Drain Pan Welding Jig

Create an ergonomic “proof of concept” clamping jig that allows welders to safely, easily, and quickly perform welding and assembly steps on the top and bottom of the drain pan. The jig will need to accommodate seam welding, hot gas defrost clip welding, hot gas piping assembly, and ideally, hot gas pressure testing.

The Client
Colmac Coil is a large manufacturing plant located in Coleville, Washington. Since 1971, Colmac Coil has become a world-class manufacturer of cutting edge technology and has grown significantly as a company over the past few years. Colmac manufactures new and replacement plate fin heating and cooling coils, dry coolers, heat air-to-air heat exchangers, and air-cooled condensers for commercial and industrial markets. On the cooling side of things, Colac manufactures air coolers, custom evaporators, unit coolers, blast freezers, tube bundles, and hydro coolers for the industrial and commercial markets.

The Project
Colmac Coil came to us to improve a jig created by one of their engineers. The purpose of this jig is to help technicians weld together drain pans. These drain pans are attached to the bottom of the heat exchangers that Colmac produces. These are used during defrost cycles to catch the drainage liquid (water from condensation) and move the liquid to one end where it will be collected and removed. Due to the scale of the heat exchangers produced, these drain pans can reach lengths of 30 feet long and 4 feet wide. This requires the lengths of drain pan stampings to be butt welded together. The drain pans are also built with a triple pitch that causes the liquid to flow down to the center and then down the length as pictured below. These welds must be as smooth and consistent as possible to flow the most water as easily as possible. Additionally, due to the length the lateral alignment is very crucial, as little discrepancies at the joint will be exaggerated along the length of the drain pan. Upon completion the jig will need to meet the given requirements:

Old Design
To speed up the production of drain pan fabrication, the engineers at Colmac Coil made a prototype jig for the welding team to use. The goal of this prototype was to establish a repeatable welding process that allowed the welders to produce drain pans without warping effects and misalignment flaws. However, the jig proved to not work how Colmac Coil envisioned it to, and ultimately it became a huge safety hazard due to the large moving parts and minimal safety nets. The original welding jig was not being used and the welders went back to welding it by using table clamps and stabilizing it themselves during the process.

The original design features a heavy duty base with locking wheels that allows it to be stationary while welding or to be moved around if necessary. The welding surface of the jig is V-shaped to accommodate the triple pitch of the drain pans. The jig has two main aspects that Colmac Coil was aiming for: a stable clamping method and rotation. The prototype's clamping method involves two large arms with pneumatic air brakes positioned at the end. Once two halves of a drain pan are placed on the welding surface, the arms are manually lowered and locked in place. The pneumatic brakes are then activated and push down on the the drain pans via angled plates made out of sheet metal. Rotation was the other major aspect the engineers had in mind when designing the prototype. A rotation method was devised by using two pneumatic cylinders underneath the V-shaped welding surface. This allows the entire upper portion of the jig to be rotated vertically, making it easier for the workers to weld the entire seam of the two pans without taking them out of the jig.

The original design is very bulky and very unsafe. The pneumatic rotation system has an inefficient damper which causes the upper portion of the jig to slam down on the base when lowered. It is our job as NotoriousENG to cater to the prototype flaws and make a working assembly-line style jig for the drain pans.

New Design
The design we have developed focuses on three main design elements: the alignment of the drain pans, the clamping method to hold them in place, and the method in which the rotation of the table is damped.

Alignment
The alignment concept was an all new part of the jig. Previous designs simply relied upon the "V" shape of the jig's surface to align the drain pans. However, due to sudden movements of the jig when rotated, the drain pans would become misaligned causing a less precise weld. This is fixed with the implementation of a pair of self centering and easily operated alignment blocks. The alignment blocks are able to move across the width of the table to fit various widths of drain pans and keep them aligned. Essentially, these alignment blocks pinch the sides of each drain pan on the vertical sections next to the flanges. The alignment mechanism done with a couple of right and left hand threaded lead screws operated by a handle.

Clamping
The clamping method is a simple retractable metal slide with two strong welding magnets attached at either end. This apparatus is placed on the table in parallel with the width of the pan and sits nicely in the "V" of the table with its triple-pitch design. The apparatus can be extended or retracted to meet the width of the various drain pans being welded. Once the clamping apparatus is placed on the drain pan, the width can be adjusted and locked into place via a wingnut. The magnets can then be turned on, each supplying 600 lbs. of pull force. With the use of two of these clamping devices (each with two, 600 lbs. welding magnets), a total of 2400 lbs. will be securing the drain pans in place while they are being welded. Drain pan warping is a major concern and our clamping system will almost completely eliminate that issue.

Rotation & Damping
After testing the pneumatic actuators, a decision was made to keep the current means of rotation and implement a damping system that slows down the rotation of the heavy table top when it reaches its vertical position. With the initial prototype, the drain pans would become misaligned due to the jolting of the table when it was harshly stopped. The dampers provide a smooth transition from a moving table to a stopped table. These dampers are very simple and can be found under the hoods of most cars. When the table is rotated back down to its horizontal position, four rubber suspension bump stops offer help by eliminating the harsh metal-on-metal hit, which was present in the initial prototype design. The bump stops mitigate the jolting caused by the abrupt stops of the heavy table.

Team Information
Michael Botterbusch

Mechanical Engineering

My name is Michael Botterbusch and I will be graduating from the University of Idaho this Spring with my Bachelor’s in Mechanical Engineering. I plan on going into a career dealing with manufacturing post-college. Classes I enjoy include solid modeling and fatigue analysis. My hobbies are mountain biking, working on my bike, camping, and hiking.

Scout Ferguson

Mechanical Engineering

My name is Scout Ferguson and I will be graduating in Spring 2017 with a BS in Mechanical Engineering. I plan to go into the workforce after graduation and get a job in the aerospace industry. After a few years working, I want to go to grad school and eventually obtain a Professional Engineering certificate. My hobbies include playing guitar and mountain biking.

Dakota McDaniel

Mechanical Engineering

I am a senior at the University of Idaho. He plans to move into manufacturing and/or process engineering post college. Dakota likes to hunt, fish, ski, and snowmobile in is off time. Dakota has a professional certification in CAD modeling from SolidWorks and like to tie this with fluid and stress simulation. Taylor Tosaya

Mechanical Engineering

I am 22 studying Mechanical engineering at the University of Idaho. I grew up in Boise Idaho. Since early in my high school career I decided that Mechanical Engineering would be the best fit for myself. Currently I work at WSU’s Sports Science Lab as a lab technician. After finishing my undergraduate studies I wish to pursue a graduate degree in Mech. Engineering. Outside of school I have two main passions, the first all things automotive, if the weather is nice enough I will frequently be working on my personal car or helping friends repair theirs. If there are now cars to work on then I will mostly likely be outdoors, either backpacking or rock climbing.