Originally Posted by rutexus Peter, I believe the issue with rounding corners has nothing to do with the rutex drives. It is related to the mach2/3 software. All servos have a very slight lag, but I don't believe this is the issue either. Mach2, like most other programs sometimes have minute delays between moves, or at least some change in velocity. When the control software tries to blend the moves in continuous contouring, it tends to smooth out the transistion between moves. In order to change directions, velocity changes sometimes require the move to have ramping up or down. This is particularly important in controls designed to control stepper motors. If you change velocity with a stepper motor too quickly, it will lose steps and thus position. The inherent (but slight) delay can also "integrate" these moves.
I expect that Art (author of Mach2) will impliment the spi functions which will allow buffering of the moves. This may help with this problem, but we will have to see when we get them. |
Mach2/3 doesn't pause, or have a delay between moves. Say for example you're making a 90° corner. Only one axis is moving. When you get to the corner, that axis has to decelerate. The other one can't start to accelerate until the other one is at 0 velocity. This may appear to be a pause. This can be undesoreable for many reasons. For plasma, it can cause a hole. Routers can leave burn marks. Perhaps the biggest problem is that it can take a long time running complex 3d programs. Mach3 has what's called constant velocity mode. What it does, in the previous example, is start to accelerate the second axis as the first one begins to decelerate. This causes a rounded corner. The faster your acceleration, the less rounding will occur. Unfortunately, motors can't start and stop instantly, so some rounding will occur. Mach3 does have an angle setting, so sharp corners will not be rounded and larger angles will be. There is also a plasma mode which helps to minimize the rounding for plasma users.