|If you've been following along, you know that we have set, started, ran and pulled our 32-cavity (unscrewing) cap mold. We have all of the appropriate worksheets (i.e., IML and last shot) completed and have entered this information into our database and created a repair sheet. All three worksheets have been stapled together and placed in the maintenance manual. The next few articles will deal with repairing the mold using tools and techniques that some of you may or may not use in your own shops.
Separating Mold Plates
There are two methods used to separate mold plates. Vertically, with the mold plates standing on end, or horizontally, the mold laying down on the front or rear clamp plate. There is available machinery to mechanically separate large molds, but for this application we will discuss the two most commonly used bench methods.
- Visualizing—The mold is viewed and worked on as it runs in the press. Understanding mechanical movements during the maintenance stages (disassembly, troubleshooting, cleaning and assembly) is much easier and more accurate.
- Leadtime—Reduces repetitive handling of plates and tooling. With many molds, tooling can be cleaned while still in the plates.
- Troubleshooting—Suspect tooling can be located, removed, inspected or replaced more quickly, allowing for easier and more accurate troubleshooting.
- Inspection—Ejector and stripper plates can be actuated manually when checking for worn pins and bushings or sticking/binding issues.
- Improper bracing—The chance of the catastrophic domino death if plates are not braced properly, or if the technician works haphazardly.
- Awkward handling—Tall molds and rack systems are awkward to handle.
- Safety—There is no domino death here, but take care during assembly and verify tooling alignment in situations where the length of the tooling (cores, sleeves, etc.) is longer than the leader pins that engage and align mating plates.
- Ease—It is easier when dealing with tall or awkward molds with plates that vary in size or do not have flat bottoms on which to stand.
- Increased handling—Mold plates will need to be stood up to get the retaining plate off to access tooling, then these steps have to be reversed to assemble.
- More bench space required—Since mold plates are being removed lying down, they will require more bench space. Most benches can't accommodate total disassembly, meaning the four repair stages must be performed independently to mold halves.
- More confusion—It is very difficult to visualize mechanical movement accurately in complex molds.
- Plate alteration—Requires drilling and tapping eyebolt holes on opposing ends of plates, for balanced lifting.
It is necessary to take a few minutes to prepare for the C/R of a mold. This important preparation consists of reviewing:
- Current IML sheet performance statistics and pull reason
- Current last shot sheet for all observed product defects
- Current repair sheet for defect status, type, position and maintenance instructions
- Several past repair sheets for defect resolution effectiveness and last cleaning level
- The Tech Tips section of the manual for disassembly, cleaning or assembly procedures
You now should be familiar with all of the critical information that will allow you to implement a safe, efficient and accurate repair before the first bolt is ever removed. Prior to setting the mold on the bench and separating the plates, hang the mold beside the bench and remove any external components hindering safe mold disassembly, such as bottom water fittings, hoses, hydraulic cylinders, etc.
For example, when working on molds of six thousand pounds or less in the vertical position, run a stone across the bottom to remove any burrs or dings, blow out the waterlines and then set the mold directly on the bench—no parallels. Some technicians like to set molds on parallels, thinking that this makes the mold plates slide easier during disassembly/assembly. This also is how I was taught initially, but abandoned the idea when a toolmaker showed me that a braced, smooth plate slides just as easy on a flat, waxed bench-top. Also, it is much easier to reposition the plate allowing easy access to tooling or visual inspection. Using parallels limits plate movement, forcing you to lean over and twist your body around to see into counter bores and to work in awkward positions. You also will have a tendency to clean your bench less frequently, since the mold is up on the parallels, so your tools lie in crud.
Setting the mold on the bench and using a pry bar, separate the mold halves. Attention must be focused toward keeping the plates parallel as they are moved apart. Most experienced technicians can eyeball the distance and know where to apply the needed pressure to separate plates smoothly. Once separated, use the repair sheet and verify all blocked cavities and positions. If a cavity is blocked off and not recorded, stop and investigate why. After checking all cavities, observe the mold faces for vent residue level, the condition of the main leader pins, bushings, interlocks for grease level and signs of galling. This will tell you if the in-press servicing frequency (every seven days for this mold) is adequate to keep the frame tooling from drying out, the mold faces clean and if the mold halves dropped in the press from improper clamping.
If you are satisfied that all is well, continue to disassemble the ejector half of the mold until all plates are standing about two feet apart and supported by robust feet that will keep them upright as you move them around. At this point, check the repair sheet and determine what defects to correct first.
|There are many ways to work on molds. At a recent seminar, I asked for a volunteer to help me disassemble a model mold used for demonstrations. Two men came forward and said they had worked together for more than 10 years. The 12-cavity model mold consisted of 10 cherry wood plates with standard steel frame and cavity tooling. I narrated the event while the mold was reduced to a stack of empty plates, a pile of tooling and bolts, in about 15 minutes. The men informed us that this style was practiced by about half of their shop technicians.
So how does a supervisor know the difference between the right or wrong method? Critiquing the pros and cons of individual maintenance styles needs to be based on quantifiable data for a comparative analysis. Monitoring individual repair hours, tooling usage, number of molds pulled and repaired and mold performance will highlight areas that need improvement and allow you to establish baselines needed to set shop goals and influence maintenance styles.
Technicians respond more favorably, and are motivated to change old habits and improve their repair efficiency in a system that monitors the results of what they do rather than how they do it. Working in a systemized maintenance environment empowers a technician with the knowledge necessary to improve skills by exposing them to continuous training through data collection and use.
Technicians need the ability to work skillfully and quickly, and at the same time know what area of the mold requires more concentration to keep molds production ready, more reliable and your company competitive.