Casting a Light on LED Cooling with Die Cast Heat Sinks

Advanced Thermal Solutions work in casting aluminum heat sinks allows us create large, rugged, and reliable heat sinks and enclosures in a single piece.  Such work carries a number of advantages including enclosures and heat sink in a single unit, reduced part count, reduced final manufacturing complexity.  ATS’s John O’Day sat down with ATS engineers Joe Gaylord and Anatoly Pikovsky regarding our engineering in cast heat sink design to discuss two specific customers projects, both in LED Lighting.   The first company is a  company focusing on LED stadium lighting and the other specializes in LED industrial lighting.

John: What kind of value add did ATS add to the stadium lighting company for their cast stadium heat sink?

Anatoly: Well, this company tried to make the casting for their Stadium LED light for almost a year. They went to many different vendors and nobody could actually build what was needed. They started to cast the first prototypes but they developed cracks. ATS was brought in to see if we could solve the technical and manufacturing problem. Our involvement made it possible for them to ship their stadium lighting on time to be installed in the University of Phoenix Stadium.

Ephesus Stadium Light

Joe: One thing we did was to change the fins a little bit to improve heat transfer and manufacturability, changed how the actual casting tool was made.

Anatoly: We also created a version of the heat sink from sheet metal as a backup, in case the casting failed.

Joe: We did CFD modeling to determine fin efficiency too. In the current design fin efficiency is very good but we thought we could improve it further, so we found that a much shorter fin version would perform just as well but this stadium LED lighting company was already down the design cycle and needed to get this product out the door. We also did work developing a version with heat pipes too, to give the customer multiple data points on what was possible.

John: So we created multiple options for the customer as backup so they could make this shipment for University of Phoenix Stadium on time. It sounds like we take partnering with our customer’s very seriously.

University of Phoenix Stadium

Joe: That’s true we do take partnering seriously and in this case there was a great deal of investment on ATS’s part.

John: So we’ve done casting for another important lighting customer too haven’t we?

Joe: That’s right, an LED company that makes several types of LED lights, some for food chillers like you might see in department stores and they also make canopy lights for gas stations. The canopy lighting LED’s were what we worked on.

Anatoly: If you ever look up while pumping gas you’ll likely see their LED lights in the overhangs above the gasoline pumps.

Joe: So the model they had previously was a molded plastic shroud with a PCB board, LED array, and extruded heat sink on the inside of the shroud of the cooling device. Essentially a big extruded aluminum heat sink, all bolted together (credit senior). Their goal was to increase the number of LED’s, power and lumens in these lights. Thermally, their target originally was 100 Watts, then it climbed to 150 Watts, then it came down to about 120 Watts.

John: So what did we do to make their design better and casting better?

Joe: Our goal was to get rid of the plastic shroud and the extruded aluminum and replace those with a cast piece. We suggested casting for this design since it would create a shroud that allowed for heat transfer. It eliminated a two piece design of heat sink with shroud allowing this LED customer to simplify manufacturing while meeting their thermal performance requirements.

John: Was it easy to come up with this design or did it take several iterations to get to the final design?

Joe: Well, as you know, ATS has a 3-Core Design Process where we do a quick analytical model of the design, move to computational modeling using Flotherm or CFdesign, and finish with an empirical model for physical testing in our thermal characterization lab. This process helps us to reduce the actual time it takes to do a proper heat transfer solution design. For this work we did a lot of thermal modeling with CFdesign.

Heat Sink Design Engineering Process, ATS

Anatoly: There were some key challenges in this design: First it required natural convection cooling. Second, we had to design to cool 120 Watts. Third, the outside ambient temperature can be up to 40 degrees C when a gas station is in the desert.

Joe: For natural convection cooling you need some headroom for the air to convect. We had designed this thermal management solution for a minimum headroom of 1-inch from the heat sink to the canopy over a gasoline pump. Allowing air to come into the heat sink and circulate out was a major challenge requiring excellent fin efficiency, a consideration for spreading resistance, and the mechanical packaging over the LED array. The weight of this casting had to be taken into account too since it would be outside in a canopy over gas pumps with people standing under it. Finally, the industrial design was an important aspect as well since it was outside and had to look attractive. We took time to carefully sculpt the heat sink fins in the final design to account for both aesthetics and thermal performance. Our final design was a machined, open enclosure with fins on all four sides, so that air flow can come up and through from all sides.

International Lighting Canopy Light

John: When we completed testing in our thermal lab with the model we had machined, did we move to casting then?

Joe: Yes we did. Our design was set to cast in two pieces so that the cost to manufacture was within the LED customer’s requirements. The end result was a powder coated single unit, with the electronics box built into the cast, that fit both the PCB and LED. All that was needed as a cover. It simplified the manufacturing process, reduced the manufacturing cost and met their requirements for overall price and thermal performance.

To learn more about ATS’s die cast heat sinks and design services, please email us or call us at 781-769-2800.

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