Favorite way to prep your bed surface for printing PLA?

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jbarnhardt
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Re: Favorite way to prep your bed surface for printing PLA?

Post by jbarnhardt » Wed Apr 30, 2014 9:41 pm

Jin -

In the glider world, the majority of construction these days is from composites - fiberglass, Kevlar, carbon fiber, etc. For wings it's usually applied over a lightweight foam core or hollow molded with a thin composite shell and a hollow interior. These structures are much stronger than balsa airframes for a comparable weight (often lighter for similar strength in fact), and the composite construction is what has allowed for the development of things like discus-launched gliders which are subject to extreme torsional and bending forces at launch (current record is over 300' launch using only a spinning human and his arm), while weighing only ~9oz (some as low as 7.5oz) for a 1.5m wingspan aircraft. A 3D-printed glider isn't feasible with current technology and materials (well, maybe a slope glider that would require really strong winds) until those guys working on the carbon fiber capable printer get things totally dialed in (and I'm quite skeptical of molten plastic being anywhere comparable to epoxy as a structural binder). However, there are people using 3D printing for certain components where the weight/strength tradeoff is appropriate - horizontal stabilizer mounts are one application (http://www.rcgroups.com/forums/showthread.php?t=2075663), servo trays another, tools and jigs for accurate construction another (http://www.rcgroups.com/forums/showthread.php?t=2113729). I've made a handful of 3D-printed h. stab mounts myself and they appear to work quite well. Lots of cool experimentation going on. My interest in 3D printing grew out of my work with my CNC machine I use for milling glider molds and components - very nice technology overlap between the two domains in terms of 3D modeling, toolpath generation concepts, gcode, steppers and motion mechanics, etc.

Will -

Sorry to hear about your back, perhaps some day you'll have a chance to get back into DLG. Your comments on this board have been great.

-John

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Tim
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Re: Favorite way to prep your bed surface for printing PLA?

Post by Tim » Thu May 01, 2014 1:39 am

Just to add my two cents (about bed surface prep, not about gliders): I use the Suave Max Hold in a pump bottle, not aerosol can. I feel that the pump bottle puts down just the right amount of material on the bed, not too much, not too little. Takes about 6 squirts of the pump to cover the glass. I no longer try to get the glass squeaky clean. Just regular-clean is good enough. Washed under hot water and wiped off with a paper towel. That's all. I will make print after print on the same surface. If the print is a bit iffy on surface area against the glass, I'll make sure I clean the glass first. Also, if I don't want to see the ghost of outlines of prints past on the bottom of my next print, I'll clean the glass. Otherwise I just keep printing on the same surface with no additional prep. I haven't tried testing the limit of how many prints I can do between prep cycles, but just on basic principles I've been running no more than about eight to ten prints before washing the glass off. The hairspray has really turned the job of bed prep from being a chore to just being an occasional maintenance thing.

I tried painter's tape and liked the rougher surface finish it gives, but too often the painter's tape would get stuck to the plastic so firmly that no amount of soaking and scraping would get it off. Printing on top of a raft will also prevent having a glassy-smooth surface at the expense of a bit of extra plastic used, without the hassle of trying to get the painter's tape off of it. But then there were other times when the prints would come right off of the painter's tape with no fuss, and I never could pin down any obvious difference between the times that it was easy to get off and the times it was impossible to get off.

jsc
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Re: Favorite way to prep your bed surface for printing PLA?

Post by jsc » Sat May 03, 2014 5:20 am

Toby wrote:
jsc wrote: 5) Diluted white glue: this seems better in that you can control the strength of adhesion more directly. I have not tried it yet because of storage issues: you need a jar, and a brush, and ideally some way to keep the brush in the jar without letting the contents dry out.
I've just been using a small plastic container and an artist style paint brush. The brush can be rinsed out after each application, but you're right it is a bit of a pain and it would be better to store the brush in the container.

I remember as a kid we had these "glue pots" in school which had a brush built into the metal twist-on top. I wonder if they still make anything like that.

Edit: Well come to think of it, I wonder if we can make anything like that. Of course we can.
So, Toby, did you? End up doing anything with this?

The easy way would be to cut a hole in a jar lid and epoxy a brush into the hole. But I lack all proper tools for punching clean holes in metal, so my preference would be to print a replacement lid. When all you have is a hammer, everything looks like a nail.

Toby
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Re: Favorite way to prep your bed surface for printing PLA?

Post by Toby » Sat May 03, 2014 6:20 am

jsc wrote:
Toby wrote: I remember as a kid we had these "glue pots" in school which had a brush built into the metal twist-on top. I wonder if they still make anything like that.

Edit: Well come to think of it, I wonder if we can make anything like that. Of course we can.
So, Toby, did you? End up doing anything with this?

The easy way would be to cut a hole in a jar lid and epoxy a brush into the hole. But I lack all proper tools for punching clean holes in metal, so my preference would be to print a replacement lid. When all you have is a hammer, everything looks like a nail.
Lol, nah. I was hoping you would.

Instead I started bringing a glass of water and a paper towel to the area I prep the glass. This was useful this morning when I prepped one bed with diluted elmers and the other with suave max hold. Just dip the brush in the water, or leave it there between applications, and wipe off with a paper towel before the next one.

I'm just getting started with ABS so I wasn't sure which method was better. But after two prints, I'm sticking with elmers.

Of course having one little container with diluted elmers in it and one with suave max hold in it got me wondering, "What if I mix the two....?" Anyone ever try that?

BTW, on my first test print I thought I might as well do something useful so I tried testing your (Jin's) suspicion that rounder objects print with less warping in ABS. Makes sense to me. I modeled two bolt-like things, one 8 sided and the other 4 sided, but otherwise the same size (50 x 50 x 5), and printed them at the same time.

And yep, the 4 sided one turned up at the corners but the 8 sided one didn't. I wrote up a post with an eye level picture of the two on the bed and was just about to submit it when I noticed the camera seemed to show an upturn on one corner of the 8-sided bolt. I missed it with my eye, but it was there. Very tiny and I still think your theory is correct, especially if corners are replaced by rounded edges, but at that point I could hardly post it.

Wayneswift
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Re: Favorite way to prep your bed surface for printing PLA?

Post by Wayneswift » Thu May 29, 2014 9:39 pm

I HIGHLY recommend blue painters tape and I always shut the bed heat off after the start of the print. I wish that I could give credit to where it is due but the best "first layer" tip i ever got was, with a level bed, (which I only check once in a great while) Begin the print, let it do the nozzle wipe, then as it begins the outside test layer, grab the Z axes knob and "click" it clockwise until it quits extruding then pop it back until it does a mashed layer that you know for sure that it is allowing extrusion. Totally easier than messing with Z axes screw adjustment and the like. Way too time consuming. I have had many successful prints between bed leveling and rarely if ever set the Z home position if anything i set it with more than enough clearance then pop it to the best level. HTH!

jsc
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Re: Favorite way to prep your bed surface for printing PLA?

Post by jsc » Thu May 29, 2014 9:56 pm

https://groups.google.com/d/msg/makerge ... yfpC1xjhkJ

Although it looks like "Joshua" got there before me: https://groups.google.com/d/msg/makerge ... -R5En65yEJ (that was before my M2 time).
He provides the additional useful information that each click is about 0.16mm.

Asadinator
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Re: Favorite way to prep your bed surface for printing PLA?

Post by Asadinator » Tue Aug 05, 2014 8:53 am

I still have adhesion problems with painters tape with bed at 70C.

What are the first layer height, extrusion width and z offset you guys use?

I use 0.35mm height and width for 1st layer, z offset 0 with endstop being 0.25mm above bed. No fan for first layer and a speed of 15mm/s.

Also is the infill style important for the first layer?

Asadinator
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Re: Favorite way to prep your bed surface for printing PLA?

Post by Asadinator » Tue Aug 05, 2014 9:16 am

From the comments on here, it looks like my extruder is way too far above the bed. I'll try squishing it.

Also I noticed that black PLA sticks much better than my translucent green PLA. Anyone get those differences between colors?

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willnewton
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Re: Favorite way to prep your bed surface for printing PLA?

Post by willnewton » Tue Aug 05, 2014 2:46 pm

Asadinator wrote:I still have adhesion problems with painters tape with bed at 70C.

What are the first layer height, extrusion width and z offset you guys use?

I use 0.35mm height and width for 1st layer, z offset 0 with endstop being 0.25mm above bed. No fan for first layer and a speed of 15mm/s.

Also is the infill style important for the first layer?
First layer height and z-offset will depend on your machine's bed to nozzle gap. It will be a bit different for everyone depending on how you have your gap set. There are people that set the nozzle flush and then use z-offset to establish the gap, you will probably not need to use that setting unless you set your gap that way. Several folks use what I would call the z-click method, which involves tweaking the z-knob as the perimeter skirt prints and observing the change. I have tried both and they both work. However, my style is making use of the layer height percentages to get good squish/adhesion.

You may find that you may have to make changes between prints as well, if you had a rough time getting an old print of the bed while it is in the machine, it can affect the first layer on the next print

Several folks are using the .40 mm print width, set to manual.

As for height, I do most of my printing at .20mm, but switch to .30mm for fast/large prints, and sometimes
.15mm for fine detailed and small items. You may have to tweak your first layer height percentages as you change layer heights to get good sticking.

I find the translucent PLA prints a bit better at five degrees hotter than normal (220 vs 215). Most of the time I will print the only first layer at 220 and then let it print at 215 for the rest of the print, although running at 220 the whole time is OK, too. Most of my adhesion problems are solved with bed height changes, not temperature changes.
I'm finally back to where I started two days ago!

A thread with some stuff in it I update every once in a while. viewtopic.php?f=8&t=9
See some of my stuff http://www.thingiverse.com/willnewton/about

Asadinator
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Re: Favorite way to prep your bed surface for printing PLA?

Post by Asadinator » Tue Aug 05, 2014 7:03 pm

ok it worked, but too well ahahaha :?

what are good ways to get it unstuck? problem is its quite a wide & short object and hard to pull out.

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