Rotoboss Roller Rotary Belt Tension Adjustment for Start of Engraving Issue

Preface: If you notice that your rotary is not engraving correctly at the start, the designs are "flat spotting" on the edges, then this article is for you. This information is applicable to any of the belt driven Rotoboss Rotaries. The components may be in different locations and layouts, but the principle is the same.

Quickstart Video

Symptoms

If you develop "flat spotting" at the beginning of your tumbler engrave where the design is scrunched up at the start but ok for the rest of the engrave like shown below.

Flat Spotting At the Start of Circle	Flat Spotting at the start of a C
You can see multiple attempts at engraving a circle.

Cause and What to Look For

The cause of "flat spotting" is likely due to the rotary drive belt being loose and having slack. What happens is, as the rotary makes a direction change, the belt slack then has to be removed from the belt which causes a slight delay in the roller wheels rotating, so the tumbler just sits on the rollers not moving even though the motor for the rotary is turning and the laser head is engraving.

Lets take a look at the Rotary Driveline

Locate the belt side of your rotary, often it is the "left" side where the motor and cup clamp is for the rotary.

Component Identification

Loose Belt Example

Loose Belt Example 1	Loose Belt Example 2

The Fix

The tensioner will need to be adjusted so that the belt is snug but not overly tight.

Tensioner Adjustment

The tensioner requires a 3mm Allen wrench. Turn the bolt to the left for more tension, to the right for less tension.

Belt Before and After

It does not take much adjustment to get the tension right.

Loose Belt	Snug Belt
	Take note of the gap between the tensioner arm and the tensioner head compared to the one on the loose belt picture.