Please help with gaps in print

Hi there All,

First time poster here, however I have been reading lots and lots of post on this (and other forums) I have been assembling and modifying a makerfarm 12" i3v for 2 months now (wow time flies). I still have a problem with gaps in prints and would like some advice on what the issue might be. I am going to get fairly detailed in information, so please forgive the post length.

First of all the picture below is an example of a recent print
Attachment 6861

Some print settings:
1.75mm filament, PLA, 60 heatbed temp, 200 first layer temp, 190 for rest, printed onto buildtac, volcano hot end 0.6 nozzle, stock makerfarm (greg's hinged with herringbone gears) cold end (extruder). Filament is sitting on a spool roller with PTFE tube right to the cold end.

Slicer settings:
Nozzle Diameter 0.6, zoffset -0.2, speed set at 80mm a second. 50% speed for first layer. Layer height is 0.36 and first layer height is 0.36, 1 bottom shell, 1 vertical shell, random seam position, wipe and retract on layer change not set (no retraction for this print - more on that to come)

Other related upgrades/checks:
Have checked belt tensions
Have upgraded to a 6mm aluminium bed and a 3mm aluminium build plate
Have printed a new x-carriage in pla and attached to stiffen old wooden x-carriage
Have reduced stepping on x and y motors
Printed fan shroud and attached 40mm fan to cool print
Have calibrated extruder by running the 100mm check and then reducing by 5% (then add 1%) until extrusion width is 0.60
Have turned down max acceleration, feedrate and jerk settings. Feedrate (250,250,2,15) Max acceleration (500,500,500,500), Jerk (10,10,10,10)
Have turned retraction speed down to 10
Have tried different PLA from another manufacturer (colorfab)
stepper motors have been adjusted to bare minimum voltage (jeez they are buggers to turn a small amount!) and they are running really nice and are quite cool now.
Firmware is latest Repeteir firmware with a Raspberry Pi server with wifi for remote control
Slicer version is latest 1.2.9 stable, have sliced with 0.9.9 version and cura with same results


Other Print settings that have been tried.
I have also experimented with many iterations of print settings from having temps right to 215 and down as low as 170
I have experimented with retraction up to 4mm (shouldn't need to go over 2 with e3d according to their website)
I have experimented with extra feed on restart - I can give it enough to fill the 'holes', however then the print is lumpy from the extra filament
I have experimented with retraction on layer change and wipe while retracting which both also promote the blobbing effect.
I have experimented with avoid crossing perimeters
I have experimented with aligned seam position, however this just moves the holes to one corner.
I have turned the speed right down to 15, and gone as lower as 20% for first layer

As you can see I have performed some modifications and a lot of setting changes and the print quality is getting better as I go, this one problem just won't go away and I really need some assistance to solve this issue. Any assistance would be most appreciated.

Many Thanks
Dale

At least you know the problem is occurring at the layer shift point, since the gaps line up when you turn off the randomize starting position.

On a single wall print like the one shown, a spiral/corkscrew/vase mode approach might be helpful.

One thing you haven't mentioned is applying cooling airflow to the print. Without it, perhaps the large nozzle of the volcano makes it too easy to pull filament off the print when the nozzle moves away. Hardening the extruded filament with some airflow would help minimize that dragging/pulling effect.

Thanks for the reply printbus - Spiral /Vase mode works fine, and I do indeed have a 40mm fan fan with fan shroud cooling the print.

What the aim was by printing out the single wall was to highlight the issue. I haven't tried multiple wall prints for a while as I was trying to get the printer to print near to perfect before moving on. I will print some test prints with 3 walls and get back to you with a picture.

I think the next move will be to switch back to the e3d v6 and give that another go as well.