Vacuum Cups

There are various reasons for choosing a particular vacuum cup material. The first choice is normally the hardness. This will determine the ability of a vacuum cup to seal against the surface of the product being handled. The most commonly used hardness measurement scale is Shore Hardness, often referred to as Durometer. In fact, a durometer is the actual instrument used to measure hardness but is often referred to as the measuring unit throughout industry.

There are different hardness scales based on the materials being measured, such as plastics or rubbers or metals. The scale used to identify the hardness of vacuum cup materials is Durometer Scale A, which ranges from 100 (hard) to 5 (soft). Vacuum cups are typically available in compounds with a hardness between 35 to 70 Durometer.

Another, sometimes very important characteristic of a vacuum cup material, is the temperature resistance. Most pick-and-place applications occur at “room temperature”, but in the plastic injection industry for example, part temperature is often considered in vacuum cup choice due to the high temperature of parts being removed from the mold tool. At the other end of the scale is the handling of cold products, such as refrigerated or frozen food packaging. Typical vacuum cup materials have a temperature range from -40ºC to 204ºC (-40ºF to +400ºF). NBR (Vacuforce code suffix N) is the most common material and is the same as Nitrile rubber and Buna-N.
 
NBR is used in general industrial applications and is found in steel handling, plastics handling, and any other application where the cup should be resistant to oils and related chemicals. In most applications, this is the “go-to” material choice based on its fair cost and good wear resistance. The hardness of this compound is typically 60 durometer, although this can be as low as 40 or as high as 70. NBR is often overlooked for hightemperature applications such as injection molding as the user specifies a very high temperature and therefore opts for silicone. NBR is suitable for most plastic injection parts handling as its temperature rating is often in excess of 90ºC/200ºF.

SILICONE (Vacuforce code suffix S & ST) is a very popular cup compound found in many applications. Silicone offers the advantage of having extreme temperature resistance both cold and hot, ideal for handling frozen packaged food and hot plastic-injected molded parts with a temperature range from -40ºC (-40ºF) to 204ºC (400ºF). Silicone is softer than NBR, having a typical Durometer rating of 40, allowing it to seal against contouredor rough surfaces, such as cardboard sheet, corrugated plastic, and plastic food packaging. Vacuforce silicone is offered as standard with FDA (title 21) compliance to allow direct contact with food and drug products. Vacuforce Code S - Red Silicone, Vacuforce Code ST - White Translucent.

METAL IMPREGNATED SILICONE  (Vacuforce code SMI & STMI) has the same basic characteristics as the standard silicone described above, but the metal impregnated compound has been design specifically for the food industry. Iron filings inside the actual silicone compound allow metal detectors to sense that a vacuum cup has fallen into the food packaging that contains food stuffs like bread loaves, rolls, and buns or confectioneryfoodstuffs. Vacuforce Code SMI - Red Silicone, Code STMI - White Translucent. An important note about silicone that must be understood by the vacuum cup user. Silicone should never be used on surfaces which are to be painted, such as automotive body panels, as the paint will not bond properly on the area touched by the silicone compound cup. Also, it should not be used to handle decorative stone such as marble or quartz, or glass products as it will permanently etch the surface.