Blobs when printing cylinders AND strings on one side?

I figured I would combine my two problems in one post.

I am running a RAMPS, Marlin, Slic3r 0.9.1, J-Head 0.35 system.

First, I've been printing some cylinders, such as this standoff on thingiverse. It appears the start of the layer causes a small blob to appear, almost like the nozzle is shifting over momentarily. I'm going to try and capture it on camera.

I dont have this issue in straight walls. You can see in the picture of the printed object matches the pattern in the gcode.

Second issue: As you can see in the other picture of the cylinder, I have stringing on one side. This happens in the Y direction, on the left side (towards home of X). I may have to draw a picture for that to make sense. I first thought it was backlash, but I would expect it to be on both 'sides' of the X axis. This is more pronounced on the cylinders, but does appear on pretty much any object I print...on that 'side' of the printer.

Any help on either problem?

I may try a different slicing program with the cylinders. I've attached my slic3r config as well.

Do you have a fan blowing on the print?
Is it by any chance positioned on the opposite side to the strings?

No, don't have a fan hooked up.

This is PLA printed on heated glass. I was thinking of adding a fan; haven't yet though.

This stringing is consistent on the last 10-15 objects I've printed. Depending on the object, it is more or less. Cylinder is the most.

I've attached a picture of the strings_block_and_cylinder to show a comparison. The objects were printed in that orientation (at different times). Stringing stays on that side.

On my artifact issue, I've noticed it occurs on on all layer starts, it appears. It just wasnt as noticeable as the cylinder. So I'm wondering if I need to slow down (already going slow though). Or mess with the retract/restart. I've attached another picture which shows a good example of the problem I have on the layer starts. It is a small artifact, but still noticeable.

Cant help much, but I'm seing the same issue on my printrbot using Skeinforge 50 :-/

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The strings on one side are either a mechanical issue, or a temperature issue.
If you had a fan blowing on one side I'd suspect that.
Since you don't, my guess is some thing is not tight, backlash would normally present as not round circles, but I could see some thing rubbing on the bet while moving in a particular direction or in a specific part of the bed causing something like that.

B4Me,
I assume you are talking about the artifacts on the layer starts. What sort of retract settings are you using?


Polygonhell,
Thanks for the input. For the strings, I will try a few prints tonight. I think you are right is either mechanical or temperature related.

I realized that the inside walls of the cylinders do not have strings. So to me that rules out mechanical for now. It appears that only 'exposed' surfaces on that side of the printer have the issue. I am now wondering if the fan of the PSU is creating a very small breeze...maybe enough to cause this.

I will also check to see if the belt is wearing or has issues in that region of the printer. I'll try moving the printed object to a different part of the bed as well.

For now I have
retract 2mm
and Restart extra destance = -0.1

that did something to it..

And for your strings... I had the issue this morning... the side facing out to the room is PERFECT, the opposite is stringy and shit...
think its a breeze like your saying.. cause, when I added a fan on each side of the bed, running at 5V it was all gone.. and both sides was perfect
but I still have the "blobs" at each loop start..

Generally you shouldn't specify an extra distance on restart, it pretty much guarantees a problem since you've now guaranteed you don't get the right ammount of filament in the print. What is you threshold distance set to, it should be at least 2 filament widths IMO.
You will get some sort of small defect where a layer starts, usually either a small bump or void, because the pressure in the hot end doesn't change instantaneously went the filament flow restarts. Slic3r draws perimeters inside to out to minimize this, but you'll still see something.

I am trying no restart on the retract, just to look at the differences. I am changing a couple variables at a time, which I guess I can do since it is a hobby. Still feels wrong though . I moved my psu, and had less strings, but I need to print the same object as before.

Also, I noticed that the blob isn't ocurring on the layer start. It is after running 3 perimeters, and then when it makes the move to do the in-fill...a blob is pushed out to the side of the perimeter. So I don't think it has anything to do with retract.

Hopefully I'll have more time to play with it this weekend.

This is SO much a temperature issue. I was having the same trouble last week until I ran into the mendelmax group

Also, I needed to adjust the "extruder multiplier" a bit, so I this github guide comes really handy to do this

You would need to play arround with the fan speeds: too much, and the first layers would "peel off" the heated bed. too little, and the layers would twist a bit, so you woul get that weird melted look. In pronterface m106 s127 would set fans to 50%, m106 s0 would turn off fans... Its a 255 scale, nor an 100% one

Notice here the lower corner. I apply ventilation after fifth layer, and all the sudden, I went from blobby corners to straight ones

If none of the abobe sufice the temperature argument, maybe this print does http://i.imgur.com/VC5lD.jpg (see atached file)

Let us know if this works! I really really hope it does

Ps: excuse my english!

There's another factor that can cause unilateral stringing and blobs on the outside - the orientation of the hot-end's heater block. The side it "hovers" above more often will get more heat, fan or no fan. In fact, i've been fighting that same issue for a while now. Possible solutions are insulating the block well enough and rotating the hot-end so the block is hovering above the side that gets most cooling from the fan. Haven't quite ironed it out yet, i'm going to try with two fans next (60mm blowing on the heater block side, 40mm blowing on the opposite side).

An often mentioned quick fix is to reduce the fan speed (or kill it) and print multiple copies (so layers get enough cooling and the hot heater block doesn't dwell above the same spot for too long, without the fan blowing so much it causes warping or unsticking). But that doesn't sound like much of a solution to me, more a quick hack.