I have been teaching myself 3d printer calibration for 8 months and until recently, all of my experience has been on Cartesian FFF printers. Cartesian printers have a single motor responsible for all of the x axis movement. A single motor responsible for all of the y axis movement and a single or sometimes couple of motors responsible for the z axis movement.
In contrast, Delta printers have 3 towers with motors that impact the X, Y and Z coordinates of the print head. My membership at Nordeast Makers gave me access to a Rostock Max and I have not regretted the $200 I spent on a one month membership at Nordeast Makers.
For the most part, The extra complicated math of delta printers is handled by firmware and slicing software. However, if you are the person first setting up a delta printer or recalibrating it, you will have to calibrate the EPROMs to make the print head move level across the print bed.
Today I ran into a problem with one of the towers on the Rostock hitting a boundary and skipping a couple steps on the rubber belt that the C motor is attached to.
After it skipped the steps, the print head was elevated when it came near the C tower. The printer tried to print outside of the its maximum dimensions and thus skipped some steps. Most consumer 3d printers lack encoders or some other method of tracking where their motors are actually located after they leave a “home position”. Any time that a motor tries to move and it cannot, the motor gear skips on the rubber belt and the position of your print head shifts from where the software expects it to be. On my Cartesian printers a little bit of skipping, especially on the skirt (an outer boundary of the print) does not result in a failed print. On a delta printer, having just one motor skip a couple steps moves the print head’s location in all 3 axises and that z axis shift is going to result in a failed print every time.
The problem was easy enough to solve by just scaling down the print to 95%, repositioning the digital model and making new Gcode. Now the printer never tries to print outside of the boundaries that are possible. Thus it never skips a step on the C belt and the print head stays in the position.
But there still was a little bit of unevenness to the print heads location near the print bed. In the photo below you can see some gaps in the first layer when the print head is near the C tower. These gaps are a result of the print head being ~.05mm millimeters higher off the print bed and the filament not being squished as flat.
Tangent: when I had only read about Delta printers I read that the delta design allowed for faster movement of the print head. Nordeast Makers has a Cartesian Creator Pro that is easily 1.5 times faster than the Rostock Max. So my limited experience does not support the idea that delta printers are faster than cartesian printers. However my limited experience might not be representative of the potential maximum speed of the printers because I am printing at movement speeds that Micah Roth determined were the best balance of speed and quality. Just because you can drive your car at 120 mph doesn’t mean that you will like the result if you do. Similarly, reducing your print speed can be a very helpful way to increase the quality of your print.