What's causing these lines?

[Penrhos1920]

I've just started using a Mars 4 9k.  What's causing these lines across the back of the bunker and cab front and back?  There are no lines on surfaces in any other orientation.

 

 

I'm using Anycubic ABS-like water washable v2., exposure was 2.1s. I've twisted it by 20 deg from vertical on both axis ( 0.05mm layers, 0.018mm pixels).  Now I've printed some railchairs from Templot and the XP2 matrix I've decided 2.1s is too much, but haven't decided what it should be.

[stevel]

It could be stiction on the vertical drive causing jerky movements. I would suggest lubricating the Z axis threaded rod with lithium grease, and then run the build plate up and down to make sure it gets spread out.

 

Stephen 

[Penrhos1920]

@stevel I hope not it’s a brand new machine 

[stevel]

3 hours ago, Penrhos1920 said:

@stevel I hope not it’s a brand new machine 

I had issues with a new Anycubic, the grease had not been distributed completely, so spreading it all along the thread cured it for a while. now I grease regularly.

[Harlequin]

Have you got any hollow shapes in the print that would hold resin at the print orientation? If the depth of resin in your vat is greater than the platform rise such hollows may not drain out and so cause increasing levels of suction.

 

To counter this possibility you could try putting some holes in the print in places that won't show, such as the coal load support platform.

 

[billbedford]

Have a look at this video:

 

https://www.youtube.com/watch?v=Qs2Rb0ExnIM&t=681s