Focusing instead on productivity, and increasing yield, is the key, yet in order to do so requires a clear understanding of manufacturing processes and minerals.

While many ceramics can be made successfully from indigenous minerals, true yield maximization is often only possible by using quality raw materials matched to the production process. In order to make this match requires in depth knowledge of mineral science, including the interplay between rheology, mineralogy and particle size.

Sibelco assists customers in assessing possibilities for yield improvements by evaluating their best fit raw materials, and running a four-stage application support process:

1. Benchmarking: full analysis of body and raw materials using a computer based model, factory visit, reporting and yield cost/ benefit analysis
2. Proposals: targets to achieve agreed improvements, yield analysis to ensure viability
3. Trials: small scale at first, stepping up to production, with on-site Sibelco technician support
4. Production: body analysis at regular intervals during introduction of new materials and afterwards.

Can improving yield work for you? A case study

A medium sized producer had adopted the latest processing technology but had traditionally pursued the use of local raw materials for body forumlations.

Using the four stage application support process, Sibelco’s technical team worked closely with the producer to understand current factory performance and subsequently developed an optimized casting formulation and improvements to the manufacturing process.

The original factory slip was causing several problems in production, leading to factory loss in excess of 20%. Several major faults included flabby casts, drying and firing cracks and glaze crawl. Casters were also complaining of major variability in the slip quality from day-to-day.

The low density and high thixotropy of the factory slip was mainly responsible for the body related production faults, but the components of the casting slip did not allow for increasing the density without significantly reducing the fluidity of the slip, leading to other faults caused by poor slip run-off. Reducing the thixotropy led to much slower casting rates and the associated production shortfalls. Meanwhile the glaze crawling was found to be the result of a high soluble salt content in the local clay, causing surface scumming during the ware drying stage (read our Quick Guide to Soluble Salts).

By evaluating different batches of the raw materials, the inconsistent slip quality could be traced to variation in the local plastic clay between deliveries. The slip preparation methods led to further variation; the plastic clay in the area is supplied with very little moisture content, while the direct preparation method used for slip production wasn’t allowing enough time for the clay to fully disperse, thus causing large rheological changes on aging.

By substituting a proportion of the local plastic clay for Sibelco’s SanBlend 90, all of the casting properties were improved or maintained in the case of casting rate.

SanBlend not only reduced the flabbiness of the cast body by lowering the cast moisture content, but the increased density also led to reduced shrinkage-related drying and firing cracks, while the lower soluble salts in the recipe completely removed the glaze crawl fault.

Following the project, the customer saw a demonstrable improvement in production yield, with a rise from 78% to 86%. Despite a significant increase in raw material cost from the recommended formulation change, the factory was still able to reduce operating costs.

Reduce raw material costs or improve yield?

The decision is ultimately up to you, but it should be an informed decision. Only be undertaking a thorough assessment of production cycles is it possible to find the best fit raw materials to maximize productivity.

Could you benefit from an assessment of your product yields? Book your free one hour TechTalk with our ceramics specialists now.