Makerfarm iv3 z-axis lift speed

[printbus]

Some of your questions are exactly what drove me to start Marlin Motion Related Configuration.h Settings for MakerFarm i3v. If nothing else, post Testing Z axis travel with gcode might at least be helpful - it includes some gcode snippets that you can use to test Z-axis settings with.

In a nutshell, I found the most significant improvement in z-axis movements were obtained by increasing the Z-axis acceleration from the MakerFarm default of 5 mm/sec per second to 500 mm/sec per second, and increasing the allowable jerk in Z axis to 10 mm/sec. I did find I could increase the z axis feedrate some, but not a lot. I found that the increases I could obtain by raising the z axis feedrate and reducing microstepping were somewhat marginal compared to the acceleration and jerk adjustments. Think about it - the default z-axis feed rate is 2mm/sec, but an acceleration term of 5 mm/sec per second says "take a long time to get to that 2 mm/sec feedrate". And this is only half of it! The acceleration rate is applied for deceleration as well. M5 rods rotate just a quarter turn to get you a 0.2mm layer shift. It'll spend nearly all, if not all, of that quarter turn accelerating and decelerating with the default settings. You've got to increase that acceleration setting to maximize the benefit from anything else you're trying.

The big z-axis difference between the OEM i3v and AdamFilip's printer is in the threaded rods. Makerfarm uses M5 threaded rods, with a pitch of 0.8mm per thread rotation. Adam is using ACME rods - probably 4-start ones with a lead of 8mm. This means that for a single rotation, he'll get 8mm of linear movement comparted to the 0.8mm in a standard i3v. Yes, in theory that means he'll be able to drive the z-axis pretty fast. ACME rods aren't a panacea though - they bring new issues like backlash and torque concerns that need to be considered.

I also found that my limitation in the i3v was in lifting the x-carriage. I could move the x-carriage down considerably faster than I could move it up, easily explained by the weight of the x-carriage and M5 thread resistance being tough for the NEMA17s to deal with. I was tempted to experiment with, but never did, a counterweight system with a simple wheel at the top of each side of the printer. The concept was that if I could take some of the x-carriage weight off the Z-axis rods, I could likely be able to drive the z-axis upwards 2 or 3 times faster that what I was achieving. EDIT: I guess I never got around to that because after seeing how much faster the z-axis layer shift moves were with just the setting adjustments, I saw little point to it.