Geeetech

hi ive been assembling a rostock 301 printer
all seemed to go to plan
but when we tried a dry print (no filament)
the head started moving but then started hitting the bed
so we set the z axis to 170 about 50mm from the bed so we could watch what was happening and the print seems to be printing
in a downwards direction
we updated the firmware to v1.0.04 and ist still the same
we have noticed that when you auto home on the printer the z axis reads 170 (as set)
but when using easy print manual mode it reads x0 y0 z0
in both cases the control arms are at the top switching the endstop switches
any ideas
cheers

Maybe you can refer to it at first:
Guide of the level(301)
1. You need to adjust the endstop leader screw
Until all touch screws of the axis at the same level
2. You need to tighten the heat bed adjustment screws to the maximum limit
3. You need to move the nozzle at the lowest point(Z:0) via the LCD control
Then you need to 1) change the range of the Z axis to the correct value
2) change the z offset to the correct value
4. You need to change the radius value
LCD>print setting
On my printer, the value of it is "88.6".(Default of it is 93 or other values...LOL)
How to do it？Refer to what?
1)If the point"0,0,0" lower than other 4 points, you need to up the radius
2)If the point"0,0,0" higher than other 4 points, you need to down the radius
5. When you finished it you will get the result: Level the Rostock 301 done
6. Then you need to check the verf of the A4988
The default of it is 0.5V? Not sure. But you need to up it to 0.8~1.1V
The A4988 for the extruder: The recommend of verf is 1~1.1V
Guide of the print
1.I prefer to use the Cura slicing than slic3r
2.All prints between 15mm~20mm/s(Don't up it than 30mm/s.Why? The
extruder may lose the step )
Moving:30mm/s~40mm/s
Retract speed:25mm/s(Don't up than 40mm/s)
Retract distance:3mm
I prefer to change the opp to: max:"99%" and min"1%"
If you try to change it to "100%" and "0%",the nozzle may easy be clogged
Here are all experience of mine rostock301

thanks for info william
i think i didnt make it very clear
we have got the bed level with a z reading of 223.05 this reading is on the printer lcd and the print head is a4 thickness off the bed
but after the printer started a dry print it seamed to do the first layer ok second layer was abit messy
the 3rd layer the head was touching the bed
so we switched the printer off
we then adjusted the z value to 170 so it would start dry printing well away from the bed
after about 20 mins of dry printing the print head had dropped towards the bed about 25mm
were not sure if it is the gcode which is wrong or the printer settings
ie does the printer start printing a x? y? z0.03 ish then going up in value toward the upper value of 223.05 or does it start at z223.05 then drop in value by .03 ish per layer towards the lower value z0
we have changed the radius from 90 t0 88 this was in the control/delta section on printer
there are 2 radius setting
delta radius 89(factory)
and print radius was 90 but now 88
any other suggestions
cheers roy/kev

The default Z height should be 215~225mm.
If you can get this value,
try to refer to these:
1.The delta radius;(You say you change the default values to 88,it should be correct)
2.The stepper mm of X/Y/Z(Try to calibrate it at first)

Maybe you can attach the gcode then we will help to check it.
If you can attach a video link will be better(We can compare them)

The problem of the head going down is probably too little current for the stepper motors.
There are six controllers - take the voltage from the potentiometer cross in the controller to ground, while everything is connected and switched on. It should be at least 0,6V, I'd suggest a little more.
Then try to print at 25% and this issue was resolved for me.