Double-bar transfer systems mean twice the productivity.
By Charles Bates
Double-bar transfer systems pump out two complete parts in the time it takes to do one.
In most situations, one operator can run two double-bar transfer machines.
Buffoli's latest double-bar transfer machine, the Trans-Bar 55+, monitors both material cutoff and tooling for less operator intervention.
With one machining system, shops accomplish the work of three or four multispindle lathes, claims a builder of double-bar transfer machines.-These multitasking workcenters feed on two bars of any profile — T, L, or cross-shaped and round or hexagonal — or material type simultaneously to pump out twice as many parts per cycle time. They also provide fast part changeovers and manufacturing flexibility.
The part-working process is automatic through to the ejection of a finished workpiece. Rotating tools aligned on separate axes, or transversely, move in different directions for operations that include cutoff, facing, drilling, boring, reaming, milling, conical and profile turning, and internal and external recessing. The system also taps, threads, broaches, rolls, form threads, slots, knurls, deburrs, marks, gages, and subassembles components such as bushings, inserts, and pins. Independent cutting feeds and speeds for each tool optimize cutting parameters, surface finishes, cycle times, and tool lives.
In most situations, one operator can run two double-bar transfer machines without having to handle individual bars of stock because of automatic bundle-bar loaders. On the Trans-Bar system from Italian builder Buffoli Transfer SpA, for instance, the bar loader accommodates up to 3 ton in material and random bar lengths to 23-ft long.
The machine's integrated cutoff system with a 0.040-in.-thick sawblade saves material and tool costs and runs carbidetipped blades if needed. As a result of the cutoff unit, there are about 5 less barrejected parts, which automatically evacuate into a box separate from finished parts. And an electronicmeasuring unit lets users program a safety limit and track blade wear through a graphical representation.
According to Buffoli, holding centerline, concentricity, and roundness are more critical for barmachined parts as compared to forged or cast ones. For this reason, the company supplies quick-change-type clamping fixtures (chucks, collets, and expanding mandrels) that accurately hold any workpiece. Setup times on the Trans-Bar, as compared to screw machines, are 50% shorter and less frequent.
In addition to coaxial part clamping and the capability of processing three part sides simultaneously, the Trans-Bar optimizes quality by machining parts in stations independent of one another. Also, bars feeding into the system do not rotate, so there is no noise and, more importantly, no vibration to affect machining accuracy.
Controls on the Trans-Bar use shoplanguage/ conversational CNC programming without G or M codes. Graphic menus guide operators step-by-step, and Windows-type functionality, such as copy, cut-and-paste, and insert/delete modes, minimizes programming time and effort. Programming is also portable via desktop, laptop, or local network.
Self-learning and teach modes provide semiautomatic operation, and operators can input real-time, partprogram data on-the-fly while the machine runs. And through the control PC, they save all working parameters.
Buffoli's CNC and software provide accurate, real-time production and maintenance information. Hundreds of digital images and videos display alarms, diagnostics, and remedies on the machine's CNC screen. The control and software also automatically store production data and machine-failure statistics.
The most recent Trans-Bar machines include a monitoring system for the cutoff unit and independent tool control on each spindle. The machine's tool-monitoring system, fully integrated into the machine's CNC, detects tool wear for maintaining process integrity and controlling tool costs.
Benefiting from double-bar production
Traditional production for Brass Craft Western Co. in Lancaster, Tex., always meant multispindle lathes for straight parts and transfer systems for other components — until the manufacturer of plumbing products started using doublebar transfer systems.
Brass Craft has 14 Buffoli Trans-Bar systems (available in the U.S. and Canada through TPS International Inc.) that completely machine its variety of valves, straight fittings, nipples, nuts, elbows, tees, and faucet parts. The systems also save floorspace, increase productivity, and provide Brass Craft with manufacturing flexibility and easy changeovers.
According to Buffoli, since the machines produce two parts instead of one, they outproduce multispindle automatics by as much as 300% to 400%.
Because Brass Craft's products are commodity items, the company must control production costs and eliminate waste. Not only do the Buffoli machines improve productivity and efficiency, they provide changeover times of less than 2 hr.