We are going to take a look at the Stratasys J55 build size and how part placement within the build lanes effects the build times. For this demonstration we will be running time estimations on and printing a doorstop that was designed for our Design to Manufacture series.

This doorstop part features a translucent blue over molded rubber Elastico shell, a clear body, and the TriMech logo in Vero UltraWhite. The Shore 85 over-molded simulated rubber texture provides the slip resistant bottom needed for the doorstop. We chose to create this design to show off the full color and texture prototyping capabilities that the J55 can achieve.

The J55 Build Size

First, let’s talk about the rotating circular build platen. The Stratasys J55 build size is 18 inches diameter, giving you 182 square inches of overall build volume. That’s equivalent to a traditional 10-inch by 18-inch rectangular build area. That’s a very large build area. The Z axis has 7.5 inches of build height, so quite a lot of volume there as well.

One of the questions we get asked often is “Why is there a pie slice missing out of the platen?”. There are a few good reasons for it. We need a gap in the rotating printing process to move the print head and the U.V. lamp along the build lanes. There are three print lanes on the J55 PolyJet printer, the inner lane, the middle lane, and the exterior lane. The printhead moves in the Y axis from the center to the outer lane. And the same process happens with the UV lamp as well, which moves on its own Y axis to cure the layers. The space missing depends on how many build lanes are being used while printing.

The inner lane prints the fastest, then the middle lane, and then finally the outermost lane. In general, the inner lane job finishes quicker, twice as quick than the outer lane jobs. The build tray is rotating at a constant speed within a job, but varies between jobs, according to the model’s position on the tray. The speed of the rotation (RPM) is determined by the outer most model.

Part Placement vs. Time to Build

How do we apply part placement on the J55 to shorten print times?  If we place three one-inch cubes in the inner most lane it will take 7 hours and 7 minutes to print. Conversely, if we spread those cubes out to have one in each of the three build lanes, it would take 19 hours and 8 minutes. If we increased the total build to 38 cubes spread evenly, it would only add 25 minutes for a total of 19 hours and 33 minutes. This is a great example of how positioning your parts on the build tray dictates how long it will take to print. Of course, you would use more material with a full tray of parts, but the time is about the same.

Now we’ll apply this to our doorstop model. If we position one doorstop on the inner most lane, we get 7 hours and 42 minutes. If we position two doorstops in that inner lane and print about the same time 7 hours and 44 minutes. But if we move those two doorstops to the outermost lane the build time shifts to 13 hours and 8 minutes. Pay close attention to part placement on the J55 since they can dramatically affect part build times!