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#1 Hook

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Posted 20 July 2019 - 07:02 AM

Seeing as so many of you do 3d printing, I thought this question may be best asked here.

 

I checked how flat my bed was on the ender3 pro, without mat. It seems it is not that flat......ocean waves come to mind, but that would be exaggerating it.

 

Do you think getting a piece of glass cut to size would help? how flat is glass? or does standard glass have natural waves, (not visible without checking with a steel rule). Just trying to eliminate uneven beds.

 

Cheers



#2 iwannabswiss

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Posted 20 July 2019 - 07:51 AM

I definitely recommend using a piece of glass; my prints have turned out great since adding one, but I mainly print in ABS, and it has made the first layer go down super easy.  I also feel the glass is very flat, which has resulted in high consistency in each layer printed and the base of the part I peel off is literally glass smooth.  However, you do not want to use standard glass, if anything, it should be borosilicate glass.  Also, I would recommend that you get a sheet of silicone to go in between the bed and glass.  These are what I purchased and use; glass and silicone.  They are held down to the bed with binder clips on the four corners.


Edited by iwannabswiss, 20 July 2019 - 08:20 AM.

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#3 brave_ulysses

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Posted 20 July 2019 - 09:00 AM

both my borosilicate plates chipped when removing petg. took some time for it to happen and could likely have been mitigated with blue builders tape (was using elmers glue stick)

 

now, i use a ~5mm aluminum plate. many controllers have levelling routines to account for plate tilt and irregular surface


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#4 gr5org

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Posted 20 July 2019 - 09:40 AM

I have 5 Ultimaker printers - they all use tempered glass which is thicker in the middle and which sucks.  I would recommend ordinary glass.  You don't need borosilicate which has a lower thermal expansion.  Instead just make sure the glass is held by binder clips or something that lets the glass expand and contract.

 

The only advantage of tempered glass is that it is safer - when it does break it shatters into thousands of not-very-sharp pieces.

 

Normal plate glass is very very flat.  But bends easily if the substrate is not flat.  Also normal plate glass is incredibly cheap.  Your local glass cutter will cut it very accurately and grind the edges smooth.  Just get it very thick.  Ultimaker uses 4mm thick glass.  Typical window glass is too thin.  It should be fine to use mirror glass.

 

But then you also want to heat it.  plastic doesn't stick great to cold aluminum or cold glass so you should cover the glass with blue painters tape if you don't have a heater.


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#5 Sean Wood

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Posted 20 July 2019 - 12:15 PM

The issues with glass on a printer with a moving bed is that you're adding mass to the bed. More mass more stresses caused by the machine having to overcome the effects of inertia. You'll have to print slower to overcome artifacts in the print surface, especially on taller parts. If you do decide to go the glass bed route tempered borosilicate glass is the best option but IF you dont' have access to that go with a mirrored tile over a plain glass sheet. The tolerances for glass used on a mirror mean it will be flatter.


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#6 gr5org

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Posted 20 July 2019 - 02:36 PM

You don't have to lower the speed so much as lower the acceleration and possibly the jerk setting. 

 

I forgot about this as my printer has an X/Y head and the bed just goes up and down.


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#7 iwannabswiss

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Posted 20 July 2019 - 05:12 PM

both my borosilicate plates chipped when removing petg. took some time for it to happen and could likely have been mitigated with blue builders tape (was using elmers glue stick)

 

now, i use a ~5mm aluminum plate. many controllers have levelling routines to account for plate tilt and irregular surface

When I used PETG, I used blue painters tape, and the parts still stuck super well but luckily didn't ruin the glass.


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#8 scottsdalejohn

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Posted 20 July 2019 - 07:36 PM

FWIW, I have been printing PETG on window glass for about a year with no problem.  Prior to that I used 2 inch wide masking tape, but after a few years I got tired of replacing the tape after every few prints.  I give the glass a light spray of Aqua net hair spray before I turn on the printer. By the time the bed is warmed up the hair spray has dried and provides additional "stick."  The parts pop off with a gentle nudge of a narrow putty knife on one of the edges. It did take a few prints to get the glass "seasoned" but after that I have never had a problem with the part not sticking or curling on the edges which was a issue I always had when I was using masking tape.  Window glass is easily found at any of the large box hardware stores and they will generally cut a larger size down for free if they do not have the size you need.  I hold the glass to the bed with 4 small binder clips that I had around the house.


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#9 Hook

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Posted 21 July 2019 - 03:46 AM

I have a question on using a mirror. Would the silver foil backing reflect the heat from the bed? or would it cause the heat to drift toward the edges? I have a heated bed btw. 

 

Forget about borosilicate glass......never going to get that here, especially in such a small size.

 

My only option is standard glass or a mirror.

 

Thanks for the answers so far.......appreciated.



#10 gr5org

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Posted 21 July 2019 - 07:49 AM

The mirror coating shouldn't make any difference.  The back side of most mirrors is dull so it will make no difference there.  The side touching the glass is reflective and means it won't radiate as much (the glass blocks infra red anyway so it makes no difference).  It should make no difference.

 

The heat conductivity should help to spread the heat ever so slightly and make things more uniform but it's too thin to make much difference.


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#11 Zwick

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Posted 21 July 2019 - 04:09 PM

I print PETG on blue painters tape, over the glass plate. I use binder clips as described by others to clamp the glass plate to the bed, but I clamp at only three corners. Glass will flex a bit and this "tripod" approach helps insure a flatter surface. I also use a small strip of paper as a shim at each clamping point, just to help insure that these are the primary contact points.


Edited by Zwick, 21 July 2019 - 04:15 PM.


#12 robertasumendi

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Posted 22 July 2019 - 03:34 AM

Buildtak Flexplate system allows you to swap print surfaces depending on the filament. I like garolite from Matterhackers, which works on a lot of filaments but particularly nylon.

 

The flexplate system glues to the existing printbed so it provides a flat surface without requiring a perfectly flat surface to adhere to.

 

Robert


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#13 Hook

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Posted 22 July 2019 - 07:51 AM

I got borosilicate glass. The creality shop on aliexpress sells a bed of 3mm borosilicate glass specifically for my machine, 14euro free shipping. Feedback showed it was extremely well packaged.........bomb proof one buyer called it! So that got that sorted. I have a heated bed so no need for adding anything on top.

 

I think I am getting addicted to 3d printing  lol.gif


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#14 brave_ulysses

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Posted 22 July 2019 - 09:51 AM

i had an ac powered silicone heater on my borosilicate bed and it still chipped. strongly recommending blue painters' tape here...

 

good luck

 

ps: as an aside, i had the "bright" idea to put a thermistor right in the middle of the plate (didn't want to use the included thermistor on the back side of the heater). the extra heat from the plastic caused huge fluctuations in the reported bed temp to the controller. now, i use the included thermistor on the back of the heater and let it warm up a little longer

Attached Thumbnails

  • print_bed.jpg

Edited by brave_ulysses, 22 July 2019 - 09:57 AM.


#15 Hook

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Posted 22 July 2019 - 10:58 AM

i had an ac powered silicone heater on my borosilicate bed and it still chipped. strongly recommending blue painters' tape here...

 

good luck

 

ps: as an aside, i had the "bright" idea to put a thermistor right in the middle of the plate (didn't want to use the included thermistor on the back side of the heater). the extra heat from the plastic caused huge fluctuations in the reported bed temp to the controller. now, i use the included thermistor on the back of the heater and let it warm up a little longer

The glass will be sitting on the heated metal bed which has a silicon sheet on top of that. The original top layer to print on was a magnetic flexible sheet, which the glass is to replace.



#16 darkapollo

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Posted 22 July 2019 - 03:02 PM

Seeing as so many of you do 3d printing, I thought this question may be best asked here.

 

I checked how flat my bed was on the ender3 pro, without mat. It seems it is not that flat......ocean waves come to mind, but that would be exaggerating it.

 

Do you think getting a piece of glass cut to size would help? how flat is glass? or does standard glass have natural waves, (not visible without checking with a steel rule). Just trying to eliminate uneven beds.

 

Cheers

Creality has a well earned reputation for their Dolly Parton Flat glass. My CR10's had a 3mm bow. Two HUGE spring binders fixed it for a while (flip it high side up and used the binders to draw it flat) but that got old so I bought some PEI sheet. 

If you want flat get a mirror. Seriously. You can get a cheap 6 pack of 12x12 mirrors for $5. Mirrors are going to be a lot flatter than window glass. 


Edited by darkapollo, 22 July 2019 - 03:03 PM.


#17 Sean Wood

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Posted 23 July 2019 - 12:42 PM

Here is some good info about heated bed surfaces and what bed is "best"

https://youtu.be/yPy0zDpmc5U



#18 Hook

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Posted 24 July 2019 - 04:57 AM

Here is some good info about heated bed surfaces and what bed is "best"

https://youtu.be/yPy0zDpmc5U

Heating up is not the issue, my bed heats up quick and is near spot on with the reading the lcd gives.......ender3 pro. It is flatness I was more concerned with. I did watch the video, even though he tended to ramble on a bit. The part I found most concerning is the heat on all beds is not evenly dispersed.......and with todays technology you would have thought that they could get the heat even all over.

 

The problem most people have is heating the bed initially then switching it off after a few layers are down. I leave mine on and let it cool down after print is finished. It's ok with a few small prints to switch off after pla sticks, but even those small prints curl up........very minutely.

 

I am in the process of building an enclosure for my ender, which will keep the heat in, as I want to upgrade the hotend and nozzle to allow other materials to be used. I am pretty sure the glass will perform well, even though it does not perform as well as aluminium.



#19 gr5org

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Posted 24 July 2019 - 09:27 AM

The "cold spots" that the camera is showing are probably less than 1C cooler.  You can have 5C cooler spots and be fine.  PLA gets soft at 52C.  The bed temp of 60C is designed to be above that temperature.  If the bed is at 59C or 57C it won't make much difference.

 

The idea is that being above the softening temp of PLA when the upper layers cool they pull inward and lift up the corners of your part.  All the stress is on the tiny spot on the corner.  If you have the part *above* the softening temp, PLA acts like clay and the part warps (too small to notice - talking very very tiny amounts) and that spreads the forces out more and the part sticks to the bed.

 

So instead of all the force on 1mm square of plastic - it's spreads out over a few square cm.



#20 gr5org

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Posted 24 July 2019 - 09:28 AM

I have a similar camera and it EASILY detects handprints that are only 0.1C warmer than the surrounding.  They are extremely sensitive and constantly recalibrating based on the temperatures in the field of view of the camera.



#21 Hook

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Posted 24 July 2019 - 11:37 AM

I use my laser temp gun to test the bed. Everything is ok, 1 or 2 degrees difference is all. No problem with heat anyhows, everything sticks, very rarely get curl-up.




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