Shot blasting machine is most common equipment for most metal working industries. That is used for cleaning, strengthening (peening), polishing or roughening. That make it much simple and effective with better consistency compared with manual operation. Painting or coating will be usually following process.

Basic working principle of shot blasting process is simple.

An impeller is equipped in blasting wheel, the heart of shot blasting system. That pumps the metal abrasive – say, steel shot, steel grit or cut wire shot onto the blades through the control cage. Control cage is located in the center of a rotating wheel. Then abrasive is thrown toward the workpiece by  the blades. Finally the blast pattern (also called hot spot) is produced on the workpiece.

That is ideal that all workpieces are processed properly, if all machine adjustments are managed correctly for job at hand.

If not, the machine will be out of control. The abrasive may be thrown toward the roof, floor or anywhere of the blast chamber. Blasting wheel housing or guard plate of blast chamber may be destroyed quickly.

So how to get a proper hot spot is critically important.

This is a simple question, but no simple answer.

One or several blasting wheels are equipped in shot blasting system. Right quantity, position, point and wheel model will ensure metal abrasive stream can cover all workpiece surfaces. But that is not controlled by user or buyer. A shot blasting machine manufacture usually will confirm detailed workpiece information, processing effect requirement and processing productivity with user or buyer. That will guarantee shot blasting machine is designed and purchased for specific workpiece, workpiece family or majority of workpieces.

This picture shows different hot spot with blast wheel point.

So that is quite necessary to have deep and full communication between shot blasting machine supplier and user or buyer, so that right shot blasting machine is received finally.

Only right machine is still not totally enough. There are still some variables to control or adjust by operator.

Firstly operator should place or hang workpiece on reasonable position (usually chamber centre) in blasting chamber. Reasonable position means the area that blast wheel is easy to aim at.

Of course that area is not fixed. We can still change its size and position by adjusting blast wheel.

The opening position of the control cage determines where the abrasive stream will leave blast wheel from. The opening size of the control cage determines the pattern length.

This picture shows how opening size of the control cage will affect the hot spot.

This picture shows the relation between opening position of the control cage and hot spot.

A classic mistake is often made by inexperienced operator. That control cage opening is set toward workpiece directly. That is easy to guess what will happen, metal abrasive is thrown everywhere except workpiece.

In this article, we are trying to explain what factors determine blast pattern (size and position) in shot blasting system. Obviously right machine does not means right pattern. Right adjustment is also same important.

But right blast pattern is totally enough ? Right blast pattern means right result ?

The answer is No. That is just first step.

In following update, more will be shared to help readers to take full advantage of their shot blasting machines.

Please stay focused on our blog.

Thank you.