How to Increase Throughput with Racking
Q. How can I increase the throughput of my finishing line through proper racking protocols?
A. To achieve maximum line speed and parts density—both of which directly impact profitability—racks are often required for handling mass quantities of parts on and off the line, rather than hanging or removing parts one at a time.
The initial step should be choosing the right rack design. First, answer the following detailed questions about your system and parts. The proper rack design will accommodate both and maximize your finishing process.
Survey your system:
- What is your application? Powder, liquid, ecoat, conversion coating? This will determine how much part control is needed and what type of rack adjustability can be used to re-establish electrical ground, if required.
- What type of conveyor do you use: P and F, monorail, hoist or batch?
- Can you paint from both sides or must the rack swivel?
- Are there inclines and declines on the conveyor? What is the max degree? This will affect the center of gravity on the rack if hanging from two points. The max degree will also be used to calculate max rack width.
- What is the conveyor pendant style: H attachment, swivel casting? Centered on 6", 8", 24"? Max weight per pendant? Load bars?
- Will the racks be burned off to be cleaned or exposed to an acid? (Stainless hooks may be required versus high carbon steel.)
- What are the smallest dimensions of the booth, oven, washer or tanks?
- How fast does the line travel? Can racks or heavy parts be loaded at that speed?
- How will racks be moved to and from the line area? How will they be loaded onto the conveyor and removed? (The rack must be easy-on and easy-off.)
Survey your part:
- What is your coating, powder, liquid, ecoat?
- Are you painting both sides of the part or just one side? Swiveled?
- Is masking required?
- Will the part be washed? Will it drain naturally?
- Are there holes for hanging this part?
- Is the part light enough to blow off of a standard hook in the washer?
- What is the most important coverage area?
- Will a custom hook be needed?
- Is a dedicated rack needed for this part or an adjustable rack with interchangeable crossbars?
- Will the hooks need to be changed out of the rack to accommodate other parts? If so, can you change the hooks at any time?
- Can the part be stabilized on the rack, versus hanging freely?
- Are any blemishes allowed?
- What is the desired hanging position: side or front?
- Can this part be hung on both sides of a single crossbar?
- What is the max weight of the part?
- Are load bars required to carry the parts around the line relieving conveyor stress, or to distribute weight across pendants?
Let’s look at one company as an example. The critical need for the company is to increase line density from 600 parts per day to 2,000-3,000 parts per day, or roughly a 233-400 percent increase in production.
Large numbers of parts are sent out to be finished, which are “daisy-chained” with individual hooks under a load bar. There are four ways this company can “rack” up more money:
- Add more parts to the same space. The first test rack—partially loaded—held the combined parts for three load bars, increasing production by 200 percent. Three parts are now in the same space as one prior to racking.
- Eliminate labor cost of “daisy-chaining” hooks; it costs 50 percent or more in labor versus racking because of hanging hooks before hanging the actual parts. Profitable finishing lines use racks versus individual hooks to run at maximum line speeds, some up to 70 feet per minute.
- Look at offline loading and unloading. Often racks can be loaded and unloaded offline, allowing the line speed to be increased to its maximum while moving fully loaded racks to and from the line. Sadly, most lines run slower than designed; hindered by “people speed” hanging parts directly on the line.
- Reduce hourly overhead line costs, since racking increases the number of parts finished per foot, per hour, it reduces the cost per part associated with the hourly overhead of the finishing line. These include costs such as chemicals, utilities, maintenance, labor, paint, cleaning, waste disposal and so on.
When analyzing the racking potential, it is best to stage and load racks at the work station to eliminate re-handling of parts. Seriously consider off-line loading and unloading of racks. Carts can be used to transport racks to and from the line. Use mechanical lifting devices for heavily loaded racks.
You should also aim to eliminate all manual handling of racks if possible. Consider the design of the racks, how they will be stored on carts moving to and from the line, loading and unloading off-line, transporting by truck, and going into a burn-off oven and/or chemical strip tank for cleaning.
The return on investment for racking is often immediate. In summary:
- Increase line density: add more parts per foot.
- Labor savings: eliminate daisy-chaining.
- Offline loading/unloading: increase line speed and gain more parts per hour.
- Decrease overhead cost/part: increase profit per part.
Donovan Dixon is general manager of Production Plus, makers of Magic Rack. For more information, visit ProductionPlusCorp.com.
Originally published in the May 2017 issue.
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Question: I am responding to the article in the January 2001 issue regarding the comparison between powder coat and electrocoat performance.
This paper is a peer-reviewed and edited version of a presentation delivered at NASF SUR/FIN 2012 in Las Vegas, Nev., on June 12, 2012.