ENGINEERING SERVICES AND CONSULTING Srl

Industrial products: dot matrix impact printhead

Needle printheads are used in impact printers and consist of a series of high performance electromagnets each of which actuates a needle (diameter 0.2-0.25 mm) to hit the paper to be printed.

A ribbon made of inked fabric is placed between the needle and the paper, which transfers the ink to the paper. The printed character consists of a series of dots arranged following a predefined matrix: hence the definition "dot matrix" used for this kind of printer.

After the definition of the specifications for the industrial product with the customer, we elaborated the concept from a systems-based point of view, defining the main characteristics and design constraints; we then carried out electromagnetic simulations and an analysis of the problem using the TRIZ method.

Here you will find the characteristics of the needle printhead we designed.

Electromagnetic simulations

With the support of the Polytechnic University of Turin, simulation was carried out using the finite element method (fem) to define the best design of the electromagnet group in order to obtain the required performance.

Current absorption and energy dispersion in the form of heat have been minimized and the impact force of the needle (rotation torque of the armature) has been maximized.

The use of numerical simulation allowed to correctly design the electromagnet assembly avoiding the realization of prototypes for verification and consequently reducing time and costs of the product development process.

TRIZ analysis..

With the support of the University of Florence, an analysis was carried out using the TRIZ OTSM method with the aim of maximizing print quality.

Among the various working parameters of the printhead that affect print quality, the two emerging parameters were chosen: static travel and impact force.

After capturing the project team's know-how in the Problem Flow Network (diagram illustrating the network of problems and their relationships) and conducting a detailed patent analysis, the problems to be tackled and solved were chosen using the matrix in the figure.

Using the tools of the TRIZ OTSM method (clouds of contradictions, functional analysis,...), the chosen problems were addressed and conceptual solutions defined.

The use of the TRIZ method has led to clear and quantifiable positive effects both on the industrial product (performance, costs, competitive factors) and on the product development process (time and costs).

Executive design.

Starting from the results obtained with numerical simulation and TRIZ analysis, we started the cad/cam design phase using the parametric software PTC Creo.

The design phase has been integrated with the use of other methodologies to support the process: DfMA (design for manufacturing and assembly), DoE (design of experiment), DTC (Design To Cost) and Robust Design - Taguchi.

With the 3D cad models and their associated drawings, the technological prototypes were manufactured, assembled and tested in order to improve and optimize the overall project.

The final cad documentation was completed with the parts list, drawings, assembly and testing procedures and then we moved on to mass production.

We made the special automatic machines necessary for manufacturing and testing and designed and set up the manufacturing workshop.