Making Giant Church Window Grills from HDU in No Time Flat!

Coastal Enterprises, manufacturers of Precision Board HDU, is proud to host guest blogs written by some of the signage industry’s biggest movers and shakers, posted to the Precision Board Blog.  This guest blog is written by Jim Dawson with Synergy Sign & Graphics, based in Strasburg, Ohio.  Jim tells us how he fabricated several large window grills from PBLT-18 Precision Board HDU for the Christ the King Church.  He reduced his routing time from 60 minutes per 4″x60″x80″ sheet to 20 minutes using Onsrud router bits.

window grills

In Jim Dawson’s own words…

Over the past 15 years, we have developed a wonderful working relationship with a variety of vendors. Those relationships usually start out with us trying a new product and being impressed with the results, then contacting the manufacturer in an attempt to learn more and get better with that product. In 2013, one of those products we started using was Precision Board HDU.

Fast forward 6 years, and we have fabricated hundreds of jobs using Precision Board in a variety of densities. While signage and 3D carvings are the bulk of our work here at the shop, our expertise in cutting and fabrication with Precision Board has led us to do work in a variety of fields.

window grills

Precision Board’s low coefficient of expansion (CTE) makes it perfect for architectural elements indoor and outdoor. Its low weight relative to its toughness, also makes it great in situations where weight is a concern (Ed note: the CTE of Precision Board is 26 X 10-6. When an architect designs buildings, dams, houses, etc., the CTE of each different material is taken into consideration to allow for the movement of Precision Board).

Central Glass and Window of Pinellas Park, Florida, contacted us to help them with such a job. The project in question was an addition to an existing church in their area which had large window grills made from precast concrete. The architect wished to carry that same design element into the new addition without all of the weight of the existing grills. Precision Board to the rescue!

We spent a few months drawing and sampling the new window grills until we had an approval. In the end, the grills would be fabricated from 18lb Precision Board.  We used 24 sheets of 2” thick material and another 24 sheets of 4” thick material, resulting in 48 sheets of Precision Board HDU to rout. The grills would be mounted on the inside and outside of 12 separate windows, with the 4″ material on the inside and the 2″ material on the outside.  Two panels to a side, stacked horizontally with screws through the edge of the panels into the aluminum frames.

window grills

The 2” window grills were quite easy to machine. We intended to use a router bit tooling solution that had worked well for us in the past. We stumbled upon Onsrud’s 52-638 router bit when we were cutting some 2” Precision Board on an earlier job. It was not indicated as preferred router tooling in the catalogs by any of the tooling experts we talked to. It really gave us a nice quality edge with a production speed we were happy with.

The problem with the 4” foam was no one had a bit that performed up to our standards. Every time we tested an extended length bit, it had to run way too slow and chattered at the slightest problem. Edge quality was poor and machine time was even worse. After testing 10 different bits, it seemed that milling 4” foam in an 18lb density was just too much to ask.

window grills

One final search and I stumbled onto the end-all solution to milling 4” Precision Board HDU; Onsrud’s 52-728 tool. It is a ¾” shank bit with a 6.5” overall length and a 4.25” cutting length. Surely a ¾” bit would have the stiffness to cut 4” foam and allow us to speed up the machine without sacrificing edge quality.

After receiving the new tools and doing some testing, I felt a little like Hannibal from the A-Team. “ I love it when a plan comes together.” The 52-728 bit worked so amazingly that I ordered its little brother the 52-724 to cut the thinner 2” Precision Board HDU as well.

The 2” PBLT-18 material was cut at 400 IPM @ 16,000 RPM in 2 passes. A final cleanup pass was run at the same speed to take .01 off the width and clean up any horizontal tooling marks.

The 4” PBLT-18 material was cut at the same speed and finishing pass, but with 4 passes instead.

Overall speed of machining went from just over 1 hour per 60” x 80” sheet using traditional tooling, to 20 minutes per sheet using the new router bits.  Our total routing time went from about 48 hours down to about 16.

In the end, we spent a considerable amount on router bits, but saved it back ten-fold in increased productivity.

We delivered the job to Central Glass and Window in early January. Perry and his crew were extremely happy with the results.

If I had to sum this job up and what we learned from it, I would say don’t be afraid to try things with your substrates and your machines. You may just stumble onto the next great technique that makes your work faster and easier in the long run.

window grills

We think that Jim Dawson and his team do some really excellent work. Synergy Sign & Graphics has a highly experienced staff whose backgrounds include graphic design, marketing, trade-show design, print media, branding, point of purchase design, fulfillment, and more. Check out their website or give them a call at (330) 878-7646 to see about your next project!

Coastal Enterprises manufactures Precision Board HDU, a versatile, cost-effective and eco-friendly urethane sign material that is particularly effective for making professional-looking indoor and outdoor dimensional signs.  It is a closed-cell rigid substrate that does not rot, warp or crack.  You can request free samplesget a quote or sign up for weekly newsletters packed with helpful information.