Questions about Slic3r?

[Fastest1]

I am getting closer with my Repstrap (using an H1 extruder). I am running Slic3r 7.1, 3mm PLA @ 175c with a .64mm nozzle.
In the present configuration using a layer height of .285mm I am getting fairly good results however oozing is an issue to some extent. I am using a retract of 4mm @ 200. I still getting a little blobbing right where the head starts to lift away. Upon reversal it was also extruding too much when restarting, I installed a negative number in the extra filament column and it has helped with the 2nd problem but not the first. Any ideas? Also I am using .33mm between the nozzle and the bed when starting up. Is there a calculation based on nozzle size of how far the nozzle should be off of the bed? I am having a blast anyway!

[Polygonhell]

200 is really fast for an extruder, the units are mm/s, are you sure it's not just stalling the extruder on the extract?
Mine is set to 20.

[Fastest1]

Polygonhell,
Thanks for the response. Though 200 is fast I get no stalling on retraction. I do think if I was trying to feed that fast stalling would be an issue. I have tried retraction at many speeds with no apparent change. I also have tried using negative numbers in the extra filament dispensed after retraction column assuming plastic expansion is the issue causing the oozing.
I am suspicious of a few things that could be causing the blobbing. 1 could be an incorrect value on the A axis steps per unit. Presently I am in the 324 range (I am using a Hobby CNC Pro board not Seemecnc's board). My infill improved dramatically as I was way off before. (Damn metric system! LOL) I used the axis calibration tool within Mach but accurate filament measurement could still be off a few %.
The blob I have an issue with is right before the toolhead moves to another location. I have Mach set on CV and not exact stop so motion should be smooth. I also have it looking ahead 200 lines. Lift and or retraction doesnt help though elimnating both does but then stringing is a PIA. IMO The PLA oozing is the issue. If I lower the steps per unit of the extruder 1% at a time to see the results and go from there.
I am also thinking the toolhead might be dragging in the print itself. I dont see any build up on the nozzle but the top does look heat sealed for lack of a better term.
All in all for this type of technology I am impressed with the results. Also I have c clamps and fans on my extruder as it flexes quite a bit (it did!).
What clearance are you using for the nozzle upon start up? I am using .33mm (a glossy postcard).

[Leeway]

I actually use 200 mm/min on my extruder. It is a Gregs open extruder with a Jhead hot end. .35 mm orifice. I can go faster than that and do on PLA, but ABS is cantankerous enough to get zeroed in on.

[Polygonhell]

I actually use 200 mm/min on my extruder. It is a Gregs open extruder with a Jhead hot end. .35 mm orifice. I can go faster than that and do on PLA, but ABS is cantankerous enough to get zeroed in on.

Oh I can run 200mm/min but the Slic3r retract setting is in mm/s. 200mm/s is 12000mm/minute, or roughly 470in/minute, Mach is probably capping the speed for him based on his extruder motor tuning, and given the short length of the retract he's likely never reaching his maximum speed because of the acceleration settings.

You may want to try adjusting your motor tuning in Mach for the extruder, making the acceleration very agressive and possibly dropping the maximum speed.
If you're sure the retract is happening then the next thing is to start lowering the temperature.
Print the 10x10x40mm tower, when you can print one that doesn't look like a blob call it good.

FWIW I had blob and string issues, but I had misread the "extra filament" box and assumed it needed to match the retraction setting.
It also varies a lot with the filament, the White PLA I have here I can't get to not produce strings, the Blue PLA is much better.
I also imagine there is an element of hot end design. On my list of things to do us to compare various hot-ends.

[Leeway]

I see what you are saying now and agree.

[Fastest1]

Thanks for all of the input guys! I need it.
Today I lowered my A axis steps per unit in 1% increments until the bulging went away. That helped a bit. I was at 324.7913519 and am now at 316.7913519. My sides are now much straighter.

I do still get a small blob right as the filament is starting to feed on each layer (NE and NW corners only as I face my mill, oddly enough only the SE and SW corners blob on the first layer).

I experimented with .33mm to .43mm clearance from the nozzle to the bed.

Tried lowering my temperature from 180c to 170c. I am getting much closer but the small blobs are irritating and they dont change whether backlash comp is on or off. My machine has very low backlash in the X, Y & Z anyway (Kerk leadscrews with anti lash nuts)

Otherwise sizing is very close, finish is great, infill is almost there.

Btw I do understand what you are saying about the maximum settings within Mach. My A axis tuning is 316.7913519 SPU, 277.08 velocity, 100.4491 accel. So I see the limitation via settings and that explains why it isnt stalling!

I have experimented with negative number retraction values of -.15 to -.075

All the testing did improve things quite a bit, Post it notes are a wonderful thing.

Most of my tinkering today was 3mm black PLA done with temperatures in the 170c-180c range. Perimeter and bridge print speeds of 60 and infill and solids at 30. Layer height was .285mm. Retraction was 4mm (though I tinkered with this a bit). First layer height at 1. Fill density of 1. Extra length on restart of anywhere between -.15 to -.075 ( again I tried other values but bridging or the initial reattachment of filament was spotty). Bottom layer speed of .3.

Jump in with any and all tips. I will attach some photos later

[Leeway]

Those blobs may also be in the stl file. I have noticed if there are small radius on a part, it will tend to dwell too long and blob.
Redoing my Cad drawings have helped with that. In most cases, simpler drawing is better for printiong.

[Fastest1]

Those blobs may also be in the stl file. I have noticed if there are small radius on a part, it will tend to dwell too long and blob.
Redoing my Cad drawings have helped with that. In most cases, simpler drawing is better for printiong.

Leeway, Thanks for that tidbit. I was curious earlier today as to my trust of STL files on Thingiverse or elsewhere. After you mentioned this, I looked thru my box of other prints and dont seem to see this corner problem as pronounced. I am printing the Wistle as I type this however it still has some issues too. Not bad but not perfect. I will have to investigate that a little further. Any file you know of you cant trust and run easily as a test?

[Leeway]

Not any in particular. I have been drawing my own parts for the most part except for some of the Calibration cubes. Those don't generally have any radius corners.
Those also make for larger files too, so if you can get away with it asthetically and structurally, then make bare corners and joints where possible.

[Leeway]

Before printing a whistle, you really want to dial in on your bridge settings.
For a nice quick print to test this, I use this cube.

http://www.thingiverse.com/thing:16510

Once it starts printing the columns, I use a fan.

[mhackney]

Lee, you use a fan pointed at the printed item? I am thinking about doing this. Are you using a printed mount/tunnel?
cheers,
Michael

[Leeway]

It is just a small fan mounted to an adjustable arm. It used to hold a light. It has a clamp to fix it to a table edge.
I only use it when printing items that are thin like this cube or very small parts. I don't use one at all on the hotend.

[Fastest1]

Lee, I will run that cube. "Wistle" is the name of the file on Thingiverse that I have tried to print numerous times with no success. All leak just enough to not work (well one worked, but only if blowing really hard).I have run a thin wall box with great results and a hollow pyramid. That was fun to print and amazing to watch. Trying to get the restarting of the filament after a lateral move to another point is an exercise in patience. Though on PLA I am coming to the conclusion on my machine that retraction is around -.05mm. Retraction stopped almost all stringing. Running prints like those really makes me try 10's of configurations within Slic3r in an hour or so. I have stacks of post it notes with the print and the settings attached. I review them to see the variations within the settings of Slic3r. I also try the same with different temperatures and nozzle heights. I also run a fan on the side near the stepper to cool the drive roller and the stepper. Mostly because my controller is different and I am running a different Nema 17. My next drive will be aluminum, similar to an MK7 but home brewed.

[Fastest1]

I am running the hollow cube right now and have had a few surprising results. After the statements on A axis tuning speeds, I sped all of my axis up till stalling (huge offsets in the cube). I then lowered them by about 1/3. The results are much better. My A axis has a velocity of 1600 at the moment, IIUC this is a retraction speed of 26mm/sec. It is definitely moving. I am getting no stringing to speak of. The columns are straight though the infamous blob (though very small) is still affecting the the NE & NW corners (columns in this case). I also noticed on my first print of this cube my bridging speeds were also too slow due to my maximum velocity setting within Mach. Hopefully my new tuning will allow faster bridging and less sag. My present attainable speeds should be right in the 100mm/sec range. I am also finding the only way I get good adhesion to the bed and uniformity is to run a single "post it note" (.04mm-.06mm) for clearance. This gets the seemingly correct amount of squish into the filament. Other's experiences in nozzle heights of the bed at start up would be great.

[Fastest1]

Not sure about posting a picture here.

[Fastest1]

This was a GoPro bracket I was attempting. Btw Sorry for the low quality photography!

[Leeway]

Looks like you will need to calibrate your extruder. Also the settings I used on the cube the last time were for ABS, so won't do much good for PLA. That is also the typical way I set the Z axis.

I lie to Slic3r and tell it that I am running a .33 mm nozzle instead of .35. That helps on several of these smaller prints to get full printing without voids.

[Fastest1]

What did you see that makes you think I need to recalibrate? Not saying I dont, just wondering what you saw? Infills missing? I have tinkered with extrusion multiplier values a little but not nozzle size.

[Leeway]

I saw that there was no infills, but now it occurs to me that you may have set it that way.
That calibration is always to first step to do before you start playing with the slic3r settings. Just didn't know if you have done that or not.
Also if your computer will allow it, you can set Mach to a higher kernel speed and thus increase the speed inside Mach.

[Fastest1]

Lee, I have tried the calibration tool within Mach but I am suspicious of my measurement technique ( I am using a digital caliper I trust but being as little .05 off makes a difference it appears). Originally after using it, I would get slight bulging on the straight sides of the cube. I went down in 1% increments until the sides were straight and the bulging was gone. I might be a bit too little now. Most likely only a percent or 2. My settings for that print (the cube) were first layer height ratio of 1, rectilinear fill pattern @ 45 deg. Fill density of 1, 3 perimeters, 4 solid layers, 4mm retract with -.05 extra length on restart @ 30mm/s, 2.96mm average filament diameter, extrusion multiplier of 1, nozzle diameter of .64mm, bottom layer speed of .3, perimeters small perimeters and bridges were at 100, infill and solids at 60. I dont see a need for the kernel speed change within Mach. With the screws i am running I barely start to raise the velocity slider to get to to 2500mm/m, my X axis steps per unit is only 62.55798565. Once again now I see the limitation. I just raised the velocity of x and y axis' to 6000 for a theoretical top speed of the 100mm/s. Ok so my perceived bridging speeds were not being reached. Might explain some of the sag

[Fastest1]

Lee, You have now really made me think. When you suggested the moving of the kernel speed within Mach it made me wonder. In the last month I have changed a computer or 2 that run Mach. I also changed over to mm on this machine (printer). I do believe this computer is more limited or wont move the mill as fast without stalling. I was calculating just how much my velocity would have to be to have a retraction speed of say 30mm/sec. I was setting my bridging perimeter and associated speeds to 100. After pulling my head out of my a$$. So I tuned up until stalling or getting a skewed print. At the moment with no lost steps my X & Y axis are v2800/a600. Over 680 was creating skewing. I might be able to attain a higher speed but my accel will have to stay down where it is. Just more testing. I do notice that the cube is much nicer as I will show when it finishes. The NE/NW blobs that were driving me nuts are now pretty even on all 4 corners leading me to believe I am over extruding slightly. I did fudge the nozzle size at your suggestion and seem to be getting some solid infill. However I am also running the nozzle much closer to the bed. I was running it between .33-.43 and now at .04-.06. I was thinking that would cause the nozzle to drag but it doesnt look that way. Very nice so far.

[Leeway]

I didn't see any solid fill on that cube. The top of the base should have filled solid as should the top. Now the top is likely because of the width of the nozzle and the actual width of the part. It didn't have enough room for the last perimeter, so didn't infill. Not sure why it didn't do it on the base though.

Mach dpends heavily on acceleration settings as to whether it can reach full speed on a given axis. That setting moreso than velocity setting will will stall a stepper fast than anything. Typically you increase that until you get missed steps, then back off at least a quarter. You did that I think.

Do you really have a .64 mm hole?
You can open a drawing in a CAD viewer and measure the actual size of the model for small areas like to top of this cube. The lie to Slic3r about the actual size of the nozzle to get a multiple that will fit in those CAD dimensions. It has to be fairly close to actual nozzle size though.

Sorry. Didn't catch you last post before replying.

[Fastest1]

The nozzle that came with my H1 3mm extruder was marked .025, I was guessing that was in inch. I did fudge from a .64 to a .60 and now that the settings and working are better infill maybe a hair too much. I did speak too early on that last print. Though the infill and top frame are now solid, the begginning bridges droop big time. It improves after a few passes but I am sure either faster bridging speeds or a little cooler temperature might help in those areas. Maybe even a fan on the print?

It is getting better though, small steps. Actually what is printing right now is much better already just due to obtainable speeds, getting to the bridges, fingers crossed.

[Leeway]

It took me quite a few scrap prints to get anything that started looking pretty good. Maybe 2o items in PLA and a dozen in ABS.
Take and measure your actual extruded filament with your caliper. My nozzle is .35 mm. It actually extrudes sometime .39 to .42 mm depending on settings. The plastic seems to swell a little upon exit.