Pause on Z movement

For some reason, my printer has started randomly pausing when a Z movement takes place. Initially, it started doing this when the fan came on and now it does it on Z movement (but not every single Z movement, just every 5-6 say).

I'm running ramps 1.4 on a Cartesian machine, and the pauses can be from 5-20 seconds long causing a big blob to be made, and the next few cm's to not extrude. Turning off force retraction on Z movement has helped somewhat... it pauses less now.

I have a feeling that ramps is going to die soon, or something will.... I have a Duet WiFi to replace it with, but printing backlog for clients means I haven't wanted to troubleshoot a new board just yet! Although, I might have to.....

I'm not looking for a solution as such, more a reason why! (I wouldn't say no to a quick solution though.....) I already have a nice solution with the duet WiFi, which I'm sure will also fix a suite of problems at the same time.

it's not your layer time is it, for small objects?

I thought this after I posted, embarrassingly... but no it's not. I'm printing a cookie cutter at the moment (batch of 20, so plenty of chance to experiment on each piece). The issue does not happen on each layer, which it should on such repeatable layers. Weirdly, it doers not happen at set intervals, but these intervals do seem to occur at the same rate.

Lining up the blobs on prints, once it has started it will repeat itself after 5 layers, and then again after about 8 layers. But it does not always start on the same layer in the print. I have now also noticed it pausing not on Z retracts, but also on infill but these are fewer and for less time. The majority are still occurring at the Z change spot.

The issue has me stumped... I have not done any drastic changes to the machine, in fact it has been running reliably for months which has been a great victory and why I haven't switched in the new board yet! However, with a few deadlines on the horizon I might have to take the plunge and fit the new board and hope it doesn't bring any major problems with it (it will....)

Edited 1 time(s). Last edit at 10/09/2016 12:38PM by Origamib.

Are you printing from usb or sd?

It could be the gcode has a high number of segments to queue during the pauses.

Watch this space, but I believe the USB might be the issue. I've always printed off USB since removing the screen off my printer. I never liked using it, and the lack of control and awkward menus weren't my thing. That, and after hearing about it taking up too much processing power on the arduino it was the logical decision to ditch it.

I believe, the change is either caused by weird segments (after analysing the model, it seems to not like a strange repeated retraction whilst lifting Z) AND windows 10 recently did a big upgrade. I've printed this model several times before without the weird pausing, but perhaps the new windows upgrade and the number of segments is causing the pause. Today I slotted in an extra 8gb of RAM into the laptop, and the first print off USB with it has no pausing.

I might try ditching my screen too(or move it to other machine)...it seems to be there just for show these days now i'm printing direct from win8(had to DL a tool to kill the upgrade), would make things much tidier dont like the short ribbon cables are a PIA.