doron
Posts: 1
Joined: Mon Nov 11, 2019 4:06 pm

raft question

Mon Nov 11, 2019 4:16 pm

hi
may be a silly question but what is the different in print cycle of the raft and print cycle of the part . is it the speed of print?
and is a way to change any parameter to mimic raft print in first stage of part print cycle so will be no need to print the raft and struggle to remove it?
Hope i was cleared in my question
Regards Doron

Wallabear
Posts: 17
Joined: Wed Feb 13, 2019 4:33 pm

Re: raft question

Tue Nov 12, 2019 11:44 am

In my experience there really should not be that big of a struggle to remove a properly set up raft. Most of the time when I have to use a raft they just peel right off. I would recommended choosing a small model and try printing it with a raft and adjust your raft settings till you get it dialed in. you can probably even setup a couple of processes with raft changes and print them at the same time, just make sure that you keep track of what setting were used on which parts. I believe that there is a Video on S3D about properly setting up a raft and that was helpful.
But you answer you exact question when I print without a raft I usually use a little higher first layer height and a little large first layer extrusion factor. No print fan and have my speeds reduced by about half or not exceeding about 35mm/s.

User avatar
dkightley
Posts: 2095
Joined: Tue Mar 10, 2015 4:09 pm

Re: raft question

Tue Nov 12, 2019 7:23 pm

To expand on the answer.....

The processing is somewhat like this.....
Raft base layers are printed slightly slower than the default speed (I think) and are up to 5 times thicker than the set layer height.
Raft top layers are printed at the same speed, but at approx. 2 times the set layer thickness.
The first layer of the part is then printed slightly higher high as per the "Separation distance"
The First layer settings are applied to the first layer printed.....ie in this case, the first raft base layer....NOT the first layer of the part!

The adhesion of the part to the raft is mainly controlled by the separation distance....but varies if you play around with print speed, extrusion multiplier, filament thickness, etc. Where the part is liable to warping, you'll need to reduce the separation distance to increase the adhesion......

In my experience, I find that the first raft top layer tends not to adhere very well to the last raft base layer....so I leave out the raft base layer and just use one or two raft top layers. With a separation distance of 0.2 or 0.3mm, I find the raft will peel off mostly in one piece...bearing in mind it is weak because it has no base layers...and I have to use a scalpel to gently separate any remaining raft where it has stuck to the inner perimeter (s) of the first layer of the part.

As far as trying to mimic the raft.....forget it! Set it up correctly in the first place, and rafts will work!
Doug Kightley
Volunteer at the National Tramway Museum http://www.tramway.co.uk
Railway modeller and webmaster at http://www.talkingtgauge.net

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