Automatic rim rolling unit model B1400 is the solution for clients who are looking to improve the product quality of their conical cups or containers (such as tubs). These rimming units are widely used in the production of cups made of PP, PET, PLA or PS.

About rim rolling

Disposable cups most likely require a rolled rim on the upper part of the cup. The rimming process rounds off the edge by folding the lip under the rim. The result is to provide a more comfortable contact when drinking from the cup and at the same time a greater rigidity to the product. Disposable plastic cups are mostly produced on “form-punch” thermoforming machines, simultaneously forming and punching in the same station, such as the FT range. These machines have a tilting lower half-mould which rotates 75 degrees, allowing the automatic extraction of the products from the mould, followed by product stacking and conveying.

Watch Rimming Unit B1400 on FT900

Rimming process and material

When we want to rim a product, it is necessary to form and cut in the same station in order to guarantee a constant perimeter cut tolerance. This is the most valid choice especially for very high capacity productions the INTEC inline range, which includes also the extrusion process. These production lines go from processing the raw material of pellets up to the packing of the finished product. A true production island.
A very common in-line product is the 200cc disposable cup with production levels of 120,000 cups/hour in polypropylene. WM has created a single type of automatic rimming machine covering all types of material such as PP, PET, PLA or PS.

When rimming, the heating occurs along the total length of the three rim-rolling screws creating a closed heating chamber while the cups are passing through the screws. Then, the rimmed cups are automatically transported on a conveyor belt before reaching the downstream units for counting, sleeving and boxing.

When the cups leave the punch and die mould, the upper edge of the cup has been formed into an inverted U-shape. The size and thickness of the edge are critical and must be considered carefully when designing and manufacturing the mould. To maintain all these parameters during the thermoforming process is very important in order to ensure a perfect flange and an adequate uniform aesthetic appearance.

The rim-rolling screws are the heart of the system and the profile of the grooves that constitute the thread of the screw are produced according to the type of edge design, stacking step and material dimensional shrinkage value. There is a very wide range of cups with different diameter openings, approximately from 45 mm to 120 mm.
Just think of the difference between a classic coffee cup and a beer glass.
For this reason, the rim-rolling screws can be easily exchanged according to the design of the cup and adjusted in relation to the cup’s diameter. The retooling of the rimming machine is very simple. In a few steps, the operator will be able to make fast, easy and safe production changes.

WM Thermoforming Machines SA has more than 40 years of experience in designing and manufacturing these kind of auxiliary units, to offer a full thermoforming machinery range, whether they are in-line with extruders or off-line machinery with material fed on a reel.

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