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blackomega

Build plate temperature

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I'm constantly getting problems with my PLA prints failing to stick to the print bed properly.

So far I've tried...

1. The blue tape. Laid down in strips with no gaps and lightly brushed with water to lift the fibres a little. - Found no difference is adhering. In fact I'd say it was actually worse than when I just wash the plate thoroughly in the dish washer and print straight onto it then (after drying of course).

2. Pritstick rubbed over the glass plate and then smoothed out with a wet cloth to leave a uniform thin layer of glue - Works but not good for large prints or very small pieces.

3. Extra hold hair spray - Found little difference to using pritstick

Now I'm thinking of experimenting with heating the build plate to as high as it will go (185 degree - not sure what that translates to at the glass surface though). The theory being to keep the PLA sort of soft and so hope it stick better. I am concerned about how each subsequent layer might affect the one underneath though so I'll need to report back on that.

 

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I assume you have problems only on larger prints.

There are many solutions to warping PLA prints. They all work. The older methods have more drawbacks.

Oldest method: use a raft. This isolates the part from the bed in a flexible bed that can take up some of the bending forces. Leaves ugly scar on the bottom. No one seems to do this anymore except maybe makerbots?

Newer: heated aluminum bed with kapton tape. Works okay - not great. Unless you go the 75C route. At 75C (which you can do on UM2) for PLA the bottom 5mm or so stay *above* the glass temp. This allows the bottom layers to warp every so slightly such that nowhere is the force strong enough to even remotely pull off the bed. The downside is that if you so much as touch it at this level it will leave a fingerprint and the bottom few layers are as soft as clay for a while. Also you get a warping like curved inward corners because the PLA is so soft it acts like a rubber band as it is laid down and pulls inward. Also vertical holes are MUCH smaller than expected in this bottom 5mm or so.

Newer: blue tape - clean the blue tape with isopropyl alcohol. That is critical step. It removes the wax surface that keeps the tape from sticking to itself. The drawback is the bottom isn't as smooth as if you use glass and it's more work as you are always tearing the tape and you have to soak the bottom of parts in a pan of alcohol sometimes for 5 minutes to get the tape off. Larger parts may need thicker tape (150-200mm wide) if the tape is peeling off the bed.

Newest and best: glass with PVA glue. This method is so damn good the glass occasionally breaks off pieces and embeds glass into the bottom of your print. If this method isn't working for you then you are doing something wrong. glue stick, elmers wood glue (my favorite) and hair spray all have some PVA in them. I have tried all 3. All 3 work well for both ABS and PLA. My favorite is Elmers Wood glue mixed with about 10 parts water, 1 part glue in a glass jar, shake well, apply with paint brush, let dry. Actually 50 parts water might be better as I often later squirt with water for the next print and respread with paint brush and the more dilute it gets the stronger it seems to be. It's invisible when dry. Glass needs to be at 40C for parts to stick. 50C is safest temp as it is well above the (suddenly it sticks) temperature and well below the 70C warp-foot temperature.

Other key points:

1) Squish the glue into the tape/glass - your bottom layer should be squished. If not, turn the 3 set screws 1/4 turn until it is flatter than tall. Warm bed (above 40C) helps the plastic flow and make good adhesion. Even for blue tape.

2) Brim! Lots of brim! 10 passes is usually enough. Sometimes not enough. This helps for SEVERAL reasons. One of which is that square corners have all the forces right at the tip of the corner. Rounded corners spread the forces over more area. Also the brim keeps air from getting in and keeps the lifting from getting started.

 

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Or you could get a special 3D-printer build plate.

Example: http://printinz.com/229mm-x-257mm-printer-plate-um2/

Yeah, these are expensive. But you shouldn't have to worry about PLA parts sticking to the plate anymore. At all.

I have a http://mtplus.de/3.html which should have a very similar performance. I've never had a single issue with prints not sticking, or warping, since I installed my plate. I also bought one from PrintInZ, but still didn't get to testing it o.O

In the long run, you might even save money because you don't need any kind of tape or solvent / glue anymore.

 

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Or you could get a special 3D-printer build plate.

Example: http://printinz.com/229mm-x-257mm-printer-plate-um2/

Yeah, these are expensive. But you shouldn't have to worry about PLA parts sticking to the plate anymore. At all.

I have a different plate which should have a very similar performance. I've never had a single issue with prints not sticking, or warping, since I installed my plate. I also bought one from PrintInZ, but still didn't get to testing it o.O

In the long run, you might even save money because you don't need any kind of tape or solvent / glue anymore.

 

Looks good. I've order one and will see how it goes. I always print PLA (or one of its variants at least). Have never done ABS. Seems like it would be even more troublesome and besides the things I build don't really need it. Mind you being able to have a completely smooth and shiny surface would be nice. I've ordered some colorFabb XT which i understand can also be treated with a mild acetone solution to get such a finish so I'll see what that is like too.

 

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I will add two points to George's comments. I use a glass plate on my print bed (it attaches to the 4 corners via magnets) and needs a z-offset of circa 6.9mm). Once cleaned using soapy water followed by a non alcohol rub, I heat the glass on the bed to 60-65c then spray the glass lightly with one coat of extra strength hairspray, wait 20-30 secs and than apply 1 more coat with a light spray, ready to go. I have used this solely for 18 months with PLA and nylon.

Do not forget when using a plate that firstly your bed temp. measure will probably be of the bed not the plate. The plate will probably be 5-10 degrees cooler; e.g. on my printer I set the bed temp. to 75 to get 65 and 68 to get 60c. Secondly, if doing a print with a large base, when the print bed centre hits your desired temp. various perimeter areas can be a lot cooler, 10-15c You need to wait (10 mins?)and check to be sure all of your plate is at the desired bed temp before starting the print.

of lightly sprayeddrers via

 

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Food for thought indeed. I would concur though. Thermographic pictures I took of the build plate (see another thread by me) indeed shows that the temperature range across the build plate is far from uniform even after leaving it for 30 minutes. Not a problem for smaller builds but for larger ones where the edges reach well into the cooler areas are particularly prone to warping.

I'm wonder if it would be worth me looking to see if a redesign of the heating element for the build plate would give better results. At the very least by providing a uniform temperature across the entire plate which can only but help. Something akin to the heating arrangement of say an electric blanket under the metal plate (one that isn't warped in itself) and with copious amounts of Arctic Silver heat paste to fill the transition between the glass and metal.

 

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...

I'm wonder if it would be worth me looking to see if a redesign of the heating element for the build plate would give better results....

 

That can be a difficult task..

You could try adding a copper layer between the heater and the build surface. I doubt that would make a huge difference though.

The first problem is that the build plate's temperature is only measured in one spot. If that spot is near the edge of the plate, it will be hotter in the middle. If the spot is in the center, the edges will be colder.

If you were to make multiple heater segments, each with it's own temperature sensor, then you'd get a much more uniform heating. But that makes things a bit more complicated for the MCU.

What's also very important, is that your build plate is evenly pressed against the heater - with no air gaps in between.

 

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