My Experience with 3D Printing
I am a consulting electrical engineer (consulting EE), and want to share my first attempt in the world of 3D printing. Last May I acquired a SeeMeCNC “Orion” delta-style printer at the Maker Faire in San Mateo, California. Since then I have used three pounds of plastic filament and printed many terrible failures on the road to some beautiful components. Figure 1 shows an example of a gear from a gear cube that I designed using Solidworks ™. The blue part is an early print and is very rough. The red part was printed after I adjusted the process. Figures 2-6 show the evolution of a vase throughout the 3d printing process.
Figure 1: Gears From rough (blue) to smooth (red)
Figure 4: A 10-hour print run of a vase almost completed.
Figure 5: A 10-hour print run of a vase.
Figure 6: A completed vase.
The Control of 3D Printing
Despite the advances made by countless experimenters, hackers, and hard-core engineers in the field, 3D printing is still in its infancy. As a hobby, it is comparable to the very early days of personal computers (remember the IMSI 8080?) in which useful results could be obtained but only if you were willing to do a lot of very manual stuff. As a business, it is not yet plug-and-play, and I have a sneaking suspicion that companies who offer printed parts for hire make a fair bit of scrap that the end customer never sees. I look forward to more prototyping with 3D printing.
My electrical engineering career has been tied to the semiconductor equipment industry for many years so I am no stranger to process control. In a semiconductor fabrication factory (FAB), the ability to diagnose, measure, and control fairly complex processes determines ones success. Tiny variations in gas flow rates, annealing temperatures, etch time, and a hundred other factors can be the difference between a wafer full of pricey graphic processing units (GPUs) and one that is the failure analysis (FA) lab’s worst nightmare.
In my attempt to master the 3D printing process I have had to bring my process control and continuous improvement experience to bear and work out a series of experiments to help me “dial in” my printer.
Figure 7: The Deming Circle – Classic Continuous Improvement cycle
3D Printing Process Variables
This may seem like a bit of overkill for a “hobby” but is it ingrained in my electrical engineering DNA and I know that careful planning, with incremental change experiments and careful examination and analysis of the results will yield better and better outcomes. Good results are all about the process control.
There are many process variables that affect the quality of a 3D print. Like any real-world system, they are interrelated; no single parameter can be changed without having a ripple effect on other parameters. I have been experimenting in a careful manner with each parameter, a little at a time and printing and re-printing test models in the same fashion I would for a consulting client. I have designed simple geometric shapes in computer-aided design (CAD), which stress a particular feature or function of the print. In future posts I will touch on more of them in more detail, but for now, here are some of the “high nails” of the process.
There is no real standard for the purity or content of any of the plastic filament available today. As a result, the melt point, glass transition point, and other physical properties of plastic filament will vary from batch to batch and color to color. The range can be as much as 20 – 30° C! Too hot and the plastic will dribble out of the nozzle like a bad head cold and too cool and the extruder motor will be unable to push the filament through the nozzle fast enough to give consistent flow.
3D printers are “dead reckoning” systems. They depend on stepper motors to drive filament through a heated extruder nozzle and have to guess at how much plastic is coming out. Clever software calculates expected flow based on filament diameter and commanded filament speed, but there is no feedback in these systems to make adjustments.
Layer Height vs. Extrusion Diameter
In each printed layer, a ribbon of molten plastic is extruded from a nozzle of given diameter. Each layer sits on top of a previous layer and is flattened slightly based on the height of the nozzle above the previous layer. Too close and the layer deforms as it is extruded. Too far away and it may not adhere to a previous layer. These things are a major factor in surface finish and strength of the final part.
I have learned a lot over the past few months and continue to learn from experiment and collaboration with the vibrant community of owner/experimenters here in the SF-Bay area and silicon valley. The RepRaP Wiki is an incredible source for information on the general 3D printing subject. Presently, my success rate is about 70-80% and thus the experiments continue in between prints of artistic or functional pieces. This is a journey in which my engineering background compliments my hacking spirit. More to come in the following series on 3D printing.