A tale of two nobake start-ups.

"It was the best of times; it was the worst of times."

Like the opening lines to Charles Dickens' A Tale of Two Cities, the news that your foundry is ready to install a new nobake molding line offers a mix of emotions. Sure, it's a great opportunity to modernize, increase production and make employees' jobs easier, but it's also a big project with opportunities for mistakes and "if onlys."

Whether the planning stages have just begun or installation starts tomorrow, the lessons learned by these two foundries may help smooth the installation path.

Wollaston Alloys

Wollaston Alloys, Braintree, Massachusetts, is a 141-employee jobbing shop specializing in the production of corrosion, heat and wear-resistant stainless steel and high alloy castings. The foundry produces castings primarily for pressure-containing parts for corrosion-resistant service, using both the shell and nobake molding processes.

In the summer of 2000, Wollaston installed a new nobake molding and pouring line.

The new line replaced Wollaston's former cope and drag nobake molding line and added automated mold movement for mold storage, pouring, cooling and transfer to shakeout, along with a manipulator to extract castings from the shakeout deck.

Motivation and Goals

The foundry's old nobake molding equipment was installed in the mid-70s and depended solely on manual operations, including the movement of molds on roller conveyors. Concluding that the nobake molding and pouring operation must be upgraded significantly to remain competitive in the long run, Wollaston investigated designs for the new line with the following parameters in mind:

* larger capabilities--the existing mold size range was from 24 x 24 in. to 36 x 44 in,, and an expanded mold size range would allow some jobs made on the floor to be transferred over to the new line

* automated mold movement;

* a manipulator to extract castings from shakeout;

* a target molding rate of 20 molds/hr for equipment specification purposes;

* a single fill station for servicing both the new line and the floor molding operation.

Wollaston also wanted to preserve its floor molding capability. The footprint of the new line needed to allow ample room for filling and pouring floor molds while providing access to the shakeout area for both the molding line and the floor molds.

Blueprints Become Reality

With its requirements in mind, Wollaston chose and installed a complete system with little downtime. A distinctive feature of the new molding and pouring line is its vertical pattern storage system. The molding loop uses a standard size bolster plate for all size patterns. Roller tables inside the pattern storage structure are used to transfer set-up patterns on bolster plates both to and from the pattern set-up tables and onto and off of the pattern-in and pattern-out conveyors.

An elevating transfer car transfers the set-up patterns between any of the roller tables located on the ground level and any of the 28 storage positions located four levels high. When the set-up pattern is needed on the molding line, the pattern is sent to the molding line via the pattern-in conveyors.

Wollaston's existing 1470 lb/min continuous sand mixer was relocated to serve the new molding and pouring line. The relocation of the mixer required the addition of a sand transfer belt and appropriate electrical controls to supply sand to the mixer from the existing sand silos. The new mixer location allows the filling of molds on the molding line or the floor molding operation from a single filling station.

The fast loop section of the molding line includes a filling station with a vibratory compaction table, an automated strike-off device and a sub-floor sand collection system for the strike-off sand. All mold filling parameters can be computer controlled and archived by pattern. Sand weight, sand program, resin level and compaction cycle can be specified for each mold half.

The stripped mold is discharged forward from the rollover into the painting, drying and core setting section of the molding line. Molds are washed by flow coating and dried before being transferred to the core setting conveyors. The completed molds are closed on pouring plates by the automatic mold closing machine.

After closing, the molds are stored prior to pouring. The three-level mold storage and cooling lines and four-level pattern storage system maximize the number of molds and setup patterns that can be stored in the amount of floor space available.

Keep that Mold Line Rolling

An elevating transfer car moves the pouring plates to a storage level. This transfer car and an identical transfer car on the opposite end service the mold storage, pouring and cooling lines. To move through the system, one car pushes a pouring plate onto a line and the other car receives the pouring plate at the end, In this way, unpoured, poured and cooled molds are moved through the storage, pouring and cooling lines.

Poured and cooled molds are transferred to the shakeout deck by a tilting dump table. The castings are removed from the shakeout deck using a hydraulic manipulator. The manipulator can pick up castings of various sizes and place them into tubs for transportation to the cleaning room.

Installation + Current Production=No Problem

Wollaston installed the entire nobake molding and pouring line in the same footprint as the old operation, with only two weeks of downtime. Dividing the installation into two separate, but continuous, phases made this possible.

In the first phase, the old molding line was demolished and the essential elements of the new line were installed in its place. The fast loop, rollover, flow coating station, drying oven, coring belts and manual mold closing station were installed. Phase I installation required intensive planning and preparatory work to minimize production problems. Some orders were made early on the old line to allow extra time for the learning curve and any start-up problems on the new equipment.

Wollaston resumed post shutdown production using the new molding equipment and continued with the installation of the Phase II equipment. Phase II included the automatic mold closing machine, the vertical pattern storage system, the mold storage, pouring and cooling lines, the tilt table for loading the shakeout deck, and the manipulator. The foundry manually closed molds off of the new line for pouring during the two months that it took to complete the Phase II equipment installation while working around the construction activity.

Productivity Payoff

Wollaston has realized a sustained 75% increase in molding productivity thus far. The foundry believes that further improvements are possible, but recent business conditions have not required higher productivity levels. In addition, casting quality off of the line is excellent, and operational and quality performance targets were realized during the first full year of operation.

Spokane Steel Foundry

Spokane Steel Foundry, (Spokane Industries), Spokane, Washington, is a steel jobbing shop with 140 employees and 120,000 sq ft of manufacturing space. The foundry casts low carbon, low alloy, armor and high alloy wear-resistant steels for the industrial, transportation and military industries.

After studying various areas of foundry expansion, Spokane Steel decided to put in a new mold line, in part because jobs were increasing in size and volume while requiring dimensional control beyond the current green sand molding capabilities. The foundry investigated flaskless nobake molding and realized that installing a complete molding and pouring system would be the most effective course.

Design Decisions

Foundry management identified the necessary parameters and specifications, including:

* flaskless molding;

* maximum mold dimensions of 48 x 84 x 23/23 in.;

* the ability to place two molds (up to a maximum size of 42 x 48 x 23/23 in.) in a pouring plate;

* minimum mold dimensions of 32 x 38 x 8/8 in.;

* production rate of 10 molds/hr (maximum size) or 20 molds/hr (minimum size);

* 4 patterns in the mold loop (maximum size);

* 15 min strip time;

* automatic rollover-draw and closer;

* 48 pouring plate positions and 48 cooling positions;

* mechanical sand reclamation at 30 tons/hr.

Several other decisions also impacted design parameters. The foundry chose to use a furan binder because of its high strength to low binder level characteristics. Furan also creates low volatile emissions during curing and after pouring and allows favorable mechanical reclamation with minimal cost impact because of low sand-to-metal ratios.

Water-based flow coating was an inevitable choice due to the restrictions or elimination of alcohol-based wash. However, by making the decision early and having the system configured for a water-base flow coating unit, the foundry eliminated future disruptive additions.

Spokane installed the new molding line in an 18,000-sq-ft area of the foundry that wasn't being utilized fully. Its other two green sand molding areas continued production as usual. The installation lasted 4-5 months, and the official system start-up occurred in the first week of June 1999.

New Nobake System Features

Patterns--Patterns are introduced to the system at the pattern staging area, which can store four different large size patterns or eight dump boxes. Each cope and drag is mounted onto a bolster plate, and patterns are automatically loaded on the molding loops via a transfer car.

Molds--After the strike-off station the molds are moved around the loop on sections of powered roller conveyors indexing every three minutes. An automatic rollover-draw machine extracts molds from their patterns. The mold halves proceed to the wash station and the pattern dump boxes return to the molding loop.

The mold halves pass through an infrared drying oven, which ensures curing of the bonded sand and heats the mold wash surface to prevent the water-based wash from penetrating too deeply. After the mold halves return to the horizontal position, they enter a five-station gas-fired drying oven that evaporates water from the wash. This helps to minimize water penetration into the bond sand and quickly cures the wash.

Molds then move through the core setting area on powered belt conveyors, Gores are set and the drags and copes are prepared for closing with an automatic closer.

A rotating platform feature allows the pouring plates to be rotated 90[degrees] to the normal flow to allow two small molds to be placed and closed. This greatly improves the pouring and cooling line capacity.

Pouring--The pouring plate with the closed mold uses a powered transfer car to reach one of four pouring rows. Each row has 12 positions that can accumulate twelve large molds for the next heat. After the heat is poured, the pouring plate with mold and metal is moved to a cooling row.

Cooling--The two powered transfer cars operate in unison. Movement of any cooling row is accomplished from a push mechanism on either transfer car. The opposite transfer car matches up with the car doing the pushing and receives the mold at the opposite end.

Shakeout--The cooled mold is transferred to the shakeout platform, where the broken mold and castings are pushed off onto the shakeout screen. The sand is broken down and transported to one of two 100-ton surge silos while the castings proceed to the cleaning room.

Computer control--All functions are controlled by a production management system. Two personal computers, networked to various PLCs, retain the software that controls process parameters for patterns entering the system, including sand feeding type, resin-catalyst combinations, compaction table cycle, curing time for stripping, rollover cycle, core setting time and automatic closer control.

Also included is the traffic control for pouring line destination assignments. As molds are poured, they can be tracked and documented. Minimum cooling times can be assigned and premature shakeout can be controlled. Any mold on the system can be found easily since the computer tracks all movements.

The software program includes storage capacity of production information for 6000 patterns. A system diagnostic package monitors operations to detect malfunctions quickly.

Improvements on All Fronts

In the three years since installation, cost reductions and capacity improvements have been realized on the new flaskless nobake molding, pouring and reclamation system. Following are some of these benefits:

* improved molding, pouring and cooling capacity;

* reduced molding labor;

* the ability to change out tooling with no disruption to molding;

* better dimensional control of larger castings;

* better internal shop air quality;

* improved material handling and flow.

The original intent of the installation was to double the capacity of the foundry while maintaining the same size workforce. Due to the economic slowdown, this doubling has not occurred yet, but the improved capabilities remain ready for any increases in business.

This article was adapted from papers presented at the 1999 and 2000 Annual Technical & Operating Conference of the Steel Founders' Society of America.

For a free copy of this article circle No. 345 on the Reader Action Card.

For More Information

Visit www.moderncasting.com for the AFS International Conference on Chemically Bonded Molds & Cores article, "The Basics of Nohake Systems," J. E. Cavanaugh ( 1998).

"No-Bake Moulding: Guidelines for Selection and Optimum Use," V. Kapur and 0.0. Vyas, Foundry (2000).

RELATED ARTICLE: Making It All Pay Off: Tips to take with you

Looking back, what can be learned from these foundries' experiences in installing a new line?

Jack Lilley:

* PLAN, PLAN, PLAN--All of our prior planning and preparation paid off. If we had to do it again, there would be more planning. We rigorously planned Phase I, with good success. Our planning for Phase II was less rigorous, believing that we would apply lessons learned in Phase I to the implementation of Phase II. In reality, there was no time to analyze Phase I and refine the plan for Phase II. Make the best plan you can with the information that you have and execute it.

* prepare for electrical complexity--Our nobake molding and pouring line is the most electrically complex and sophisticated system in our foundry. The automated operation resulting from this complexity is a real benefit, but you need to invest in adequate training for key operations and maintenance personnel to support and protect your investment in equipment.

* find good contractors--The installation of a nobake molding and pouring line may require you to hire contractors you have not worked with before. Take the time to screen as many candidates as possible and get competitive quotes. If possible, try out new contractors on smaller projects first to see how they perform.

Cameron Girton:

* share some existing work--One choice the foundry made which eased the installation was to offload some jobs to a nearby foundry. In doing this, it is important to look for a foundry with similar capabilities and quality to avoid altering the customer's product.

* pouring ahead of time--The one change I would definitely make is to pour extra castings ahead of time to ensure you have inventory for customers. By pouring castings and cutting off the gates and risers, these reserves can be stored until the customer needs them, and then sent through the cleaning room.

* keep customers informed--Foundries should inform customers of the installation and keep them apprised of the situation. An arrangement can be worked out to make castings earlier so as not to affect customers production requirements.

Lisa Swenson, Assistant Editor

About the Authors

Prior to becoming the owner at ACC Embroidery and Screen Printing, Cameron Girton spent 10 yr at Spokane Steel Foundry and was the technical director at the time of the molding line installation. Jack Lilley is the technical manager at Wollaston Alloys and has been working there for the last 10 yr.