James Smith's blog

I've been thinking about how to better solve to issue of the build table not being perfectly level on the Fab@Home. I have tried shimming, but for 3D printing large parts we really need to hold plus/minus 0.10mm across the build base and It is very hard to do this with manual shimming. Yesterday I decided to take a caliper to my machine and measured a number of points across my plate to create a contour map.

You can see that my plate isn't very level at all and for printing large parts I see a +0.45mm to -0.45mm sweep across the plate. That is over 3 printed layers think for me. Not good.

The solution is to fix this with software. This is how the motion control industry fixes these exact problems. I think this would make an important project for the CS team. Imagine a GUI similar to the above image image where we have a complete grid of points (lots of points, maybe it is an option how many points you have) with each point having a blank number input field. The user would measure all these points and input them into the GUI. FabStudio can interpolate between these points and automatically compensate its Z height as it moves around the build table.

Think about it, I don't think we are really going to ever get every Fab@Home's z table to be square. There is just too much variation during production, etc. All a user would need to do is move the build table up until it contacts the tool and note the position from FabInterpreter. Repeat this for all the points. Thus, every Fab@Home will have a perfectly squared build table no matter where or how it was made. I think this would be the most elegant solution to this issue and warrants some attention.

I have been printing lots of things with the plastic tool system for a while now and I have noticed some areas that will need improvement down the road.

Printing Calibration
Path planning is critical. Based on empirical calibration of the plastic tool, in terms of suck back and push out, you can only go so far. The new Fab Studio features a modular pather, so you can create and select different pathers during the planning process. I am still tweaking the paths to get a perfect part surface finish.

Heated Bases
After many days of printing, my heated build base burned out and smelt terrible. The cause? the entire bottom of the plate is heavily insulated. including over the heater. Over time the heater itself was surpassing its maximum operating temperature. This caused an air bubble to form between the heater and the plate, which expanded then causing the wires within the heater to short. So the solution is to use a large 10"x10" heater with no insulation. This actually costs the same because the cost of the larger heater is offset by not having to buy the ceramic insulation.

Burned out heater                                               New fix

EMI
For awhile now we have been stumped as to why our software keeps freezing in the middle of plastic prints. Turns out it is not a software issue but an electromagnetic interference (EMI) issue. The EMI is coming form the relays in the temperature controllers which are constantly turning on and off. The SNAP hub is located right next to these temperature controllers. So the fix for now, until we find a shielding solution, is to put the snap hub as far away from the machine as possible. Aluminum foil does not really do much, as you can see I was testing an inexpensive solution here.

Next up: 3D printing kittens

Jeff and I were at the Bay Area Maker Faire this year and it was quite a success. We had three Model 2.0's running all day Saturday and Sunday each demonstrating a different tool. The SteamPunk machine was milling, the Blue used the dual syringe tool to print silicone and the white machine was printing out plastic parts. We both completely lost our voices speaking to thousands of excited people over the two day event.