Used Gravimetric Blenders for Sale

A gravimetric blender weighs each ingredient into a batch, mixes that batch and drops it toward the screw. Load cells, not auger turns, are the control. A weigh blender and a batch blender are the same machine. A color feeder is not. A feeder meters volume and never sees grams. Separate bins hold virgin, regrind, color and additive. Gates or small augers dose into a weigh pan until each target is met, then a mixer homogenizes the batch before the throat. On a common weigh-scale sequence, regrind goes in first, virgin next, and color or additive last, figured from the virgin that actually landed. A slow gate on the resin then does not throw the color percent off by itself.

Batch weight is the first size, because throughput is batches per hour times that weight. The mixer has to finish before the press or the extruder runs the throat empty. A small batch suits a slow press and a tight color. A larger batch suits a faster rate and is less bothered by one slow valve. Four stations is the usual count: virgin, regrind, color and one additive. Empty stations you cannot pipe do not count. Scale resolution is what lets a small color target exist beside a large virgin weigh-in. A coarse cell will not hold a light letdown. Sticky regrind bridges in the bin, and the pan never sees it. The frame has to sit level. Vibration from the press has to be isolated or the cell hunts. A move can shift the zero. Recalibrate on an empty pan before you trust a recipe that arrived with the machine. That habit is what keeps a gravimetric blender honest after a truck ride.

The unit mounts on the feed throat or on a stand beside an extruder. A color feeder is enough when you only need one volumetric dose. Dryers and hoppers sit upstream. This machine does not dry resin and it does not convey it. A vacuum loader refills the bins. Keep the discharge adapter tight. A leak there loses the batch you just weighed, and the screw sees whatever ratio happens to fall through.

Lots beside the press are where one of these usually arrives, still wearing the hoppers from the last recipe. On a used gravimetric blender, hang a test weight and see whether the reading repeats, then cycle every valve and run the mixer. A painted frame with a dead station is a smaller blender than the hopper count suggests. Ask whether you can read and clear the last recipes. Level the frame before the first batch, or the cell will alarm until the scale is quiet.