<< Part 15
By David Lewis
A Solution to Warping
As we have approached building the woofer boxes for The Herd’s elective class we have been plagued with warping issues. The box is 4.25 inches long, 2.75 inches wide and 2.75 inches deep with a 2mm solid back. And it has been making us nuts to build. The first box built out of PLA worked pretty well, but had bulging sides.
The next three attempts all failed due to one or two of the corners lifting from the bed and giving us a completely unusable result, so we did some research and tried a number of recommended solutions.
We heated the bed – warp
We taped the corners – warp
We roughed the bed -warp
We put a heat lamp on it – warp
And then we ran out of PLA.
So back to ABS and what a result!
Not only did it lift, but there was significant failure to adhere between the layers. Modern art perhaps, but not an acoustically sealed box that would produce good sound. We thought the solution was to go back to PLA. Our friends at 3D Systems (thank you Cathy Lewis!) sent us more PLA and we were back at it again today working HARD to finish up the semester project.
The corner lifted, the layers released and I was frustrated. Riley, Ben, Justin & I put our heads together and decided on thicker sides to help with the adhesion, a slightly higher temperature at the extruder head to also help the layers stick and then the breakthrough (we think)!
Polygons for the base.
Previously we had been using an 80% fill with .25mm thick strands laid out in a diagonally to build the base. Every time we got to a temperature differential, we got warping as the stands apparently contracted. By using SolidWorks polygon fill in the base layers (2mm thick total) we apparently built in some stretch that allowed the base to stay flat in spite of the temperature changes.
This took care of all the warping problems and allowed us to get into production with the speaker boxes that will complete the project for the students.
The back of the box will be filled with either “water putty” or epoxy to provide an acoustic seal and we will assemble the kits over the next week.
Part 17 >>