Hi LarsK,
Your question is pertinent: If system parameters are within reason, missing steps is an unlike event. However, things are at times slightly off and trouble may happen: a small plastic blob that may block the nozzle for a moment triggering a bad print, a hotend that presents momentarily a bit more backpressure and thus fewer plastic is deposited leading to de-lamination of the part later, dirt on the rods that requires now more torque from the motors that when the system was built, etc
The reason 2d printers switch from steppers to DC motors is two-fold: lower cost of the motor and lower power consumption (which in turn will reduce the cost of the power supply). But beyond cost issues, using a closed-loop system provided them higher resolution and better linearity. Both features could be welcome in a RepRap near us too.
Minute printers like M3D are already using DC motors in closed loop. [printm3d.com]
There are some advantages of servos that we might brougt in later (but are not now the driving factor) like end-stop emulation (you could have max and min endstop for free from the motor controller when it detects it bumped into each side ie. overcurrent), lower current consumption, quieter operation or smoother motion that might make possible better quality prints (I am speculating here).
But the main point of discussing the matter openly is to test the ideas and to enrich our knowledge with other people's ideas. So once again, thanks for chiming in.
Quote
LarsK
Misan, I do not understand why missed steps is a concern. I don't say this out of arrogance but I am fairly late to the 3d printing world - SO what I would say is that, if your 3d printer is missing steps, it is because it is not designed properly or is in need of maintenance. The only time I see my printers (Delta and a CoreXY) missing steps is when something is terribly off - Such as wrong heights so it is hitting the sides. Am I misleading my self here?
Your question is pertinent: If system parameters are within reason, missing steps is an unlike event. However, things are at times slightly off and trouble may happen: a small plastic blob that may block the nozzle for a moment triggering a bad print, a hotend that presents momentarily a bit more backpressure and thus fewer plastic is deposited leading to de-lamination of the part later, dirt on the rods that requires now more torque from the motors that when the system was built, etc
The reason 2d printers switch from steppers to DC motors is two-fold: lower cost of the motor and lower power consumption (which in turn will reduce the cost of the power supply). But beyond cost issues, using a closed-loop system provided them higher resolution and better linearity. Both features could be welcome in a RepRap near us too.
Minute printers like M3D are already using DC motors in closed loop. [printm3d.com]
There are some advantages of servos that we might brougt in later (but are not now the driving factor) like end-stop emulation (you could have max and min endstop for free from the motor controller when it detects it bumped into each side ie. overcurrent), lower current consumption, quieter operation or smoother motion that might make possible better quality prints (I am speculating here).
But the main point of discussing the matter openly is to test the ideas and to enrich our knowledge with other people's ideas. So once again, thanks for chiming in.