Nowadays the demands on engineering parts like highly integrated hollow media pipes which are often used in automobiles are rising constantly. Especially the requirements in automotive industry are high. Mechanical properties must be guaranteed which often can only be achieved by using technical polymers with fillers like glass fibres. Those polymers can not always be processed by fluid injection technique (FIT). Only by combining FIT and sandwich injection moulding these materials can be used as outer layer. Through injection of a suitable core component, good hollow quality and component properties can be achieved. This makes it possible to choose the polymer of the outer layer independently from its suitability for FIT. In this work the effect of process parameters on the moulded part have been investigated, with regard to the dependent variables like wall thickness, its distribution and hollow quality. Relevant parameters have been evaluated with a literature study and discussions. With preliminary tests the most influential parameters have been identified. Subsequently a statistical test plan with the identified parameters was generated by using ASSISTANT, a test planning and optimization software. With the results of the test plan a mathematical model for the correlation between parameters and dependent variables was generated which was also used for optimizing the parameters (Core component flow rate, water flow rate, outer- and inner component temperature, tool temperature, delay time of core component- and water injection) to obtain thinner walls, better distribution and hollow quality. Moreover, the possibility of ultrasonic wall thickness measurement has been investigated. The results of this work show, that the identified parameters have a limited influence on the target variables. Slightly better wall thickness and distribution as well as hollow quality were achieved. It was also shown that the measurement of the wall thicknesses with ultrasonic is possible. But for an inline usage of this technology further investigations are necessary.