A raft isn't going to help is PLA sticking problem!
There are three critical factors:
HEIGHT,
SPEED and
TEMPERATURE.
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: PLA 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.
In the Summer I had no problems with the PLA sticking, in the Winter I sometimes need to preheat.
You do NOT need a raft, you need the PLA to stick well on the first layer.
Use Skeinforge.
Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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