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nooby1973

Shearing and delamination

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Posted · Shearing and delamination

You can print to 205 by 205 but only if you have no skirt or brim. But things that large need a skirt or a brim! So catch-22. I guess if you print something that has rounded corners you can do 205 by 205.

 

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Posted · Shearing and delamination

So.....

Test print came out fine - no obvious backlash/over/under/extrusion. Set to print my big square object and I had exactly the same problem as previously posted - except this time the top half of the print was only out on the x axis - not the x and y axis. I did notice some very rough section of infill so I'm guessing it caught on one of those again. Temp and extrusion speed was the same for both objects though 100mm extrusion speeed/100mm travel speed, 210 degrees temp.

Maybe a higher temp to get a smoother layer?

I am printing as we speak at 50% scale - maybe the size of the object is part of the problem?

 

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Posted · Shearing and delamination

Just noticed the short belt - particularly on x axis has a very noticeable shift back and forth when the direct of the print head moves back to front (y also but less so). I did tighten these not 12 hours ago and there was no discernible lateral movement - wondering if it might be worth replacing the grub screws that attach motors to frame? I have also noticed that there is what looks like backlash on some interior areas where there are concave areas in the print (fill not meeting walls) although the exterior walls seem to be fine.

 

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Posted · Shearing and delamination

Just noticed the short belt - particularly on x axis has a very noticeable shift back and forth

 

You mean the belt twists a different direction each time the stepper switches directions? If so this means it is rubbing on the wood. You need to fix this soon before you belt is converted into powder. It also tends to cause parts to "lean" or "tilt" or have other missing steps.

The fix is very very simple. Just put washers under the 4 plastic spacers.

First lower the Z bed until it is a little lower than the X stepper. Then remove the 4 screws and place the Z stepper on the bed (so you don't have to mess with wires. Then add the washers and put the stepper back on. One washer per spacer should be enough. While the stepper is off make sure the pulley on the motor shaft is as close to the motor as possible without touching the motor. 0.5 mm is about right.

 

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Posted · Shearing and delamination

Set to print my big square object and I had exactly the same problem as previously posted

 

Why do you even try to print without looking at the gcode first? Look to see if X or Y goes beyond 205mm. Have you actually checked to see if the hardware stops are hitting earlier than 205mm? Such as for example at 204mm or 199mm? You can do this by homing xy, then moving X out 200mm then move 1mm at a time until it hits the end stop or can't move anymore. You can do this with either Cura or Pronterface (I prefer pronterface for calibrating - it's easier to use, it's free, and has lots of nice features that Cura doesn't have). You can even do it with the Ulticontroller but that's the hardest way to do it.

 

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Posted · Shearing and delamination

The problem wasn't hardware related. I dropped my 3d model into cura (200mm x 200mm x 50mm) and the print dialogue wouldn't activate. I scaled the object to 0.99 and the dialogue was then available, so I am unsure why this should be.

I wouldn't say the belt was 'twisting' as such, more moving backwards and forwards, I am printing uch slower now and that has reduced the effect but reading on the topic suggests replacing the pulleys and gears with GT2 as they are designed for switching direction, which the standard ones aren't (apparently), but I will look at adding those washers as I was having an issue with the short belt rubbing the wooden case.

 

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Posted · Shearing and delamination

Works for me!

I just did it with a 200mmX200mmX10mm "box" and it was fine with a few issues (cura 13.0.4).

I found if support type=none and skirt was set beyond 1 pass and beyond about 1mm then it wouldn't slice as this puts it past 205mm.

Or if support type=brim and brim was more than about 5 passes then also it wouldn't slice at all. Again this puts it past 205mm

In fact it wasn't obvious that it wasn't slicing and was showing the model from previous slicing settings.

Also please check "file" "preferences" menu and make sure x,y set to 205 and z set to 200. This is done automatically if you do the first 2 steps in the wizard and then cancel.

 

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Posted · Shearing and delamination

It sounds like either the grub screws aren't holding the pulleys properly, or the pulleys simply aren't lined up. Or, as George mentioned, maybe the belt is catching on the frame.

Either way, changing the pulleys or upgrading to a totally different type of pulley is overkill for the problems you are having.

Again, I recommend that you focus on printing something that fits comfortably inside the bed area, and get that right, before you complicate things further by pushing the print envelope.

 

The problem wasn't hardware related. I dropped my 3d model into cura (200mm x 200mm x 50mm) and the print dialogue wouldn't activate. I scaled the object to 0.99 and the dialogue was then available, so I am unsure why this should be.

I wouldn't say the belt was 'twisting' as such, more moving backwards and forwards, I am printing uch slower now and that has reduced the effect but reading on the topic suggests replacing the pulleys and gears with GT2 as they are designed for switching direction, which the standard ones aren't (apparently), but I will look at adding those washers as I was having an issue with the short belt rubbing the wooden case.

 

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Posted · Shearing and delamination

Ok - so I printed a small (10cm) version of my object and all in all it wasn't too terrible:

rough infillrough infill And backlashfinished surface And backlashrough 1st layer 200mm printrough 1st layer 200mm 250% print size

 

Good points.

 

1. It finished without a major screwup

2. It looks like the 3d model I designed

3 issues.

1. Rough infill

2. Infill not meeting edges (backlash?)

3. Rough surface/bubbling (too thin/too hot?)

I ran this at 200 degrees, 100mm/s print and movement, 0.2 layer height, 0.5 top/bottom layer, 0.5 walls, 20% infill and 5 seconds cooling.

The larger object is still printing, set to 75mm/s for print and movement, 0.05 layer height, 0.7 top.bottom layer, 0.7 walls, 20% infill, 225 degrees, 5 seconds cooling.

Am i over extruding or running too hot to get these awful rough surfaces? There is some flexibility in the bed since I changed the springs so the head is not jamming and causing the print to become offset like earlier posts.

By running below 100mm/s I have pretty much eliminated the backlash issue, but it does mean prints take an age (anyone else noticed the Cura estimator is way out in terms of time per print?) so it is entirely possible that I will lose the current print as it will take around 24 hours or so and every time I have left a print to run overnight it has failed for various reasons.

 

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Posted · Shearing and delamination

I would go to 10 seconds cooling. It's not going to be an issue until you get to those tiny little things at the top of the print - feet or whatever they are. Towers.

 

 

1. Rough infill

 

Um - so what? Does it matter? Well are you sure the infill is at the same speed? 75mm/sec and not 100mm/sec? I would try slowing it down to 50mm/sec at .2mm *or* raising the temp to 240C. But I noticed some stringing on the final bits of your part when printing those towers/feet or whatever and for those I would go down to maybe 190C (careful as PID temp controller tends to overshoot and if it hits 170C for an instant it will ruin your print so lower to 200C then wait until it gets there, then lower to 190C).

So my answer is - probably underextrusion as .2mm/75mm/sec/200C is on the fast side - it's doable but a bit fast. Maybe if you just tighten the extruder spring another few turns (my spring is at 11.5mm when extruder is closed). But simply raise temp to 240 or lower speed to 50mm/sec my fix this.

 

 

2. Infill not meeting edges (backlash?)

 

Probably. Maybe. But didn't the bottom layer look good? If the bottom 2 solid layers are meeting edge then I'm not sure if it's backlash. You could increase the infill overlap from the default 15% to 30% if it's a problem. Or check the belts.

 

 

3. Rough surface/bubbling (too thin/too hot?)

 

Bottom or top? You don't have enough layers for the top. .2mm layers with .5mm top means 2.5 passes - what does that mean? I don't know. Make sure the top/bottom thickness is a multiple of your layer height. I recommend at least 3 layers so .6mm for the .2mm part. .7 for the .1mm part is fine.

Similarly walls/shell should be multiple of .4. I recommend .8. Although 1.2mm is pretty good too.

So bubbbling? On the bottom layer? On the bottom I don't know what the heck that is. Is your first layer .3mm thick? I think what might be happening is the nozzle is a tiny bit too close to the bed and pressure builds up and then a bunch all leaks out all at once - for example in the gap between the blue tape it starts to come out extra and keeps going for a bit.

Make the bottom layer .3mm to avoid this - and smooth out your tape better - and level really carefully. Use a piece of paper. It matters if the nozzle is hot or cold (it expands). It matters if there is an almost invisible blob of cold plastic on the tip of the nozzle when you level. You will get good at levelling by your 30th print as it is soooo important.

Just making the bottom layer .3mm thick will help quite a bit (now you can level and have error of .1mm and not big deal - but error of .3mm will be a problem). Paper is typically .1mm thick to give you an idea.

 

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Posted · Shearing and delamination

By the way - I often change temperature and speed for different parts of a print to save time. I might print most of the print at 240C and 120mm/sec and then when printing say the ultimaker robots antennas slow it down to 50mm/sec and 190C.

 

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Posted · Shearing and delamination

Ok, now we have something we can start to analyze meaningfully. :-)

It's generally best to set the skin thickness to an exact multiple of your nozzle size. By setting it to 0.5mm, Cura is basically going to act as if the nozzle is really 0.5mm wide, and extrude a single bead that wide.

Furthermore, by running at 100mm/s, with a 0.2mm layer height, and a 0.5mm effective nozzle size thats 100 x 0.2 x 0.5 = 10mm³/s - which is really pushing it for the standard nozzle and extruder. You're going to get 10 to 20% under-extrusion due to the pressure required to try and push plastic out that fast, and you might cause jams and print failures. Especially as 200ºC is rather cool, and the plastic will be more viscous.

I'd drop the speed to 75mm/s, raise the temp to 220 or so, and probably put the skin thickness up to 0.8mm, so you get two passes. It looks like maybe you're getting some damage to the exterior surface because the infill is starting to show through a bit. Two passes around the outside will help with that.

On the other hand, your travel speed can be a bit faster - you should be able to do at least 150. That will help avoid stringing on retractions.

0.05mm is very thin for layers - I'm not sure how well it will cover over such a huge area of sparse infill. I think I'd want to test that on a smaller piece before I wasted hours printing the rest of it. I'm really not sure that you need to print this that thin at all. You should be able to get nice results in the 0.1 or 0.15mm range, and bridging will work better to fill in the solid surface. You do always want to make you top/bottom thickness an exact multiple of your layer height, and for thin layers and low infill %, you may want ten layers or more. With 0.15 or 0.2mm layers, and/or infill % of 25 to 40%, you can probably get away with fewer layers, but I'd always want to go for at least 5 if I really wanted a nice surface.

I think the bubbling on the bottom may be related to either the tape being uneven and/or the nozzle being too close to the bed. You'll want to have fresh blue tape, and wipe it down with alcohol before you start, otherwise I imagine that warping is going to tend to pull the corners up off the bed.

 

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Posted · Shearing and delamination

I think the poor infill is partly due to the fast extrusion rate - resulting in under-extrusion - and partly because of a bug/feature in Cura at present which causes the infill layers to not line up with one another. Slowing down and heating up will probably help with the overall finish, although the mis-alignment may still make it messier than it should be.

 

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Posted · Shearing and delamination

So, finally got a complete print of a part, I would say 90/95% accurate print.

stringing 1stringing 2basic clean Up 1basic clean Up 2

The stringing was easily cleaned up, a bit disappointed that the four corner supports failed to print correctly (they actually printed fine in earlier attempts), but no biggy, I can amend the other objects that I need to print to compensate for that. The support in the four recesses are very densely packed however, which wasn't the case in my earlier failures.

I think, as illuminarti suggests, adjusting the extrusion rate will resolve these issues for my remaining prints.

 

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