Prusa ok to not do the heated bed initially?

I'm at the early stages of a Prusa Mendel build. My thinking is to keep it simple & leave off the heated bed, maybe adding it later as needed. Understood that restricts me to PLA filament, no problem with that at present.

Is my plan reasonable , or a mistake?
Is adding the heated bed later if needed 'straightforward' ?


Thanks in advance.


Mike

Sounds like you have it correct. I only print with PLA and do not have a heated bed.

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Adding the heated bed should be straightforward. Mechanically, it's just a replacement for the unheated bed. Electrically depends on what your are using for a controller. It's not any harder than wiring in an extruder if your electronics supports it.

PLA only and no heated bed and it's glorious. Dealing with ABS is an almighty pain in the neck! A heated bed will (can, may, might) help with corners pulling up, but it will not help with individual layers pulling away from one another. And forget trying to print anything really big; even on my old Thing-O-Matic with a very nice HBP, large ABS prints were nearly impossible to keep together because the layers would start peeling away from one another.

Im using PLA without a heated bed and make going looking forward to getting one.
Once i do, i plan on doing some comparison prints.
I find that if i can get to 5 layers in, the print stays pretty much intact.
The problem is that larger prints take too long to get to 5 layers and everything cools and once reheated by the second layer, it begins to pull up.
I feel certain i can get everything to stick by heating the surface.
I have used a desk lamp to heat the bed before a print and it was pretty well stuck.
But wiping everything down with alcohol makes a difference too.
Im on kapton, tried blue tape but didnt like the texture it left on the bottom of the print.
Kapton, if applied with care, leaves no texture. Flawless. mostly...
My advice, stick with what you can afford and what your capable of.
PLA is easy. So easy but every print leaves something new to think about.
I have narrowed down over the past few months to a cool print surface as my biggest enemy.
Small things print great. Check this out:
space shuttle
The top of the shuttle had no warp. Small, compact base all the way up so no problem.
The bottom of the shuttle, the middle fuselage was the problem.
The wings wouldnt stay down. but i wouldnt give up.
I cleaned everything. Leveled everything. Slowed the first layer to half speed.
Didnt work. So i finally taped the wings down with 6mm wide kapton on the 3-4 layer, about a half cm from the tip.
help a bit and the kapton pulled right out, didnt leave a trace.
There was still warp. but limited to maybe 2mm off the surface, vs 6-8 mm off, ill take it.
But that leads me to the point, no need to heat your bed.
for good prints with out heated bed or raft, one must:

1. Level the print surface to the nozzle from time to time (3-5 prints depending on the size.) Do this by bringing the nozzle as close to the top right corner on the print bed. From there move it about the X/Y axes and make sure there is no more than .5mm or smaller elevation. closer the better stuck your prints ill be but not so close you first layer squishes out the sides of the nozzle.
2. Clean everything. Alcohol in a spray bottle and a clean rag or paper towel, dries fast and the stick is good.
3. Temps are crucial. Odds are your nozzle isnt what the thermistor is reporting. Use a thermocouple on a dmm or just tweak the temps up and down, and print something that has a hole in the side that it has to cross. Search thingiverse for calibration items. Or, for me, pronterface and skienforge couldnt decide who had control of the temp. I set it in pronterface to heat it up and no matter what skien told it, it stayed there. found 190 as my temp for most colors of pla.
4. Be patient. This is cutting edge we are doing here. Its a freakin 3d printer!
Whew.
thats all for now.
Good prints to all.
-Erik

@420e
Are you sure your first layer simply isn't smooshed down far enough? I find that if I can get the nozzle at just the right distance from the build surface, it will jam the molten PLA down such that the model will adhere very well but be easily possible to remove afterwards. Of course, any closer and you can get that first layer to adhere so well that it's almost impossible to get off! I've really never had any problems with a PLA print—no matter the size—prematurely coming of of the bed that wasn't caused by the nozzle being too high.

To give you a sense of what's possible, I printed my 8" Star Destroyer model in silver PLA straight on blue tape and it stuck like its life depended on it. Each half was printed on the bed, so there was a huge surface area on the bottom layers. But they stuck anyway.

@Topicstarter, 3D2B

If you're short on cash and/or don't feel confident about making your own nichrome heated bed, sure you can leave it out.

When I started out I thought the same as you, but after I hacked a nichrome heated bed together I absolutely adore it, and wish I had done it sooner. Personally I find printing PLA on heated glass @50C, to be the most effortless and consistent method to avoiding warping. Your mileage may vary, and there's no denying a lot of people have great success printing PLA without a heated bed, just thought I'd chime in from my perspective.

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-Nudel
Blog with RepRap Comic

I have also found that you need a heated bed even for PLA.
Certain objects (depending on the fill) and large objects need a heated bed.
I intend to put up some pictures of the same objects with and without the heated bed.
And yes printing PLA on glass is super, using a 0,9mm GFK plate is even better!!

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Pointedstick Wrote:
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> PLA only and no heated bed and it's glorious.
> Dealing with ABS is an almighty pain in the neck!
> A heated bed will (can, may, might) help with
> corners pulling up, but it will not help with
> individual layers pulling away from one another.
> And forget trying to print anything really big;
> even on my old Thing-O-Matic with a very nice HBP,
> large ABS prints were nearly impossible to keep
> together because the layers would start peeling
> away from one another.

Interesting. I've printed parts that were the full diagonal length of my Prusa's table, in ABS. I've never had layers separate due to warping. Lifted corners yes, delamination, no. Not even when I was first learning to calibrate.

Dale Dunn Wrote:
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> Interesting. I've printed parts that were the full
> diagonal length of my Prusa's table, in ABS. I've
> never had layers separate due to warping. Lifted
> corners yes, delamination, no. Not even when I was
> first learning to calibrate.


In the end, I figured out that this was caused by air currents cooling the upper layers while the lower ones were being heated, resulting in thermal stresses. Turning off my A/C unit and closing the windows helped, and completely enclosing the build area got rid of most of this problem, but it was a pain in the neck and didn't totally eliminate it. Printing nicely and reliably with ABS is definitely possible, but I've definitely found it to be not worth the hassle if you don't need the extra thermal resistance that ABS provides the finished part.