Process Planning I – Tombstones

Manufacturing Process Planning Report


Grave markers have likely been around as long as people have buried their dead. It is known that they have existed for at least 3000 years. A tombstone was originally a stone lid of a stone coffin, or the coffin itself. This is similar to a gravestone, which is a stone slab laid over a grave, or stela, which is a stone or wooden slab with a curved top used as a grave marker. Today, both are interchangeable to describe any type of monument used to mark the location of a grave or show memorial to the deceased.

As the name implies, both gravestones and tombstones have always been made of stone such as granite or marble. Grave markers have been made of wood, dirt (such as burial mounds), bronze (for plaques), marble and granite (for statues and plaques as well as the Pyramids of ancient Egypt). The most popular choices for material have always been low-corrosion metals and stone, as they will last nearly forever, providing a lasting tribute to the deceased.

Monument shapes are very often religiously oriented, especially crosses or angels. Also very common are slabs, whether standing upright or flat on the ground. These slabs often have engravings or religious-oriented shapes as well. Markers are often used to symbolize the deceased’s wealth too, with larger ones costing much more, and hence signifying greater wealth. A single marker may be used for an entire family, with family member’s names added as they pass away and buried near the marker. A marker may not actually mark anything, such as the case of a crematorium where the ashes may or may not actually be kept, but instead serve mainly as a place to observe remembrance.

We chose tombstones because we felt that it is an interesting product that is often taken for granted, but serves an important need. Tombstones are one of the largest investments we make, after homes and autos, though many people will never even see their own tombstone. They are also one of the few things that can truly stand the test of time, with some of the oldest structures on the planet being elaborate tombstones.

The purpose of a tombstone being to memorialize and create a tribute to deceased loved ones, a tombstone should be able to last several hundred years exposed to the elements without significant degradation of it’s engraving, surface finish, or other details. They need also be made of a material that is somewhat easy to form to avoid excessive production costs. Further considerations are that they be available in multiple colors, designs, and shapes to provide a selection to the consumer, as well as to abide by the varying regulations or different cemeteries, such as being flush with ground level for ease of grounds care.

To produce tombstones, several decisions must first be made, including materials, processing, and factory layout. For materials, we looked at what has previously been used, stone including granite and marble, metals including bronze, and too a lesser extent wood. Wood is not a very lasting material, so it is a poor choice unless cost is a very limiting factor, which in most cases it is not. Bronze is also used less often due to being more susceptible to the elements. For these reasons, most tombstones today are made of stone, particularly granite as it is more durable than marble. We chose to go with granite also because it provides a greater choice in colors for the tombstones to be made in.

The process for producing a tombstone can be divided into the basic steps of rough shaping, polishing, detailing, and final finishing. In rough shaping, the raw material of granite is first received in slabs 3 ft x 3 ft x 10 ft and weighing around 20,250 lbs. These slabs are first cut by a diamond saw into smaller slabs of between 6 and 12 inches thick, then surface polished by a polisher that moves down from a harsh diamond pad to felt pads with a fine aluminum oxide powder abrasive. The next step is to break the slabs down further using a hydraulic breaker capable of up to 5000 psi compressive force. Final rough shaping is then accomplished with a diamond multi-bladed diamond saw followed by polishing the edges in the same way the surfaces were earlier. The next step is detailing, which requires specific input from the consumer, so the slab must be stored until an order is received.

Upon receiving a customer order with specific shaping and engraving, a slab is moved to a diamond wire saw to cut any intricate details. A rubber stencil is then made with the layout of all engraving, and glued to the slab. A sandblaster is used on the slab to make an engraving that may include text and pictures, then the stencil is removed exposing the design. The slab is then cleaned with a pressure washer to remove glue, sand, stencil remnants, and any other debris. The slab is now a tombstone and is ready to be shipped off to a cemetery or funeral home.

Quality control is exercised at several steps, particularly when the raw slabs are first received to check for any blemishes that may cause processing troubles or surface defects. Also, the slabs are checked after nearly all processes, as many of the processes used exert much force on the granite and can weaken, crack, or otherwise degrade the integrity of the stone. A final inspection is also given before packaging to ensure the product meets all customer requirements. This much inspection may seem excessive, but when dealing with slabs of granite that weight several hundred and even thousand pounds, even small blemishes can cause cracking and chipping, resulting in the possibility of product or equipment damage, or worker injury.

Our factory layout was designed to avoid unnecessary movement as much as possible. By creating a U-shaped production line we can place a shipping and receiving area at one end of the building, and both begin and end the production process in this area. This avoids the use of separate shipping docks or the need to haul raw materials or finished products long distances across the building. We chose conveyor belts to move materials because they are capable of carrying heavy loads, and they avoid the excess movements that would be created by using multiple fork trucks or similar methods. Fork trucks and overhead hoist cranes would be used in shipping and receiving though, or in processes where the slabs would need to be removed from the conveyor belt such as when being stored or for sand blasting. By reducing excess movements we help to reduce costs to us, which we can pass along to the customer, helping further satisfy their requirements.

Our choice of processes is based largely on those used in the article from the How Products are Made – Illustrated Guide to Product Manufacturing books in the L.L.I.C. We did make some changes to those processes though, including combining some processes that were listed as being done separately, such as a few polishing processes. We felt that these processes were similar enough to be done at the same time, and would have little effect on the overall process. The reduction of these steps helps reduce waste in the form of excess processing, saving further cost to both us and our customers.