Beginners mistakes?

This topic contains 13 replies, has 4 voices, and was last updated by  Ryan 2 years, 9 months ago.

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #24973

    Bill
    Participant

    So I have my MP3DP assembled and after most of a day of debugging (bad stepper on the extruder) can pull filament through with approximately the right speed (I need to do the 100mm test a couple more times yet to get it dialed in). I’m having difficulties getting the part to stick well during the first pass, so it ends up pulling off on subsequent passes. I know it’s been discussed here before, but does anyone have a rule of thumb for PLA on the aluminum bed? My extruder was purchased here, except for the new stepper that’s on it. I’m using Ziro filament and the temperature controls seem to be doing a good job of holding the values. I started with the defaults in Repetier-Host of 60C and 200C and have tried +5C and +10C from there.

    #24974

    Ryan
    Keymaster

    Next few test lest some some pictures of your first layer. That is the hardest. You are probably too far off the bed, and I print the first layer at 40-50% speed.

    Try wiping the tape with some rubbing alcohol when it is hot just before the print. Higher the proof the better. Not a necessity but helped for me and most people have some sitting around.

    I used 45C for my bed with tape.

    At this point the filament temp isn’t usually the problem, that comes a few layers up and is much easier to diagnose.

    #24979

    Bill
    Participant

    I went through and made sure my slic3r settings matched the recommended ones here, except for bed heat stuff since the MPCNC assumes no bed heater. It’s now sticking down for the first layer then pulling up on the second. Looks like the speed up it does on subsequent layers might be too fast, since it’s when that kicks in that the edges start lifting.

    #24987

    Barry
    Participant

    What are you wiping your tape with? The tape still looks shiny.

    #25003

    Ryan
    Keymaster

    I still think it is first layer height. The first layer should just almost very slightly be squished…..or noticeably squished.

    Pla doesn’t really warp because of heat issue as much as any other material. Too hot and it sags, doesn’t handle overhangs well, and bridges are bad. Too cold and you get poor layer adhesion, or you hear the extruder skip once and a while.

    Here is ulimakers opinion, https://ultimaker.com/en/resources/21330-what-does-a-successful-first-layer-look-like

    I usually have mine more on the side of too tight, if you go too far you will get a transparent layers that of course is bad.

    #25006

    Bill
    Participant

    I spray the tape with the 70% isopropyl in the spray bottle behind the printer, then wipe with a paper towel. Should I spray and let air dry? Maybe spray and heat gun it dry?

    I’ll move my X and Y zeroes so I’m not trying to zero Z over the hole. I’ve been using a plastic parts bag to test Z zero, figuring if the bag has friction pulling it out from between the nozzle and the bed it’s pretty close to the actual zero depth. I’m also guessing the tape is similar in thickness to the bag. Is there a better method for testing zero height?

    I sure wish Repetier-Host would let me just type values into displayed position to move around instead of making me jog in increments of 10, 1, 0.1 etc…

    #25010

    Ryan
    Keymaster

    Now its easy. Most important is make sure your x is level across the bed. Just slide the carriage at any height and visually look for level. if not hold one lead screw and turn the other a tiny bit. Then just slowly turn in your z height screw and start a print. To high, use some pliers and give it a little more or less. once you have it right you do not need to do it again until you mass with your nozzle. No need for tools to check just use an actual print.

    I know the first few times suck, but once you see it print a first layer correctly it is a 1 minute process to dial in any printer you ever see.

    I just spent 20 minutes trying to unsuccessfully fix my Robo3D auto level….one side is always about .15mm higher….I hate auto level. (and I helped implement it on the robos….). I took it off one of the robos, looks like it is time to take it off the other.

    #25012

    Ryan
    Keymaster

    I guess what I was trying to say with waaaay to many words is, Once it is pretty close, the guess and check method is much easier and faster. I start a print, if it looks incorrect, I stop it, turn the z adjustment screw in or out with some pliers, start it again.

    In the forums here someone made a really cool thumbscrew for adjusting that z screw. It is awesome and something my design lacks….but you should only need to tweak it every blue moon.

    #25017

    Barry
    Participant

    Man, cartesian printers are sooooo much easier to level than deltas!!

    As for the tape, I usually just squirt some alcohol into a paper towel and rub the tape down. Then start the print. By the time the bed gets to temp the tape will be dry. Usually I print straight onto my glass bed with gluestick. I only have to resort to tape for long thin stuff that doesn’t have enough surface area to stick to the glass.

    #25025

    Bill
    Participant

    I’m planning on printing that thumbwheel for the Z axis and probably shorter ones for the X and Y. I’ve got a couple more errands to run yet and I’ll get back to it as soon as I return.

    #25058

    Bill
    Participant

    Not quite the right color, but still pretty OK IMHO.

    #25060

    Ryan
    Keymaster

    They look perfect

    #25170

    Dave Gun
    Participant

    Here is a close up picture showing the “squish” of the first layer outer ring with PLA. I use 3M Scotch Original blue tape wiped down with Alcohol Prep Pads. Most prints will bring up the tape when the print is removed.

    I use printer paper as a gauge for the first layer (~.1mm). For PLA and heated bed, I have been using a bed temperature of 45C. It also works on a cold bed, but it helps removal a little when it cools down. Any hotter and the first layers stay too soft and affects the print quality.

    Good luck,
    Dave

    Attachments:
    #25175

    Ryan
    Keymaster

    Dave that first layer of yours is much much too close. You should be able to make out each individual extrusion line. have a look at the ultimaker link a few posts above.

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