shift, thus requiring another pause in production to refill the hopper before resuming operation.
This routine is improved now with the implantation of the Flexicon Corp. JET-FEED™ garnet delivery system, an automated bulk bag discharging-conveying process that feeds the cutting media directly from 4,000-lb. (1814-kg) bulk bags to the pressure pot.
Moving garnet effectively — The JET-FEED™ installation includes a BULK-OUT® bulk bag discharger, specifically, a BFF model with a removable bag lifting frame that is positioned by forklift above a bulk bag. An operator can connect bag straps to the frame, which is forklifted into cradles of spring-loaded POP-TOP™ bag extension posts.
The spout is connected by pulling it through an iris valve, closing the valve around the spout, untying the drawstring, and closing the hopper intake chute. Opening the iris valve slowly prevents uncontrolled bursts of garnet from the bag and dusting from displaced air, and eliminates the spillage that sometimes happened during manual bag slitting and dumping.
When full, the heavyweight bag compresses the spring-loaded bag extension posts, which begin to stretch upward as the bag lightens, elongating the bag to promote complete discharge through the spout. Material flow is further promoted by FLOW FLEXER® bag activators that raise and lower opposite bottom edges of the bag with increasingly longer strokes as the bag lightens, raising the bag bottom into a steep 'V" shape free of dead spots.
The fully enclosed, high-flow hopper is designed with a steep back wall and skewed sidewalls that form a trapezoid, and this shape reduces the ability of garnet to establish a bridge between the hopper sidewalls. Instead, garnet topples and flows toward and down the step back wall, eliminating the need for pneumatic or mechanical hopper agitation devices.
Preventing conveyor damage — The qualities that allow garnet to abrade through hardened steel also make it difficult to move without damaging the conveyor. So, the system includes a Flexicon® flexible screw conveyor; the only moving part contacting material is a rugged inner screw.
The "loose-footed" stainless steel screw is driven from its upper end beyond the point at which garnet exits through a discharge spout, preventing material contact with seals and associated maintenance, wear, and downtime. As the screw rotates, it self-centers within the abrasion-resistant polymer tube, preventing garnet from grinding between the screw and tube wall, maximizing the life of material contact components.
The conveyor elevates garnet at a 45-degree incline before curving to horizontal, for a total run of approximately 40 feet (12 meters.)
The enclosed system maintains the same humidity levels as within the bulk bag, preventing garnet particles from agglomerating and resisting flow when too moist, or developing static charges when too dry.
Garnet exiting the conveyor gravity discharges through flexible downspouting into the waterjet's pressure pot. Then, the conveyor can be started and stopped manually, or automatically by a PLC linked to high and low level sensors installed on the pressure pot.
Completing the garnet circuit — In the closed-loop system, spent water and garnet collected in the catcher table are pumped to a centrifuge that extracts solids, depositing it in a bulk bag-lined hopper for recycling. Spent garnet is returned to the supplier, which cleans and screens it to reclaim the portion that is suitable for re-use.
Learn more at www.flexicon.com