Is it a new or used unit? There are several adjustments you can make to true the cut it makes. To set it so the blade is running perpendicular to the piece, I put the blade down all the way and lay a square against it, and set the clamp piece exactly 90 degrees to that.
But you are saying yours is cutting more off the top than the bottom, so it looks like the blade is twisted from being exactly straight up and down. There are also some adjustments to tilt the cutting head to make it straight. I have never had to so that on ours, so not sure what it entails.
There are also guide rollers that are adjustable and they take the blade, which is coming out of the pulleys crooked, and they twist it straight. I think that might be your problem, they may not be adjusted right. There should be two sets of these ball bearing guides that spin when the blade is moving. They should be right up against the blade, squeezing it and forcing it to run horizontally between the two sets. Mine has a nut and screw driver slot arrangement so you can loosen them and turn the screw until it moves over and touches the blade. These guides wear out and crack from metal shavings hitting them, so I keep some spares on hand.
Another thought is that you have too much space between the two roller assemblies. You should have as little room as needed to just clear the piece you are cutting. For example, if you are cutting something 1 x 1 you can slide them almost together so there is almost no room between them. But if you are cutting something 2 x 2 you have to move them further apart. These are usually held by knobs that you hand loosen and tighten.
Post me some pictures especially of the area of the blade where it contacts the piece being cut. In the meantime, look at the blade in that area to see if the contact guide rollers are doing their job and are twisting the blade straight right there.
Don
