in the fabrication of a plastic sleeve by heat sealing overlapped ends of a plastic film blank wrapped around a mandrel , a part of the underlying overlapped end is often melted inadvertently and adheres to the mandrel , obstructing easy stripping of the sleeve off the mandrel . accordingly , a tensioning groove is formed in the mandrel surface , and a pressing - in bar is pressed thereinto over the sleeve while a part of the sleeve is held stationary against the mandrel by a holding plate to pull the sleeve part thus adhering sidewise in the peripheral direction of the mandrel and thereby to peel away and free the same .