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punpunm

Print Spider Fail

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http://postimg.org/image/49prugxen/

Source:http://www.thingiverse.com/thing:179544

I have print it about ten times, with no success print :sad:

I have try platform-adhesion Brim and Rift, the leg still fly away. I could see that the printing is a little bit shrink, it cause the object higher then the current printing layer and the extruder will drag the object. Finally get this result.

Should I print it with 20% infill or other idea?

If you have print it successful, please share the UM2 G-Code to us.

 

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May I ask why you are using tape? Are you printing with a cold platform? I don't know how well tape works with a hot bed, I imagine not very well at all.

I would remove all that tape, clean your platform well, apply a very thin layer of the supplied glue and spread it out with a damp cloth/sponge and then try your print again with the heated bed activated (it should be active by default) and with brim.

20% infill is a good standard amount of infill that should work well for most prints.

 

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I have tried tape on glass on the UM2 and it works just fine.

 

, it cause the object higher then the current printing layer

 

This is caused because of shrinking. When something like the bottom portion of the spider's abdomen is printed, as the upper layers are pulled inwards, the sides go up and the head hits it as it tries to print.

There are 2 solutions. You may need to do both solutions:

1) Heat. Keep the bed near the glass temperature of the plastic so that it doesn't shrink so much (70C for PLA, 100C for ABS). This might be sufficient. You might want to also reduce the fans to 50% and add a box over the top of the machine or a piece of plastic covering the front of the machine so that the air near the spider stays warm but hopefully this is not necessary.

2) Support. Usually support holds the parts *up*. In your case you need to hold the part *down*. I recommend meshmixer and add support in the places where the print head was hitting the spider. This solution alone is also probably enough to fix your problem. More on meshmixer:

http://www.extrudable.me/2013/12/28/meshmixer-2-0-best-newcomer-in-a-supporting-role/

pay particular attention to how to rotate your part in the "annoyances & limitaions" section and also note that there is a small error where he set layer height to "0.5" mm and it should be the layer height you print at e.g. .2 or .1mm.

 

 

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If you *do* use blue tape, after placing down the tape you must wash it with a small amount of isopropyl alcohol to remove the waxy surface. I agree with Robert that "not using tape" is probably better.

 

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I have not use blue-tape at first print (Mission: Impuzzible), but it is extremely hard to remove the model. I use several hours to remove it, after that I have find a little crack on my glass, so I use blue-tape on my glass.

I have add support to the spider, either MeshMixer or Cura. It still not hold down my object. The temperature is 220/75 deg.

Next time I will try to decrease the fan speed. Thank you for your opinions.

 

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I have not use blue-tape at first print (Mission: Impuzzible), but it is extremely hard to remove the model. I use several hours to remove it, after that I have find a little crack on my glass, so I use blue-tape on my glass.

I have add support to the spider, either MeshMixer or Cura. It still not hold down my object. The temperature is 220/75 deg.

Next time I will try to decrease the fan speed. Thank you for your opinions.

 

I saw a video by barnacules nerdgasm whereby he turned a can of compressed air upside down utilizing the propellant in the can to cool a part to remove it from the build platform more easily. He sprayed the interface of the piece and the build platform and the part popped off pretty easily the first time he did it, he tried it in subsequent videos with varying success. I believe he is trying to contract the bottom layer of the build piece thereby shearing the bond between the plastic and the glass. I don't think this is a good idea if the build platform is heated though, the sudden thermal change could crack the glass. If you have big prints you could try waiting until the glass cools to room temperature and then put it in the freezer, it may help.

 

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I find that PLA parts pop off the glass without any issue once the bed is properly cooled.

As previously noted, when printing PLA on blue tape, I wouldn't heat the bed, and just wipe the blue tape with isopropyl alcohol prior to printing. That should stick just fine then.

 

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I think the freezing idea is also not a good idea. I've seen on some other forums how the bond can be so good between the hot glass and plastic that during rapid cooling/contraction some people have actually had small shards of glass plucked off their heated plates by the plastic. I suspect that is a combination of extreme differential cooling (causing high surface stresses) and the plastic adhesion. It only takes a few minutes of natural cooling before the print can be easily removed. Damaging your glass plate isn't the end of the world but I don't think a few minutes extra waiting is really that much of a problem IMHO.

 

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Both glass and plastic shrink as they cool, so one point here is that if you spray freeze spray on the part, it will cool faster than the glass and pop off.

A different point is that although both plastic and glass shrink - they apparently have different coefficients of expansion. Therefore if you put in the freezer or at least cool to room temp, it gets easier to pop off the part.

A third point mentioned is that if you cool or heat glass too fast, you get cool/warm spots and the differential shrinking can cause the glass to break. If I am impatient I remove the entire glass plate and wave it up and down gently in the air or put it on a towel. Or on my lap. Leaving it on the aluminum plate I assume means it will cool more slowly than on a towel but I don't know.

 

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I also use my hands or lap as a heat sink. Our bodies are like very intricate water cooling systems with our blood acting as the water. It's a pretty efficient and gentle system to wick heat away from the glass :)

 

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I made the mistake of using freezer spray on hot bed too many times so small pieces of glass did come off eventually...now I've stopped using freezer spray directly on hot bed.

For large prints that still is firmly held by the build plate after cooling, I imagine that you could rinse the glass plate in hot water so the glue would dissolve...providing you used the glue stick of course :)

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