Object sticks to the raft like ____ to a ____ (use your own words)

Hi All

I am using a raft at the moment, and am finding the object sticks to it like ____ one a ___!

Of course I want the first layer to stick, but I don't want to have to spend ages trying to seperate the object from the raft.

Any suggestions?

Cheers

There are four critical factors: HEIGHT, SPEED, TEMPERATURE and SURFACE.

HEIGHT: Above the bed. This is the most critical aspect. As little as 0.1 mm can make a big difference.
SPEED: Low and slow as opposed to high and fast. With Skeinforge you can set different settings for the first layer. Make it much slower e.g. half as fast.
TEMPERATURE: ABS and bed are both important. With Skeinforge you can extrude the first layer at a higher temperature (maybe as much as 10°C higher) which makes it stick better. And the last factor is the temperature of the bed. With a cold bed you will have problems. You can warm it up with a hair dryer but the best solution is to install a heated bed. This will fix your sticking problem and also allow you to print very large objects without warping.
SURFACE: For ABS kapton tape seems to work well for most people. For PLA glass or blue painters tape.

Use Skeinforge!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

lol

I don't have problems with my stuff not sticking.

In fact, the first layer sticks to the raft and it is very hard to seperate.

I would like to get some guidance in how to reduce the adhesion between the raft and my object. I am printing in PLA at the moment.

The BIG question is WHY ARE YOU USING A RAFT?

I have never used a raft.

I currently print PLA on blue painters tape, once I install my heated bed I will print PLA on glass.
ABS you can print on Kapton or PET tape on a heated bed at ~ 110°C.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Dude - no need to shout at me!

I am using a raft because I am unable to get my print bed perfectly flat. A raft produces a perfectly flat surface (in relation to my print head) for my object to be printed on.

I am thinking of moving off the raft, but for now, and the point of this post is...

...are there any steps which will reduce the adhesion of my object to the raft or ease the seperation of my object from the raft.

maybe you could put some code in to move and pause the toolhead after printing the raft, and paint the raft with machine oil?

I think Adrian has tried this trick with the oil and it apparently worked pretty well.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I have also never used a raft with PLA. I can imagine it would bond very strongly though.

If you raise the height of the first object layer then the contact point with the raft will be smaller so the weld less strong. You also need to reduce the temperature of the first layer as much as you can (but that is not much with PLA as viscosity changes sharply with temperature). Not only will it being cooler reduce the strength of the weld, it will also make it more filament like and less liquid. That will stop it slumping, which would increase the contact area.

Allowing the raft to cool before doing the first layer will help. I used to use a fan to cool my ABS rafts to room temp before starting the object.

Extruding the first layer of the object faster will reduce adhesion.

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[www.hydraraptor.blogspot.com]

How bad is the bed? if you can print a good raft, the object should also be ok?

I used a semi-bouncy polycarbonate bed that could flex down slightly, this compensated for about 0.2mm warp in the base of my first repstrap.
It had Kapton over the Polycarb so the nozzle could touch very slightly at some points and be about 0.3mm everywhere else, the first layer is not perfect and you get a bit of ploughing of material on the first layer but after that it's all nice and flat and building can begin at layer 2.

Use sheets of paper at the low bits to prop up the polycarb and allow if to flex, I hope that all made sense.

Then you don't need a raft...

Rich

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[richrap.blogspot.com]