FREEFORM CONSTRUCTION PROCESSES

Investigation of Process Parameters for Multi-resolution Bulk Aggregation Freeform Construction Machine (BAiRD)

Russ Harris, Alistair Gibb, Andy Norwood, Rupert Soar, Tony Thorpe

Loughborough University IMCRC, BPB Plc

  BACKGROUND

BAiRD represents the first of a series of projects which will look at Freeform Construction machines can be implemented on construction scales.  Behrokh Khoshnevis’s Contour Crafting process, at USC California, is one such development, being specifically developed for Freeform Construction applications http://www-rcf.usc.edu/~khoshnev/, which addresses the challenge of bulk deposition and aggregation using an extrusion based approach.  The challenge of defining resolution to the extrudate is achieved using a novel shaping or trowelling process as material leaves the nozzle.  Freeform Construction machines will inevitably differ by the scale of application, which may equally be for ‘off-site’ pre-assembly and direct ‘on-site’ fabrication.  It is not just a case of scaling up existing Rapid Manufacturing processes, new methods and requirements emerge specific to the construction industry.

  OBJECTIVES

When considering scaling up an existing Rapid Manufacturing process, to match construction bulk deposition rates, there is an inversely proportional impact on the minimum resolution which can be achieved in the subsequent structure.  This issue is present when fabricating at any scale in that, quite commonly, the ‘functionality’ of a component is linked to the minimum resolution achievable with that process.  By way of analogy, the Z-Corp process builds panels at approximately 300x300x300mm, which would allow for detail such as 10mm Ø conformal channels to be included within a structure. 

If the process were literally scaled up, to deliver components on the metre scale, then problems emerge as liquids/binders deposited through micron scale jets, at one scale, have greater fluidity than when delivered through millimetre scale jets.  To ensure the same deposition rates of materials at comparable delivery speeds (i.e. if a Z-Corp build takes 24 hours then, ideally, so should the freeform constructed structure).  However, the ability to reproduce the same 10mm Ø conformal channels is lost as the minimum drop size is now a millimetre.

This will become an important factor for any Freeform Construction machine where minimum resolution, say for integral pipes, ducting and services, will oppose the requirement for high deposition rates and this raises fundamental questions: 

  Should an Freeform Construction machine be able, for example, to utilise the multiple beam width strategies, used by the SLA process, so that deposition will occur at different scales/rates simultaneously?

  Should an effective Freeform Construction machine be capable of depositing at the minimum resolution of the structure, in which case what is that and how might that vary by application or the need for greater levels of functionality?

  How is functionality linked to resolution and what are the implications for the volumes which can be deposited?

To ensure that bulk deposition can be performed whilst high resolution features are ‘printed’ into each layer (such as ducting and channels), Freeform Construction machines need to be able to deposit materials at multiple resolutions simultaneously.  This is a challenge, and has lead to the development of a new process to meet these opposing requirements.  The design therefore attempts to satisfy the following constraints; range of resolution which can be reproduced, volume of material which can be deposited, speed of deposition at different scales, materials which the process can handle, cost of implementation, ease of assembly in construction environment, opportunity for IP exploitation and avoidance of IP conflict.

Please click HERE for contact details.

Please click HERE for sponsor and collaborator details.

© 2005 Rupert Soar. All rights reserved.