Drain Pan Welding Jig

Intro Statement

The Customer
Colmac Coil is a large manufacturing plant located in Coleville, Washington. Since 1971 they have become a world class manufacturer with cutting edge technology. 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 they also manufacture Air coolers, custom evaporators, unit coolers, blast freezers, tube bundles, and hydro coolers for industrial and commercial markets. They are fast growing and always improving in their safe work environment.

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 in 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 be up to 30 feet long and 4 feet wide. This length requires 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.

Our Design
The design we have developed focused on three main design elements: the alignment of the drain pans, the clamping method to hold them in place, and the method in which to rotate the drain pans for welding.

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 this failed to align the critical edge geometry in the design. This should be fixed with the implementation of a pair of self centering and easily operated alignment blocks. The alignment blocks will be able to move up and down the "V" shape to fit various widths of drain pans. This will be done with a couple of right and left hand threaded lead screws operated by a handle. Additionally, these blocks will be height adjustable in order to fit the various depths of drain pans.

Clamping
The concept for a new method of clamping involves using a modified arm apparatus. This apparatus is attached to a rail and can slide along the side of the table. The arm can rotate up and down with the rail being the pivot point. The arm can be extended or retracted perpendicular to the sliding motion along the side of the table. Therefore, there are three methods of motion for the new concept arm design. All three methods can be locked into place so that motion is restricted and the arm cannot move. Toward the end of the arm, the design is contoured so that the side of the drain pan is held in place securely. This means that when the arm is in place, the edge of the drain pan is held tight by the arm contacting the vertical side wall as well as the horizontal portion of the drain pan flange. Lastly, the furthest portion of the arm holds the bottom “triple pitch” of the drain pan flat. This is so that the metal cannot warp when it experiences the high temperatures of welding operations.

Rotation
This concept was inspired by the works of Colmac itself. Their concept had an edge pivot with the use of pneumatics for mechanical advantage. By moving the pivot in toward the center thus reducing the moment arm and therefore relieving some strain on the pneumatics. Also by switching the mechanism for rotation from pneumatics to a high torque electric motor or hydraulics. This will reduce jolting when jig passes the tipping point during rotation. By adding in some dampers we have also reduced the jolt. This concept has become part of the final concept of the jig.

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 21 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.