Control vs. Quality The most important anodizing tank

Considering converting your manual hoist to automatic? Read this first

By implementing an automatic hoist, you are essentially turning the entire line into an automated process line. This would allow you to create process programs that include specifying tank immersion times and possibly tank parameters such as temperature, conductivity, etc. Once these programs are created, your operator will load the work bar, choose the appropriate process program and run it. After processing is complete, the operator will pick up the parts at the other end of the line. It becomes a hands off process for the operator. This can be a good thing or it can be a bad thing. If the automatic line is running well, you can be reasonably assured that you will get a consistent coating. If however things are not running well, the automatic line will not detect those things an experienced operator can. Take part cleaning for example. An automatic hoist cannot see a “clean water break” whereas an experienced operator will know to look for this and continue cleaning until it appears. Also the experienced operator can, to a degree, know the part’s coating thickness based on the color after anodizing. The automatic line cannot. There are a number of benefits from an automatic processing line, but there are also a number of limitations and drawbacks as well.manual hoist

You should also consider what will happen when the process load reaches the anodize tank. If the rectifier is still going to be mmanually operated, the hoist would need some method of waiting for the rectifier to create the coating. After that, it would need some method of resuming when the coating is done. This can certainly be accomplished, but the correct way to implement an automatic hoist is to implement rectifier control as well. With rectifier control implemented in the same control system with the hoist, a seamless process flow is created. When the hoist moves the process load into the anodize tank, the control system runs the rectifiers based on the program chosen by the operator. Although an automatic hoist can be implemented without rectifier control, it would create a bifurcated control system that eventually will have problems.

Whether you implement an automated hoist or not also depends on the type of facility you have and your work loads. Automatic hoists are mainly used in captive shops. These are facilities that typically manufacture and process their own parts or have only one or two customers they process parts for. These shop normally have only 3-4 different parts that are run and the loads sizes and configurations tend to be the same. On the other hand, it is very rare to see an automatic hoist in a job shop that does anodizing work for their customers (who are the manufactures). In job shops, there are just too many different parts, load sizes and load configurations to be supported by automatic processing. Normally automatic lines have a limited number of process programs which limits the line’s flexibility. Also since a job shop may run a specific parts only once, creating and validating the automatic line’s process for the parts become a hindrance.

The cost of converting a manual hoist to automatic line should also be considered. You cannot simply plug your existing push button controls into a PLC and expect it to work. In fact it’s much more likely the hoist mechanicals themselves (chains, gantry, booms, etc), are the only parts that can be reused. Plan on replacing the drive servo motors. Also a servo drive, positioning system, PLC, cabinet, software and a computer for the operator interface will be required. Part cost alone can easily reach 6 figures. Add labor and engineering cost and you could be in the $250,000 range.

For absolute process control, you need absolute consistency. The automatic line affords this. You can be reasonably assured that when the line runs well and your chemistry is maintained, the parts are being processed the same each time. Unfortunately, when the automatic line doesn’t not run well, or if you have under maintained chemistry, there is no operator to provide the all important “reality check” that could save the day and the customer. Couple this with the limitations and cost of implementing an automatic hoist and in some cases, it simply may not be worth it.

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