Expenditures for masks and racks in a coating operation can add up. Annual expenses related to masking for coating operations can run between $5,000 for smaller shops up to—or exceeding—$50,000 at larger operations. While the use of these materials is necessary, they are not viewed as value added to the coated products and are rarely looked at in ways to save costs.
Maximizing the Use of Masks and Racks
Masks and racks are two of the most pivotal equipment categories for any powder coating operation, aside from the actual powder being sprayed on the parts. Most operators assume costs associated with maintaining masks and racks are fixed costs that eat into precious profit margins and increase operating expenses. However, in recent years, several powder coating operations have found that by using chemical paint stripping, there are cost savings in the way they maintain and maximize the masks used to protect uncoated surfaces and racks used to hold parts.
Chemical paint stripping is a two-stage process that involves chemical immersion followed by rinsing. The immersion stage requires agitation as well as a heated tank. The first step in defining your paint removal process is to determine what kind of materials are to be stripped. Silicone, plastic, or light metals such as aluminum require a mildly acidic liquid concentrate to remove a powder coat, liquid paint, or CARC coating. It is best to use a product with properties that have the ability to break the adhesion of the coating and remove paint from the surface in sheets, typically in 30 minutes or less, while providing a longer bath life.
In the case of steel, chemically stripping paint will require an alkaline product that removes both e-coats and powder coats from ferrous metals, eliminating the need for multiple paint strippers and long bath times.
Regardless of the material stripped, agitation in the tank(s), via circulation, forces the powder or paint coating to delaminate from the parts.
The second step of the process is to rinse the stripped masks or racks with fresh water. Using chemicals that are free of chlorinated solvents and phenols enables stripped products to be rinsed and immediately reused, eliminating dry and wait times. While chemical stripping vastly extends the life of masks and racks, they don’t last forever. When plugs no longer fit parts, or masks become brittle or nonpliable, it is time to replace them. In the case of racks, if the proper solution and process are used, racks can be reused until normal wear and tear take their toll.
Mask Stripping Keeps the Line Running
Looking to reduce costs, one large coating operation in South Carolina decided to investigate ways it could reuse masks more often. Since they finish more than six million parts per year, any cost savings they could achieve would add up quickly.
The company was operating seven days a week, 24 hours a day, and struggled with a bottleneck caused by a backlog of dirty masking materials. Compounding the problem was the lead time to order masking products; it often required a three-month advance purchase to get supplies in the door. A process to reuse masking components several times over was now becoming a necessity.
They experimented with a variety of tactics to get the powder coating off the masks, including tumbling in a dryer with golf balls in hopes they would rub the coatings off the plastic components. In addition, they looked at multiple chemical treatments to clean the masking components, but none seemed to do the job.
Ultimately, the company set up an in-house stripping system to clean the powder coating off the caps and plugs. Working with their chemical supplier, they were introduced to a relatively new product, a mildly acidic liquid concentrate used to remove polymeric coatings, including CARC and TGIC epoxy-hybrid powder coat, from ferrous and non- ferrous metals. It cleaned the masks in just 15 minutes.
By implementing the new stripping system, an almost immediate savings in the mask cleaning process was realized. This was not a surprise since prior to chemical stripping, the company had been using a washing machine and hand peeling coatings 24/7 just to keep up with production. With the new system, labor requirements for cleaning masks and plugs were reduced from seven days a week to five requiring just one person, one shift per day. This new approach not only enabled them to keep up with production which continued at a pace of seven days a week, 24 hours a day, the powder coating process increased to a three-shift operation.
Very quickly, the company saw powder coat productivity increase by as much as 50%, and after stripping the powder coating from plugs and masking materials, masks can now be reused as many as six or seven times, reducing annual expenditures on these materials by as much as 85%.
Keep Your Racks in Line
The chemical stripping process used for cleaning masks can also be applied to hook and rack stripping, parts re- work, and remanufacturing. In-line powder coating lines feature a continuous process of stripping, washing, drying, coating, and curing that can be labor-intensive and incur downtime. By adding an immersion tank into the coating process between unloading and loading the parts, a stripping solution can be used to remove a single coat of paint or build-up. Including a heating element and circulation pump in the immersion tank reduces stripping time. Racks that go through this process are rinsed and immediately put back into the production line.
A plumbing hardware manufacturer that was coating 200,000 faucets, handles, and other components per day saved more than $300,000 a year when they set up an in-line rack stripping system as part of the powder coating line.
Previously, a fluidized sand bed was used requiring the racks to be taken offline for stripping. As a result, the company needed to have three times the number of racks just to keep up with manufacturing requirements.
In addition to the cost of the additional racks, the legacy system had several other challenges:
- Sand residue carried into the washers on the pre-paint line destroyed pumps, risers, and nozzles.
- Damaged paint application components led to paint failures and increased maintenance costs.
- Constantly removing and transporting the racks to the fluidized sand bed was costly.
- Racks needed continual replacement due to metal fatigue caused by high temperatures of the fluidized sand bed.
- The production line had to be shut down for six days per year for maintenance.
- Power outages destroyed racks that were trapped in the fluidized sand bed.
- There were health and safety issues due to the physical handling of the hot racks.
There were pervasive fire hazards due to organic material being burned off the racks.
The integration of the stripping process into the plumbing manufacturer’s powder coating lines has reduced rejection rates and provided a more consistent, uniform, and reliable coating on the faucets and fixtures. In addition, in-line stripping virtually eliminates the damage and wear caused by other removal methods. According to the plumbing manufacturer, since implementing in-line stripping, labor expenses related to rack cleaning and maintenance have been reduced by 67% and man-hours allocated to replace and repair racks decreased significantly, requiring only one worker per shift versus three. There has also been a 30% reduction in real-time accidents and strip time has been reduced to 15 minutes.
If you are looking for cost savings in your powder coating operation, be sure to take a look at your cleaning processes for masks, racks, etc. As illustrated by the two shared examples, chemical stripping can reduce material expenditures, labor costs, and safety issues, while increasing productivity and throughput.
Larry Ensley is technical service manager at Hubbard-Hall.