This case study is based on a published analysis of two process routes for making granules used in ceramic tile production.*

We start with a Current State using the incumbent wet method and ask you to develop a future state using the more energy efficient dry method.

Case Study, Castellon Tile. Currently, the tile manufacturing industry is striving to reduce their carbon emissions and make their processes efficient. Castellon Tile aspires to modernize its production and gain market share by becoming an industry leader in this effort. We know the following information for Castellons tile manufacturing process.

The Product:

Tiles are available in a variety of styles, allowing customers to create truly personalized designs. Style/color combinations are based on 2 clay bodies (white, red), 2 glazes (clear, blue), and 5 tile patterns; net, there are 20 product types. Each tile has a mass of 375 grams. Tiles are packed and shipped in cases of 24 tiles, 9 kg/case net, 10 kg/case gross shipping weight. Each case has tiles of a single product type. The minimum order quantity is 1 case. The tiles have three main raw materials viz. Quartz, Clay & Feldspar along with minor (

Customer Requirements:

Castellon services ~100 customers including hypermarkets, construction, and remodeling companies. Castellons annual sales is about approximately 1.2 million tiles or 50,000 cases per year. The sales department offers a 60/30 day forecast to the production control. The sales department receives orders from customers which they add to the Production Control MRP. The customers are offered an order quantity lead time of 30 days and can adjust their order mix for 15 days after placing the order quantity. Multiple shipments go out to customers every day.

Production Control (Current State):

Sales orders are batched by product type to fit the production schedule, minimizing changeover in the base clay, tile press setup, glaze application, and firing operations. Receives orders every day; enters orders in the Production Control MRP. Generates a weekly schedule for Slurry, Spray-Dry, Tile-Making through Firing, and Packing operations. Provides 30-day forecast to suppliers to ensure raw material availability. Releases weekly purchase orders for procurement of raw materials from three different suppliers. Receives change in orders 15 days before shipment. Issues a daily priority list to the production supervisor. Issues daily shipping schedule to the shipping department.

Production Process: Castellon currently uses the wet method for preparation of granules used in tile manufacturing. The production plant works 20 days a month. o The wet method of making granules by slurry-making in a ball-mill followed by spray-drying runs 5 days/week, one shift/day. The spray-dried granules are stored in intermediate silos. o Granules feed the main tile production line including pressing, glazing, and firing operations; these run together semi-continuously, 5 days/week for 3 shifts. Firing is done in a continuous tunnel kiln. Quartz, Clay and Feldspar are delivered in powder form via bulk shipment, totaling ~36 MT/month. An average of ~50 metric tons of total powder inventory is stored in raw material silos on site at Castellon. A glaze preparation process (not shown in VSM) runs in parallel; under normal conditions, it does not affect timing of the main process. There is a packing process after firing. Cooled tiles are unloaded from the continuous kiln, placed on carts and transported to case packing. Cases are stored in a warehouse area prior to shipping.

Making granules (slurry making and spray drying) Slurry making and spray drying operations are coordinated lot campaigns, first preparing a clay-body slurry and then spray-drying the slurry into granules that are suitable for tile pressing. An 1800 kg lot of dry granules can be made in a 4-hour campaign, first starting the slurry-making process, transferring a first batch to the hold tank, starting the second batch of slurry while the spray-dryer is starting up. If two lots are made with the same clay body, then two lots can be made in 7 hours (within 1 shift). All campaigns are run within single shifts, and the processes (including the hold tank) are rinsed out at the end of each shift. Depending on the schedule, the process can make two lots / shift (same clay body), or one lot plus a full cleanout for a changeover to the other clay body the next working day.

Slurry-making in the Ball Mill:

For many ceramic products, including tile, the body composition is determined by the amount and type of raw materials. It is important to mix the right amounts together to achieve the desired properties Once the ingredients are weighed, they are added together into a batch ball mill along with water to make a slurry. As the process grinds and mixes the ingredients, minor ingredients are added as binders and stabilizers to aid spray drying and subsequent tile-forming processes. Each ball milling batch processes 600 kg dry powder plus ~350 kg of water; the slurry solids-loading is ~63%. It requires 2 operators to make the batches measuring the right amount of raw materials. Ball mill cycle time is 1 hour per batch. The slurry is pumped to a hold tank which has a capacity of ~2000 kg wet slurry (i.e., it can hold 2 batches from the ball mill). Ball mill changeovers between clay types require a full washout; washout changeovers take 2 hours. The combined reliability of the ball mill and transfer (to hold tank) system is 90%.

Spray Dryer:

Slurry is pumped from the hold tank to a atomizing nozzle and sprayed into a drying chamber (aka tower). Slurry droplets are dried as they are heated by a rising hot air column, forming small, free flowing granules that result in a powder suitable for forming tiles in a pressing process. The average residence time in the spray dryer is about 5 minutes. Spray drying is a continuous operation requiring 1 process operator. The rate of the dryer is matched with the ball mill, i.e., the dryer converts 950 kg/hr of wet slurry into 600 kg/hr of dry granules. The drying load is ~350 kg/hr of water. Spray dryer changeovers between clay types require a full washout taking 3 hours. Spray dryer process reliability is 90%. On average, there are ~3600 kg of dried granules in storage silos after the spray dryer. There are two silos, one for white and the other for red clay granules. Each silo has a capacity of 4 MT.

Tile Making Tile making includes pressing the dry granules into tiles, applying a glaze to the surface, and then firing to form a vitreous ceramic. The pressing, glazing and firing operations are essentially coupled in a semi continuous production line with no surplus inventory between steps. In this sense, we could have mapped the value stream as one integrated process. We chose to show the individual operations to better illustrate the process (see current state VSM). The firing step is done in a continuous tunnel kiln where tiles are loaded onto cars which slowly pass through the kiln, through pre-heat, firing, and cooling ones, taking 18 hours. The kiln is designed for continuous 3-shift operation, having a continuous flow of carts stacked with tile in the process of converting from clay to ceramic.

Tile Forming:

Castellon makes tile using a dry press method. In this method, the free-flowing granules containing a plasticized binder is fed from the storage silo into a steel die having the shape and style of the tile. Granules are compressed to form the tile, and then ejected. An automated press is used. Pressed tiles are placed on a belt the goes directly to Glaze Application. Process requires 1 attendant with machine cycle time of 10 secs per tile. Uptime is at 95%. There is a 30-minute changeover in the press to change the style of the tile. Because of the long firing schedule and the weekend shutdown, the last shift of the week on Friday does not produce tiles; tiles produced during the previous shift continue though the process and are left to cool at the end of the last shift.

Glazing (application):

The tile-glazing process is semi-automated with tiles from the press on a continuous belt passing under a sprayed-glaze curtain followed by a drying tunnel that uses waste-heat from the firing process. It requires one operator to monitor the process and runs at a rate that is matched with tile forming. The cycle time for glazing and drying is 30 minutes. Changeover to a different glaze is 30 minutes. Uptime stands at 95% for the process

Firing:

Castellon Industries uses a continuous tunnel kiln having pre-heat (4 h), firing (6 h), and cooling (8 h) zones. The full firing takes 18 hours. There is no changeover for clay body or glaze type. The process requires 3 attendants: one to transfer tile and stack in the kiln cars; one to unload the finished tile, and one to monitor the firing process. Uptime is 100%. There is an inventory of ~12,000 tiles before packaging

Packing department:

Packs 24 tiles per box and stores in the finished goods warehouse. Each case has a net mass of 24 x 375 g = 9 kg tile; ~1 kg of corrugated packing material is used to protect the tile in shipping and handling. The gross mass for shipping is ~10 kg/case. Cycle time is 60 sec per case with a changeover time of 5 min for a different style of tile. 3 operators work for on 1-shift operation with uptime of 100%

Shipping department:

Removes cases from finished goods warehouse, which has on average 1000 cases of tile, and stages for truck shipment to customers Delivery trucks have a 2 metric-ton (1 MT = 1000 kg) capacity and can make 2-3 trips everyday

1. Fill in the data box fields (highlighted) and complete the timeline on the Current State VSM, previous page. How many annual inventory-turns does this represent?

2. Castellon Tile is considering converting their process to the dry method for tile manufacturing recently reported by Mesquite et al.* You are hired as a Lean Consultant to make the new operation more efficient, productive, and unlock capacity to grow the business from the current 50,000 cases/y to 80,000 cases/y. The new dry-process method replaces the current slurry making and spray drying processes (i.e., the wet route) with a continuous mixer-granulation process (the dry route). In addition to energy savings, the new dry-process route can be configured with continuous flow operations through its individual unit operations (i.e., for the purposes of VSM, consider mapping the combined dry-granule process as a single process). Consider what scale of dry-granulation you want to install do you want to match the rate of the current wet system, match downstream tile-making, or perhaps something in between?

a. What is the takt through the current tile-making process?

b. With the current process, what would be the tile-making takt at 80,000 cases/y?

c. Draw a proposed future state VSM for Castellon. In your future state VSM, assume production to a finished goods supermarket having packed cases, 20 product variations. Consider: Castellon already has continuous flow through tile-pressing, glazing and firing; where else can you use continuous flow?

Are there any other places where supermarket pull systems are needed?

At what point will you schedule production (i.e., where is the pacemaker)?

How will you level the production mix, i.e., how will you handle the critical changeovers?

What increment of work (i.e., pitch quantity) will you consistently release and take away at the pacemaker?

What process improvements will be necessary for the value stream to flow as specified by your future-state design?

As a further opportunity, you may consider a hybrid design having make-to-ship for larger orders, and a supermarket for small orders, similar to the TWI example discussed in class.

Dry-route granulation details:

The continuous version of the proposed dry process has continuous feeders that can supply raw material powder to the process from current silo storage.

The mixer granulator in this process adds a relatively small amount of aqueous binder form granules suitable for dry-pressing.

The output of the granulator is screened to remove any oversize granules which are recycled through the milling process.

The screened granules are then dried in a continuous fluidized bed drier to remove excess moisture. The dryer can be outfitted to run with excess heat from the continuous kiln.

The process requires 1 attendant to monitor recycles and adjust open-loop controls on the binder level in the mixer-granulator.

Washout changeover from red to white base clay takes 4 hours. The reverse changeover (white to red) can be done in 2 hours. You can assume an average C/O of 3 hours.

3) (20 points) Castellon wants to reduce the lead time for customers orders and increase their annual inventory turns. In addition to the new dry-granulation process, include two additional features in your Future State VSM that can significantly address this. Identify these two features and quantify their benefit in terms of lead-time reduction.

4) (20 points) Anticipating growth in their business, Castellon wants to be able to increase its tile-production capacity. Analyze and suggest opportunities to increase production to 80,000 cases/year.

5) (10 points, extra credit) Business is great! If Castellon goes to a 7-day 3-shift schedule for tile making, what is the upper limit on the capacity according to your future state VSM?

Castellon Tile Value Stream Map, Current State Monthly forecast PRODUCTION CONTROL 60/30 day forecasts Raw material suppliers Multiple customers Weekly order MRP Dry bulk Orders: 30-day LT on case qty, may adjust mix for up to 15 days. 50,000 cases y 20 Tile types: 2 clays, 5 styles, 2 glazes 24 tiles/case 10 kg/case (ship mass) Bulk shipments -36 MT/month Weekly Schedule 2-MT cap Daily Priority: Production Supervisor 2-3 x Daily Daily Ship Schedule SHIPPING Order staging PRESS GLAZING FIRING Granules ! Apply Convert into tile glaze, dry to ceramic 1 0,1 03 SLURRY I Ball-mill 950 I RM Silos: kg batch (wet) Quartz, Slurry 02 Feldspar, tank Red clay, CT: 1 hr China clay. C/O: WIP Total MT. Uptime 1 shift . SPRAY-DRY 600 kg hr I (dry basis) Granule 01 silos kg C/O Uptime 1 shift PACKING I Assembley I cases 03 Ware- tiles house : : C/O: cases Up 100% 1 shift CT: : CO: Up 95% 3 shift CT: C/O: Up 95% 3 shift CT: C/O: Up 100% 3 shift Lead time days Proc time hrs Castellon Tile Value Stream Map, Current State Monthly forecast PRODUCTION CONTROL 60/30 day forecasts Raw material suppliers Multiple customers Weekly order MRP Dry bulk Orders: 30-day LT on case qty, may adjust mix for up to 15 days. 50,000 cases y 20 Tile types: 2 clays, 5 styles, 2 glazes 24 tiles/case 10 kg/case (ship mass) Bulk shipments -36 MT/month Weekly Schedule 2-MT cap Daily Priority: Production Supervisor 2-3 x Daily Daily Ship Schedule SHIPPING Order staging PRESS GLAZING FIRING Granules ! Apply Convert into tile glaze, dry to ceramic 1 0,1 03 SLURRY I Ball-mill 950 I RM Silos: kg batch (wet) Quartz, Slurry 02 Feldspar, tank Red clay, CT: 1 hr China clay. C/O: WIP Total MT. Uptime 1 shift . SPRAY-DRY 600 kg hr I (dry basis) Granule 01 silos kg C/O Uptime 1 shift PACKING I Assembley I cases 03 Ware- tiles house : : C/O: cases Up 100% 1 shift CT: : CO: Up 95% 3 shift CT: C/O: Up 95% 3 shift CT: C/O: Up 100% 3 shift Lead time days Proc time hrs