Prints have ribs

My present camera dosent do macro, so I will describe it. My prints have ribs on the sides, or bumps, vertical like. I printed a gear and a box, both have the ribs like every 1/8 inch or less on all sides. When I print the gear the teeth are great but the base (Plain round part) has ribs on it. I dropped the print speed in half and no change. Please help me and thanks in advance if you can.
Dave

Oh,
I'm using the damn awesome Cura slicer!

First I would check if it is the printer or the the slicer, so give a different slicer a try first.
A very uneven outside (if the temp is correct) can be caused by too much extrusion, too thick perimeters and an infill that is already pushing.
If x and y lines are good but everything that is at an angle to them looks bad it could be loose belts that have too much play.

Thanks,
I will try changing the belt tension, but cant see that being the problem because the waves are on all sides. I dont remember having this
problem with Slic3r, but I need infills to work right, thats why I use Cura, perhaps I should try their forum.

It looks like z ribbing to me, have you ever tried using the prusa calculator?

z ribbing, not same as z wobble, often caused by using non-optimal z layer with your current z axis lead screw.

For example an m8 lead screw would take 2560 steps (I forgot) per mm and the optimum layer is an increment of 25-50 microns, for example a 50 micron increment would roughly go by about 80 steps (please don't flame me on this, just a quick explanation).

In overall, you have to know what lead screw or threaded rod you are using, different ones has different optimal layer for optimum steps. imperial (I think) usually 0.9 , 0.14mm and so on, still depending on the lead screws though

Thanks for the reply, but dont get it, Z wobble? Why would Z wobble affect my print in an x,y direction? I'm lost? My prints, print a line first on the outside before printing the main print and I noticed they are in a wiggleing pattern, kind of wonder if its a power supply problem, ie. ripple. I appreciate any help, but right now I'm lost in confusion. My printer right now is printing perfect prints except for the ribs, a major let down.

All kinds of things interact when printing.

For example, it's possible that your slicer reverses direction every second layer, In that case, any play in the X or Y axes can cause this. If you use auto-levelling, and your slicer reverses direction, then play in the Z axis can cause this.

Without photos and more details, it's really hard to answer.

This is a photo, I don't think this is z-wobble or ribbing, its in the wrong direction. Also all 4 sides are the same. This is a RepRap Mendel.

Looks like the wobble of one of the axes when cornering. When the x motion stops and the y motion starts, there's a point at which the carriage stands 'still', or rather transitions from one direction to the next. The deceleration degree determines if this is with a snap, or with a softer ease-out/ease-in motion.
When it snaps into the other direction, any springyness in your carriage will vibrate until it is dampened. Usually this only happens for about 5mm or so, at higher speeds with an i3 for example.

This can be caused by play in the x/y carriage, belts not tight enough, build plate not fixed well enough to the y carriage/heated bed. It can also caused by the extruder if it's arm is too long from the x-carriage. The L shape that the hotend makes from the x-carriage may not be stiff enough to stop the vibration in sudden speed changes.

The more mass the axis has the more it wobbles when cornering. Unless your axes are built like a tank you should probably check if you can fix anything that has some play or springyness. Grab a belt and wiggle one of the carriages and see if there's any play in them. If it is, try tightening things up. You can also reduce the weight of the carriage by choosing a different material, use less/thinner material and/or use a bowden setup to move the extruder motor off the x carriage.

On the other end of the scale, it can also be that the acceleration and/or xy jerk settings are too high.

possible uneven bed, if you don't have a guarantee flat glass, I had a print like that, and the bed wasn't properly level, not that I can level it anyway, y carriage have weak and bend arms in diagonal

if it is in the case of the y carriage causing the problem, you may or may not see it straight away, since the bed can be higher in the middle, or wherever it wishes, but corners are level.

Edited 1 time(s). Last edit at 08/10/2015 07:18PM by deaconfrost.

Thanks everyone for your input, I guess I just have to keep playing with things. Both Cura and slic3r print the same way.

Are your belts nice and tight? With loose belts that vibrate/ bad vibrations there are horizontal lines like that, albeit much much less distinct.

Correct me if I'm wrong, but I think old versions of Marlin had a default acceleration setting of around 9800, which is probably way too high for an ordinary printer. Try using the acceleration feature in Slic3r to limit the acceleration to something a lot lower, like 1000.

It looks similar to the problem I have.
In my case it has to do with the decay mode of the stepper drivers, which behaves wrongly for very slow moves, causing the microsteps to be unevenly spread between the full-steps.


What stepper drivers and what microstepping do you use?


As a test, try to print the part turned by 45°, so the sides aren't parallel to the motor axes.
If I'm not mistaken, the ribbing schould be much finer.

There is a bug in Cura that causes ribbing on some prints, notably a cone printed in spiral vase mode. I don't know whether it affects normal prints as well. The nature of the bug is that Cura sometimes inserts non-extruding G0 moves of a fraction of a mm between extruding G1 moves when it gets back to the start point of a circle.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].