I'm tuning in my Eustathios Spider 2 and the Z is complicated because there

I’m tuning in my Eustathios Spider 2 and the Z is complicated because there are 2 different gears 32T on the screw pulley and 20T on the motor pulley. The ball screw is 1204, so 4mm pitch (I see Eric uses a 2mm pitch lead screw). Looking at Eric’s config file my values are somehow double in Marlin. He has 160,160,2560 but mine are closer to half that: 80,80,(1280?) - on a 3D benchy test print I find that 1280 is about 1.2x too small. I reached 1280 by:
200steps * 16microstep / 4mm pitch = 800 * 32/20= 1280 steps/mm
but 1.2x = 1536steps/mm
does anybody know the formula there?

The calculations seem fine to me, are you sure you received a 20 tooth pulley and not a 16 tooth version? If you’re using a 16 tooth pulley (or a 40 tooth pulley on the ballscrew, but I don’t think that would fit), it should be 1600 steps per mm on z.

I got these: http://www.robotdigg.com/product/29 1.8degrees so definitely 200 steps (with 16 microsteps set on my ramps 1.4 board). I am realizing now that perhaps Eric is using 0.9 degree (400 steps) motors- but all Robotdigg has in 60mm size is that one I bought, which is 1.8degrees.

I’m fairly sure they are 20 tooth pulleys- how are you calculating 1600 steps/mm on the z? I calculated 1280, but in practice I have tuned it to around 1462-1494 steps/mm on the z.

1600 is only if you’re using a 16 tooth pulley, same as your math above, 800 * 32/16 = 1600. I think I’m running at 3200 z-steps/mm (16/32 pulleys on z, 400 step motor, and 4mm pitch ballscrew).

maybe there is someway to check on the LCD in Marlin- I just started using the LCD interface.

oh ok- so the equation I am using is correct. I have no idea, but for whatever reason 1494 seems to be pretty accurate. Thanks everyone for your help.

I don’t know if @Eclsnowman runs ball screws or TR12x2 Misumi Leadscrews; if it’s the latter, that may explain why his numbers are about double yours

Thanks Ishaan- the last time I saw Eric still had lead screws on his Eust Spid 2 but wanted and recommended using ballscrew which I did. That explains why the Z is double but what explains the x and y being double? The BOM doesn’t specify 1.8 or 0.9 degree so I’m not sure what Eric has, but the RobotDigg only sells 1.8 for 60mm size.

Does the system turn smooth? Maybe you are loosing steps. Did you adjust the current of the z stepper? Are the pulleys tightened properly? It could also be slip on the pulleys, as you configured more steps that it should actually be.

@Ted_Huntington , what’s the microstep setting on your drivers?

@Daniel_F I tightened the belt and I think that helped somewhat- and I am noticing something unusual on the Z. There is a “thunk” sound in between layers (when the X and Y are moving but not the Z). I changed the step stick and still the thunk is there, regularly for every layer. The firmware (Marlin 1.1.0-RC2) is pulsing the z motor- but I have seen this when the step stick is damaged, and when the speed was set too high. I have another RAMPS board I may try- just to eliminate if it is the PCB- but I think it must be firmware.

they are all set for 16 microsteps (all 4 jumpers in place on the RAMPS).

ok wow I totally solved it, whew! When I upgraded from Marlin-1.1.0-RC2 to RC3 I found what was wrong. In Marlin, never set
#define DISABLE_Z false
to true- in particular on a Eustathios, because it will temporarily unlock the Z stepper motor and the stepper motor falls back a little. I had set this to true on a different printer because sometimes it is nice to slightly adjust the Z on the first layer- but it totally caused havoc - so I will never do that again. I guess on a RepRap Mendel it doesn’t matter as much because there is maybe less weight on the Z motor?

After I set that back to false I find that 1280 works fine- thanks everybody for all your help.