Case Study: Entryway baluster system replacement
A client approached us about replacing a baluster system on an entry stairway. The owner was not satisfied with the quality of the work by the previous contractor. The challenge lay in creating a concrete baluster rail system with a twisting profile that curved both vertically and horizontally. In addition to the complex geometry involved, this project entailed fitting these rails to an existing, slightly irregular and asymmetrical stairway. Here is a detailed, illustrated explanation of the process, which involved 3D laser scanning, 3D CAD modeling, CNC machining, wood turning on a lathe, old-fashioned mold-making, and chemical-powered demolition. Read on …
The existing baluster system exhibited quality problems, such as irregular lines and joints, as well as inferior casting quality.
We made a 3D laser scan that captured millions of measurements in a point cloud that would allow us to strip away the old balusters, rails and newel posts, leaving the exact geometry of the stair treads. This we used to build a 3D CAD model that would be the basis for our molds.
The 3D CAD model was much more elegant and flowing and was used to design manageable sections to produce molds.
Molds were designed to be cut out of flat pieces in a 3-axis CNC router and assembled into the twisting, curving shape of the rail sections.
Together, these sections would assemble into the curving, road-like surfaces needed to make the base and hand rail molds.
187 parts were cut by the CNC machine, in different thicknesses and materials.
These were assembled.
and assembled
and assembled
So we created the rails and surfaces that would be the basis for our plaster molds, using this tool to provide the desired cross section.
Using plaster, we built up our mold.
And so we created a curved profile, itself running on a twisting curve.
We added routed foam walls.
And we added end caps, leaving us a mold ready to fill with concrete — after applying release agent liberally.
Once the concrete cured, we removed the waste mold.
revealing the finished piece.
Thus we produced the various hand rail sections needed.
And we repeated the process to create the base rails, which had a more rectangular profile.
We also turned our own wooden originals on a lathe to make fiberglass molds.
Creating a dozen molds.
Ensuring we could cast large batches
To make the scores of balusters needed.
We also produced molds for the newel post caps
And the newel posts themselves.
The posts were cast in four sections each, including the cap.
We demolished the old rail system
Using expanding demolition grout to break apart the larger pieces into manageable chunks.
And a new baluster system was assembled.
From the base rails up.
A much smoother and elegant entrance.
Made to the specifications drawn from the 3D laser scan of the stair steps.
