Why not rebuild blow molding machines?

Rebuilding of aging processing machinery has been accepted practice for decades--at least for extruders, thermoformers, and injection or compression presses. Old blow molding machines, however, generally just faded away. Blow molding machines were often considered too big to ship to a rebuilder. Or the cost to retrofit came too close to the cost of a new machine, especially when downtime was included. Then, too, some machine builders were ambivalent, feeling that rebuilding old machines hurt new machine sales. So machine makers usually kept a low profile on rebuilding services.

Now it seems that rebuilding is becoming respectable. Many blow molding machine makers now actively promote it. By a conservative count, at least 50 machines in the U.S. have been totally rebuilt in the past year or two. These include accumulator-head, reciprocating-screw and continuous-extrusion types.

WHY REBUILD?

Processors who have had machines rebuilt find that cost savings are hefty compared with buying a new machine. A full rebuild with new clamp section and head may run only half the cost of a new machine. An exception is rebuilding to add coextrusion. This can bring the cost of rebuilding closer to the cost for a new machine and may not be worth the downtime.

Rebuilds are invariably done to increase capacity, primarily to raise extruder throughput to enable an older machine to make new lightweight bottles, molders say. This entails pulling the screw and barrel, adding a higher powered motor and often a bigger accumulator head as well. The jump in head size isn't usually large. A dual 4- or 6-lb head can be switched to a single 10- or 15-lb respectively for about $60,000-$75,000. Adding state-of-the-art controls also allows older machines to be integrated more easily into plantwide CIM. Turnaround time for a full rebuild is generally 12-14 weeks.

WHO'S REBUILDING WHAT

Battenfeld Blowmolding Machines Inc. in Boonton, N.J., has rebuilt a half dozen Hartig and Fischer machines in the past few years--including accumulator-head and continuous-extrusion types. Battenfeld only rebuilds its own or Hartig machines. Battenfeld is unusual in that it prefers to rebuild at the customer's plant if space allows. Battenfeld also sells hydraulic-upgrade kits and new controls packages, both of which customers can install themselves. Kits cost "a small fraction" of the price of a new machine, says Battenfeld service manager Rich DeMair. Battenfeld offers even less expensive options for partial upgrades on blow molders. "Sometimes you can greatly improve the speed and accuracy of an older machine just by replacing directional valves on clamp controls with proportional valves," DeMair says. Directional valves, because of their simple on/off action, require clamps to be run more slowly in order not to slam the mold halves together. Because proportional valves allow clamp motion to be profiled with a "soft-landing," clamp movement can be speeded up greatly and then slowed down just before closing. Such hydraulic upgrades cost about $2500.

Bekum Plastics Machinery Inc., Williamston, Mich., also only rebuilds its own machines, concentrating on three continuous-extrusion models--H111, H121 and H151M. Bekum did a few rebuilds as long as 10 years ago, but began concentrating on rebuilding three years ago as the recession took hold. Rebuilding involves stripping a machine to its frame, sandblasting the frame, and then building the machine back up again. A "basic" rebuild includes all safety upgrades, new microprocessor control panel, and machine repair without replacing major components. It costs about $100,000. A full rebuild, including new heads and platens, could cost $200,000. This compares to $350,000-$400,000 for a new H121 machine. Bekum gives a six-month factory warranty on parts and labor.

Cincinnati Milacron Plastics Machinery Systems, Cincinnati, began rebuilding blow molders two years ago and since has redone two dozen units, including other brands. Milacron has rebuilt stretch-blow machines such as its own RHB models and injection blow molding machines such as a 12-yr-old Rainville unit (now produced by Johnson Controls Inc., Manchester, Mich.). The Rainville rebuild included stripping the hydraulics and controls and a complete mechanical rebuild, reworking the existing extruder barrel and installing a proprietary head design.

For the last year, Milacron has been using a new SPC diagnostic program from Hunkar Laboratories Inc., Cincinnati, to classify the quality of rebuilt extrusion blow molding, injection blow, and injection molding machines. Hunkar's SPC-PRO 11 program, an update of its original SPC-PRO software with connectability to CIM, is "the first yardstick available for evaluating the quality of a remanufacture," says Hunkar Lab's president Denes Hunkar.

Epco Div. of John Brown Inc. in Fremont, Ohio, a leading remanufacturer of injection, compression, thermoforming and die-casting machines, has rebuilt only a handful of blow molding machines over the past 10 years. Currently, however, Epco is rebuilding a series of large Uniloy accumulator-head machines. The first is a 15- to 20-yr-old model that was completely rebuilt in 14 weeks for about half the cost of a new one for Automotive Industries' Arbor Div. in Fremont, Ohio. It included a new 35-lb head from Davis-Standard's Sterling Div. in Edison, N.J. The machine was stripped to its frame and all major components repaired or replaced, including a new head and new Epco E-8000 controls based on Barber-Colman MACO 8000 hardware. The controls feature a black/white touchscreen and "excellent repeatability," says Epco director of sales and marketing Steven Schroeder. The hydraulic system was replaced, adding a 10-station air-manifold system, proportional speed control of clamp and pushout cylinder (for up to 1200 in./min clamp-closing speeds), and powered clamp-safety gates with hydraulic and electrical interlocks.

Johnson Controls set up a separate business unit in 1988 to rebuild its own blow molders, primarily the reciprocating-screw Uniloy machines, and has done some 60 units since then, including more than 25 units last year alone. Sales manager Rich Smith says almost all are full rebuilds down to the frames that are then brought back with new electrical controls, hydraulics and safety features. Cost is 60-70% of the cost of buying a comparable new Uniloy reciprocating-screw machine.

German machine maker Krupp Corpoplast Maschinenbau GmbH (with U.S. offices in Edison, N.J.) offers kits to update its B-40 and B-80 injection stretch-blow machines. Over 30 such kits are available, including an updated preform rotating system (a stationary chain with new mandrels) that allows irregularly-shaped bottles to be made. This kit costs around $30,000 for hardware and installation. A gear-train conversion kit to add new cam-controlled stretching cylinders and pressure valves raises the output of a B-40 from 3000 bottles/hr to 4500. This kit costs about $75,000.

Slawska Systems Inc. in Bridgewater, N.J., a recent startup making industrial accumulator-head blow molders, also has rebuilt five machines, only one of which was a complete knockdown. That was a 10-yr-old Uniloy on which Slawska replaced a small clamp unit with its own 150-ton press (48 x 74 in. platens).