Heated bed just not actually being as hot as reported...

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eagle1xray
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Joined: Sun Dec 18, 2016 8:48 pm

Heated bed just not actually being as hot as reported...

Postby eagle1xray » Wed Mar 15, 2017 10:04 pm

So i been printing with Nylon and ASA, running temps around 260-270c on the nozzle and 110c heated beds....well i cant get anything to really stick....hairspray, Xtreme Gluestick you name it....and so i took my laser temp gun...and discovered...im hitting only 89-9Xc on the actual glass (or the buildtak side either way) my bed is FAIRLY leveled not perfect but its as close as i think its gonna get with the way its setup...so what gives? the temp probe SAYS 110c but the actual glass is not that at all....

What do we need to do to get this right as i feel its been wrecking my life honestly...lol

Thanks!

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Wed Mar 15, 2017 10:25 pm

#1 False assumption your laser temp gun is accurate on the glass surface without adjusting for emissivity of the surface.
#2 False assumption on your part that the glass bed should read the same temp as the actual heater of the heated bed. There is not a single consumer printer brand on the market that does this. If the temp probe measured the glass, glass is an insulator or poor conductor. That means by the time the glass reached the desired temp, the heater mass would now be hotter than the glass and continue heating long after the heater shut off creating overshoot. You always put PID feedback on the fastest possible loop to the heat source.
#3 Assumption that the bed temp you see listed in filament literature is the actual bed temp required on the surface. They know the rules above and list the target temp of the heater setting knowing full well the actual could be 10,15, even 20C lower.

Jetguy
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Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Wed Mar 15, 2017 10:32 pm

Again, #1 use a contact probe and measure the metal heating surface. The glass is an insulator and cooled on one side by the ambient air. Being an insulator- of course there will be a difference between the side contacting the heater plate and the side facing the air. You generally cannot get a reliable reading from a non-contact probe unless you have already taken a real contact probe measure the real temp, measured the non-contact reported temp, and adjusted emissivity to match and be accurate. And then, that only works on that surface.

#2 So, you set the bed target temp higher to compensate for the known temperature differential- however, there are limits in the software and firmware and may require custom firmware to run higher temps.

Jetguy
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Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Wed Mar 15, 2017 10:45 pm

And this doesn't inspire confidence, "my bed is FAIRLY leveled not perfect but its as close as i think its gonna get with the way its setup"

It's either right or it isn't and if the first layer gap is not right- then no, it's not going to stick regardless of surface prep or temperature.

So, first, let's actually see what you are trying to print. share a picture or STL of the object and resulting test print. If it's some large object over about 4 inches and you are printing nylon with high shrinkage, have a less than ideal leveled bed- nope- I wouldn't expect that to stick before I ever started. The larger the object, the greater the shrinkage. Also realize, just like metal expands when heated- so does plastic. So the hotter you extrude, the more that plastic is expanded and the more it's going to shrink as it solidifies. That puts a shear load on the bond to the bed and the bond between each layer. At some point, with both size and other factors, no fix will prevent warping and other problems as it's a function of the material.

Jetguy
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Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Wed Mar 15, 2017 11:22 pm

Just some notes since I had not ever used ASA filament
http://www.3dxtech.com/red-asa-filament/
Extruder Temp: 235 - 255°C
Bed Temp: 90-110°C, cool the bed down by about 10-20°C after the first couple of layers
Bed Prep: 3DXTech Polyimide Tape, ABS / Acetone Slurry, or Hairspray on clean glass

For iOn Nylon, they say this
Extruder: 240-270°C (ideal layer bonding at 260-270°C), or even hotter if you have an all-metal hot-end. However, do not exceed 300°C to avoid the onset of polymer degradation. Please note: that if you have layer bonding issues, this is a typical sign that you need to use higher extruder temps.
Bed Temp: 100-110°C. This Nylon alloy has a Tg of 105°C, which is higher than most competitive nylons on the market. Therefore, our bed temp recommendations may be higher than what you're accustomed to when printing with other nylons.
Bed Prep: Ideally use Polyimide Tape & ABS/Acetone Slurry [together] or any surface you've been using with nylon-based filaments. Please note that acetone has difficulty dissolving iOn™ and standard ABS should be used to make the slurry.

Now personally, I find this a misleading statement to newcomers to 3D printing
Suitable for use on practically ANY desktop 3D Printer that has a heated bed, including Airwolf, Ultimaker, Makerbot, Makergear, Prinrbot, Reprap, Mendel, Prusa, Up! Printers, Solidoodle as well as many more.

There are so many not said things there, it's just downright misleading. Just because it has a heated bed- and many of those listed should not be pushed to 260-270C with a PTFE lined hotend (not that that matters for the N series as we do have all metal). My point is, they make it sound like it's easy to print when right off the bat- they say they want hotter bed temps than many printers can reliably reach.

Jetguy
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Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Wed Mar 15, 2017 11:43 pm

Just to show you I am searching for nylon print results and what other people did and used so that maybe you can print this.
viewtopic.php?f=6&t=1198&p=10885&hilit=nylon#p10885

This is a copy/paste from that page of suggestions for various filaments:
Nylon PA 6 240°C - 280°C

Can't be printed on glass.
Print on cardboard to prevent warping. Best results achieved on Garolite. Other/cheaper alternatives include poplar wood or PVA/UHU Glue.
Set your print bed temperature to approximately 120°C. (This may vary depending on your print surface)
If foam comes out of the nozzle, the material has to be dried at ~ 148°C for 3-4 hours.
Overfilling the part will make a gooey mess.

Here is a search on ASA and a few people have printed with it viewtopic.php?f=5&t=810&p=7698&hilit=asa#p7698
Most are advising treat like ABS, ensure the vent covers are on the extruder cooling fans to restrict air blowing at the layer, most are using ABS slurry or some other material on the glass side of the bed. At no point has anyone made any changes to the bed that I saw to compensate for the measured difference you have cited in temp.

Jetguy
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Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Wed Mar 15, 2017 11:58 pm

ABS printing tips from a totally different group (ABS and ASA are very close in recommendations)
https://groups.google.com/d/msg/flashfo ... WK0NoIHkEJ
I print ABS only, you have to have all the enclosures on to get a good print.

I print ABS onto Kapton only with no adhesive at all and don't get any issues with warping no matter how large an object I print.

The recipe for good ABS is:

1. Make sure your bed is very very well leveled, and that the gap between the nozzle and the bed is consistently 0.05mm in all parts of the bed.
2. Make sure your Kapton is absolutely squeaky clean, even the slightest trace of finger grease will ruin a print. Clean the bed with rubbing alcohol before each print.
3. Use a bed temp of 110c
4. I print at 235c
5. Preheat for 15mins.
6. Print at about 50mm/s ABS is more viscous than PLA so you have to run slower. You can print faster on larger parts.
7. Make sure your machine is fully enclosed, the secret to good ABS is having a warm space inside the printer. The combination of preheating and heat radiating and convecting off the bed will help get the temperature inside the machine to 50-55c. This seems to make ABS printing more reliable.

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Thu Mar 16, 2017 12:10 am

Here are 2 links from experts that back up the bed surface does not match the reported temp in most printers.
https://groups.google.com/d/msg/flashfo ... 7X1_7uzxMJ
This one is from Ryan Carlisle
Flash Forge gives bad advice about build plate temps. They seem to just copy the Makerbot recommendation without considering the hardware differences.

I find that 90-95C is the optimal surface temp for printing ABS, objectively measured by contact thermocouple taped to the Kapton. This temperature is far enough below the glass point of ABS of 105C that the print stays solid, but still just slightly in the "creep relaxation" range where thermal contraction stresses can somewhat dissipate over time. Remember that range: 90-95C for ABS. You can't let the print actually get over 100C: if the temp is up around the glass point, the plastic is NOT a solid, and it's going to warp inward as the upper layers cool and contract, pulling in the lower layers.

Now, it's important to realize that the HBP thermistor is NOT measuring surface temp. And it is NOT necessarily calibrated to any objective standard. The Makerbot R2x stock build plate surface consistently runs 20C cooler than the measured temp. Which means 110-115C is the correct setpoint for a Makerbot R2x build plate. It is NOT the correct temp for a Flash Forge build plate. Not the newer ones, anyway -- lots of people on this forum have had heat-warping caused by running their FF HBP at 110C.

On the other hand, my Bottleworks HBP manages to maintain measured temp = surface temp, as long as I give it some preheating time. So I set my BW HBP to 95C and my R2x stock HBP to 115C and get identical results. It all comes down to the measurement error specific to the build plate.

I don't know what the offset is on the FF HBP, because I don't have one. But running it at 110C is definitely too hot. That is a good figure for the stock R2x plate, and it might be a good figure for some other build plates, but it's wrong for a lot of people here on the FF forums.

Also note that the glass point of HIPS is only 95C. So printing in HIPS actually requires HBP temps about 10C cooler than ABS. And PLA has a glass point of ~60C, so it requires surface temp of 50C or less. T-glase and nylon have glass points around 75-80C, so you would want the HBP temp below 60-65C for them.

There's some science behind the proper settings. You just need to understand the basic physics of the system. HBP temp should be as high as you can get it WITHOUT the plastic getting too close to the glass point.

This thread shows that a PEI sheet- not all that different from having a layer of buildtack on the glass and this test is a thicker sheet. https://groups.google.com/forum/#!searc ... m_R7HNwcgJ

Jetguy
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Joined: Tue Mar 22, 2016 1:40 am

Re: Heated bed just not actually being as hot as reported...

Postby Jetguy » Thu Mar 16, 2017 12:13 am

Here is a related thread to show both the firmware max bed temp (120c and I think the LCD interface also enforces this) viewtopic.php?f=4&t=289&p=2834&hilit=maximum+heated+bed+temp#p2834


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