CLICK IMAGE TO ENLARGE (+)
Estimating accurately the cost of a finishing job can make or break the job shop entrepreneur, especially given the highly competitive global environment in which we do business today. Looking at your finishing operation to determine what strengths and overall value you provide to your customers is important. But from there, accurately determining the costs involved in providing your services is key to running a profitable business.
Identifying all the variables that add cost to a finishing job is challenging, but looking at this important aspect of your business from the perspective of a finishing system design engineer will help you gain valuable insight into how to properly determine finishing costs.
The typical costs of finishing include labor, coatings (applied and wasted), energy, water, consumables, maintenance) including cleanup, waste disposal. Other pertinent costs include masking parts, hanger/hook costs including design, fabrication, maintenance/handling/storage, load/unload times (including personnel), as well as clearing the product from the line at day's end. Amortization of the costs of finishing equipment also may be included when calculating cost per part. The finishing of each product, and of each part comprising a product, can vary depending on the product's end use and complexity. Each step adds more cost to the finished product.
Calculating Labor Costs. The labor involved in finishing can be significant. This is especially true when the finishing process is complex. Multiple process steps, intricate masking requirements and complex part shapes all can increase the amount of labor required. Loading the parts onto the line and subsequently removing them also can require a substantial amount of labor.
The labor rate should include all of the workers' benefits, hourly wages, workers' compensation, uniforms and safety equipment and break/dinner periods if paid, averaged out to a man-hour cost. In some situations, a “standard time” is assigned to each specific task in the finishing process. This standard is used as an indicator of the amount of labor required for performing that task. Actual times then can be compared to standard times and any deviation compensated for in the actual pricing.
Masking. Parts being painted are often masked to prevent coverage in certain areas. Masking techniques include the application and removal of tape and paper masks; the use of precut, adhesive-backed masks; the use of reusable metal, plastic or rubber masks and the use of rubber/plastic/wood plugs and caps. Masking can be done on-line or off-line. Either way, the space, labor, energy and cost of the masks also should be included in the costing.
Conveyors, Hanging and Transfers. Conveyors are a common means of moving parts through the finishing process. They may be free trolley manual transfer overhead monorail conveyors, power-only monorail overhead conveyors, enclosed track overhead conveyors, overhead power-and-free conveyors or floor conveyors.
Hanging or otherwise, positioning parts for coating and movement through the finishing process is an important part of cost. The labor that is required to prepare the parts for coating and subsequently to remove them after coating should be included in the cost determination.
When conveyors are used, it is important to occupy every available hook or hanger. The hangers should be positioned optimally so each part can be painted efficiently and without missed hangers. A missed hanger increases the cost by requiring a longer period of time to finish all of the parts. Energy, labor, materials and waste can all increase when hooks are missed, but since this is the finisher's mistake, this cost should not be included in the cost estimate. It is a loss to the finisher.
Some facilities use manual transfer methods to move the parts through the process. Carts, free trolley manual overhead monorail conveyors or racks mounted on wheels and forklifts are all commonly used methods. Where manual transfer is used, the labor to move the pieces into or out of the area is usually greater than energy or floorspace charges and should be considered. The amount of time taken to move the parts should be multiplied by the number of workers required to move the parts.
When mechanical means forklifts are used to move parts, then the energy to fuel the forklifts, the manpower to operate the forklifts, the expense to maintain them and the amortization (or rental/lease fees) of the forklifts over their useful life should be included.
Pretreatment. Different procedures to ready parts for coating are used for metal, plastic and wood substrates based on individual requirements and end uses. Each step of the pretreatment process should be reviewed and the pertinent costs included in the cost determination. Generally, energy costs, material costs, labor costs and disposable material costs (sandpaper, grinding wheels, etc.) are included in these calculations. Typically, the labor is based on the number of persons working in that area for a specified period of time as is the energy consumed and the material consumed during this same time period.
Application. If the coating will be spray applied, then the cost of the coating consumed along with the cost of applying it should be included. The coating consumed takes into account the transfer efficiency of the application method. The transfer efficiency is the percentage ratio of coating deposited on the part to the coating sprayed at the part (paint deposited/paint sprayed).
Transfer efficiency does not take into account the uniformity of the applied coating or the uniformity of the applied coating film thickness. It does not include the labor (painters, mixers, supervisors), the energy consumption (gas to warm the area, electricity—including the generation of compressed air, lighting, in-line coating heaters, generation of electrostatic charge, pumping if non-pneumatic), the cleanup and the disposal both hazardous and non- hazardous waste, the cost of booth and air makeup filter use and its disposal and replacement costs. The cost of these must be determined and included in order to get a more accurate cost. It may be better to average these costs over a specific period of time. If solvent and/or water are used to reduce the viscosity of the applied coating, then they, too, should be added to the application costs.
Transfer efficiency does vary with the application method and the skills of the painters applying the coating, and it does greatly affect the cost of coating the product. It is possible to lower the cost of coating by controlling the applied film. Both electrostatic and HVLP (high-volume low-pressure) methods of application reduce the amount of coating sprayed and subsequently lost. This is important because both the amount of coating wasted and the quantity of coating deposited on the parts are of concern.
The required film thickness (between the minimum and maximum allowable values) should be applied while minimizing the amount of excess coating applied. Staying within the acceptable coating thickness range ensures that the part will meet the specifications (performance and appearance). Any excess coating adds an unnecessary cost and can keep the part from meeting the established standards for that part. Even though the method of application may have high transfer efficiency, adding more coating than is needed only wastes the coating. It also increases booth maintenance and waste disposal.
It is possible to estimate the cost of the coating applied to even complex parts. This cost is based on the area of the part and an estimate of the film build on the various surfaces of the finished part. Use an average film thickness based on the results of similar parts coated in the shop.
Many complicated shapes can be estimated by breaking the shape down into simple geometric figures. Figure 1 is offered as an aid to overcoming the problems involved in determining the area of product surfaces to be coated. The coating cost can be estimated from the relationship: one solid gallon (100% volume solids) will cover 1,604 sq ft at 1.0 mil dry film thickness. Differences in film thickness and volume solids can be taken into account. Transfer efficiency does not enter into this equation.
Flash Off. Before the part can enter the force dry phase of the process, it may require a period of time commonly referred to as flash time. The time required for the flash is related to, but not limited to, the coating composition, the application method, the amount of coating applied, the ambient conditions and the force dry temperatures. Flash time generally translates into a length of conveyor (equivalent to the period of time required at the conveyor/line speed) prior to the force dry chamber or oven. The amount of time required can be affected by the air circulation and temperature in the flash area.
The cost associated with flash time is sum of the cost for the energy (electricity for lighting, air circulation fans and exhaust fans, gas/electricity to condition the air and replenish the air that is exhausted) expended in the area, maintenance in the area, amortization of the building for that specific floorspace and the cost of the added energy required to convey the parts through the system.
Force Dry/ Bake. Once the part is finished it may be necessary to force dry, bake or otherwise provide a finish that will sustain the handling required to complete the processing of the part, be it assembling, packaging, transporting, etc. This can be through the use of a force dry oven (convention air, infrared or ultraviolet irradiance, to name a few common methods.)
Force dry/bake ovens are generally turned on sometime before the shift begins and are turned off when the last part is dry. The costs associated with this device can be averaged over the time of operation, including the startup time and referenced to the number of parts produced in that time period.
Rework. Reducing rejects and rework also reduces the cost of finishing. Not all rework can be eliminated, but when it can be, it should be. Rework requires additional materials, labor and process time. If the parts are run on the line, they reduce the number of pieces that can be produced in the allotted time. This can increase the cost of finishing significantly.
There are other costs, such as clean up and waste disposal, to consider when estimating finishing costs, but from a design engineering perspective, this article highlights the key operations to consider.
While finishing costs vary from minute to minute, over time, costs can be averaged and referenced to the number of pieces finished during the same time frame to provide a cost per part. The time period chosen may be an hour, day, week, month, year or shift. Averaging will smooth the highs and lows to provide a representative finishing cost that is useful in quoting new work, the lifeblood of any growing business.
blog comments powered by Disqus