A Quality Control Program at Your Factory

Why You Really Need This

Many factories have labs with fancy equipment and technicians and think they are monitoring production well. But do they rely on the numbers their lab equipment produces or do they really understand their bodies and glazes? Other companies have no in-house engineers or technicians, they rely totally on simple visual inspection and suppliers to handle production issues. Problems can strike suddenly, solutions can be very long and painful. Companies can fail because they lack collective knowledge of their bodies and glazes and cannot deal with production issues caused by material changes and unstable recipes. A logical and intensive quality control program is essential to any manufacturer, regardless of size.

Tunnel vision of your clay body. Clay bodies densify as firing temperature increases (accompanied by shrinkage increase and porosity decrease). If we imagine curves of these properties (against temperature) the lines reach maximums/minimums, then level off and then reverse direction. Your body

Stable recipes. An ongoing testing program is not just about matching numerical data from lab testing devices. It is about studying your glazes and bodies at many temperatures and learning their strengths and weaknesses, what they really are. A QC program is essential to developing the confidence and ability to tune and change these recipes to adapt and to be more stable against material and firing variations.

Studying only the materials is not a good idea. Many material changes do not impact production quality, others do. If your recipes are sensitive to certain aspects of processing or firing, then changes in specific materials that impact these are much more important to monitor.

Practical testing. It is not uncommon for a technician at a large factory to find it difficult to explain what plasticity is. What vitrification is. Or thixotrophy. Or deflocculation. Potters, on the other hand, often understand these properties well because they get their hands dirty in the production process. Factory technicians can take a lesson from them. Sometimes the practical information that comes from simple testing can tell you more about a production process than very expensive lab equipment.

History of test data. A quality control program is an information program. That information must be stored such that it contributes to a bigger picture of historical data, one in which you can place the body and glaze results that are currently being used in production.

Trust in suppliers. This trust is often misplaced. TNO (trust no one) applies here. Shipments of product may well arrive with documentation that looks very official comprehensive. But this can quickly become an illusion when there is a high reject rate coming out of the kiln! Suppliers are giving you materials. But you mix these to make a body. What matters is how that body fires in your kiln made from your ware using your process. Only you can oversee a testing program to assure consistency and quality. Do you have a supplier that delivers you a body already prepared? Do you still need to test? Of course. Again, it is your kiln, your firing schedule, your process, your ware, your responsibility. The last words of many lab techs (during the process of being fired) relates to trust in supplier information.

Production issues that impact product quality or cause product loss very often happen because of multiple issues with process and materials. Alert QC programs flag these issues early and deal with them individually before they compound into the perfect storm of product disasters.

Where to Start

Be practical. Of how much practical use is a supplier data sheet that contains detailed chemistry information about your body? What really matters is how your glaze and body fire in your kiln. It stands to reason that the key testing you should be doing involves putting samples in kilns and measuring data from them. But not must your production kiln. You need to be firing samples in test kilns. At temperatures above and below your production temperature. At different rates. True, lab kilns do not emulate production kilns, but firing can be related to each other, over time, to create a picture that can be rationalized for the production kiln.

Most people that use Insight-live use it to store and administer a database of recipes and calculate their chemistry. But in quality control you will be much more interested in the physics of your products. This is the purpose of the test result subsystem of Insight-live. Here you can define tests (we have already defined many) and collect data for them over time to build a knowledge of the physical properties of your products and factors that affect these.