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Blog: Design considerations of rapid prototyping


(26.12.2018) Normally people confuse drafting with designing. Unlike drafting, which is just a drawing to show how the product looks like, designing is something that relates the product and its intended function (process). Various trial and errors and its learning gives the proper understanding about design considerations. In most cases the end products will be an assembly of sub parts which are designed separately. The design consideration of one part influences its mating part. So, it’s up to you to decide whom you want to be, a drafter? Or a designer? Come let’s keep our first step to know about the design considerations of rapid prototyping. 


File type is the most necessary requirement which should be kept in mind while saving the design file. Different rapid prototyping machines use different decoders to decode the design to machine coordinates. Once before starting the design process, the required file type should be known to the designer. All the assembly parts should be saved in the required file format. Even though converter software’s are available to change the file format, the resultant aren’t as accurate as the original file. 

Layer overlap is another important criteria which varies according to the type of prototyping machine being used. For a 3D printer the suspending layers should have proper support. The lag of support may cause problems like uneven surface, sagging of material and defect in shape. So while designing, the suspension parts should be avoided if no support is available. The thickness of the connector between two parts should be strong enough to withhold the two components. Any angle more than 50 degree should always have a support. 

Unit is the basic size in which the prototypes dimensions are fed. Before start of the design the unit should be set. All the dimensions should be given only on the basis of the pre-defined unit. The overall dimension of the design should be less than the working area of the rapid prototyping machine.  Example; If the unit is set as mm, all the dimensions throughout the whole design should be given in mm.  

Tolerance value is highly dependent on the machine being selected. Machines like CNC, Laser printing can have less tolerance as the operation can be carried out in micron level. But in case of machines like a 3D printing, the tolerance is high and it depends on the diameter of the extruder nozzle. That’s the reason why a 3D printed part has a lesser surface finish when compared to other precise rapid prototyping processes.  
The cost spend on the prototype directly depends on the technology used to produce it. So the price should be directly computed to the necessities like precision and the process carried out by the end product. For instance if the product carries out a precise process, smooth surface or a complicated assembly to meet the customer requirements, then laser printing is preferred to 3D printing. 

Application is the ultimate aim of any prototype. So all the considerations like material selection, tolerance, surface finish should be based only on the process. So, a designer should be well aware about the process and application of the final product. 

A good designer should be enriched with the details about the product. The proper fittings and joints should be pre planned and provisions should be provided right during the design phase. Product details should be kept in mind even while designing the subassembly parts such that problem doesn’t occur during the assembly phase. 

Application is the forerunner of all the design and prototyping process. The design decisions like material selection, working atmosphere, contact surfaces and components should be well known. Once error occurs in application phase, the whole prototyping process should be done again to make the new prototype.  

Size feasibility is more necessary to run the process. Every material and prototyping process has its own size feasibility numbers. So the proper size for the walls or layers should be given according to the material being used or the prototyping method being used. 

A good designer should be well aware about the product, its application, selection of prototyping technology based on requirement, knowledge about the materials and its tolerance, process that will be carried out using the product and its working atmosphere and the technology that will be used to make the prototype. Only then wise decisions can be taken during the designing phase and errors in all other phases can be eradicated. In addition, a basic knowledge about geometric dimensioning and tolerance as well as a complete knowledge about the machine that produces the prototype is necessary to know the complete design consideration. The design considerations should be listed before the start of the design phase.