Rotational molder and machine shop Michael Bros. Inc. has developed a robot-driven cast-aluminum mold-making method that avoids need for a pattern and allows quick turnarounds.
Using hand-fabricated and sand-cast molds, the process is ``revolutionary'' within the rotomolding industry, said William Michael, president of the recently expanded Prescott, Ariz., firm. ``We use the method to build sand-cast tools and have done 10 molds using this process'' in recent months.
In March, the firm began operating a new Kuka Robotics Corp. 60-HA system with a 10-horsepower, 24,000-revolutions-per-minute spindle.
Michael is using Delcam software. The computer numerically controlled robot comes with six axes and can operate with up to nine axes. ``We may add at least one [axis] in the future,'' Michael said.
Programming Plus Inc. of New Berlin, Wis., supplied the turnkey automation package, which facilitates the use of computer-aided designs.
``We use a three-part phenolic-based binder system with which we cast up our sand blocks,'' he said. ``We machine mold cavities out of the sand, set two sand blocks together and aluminum is poured. There is no pattern.''
Michael said a draft is usually needed to get a shape in sand. ``We do not need draft. We can machine in undercuts. It raises the bar of what you can do, and we do not have patterns sitting around. They take up valuable floor space.''
Trials continue. ``We are still experimenting with mixtures of sand and coatings ... to perfect the process,'' he said. ``There are many variables.''
With the new method, Michael can make a mold in about eight days and even faster if a CAD file exists. ``The standard in the industry is six to eight weeks to get a roto mold built,'' Michael said.
The molds are relatively inexpensive, depending on volume and complexity. However, ``if you are making 10 of one kind, you may use a pattern process,'' he said.
With a rotomolded part's natural shrinkage, a processor can rotomold a component with an undercut to get it out of the mold.
Michael said he shopped for a year before selecting the Kuka. He learned that a Programming Plus customer was machining sand without a pattern for another industry. ``A light went off,'' he said. Also, ``when I saw a spindle on a robot, it made sense that you could trim [rotomolded] plastic parts.''
Michael Bros.' custom rotomolding production ranges widely and includes air-intake kits and other projects for the automotive aftermarket
Proprietary work accounts for more than 40 percent of the business. ``We try to have control of our own destiny,'' he said.
Some proprietary work is marketed through sister company Northland Products Inc. These products include extraction equipment for carpet cleaning and a two-axle water transport trailer with a 550-gallon polyethylene tank that has full internal baffling and integrally molded fenders. Initially produced in January, the baffled tank succeeded earlier versions without baffles. Construction contractors and the rental equipment industry use the trailer/ tank package.
Also, Michael Bros. molds and markets 300- and 400-gallon refuse containers of cross-linked PE.
In Arizona, Michael started rotational molding operations in Phoenix in 1986, moved to Chino Valley in 1997 and relocated 15 miles to a new custom-built Prescott facility with 50,000 square feet on five acres in August 2005.
The Chino Valley facility of 15,000 square feet is being sold.
In Prescott, Michael Bros. invested $2.2 million for the land and building. Another $500,000 was spent for equipment, including the robot and a dual mill pulverizing system from Powder King LLC of Anthem, Ariz., being installed in September.
Michael Bros. operates an internally built 10-foot-6-inch swing shuttle machine and, since August 2005, a reconditioned heavy-duty four-arm independent Ferry 280. The firm is rebuilding a Ferry 310, a four-arm independent machine that was acquired in January.
Michael Bros. employs 50 now, up from 25 a year ago, and, as a turnkey shop, ``thrives on ingenuity and design'' ideas of its workers, the president said.
The firm had 2005 sales of $3.5 million compared to $2 million in the previous year. For 2006, Michael projects sales of more than $3.7 million.