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Help with rafts, why do they insist on making prints look terrible?

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  • Help with rafts, why do they insist on making prints look terrible?

    Hello all,
    I have an issue when it comes to rafts and I am wondering if anyone can offer some advice.

    I have recently been printing a piece that simply refuses to release from the print bed, even when I add a small chamfer to help with the release, it won't budge. I thought I was going to break my print bed the last time I tried removing a print.
    This is due to them being dense with 4 parameter walls and 5 parameters on the top and bottom, so they don't flex as easily as 2 parameter prints.
    I need the parts to stand up to some wear and they do just fine, it's just getting them off the print bed that is wonky.

    So, I thought using a raft would help.
    All it has done is make my part look ugly.

    The photos I have attached show similar parts, the one on the left has been printed with a raft (2 layers), the one on the right no raft.
    Nothing else changed.

    Click image for larger version

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    The raft print insists on creating this weird molten delaminated chamfer, which is not in the .stl.
    Also the bottom of the print with the raft looks like my printer has gone rouge.

    The printer: Prusa MK2/s
    Slic3r: Prusa Edition

    I print on blue tape that has been washed with isopropanol prior to printing because this gives a nice bottom layer and it makes it easier to release (usually).

    Can someone offer some pointers?
    What am I doing wrong?
    Or is this just how raft prints look?


    Thank you in advance for all your help

  • MBH
    replied
    There's nothing wrong with printing rafts. Mine pop off like butter with no effort leaving no damage to the part. Like all other things 3d printing, rafts need to be mastered. When we get a new printer we run a series of tests through it before its put into production. We dedicate AT LEAST 1 ROLL of filament to testing before using it in production. It saves a ton of money and time as by the time we are done the printer is dialed in perfectly and ready to rock. ( visit our website: www.markheller3d.com )

    For rafts, run tests with top infill at 75, 80, 85, 90 and 100. For each of those 5 tests you need to use a separation distance of .22, .24, .26, .28 and .30. So far that's 25 test prints. For those 25 tests, use 2 upper and 2 lower layers, a minimum of 3mm offset and an above raft speed of 25 to 30.

    When you complete those 25 rafts you will be good to go. If you take shortcuts and only run say 7 or 10 tests it's a waste of time. You won't learn anything so don't bother. Crap in yeilds crap out.

    It's also important when doing these tests (also for supports) that your nozzle temp for the SPECIFIC material you are using is SPOT ON. Too hot and your parts will be so soft and overly melted that it won't release properly no matter what.

    3d printing is all about discipline. If you work sloppy, take shortcuts and rush it will show in your results. Find a different hobby or business venture. You need to be precise, methodical and consistant.

    Good luck.

    Leave a comment:


  • Roger3D
    replied
    Do not print with rafts...... instead of a raft you want a brim not a skirt but a brim that will help prints to stick better . Some people have trouble getting parts to stick. I print on glass with stick glue and to get parts off I use a razor blade, a long rectangle 3d printed block and either a small hammer or 14 mm wrench and catch under one corner of print and tap the blade under the part. It separates the part from the bed. You could also use feeler gauges but the razor blade creates a gap you can use even a putty knife after that to help. To try and just knock a part off with a hammer will mess up bed level or break something else. You have to separate the part and the bed it could even be a sharp chisel. You could also be printing too close check bed level you want a 0.1mm gap to start. And eventually try to get rid of blue tape that can lift in spots and try glass.

    Leave a comment:

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