The principal purpose for capsule segment alignment is to allow the capsules to be separated reliably and rejoined accurately. To do this, the hole in the upper segment must be accurately lined up with the lower segment, and the segment surfaces must be parallel.
Before Aligning Segments
Before aligning segments, the lower segment is placed on the machine with pins, which locate the segment in a fixed position. It usually locates on two pins that are approximately 0.002″ smaller than the locating bores in the segments. The segments are then tightened using the hold-down screw(s). Two things are notably important:
1. Lower Segment in Good Condition
The lower segment must be in good condition so that it sits flat on the encapsulator indexing table. Any burrs on the bottom of the segment will damage the machine and prevent the segment from locating correctly. The segment may be bent if it has crashed or been abused, especially if the tang is small and thin.
2. Clean Mounting Surface
The table (mounting surface) must be clean of dust and any other substances that can embed in the segment or table. Embedded matter may prevent the segment from locating properly. Examination of older segments will sometimes show that the lower segment has been placed on a piece of foreign matter before being tightened down into place.
Variations in either of these conditions will make aligning the segment impossible. This may seem obvious, but mistakes can happen when changeovers are made too quickly. Delays and poor quality caused by misalignment and part damage can cost hours of lost time and thousands of dollars.
how to Align Segments
Segments may be aligned most conveniently in the ejection and closing stations. However, the cleaning station also can be used for alignment because the top cam on older machines or the segment cam on newer machines operates in a constant radius in the area from the closing station through the end of the separation station. The segment should remain aligned through all stations. If the segment does not remain aligned through all stations, a bent shaft or mispositioned top cam could allow the segment to operate in less than a perfect arc.
1. Remove Ejection Chute
The ejection chute must be removed to use that station for alignment, and the ejection pins must have descended. The same condition must exist if the closing station is used. Segments are seldom aligned on the separation station, even though it is theoretically possible, because of the interference caused by the magazine cages, sorting blocks, etc.
2. Position Upper Segment on Mounting Surface
At this point, the upper segment is put into position on the mounting surface of the segment carrier. Many upper segments are slotted, so they are simply slid underneath the head of the fastening screws. The screws that will serve to hold the upper segment in place are then loosely tightened but left loose enough that the segment tang is still allowed to slide under the heads. Precautions should be taken with the upper segment to ensure the mating surfaces of the upper segment are flat and clean. Two alignment pins are placed in holes on either end of the segments. These alignment pins go through the upper segment and into the lower segment. It is typical that the pins are wiggled and the screws are gradually snugged down so that when the segments are tightened, the alignment pins will simply drop into any of the holes in the segment and fall until the pin contacts the cap passage surface in the upper segment.
Generally, you should hear and feel a satisfying “clunk” when the pin falls into the hole. All holes in the segment are theoretically aligned at this point, and a pin can be dropped into any hole and it should fall freely. After aligning the segments, allow the machine to rotate several revolutions so that the segments may be checked again in their relaxed operating state.
Troubleshooting capsule Alignment Problems
- Segment carriers and associated shafts that are in poor condition or misaligned on the machine will result in poor or inconsistent alignment. On older machines the top cam is exposed, and on new machines the cam is covered. However, on either type, the segment carriers, bearings, shafts, etc., must be in good condition. On all types of machines, the shafts and linear bearings must also be in good condition. If the shafts are scored or the linear bearings are frozen or dirty, the segments will perform poorly. Furthermore, the follower bearings and top cam also must be in good working condition.
- Other problems can exist where the segments are “forced” into alignment. Some other after-market tooling suppliers have sold alignment pins that expand in the holes. They imagine that these expanding pins would result in more precise alignment. In truth, when placed into the holes and expanded, they can simply force the segments into “alignment,” allowing them to spring back into misalignment when the pins are released. If you perform an alignment that does not allow the capsule segment to freely align in its relaxed position, the same result will occur. For proper alignment, the segment must be tightened, and the pins must then fall freely.
- Worn segment bores or segments that have been altered by operators will cause an impossible alignment condition. Performance is seldom improved with a reamer or drill. Alignment pins with burrs also may be a problem.
- Because the smallest holes in the segments are at least 0.001” larger than the alignment pins that go through the holes, and because the bore in the lower segment is always slightly larger than the bore in the upper segment, as much as 0.003” misalignment may be present even when the pins drop accurately and smoothly, especially in worn segments. It is also possible that the plane of the upper segment does not match the plane of the lower segment due to segment carrier misalignment or worn parts. Testing for this condition is occasionally necessary.
solutions for capsule segment Alignment Problems
In response to the aforementioned problems, Carlisle Precision Encapsulation Parts now provides Special Alignment Holes on all segments. This can help solve alignment issues, especially when the segments are a bit worn, and when granular material (which has the tendency to cause splits) is to be used. The addition of special alignment holes in segments and the use of special alignment pins will expose a planar or capsule-hole misalignment and enable slightly worn segments to operate more effectively.
The use of these precision special alignment pins changes the alignment operation from a non-qualifiable process into an operation that is now manageable. Pharmaceutical capsule producers who want to qualify all of their processes will be interested in this new precision method of capsule segment alignment.