RUG/Pennsylvania/State College/Electronics/Heated Bed
Introduction
Printing ABS or HDPE plastics using the mendel often results in warpage rendering the print useless. These deformations are due to moderate temperature gradients which develop in the plastic as a result of cooling. For example hot plastic from the extruder may leave the tip at 200 degrees Celsius while the base layer of the plastic part has cooled to room temperature. This temperature difference can be especially prevalent in larger prints causing noticeable distortions, lifting of the print off the bed, and interruption of the print. Experiments have shown that heating the print bed up to approximately 120 degrees Celsius has significantly reduced warp problems [1].
The purpose of this page is to present an engineering analysis for a preliminary design of a mendel heated bed. This evaluation takes into account a general heat transfer discussion, mechanical design considerations, as well as material costs and options. A mendel heated bed design is presented for consideration and later implementation at The Pennsylvania State University.
Discussion
The following topics cover a general approach to the design of a heated bed for a mendel. The mechanical and heat transfer calculations listed below are important for providing a reference to values such as the power needed to run the heating system, estimation of heat up time, geometrical tolerancing etc.
General Heat Transfer Analysis
Abstract:
The attached document provides a general heat transfer analysis for a mendel printing bed being heated to 120 degrees Celcius. The objectives of the analysis are to provide estimations for: the rate of thermal energy loss from the bed at a steady state (i.e. once the bed has heated up to 120 degrees Celcius but has not started printing), the minimum heat flux and power input needed to maintain a steady state bed temperature (120 degrees Celcius both while stationary and while printing), and the time it takes for the bed to reach a steady state temperature (120 degrees Celsius) with various applied heat fluxes.
References
[1]http://hydraraptor.blogspot.com/2010/01/will-it-stick.html
