Question about IR Sensor and Buildtak

okercho

Hi there,

I've installed today the DC42, with a Buildtak black surface, but there are a few things that confuses me.

I know my bed surface is not perfectly leveled (I'm building the machine and I'm doing test), but the reading I'm getting from the IR sensor are odd, example:

What are those isolated green dots in the middle?

Also this picture seems quite disturbing:

The surface, as per the sensor, is a Switzerland mountain! how can that be posible?

Apart from that, I've recorded a couple of video that shows something I don´t fully understand:

https://youtu.be/KlfR5Tt0xLE <- Here we can see the print of the first couple of layers, the sensor should be red over the part and over the bed, however, is only red over the part I'm printing… The material is White PLA that glows in the dark, BTW.

https://youtu.be/vfF4ooJ6wA0 <- Here the print of the same part, but with a higher Z, the sensor now is red (so is detecting) the bed surface and the part all the time (this is what I was expecting)

Did someone used the IR Sensor with a Buildtak surface? I'm having adhesion issues as the detection of the surface is not accurate enough, I saw when the first layer was being printed that the heigh of the layer was not equal, the perimeter closer to Y Axis was "taller" (so the nozzle was farther from the surface) than the opposite perimeter.

Not sure if this can affect, but my printer is a Hypercube CoreXY, and I'm using LEDs illuminating from the top of the printer.

Regards

dc42

I agree, that doesn't look right. Can you confirm that you are using P500 in your G31 command in config.g ?

okercho

Hi @dc42,

This is what I have now in my config.g

[[language]]
; Sensor IR
M558 P1 
G31 P500 Z2.562 
M557 X5:300 Y5:300 S20 ; Define mesh grid

I'm now at work, but I will record a video tonight when I get home. When the mesh is being executed, the bed goes up "fast", then it's being detected and slow down a bit but continues going up (sensor shows 465 in the web), and then when the sensor detects the bed the red light flashes, so I think is the expected behavior…

Here is my entire config.g file: https://www.dropbox.com/s/p7wtm16ykw3pgx9/config.g?dl=0

Thanks!

dc42

Yes, that's expected behaviour. Try measuring the trigger height at a few points, as descibed here https://duet3d.com/wiki/Using_mesh_bed_compensation#Checking_the_trigger_height.

okercho

Will do tonight.

Do you know why those green isolated points? The buildtak surface has a few remains from prints that I couldn't remove, but I don't think there are in that part. What value is the recommended for the mesh spacing? I'm thinking that maybe 20 is too much, and a bigger value will reduce the change of the probe getting the remains and giving wrong readings…

I'm still confused about the bed not being detected during the print, and the apparently random surface map I'm getting... I would expect that if the bed is not flat, if for example the back right screw is more tight, the map will show a flat inclined surface, with the lower side in that zone, but not like if the surface is a old road full of holes xD.

Regards

dc42

When the nozzle is well below the trigger height, the sensor may fail to trigger because there is insufficient reflection into the sensor from the dark surface. So what you are seeing is not unusual.

Whitewolf

I use a black sheet of polycarbonate and what I find is after a lot of prints any remaining filament or slick areas will cause different detection heights and returns a map much like what you are seeing and sometimes even worse (bought a new sensor thinking mine was bad

With mine, i just run some 60 grit sand paper with water on a vibrating sander to clean up the surface again (when PC gets shiny it gets too sticky and parts become difficult to remove instead of just popping off)

I know Fleks3d plates are the same, i do not have experience with Buildtak maybe the same or something similar can be done?

T3P3Tony

Whitewolf do you have a good source of what sticks to PC at what bed temps?

okercho

I saw some videos on Youtube about people sanding (by hand) the surface and cleaning it with alcohol in order to remove the remains of plastic from the surface… I may need to try it, although I'm a bit reluctant as I just installed the buildtak layer and is quite expensive to ruin it after just a few prints xD.

Regards

Whitewolf

@T3P3Tony:

Whitewolf do you have a good source of what sticks to PC at what bed temps?

So my old "expensive" build plate was Fleks3D…. it didnt work to well with the IR sensor because it is clear polycarbonate.

So i oredered a sheet of 3mm black PC and wet sanded with vibrating sander after cutting 4 build plates out of the sheet with my miter saw.

I use 0 degree bed temp on PLA so far with no sticking issues. I suspect PETG and others will be the same.... this stuff sticks way too good if not sanded well.

I am trying to hunt down an extrusion issue but after i will try a bunch of filaments such as flexibles and even hard to stick ones like Acetal POM and Igus iglur

T3P3Tony

Thanks, I shall get some to try.

TwoTone

After reading about Whitewolf's plate I bought some PC from amazon and PETG had really good adhesion. Going to try ABS shortly.

okercho

Whitewolf, are you using something like this, I guess? goo.gl/cXpKY3 (link to Amazon, not sure if it's ok, if not, just let me know and I will remove it).

Just a few questions about it, are you using it as it is, just over your bed surface? how do you attach it to the bed? clamps or double side adhesive? What about heating it? I'm just printing PLA and PETG, but for PETG I usually need to heat the bed to 70 degrees. Anything required to use it? (you mentioned sanding it, but I'm not sure if you sand it to maintain/remove the remains, or you had to do it in order to get good adhesion)

I'm really interested, as it's cheaper than buildtak (15Eur 3mm sheet) and seems to be more durable… What color should be the best for the IR Sensor? Those guys sells it in transparent, white, gray, black...

Regards

Edited: I just noticed that the link I've posted is for Acrylic plastic and not for Policarbonate... so I've changed the link

Whitewolf

this is the one i bought it is 1/8th inch thick black polycarbonate… this made 4 build plates (cut it with a miter saw) because i have an 8 inch bed... you will want to order one that works for your bed size
https://www.amazon.com/gp/aw/d/B01GQHA6UE/ref=mp_s_a_1_1?ie=UTF8&qid=1499104613&sr=8-1π=AC_SX236_SY340_QL65&keywords=black+polycarbonate+sheet&dpPl=1&dpID=31L6FAiwLZL&ref=plSrch

You need to sand it with 60 grit vibrating sander… keep it wet while you do for better results. If you dont sand it, it will be very difficult to get prints off. every now and the the surface starts to smooth out and parts dont just pop off. I sand it again when this happens.

Do not use your bed heater with it, it is not needed and the surface will stay flatter if you dont.

Dont use adhesive, i use large clips to hold it flat to the bed... the idea is it is removable and you can flex it in different directions to get the parts to pop off (only needed on parts that stick real good, most of the time a scraper or just twisting the part will pop it off

Whitewolf

Here is a 40mm cube with 0 top layers and 0 bottom layers and 1 perimeter. The first layer was printed at 32 mm/s and the rest at 64 mm/s

It was printed without a bed heater and without a part blower/cooler

As you can see bed adhesion is really good on polycarbonate.

TwoTone

@okercho:

Whitewolf, are you using something like this, I guess? goo.gl/cXpKY3 (link to Amazon, not sure if it's ok, if not, just let me know and I will remove it).

Just a few questions about it, are you using it as it is, just over your bed surface? how do you attach it to the bed? clamps or double side adhesive? What about heating it? I'm just printing PLA and PETG, but for PETG I usually need to heat the bed to 70 degrees. Anything required to use it? (you mentioned sanding it, but I'm not sure if you sand it to maintain/remove the remains, or you had to do it in order to get good adhesion)

I'm really interested, as it's cheaper than buildtak (15Eur 3mm sheet) and seems to be more durable… What color should be the best for the IR Sensor? Those guys sells it in transparent, white, gray, black...

Regards

Edited: I just noticed that the link I've posted is for Acrylic plastic and not for Policarbonate... so I've changed the link

I'm using the black on my Rostock Max with IR probe. I bought the same sheet he linked.
I used 1400 grit paper on it. What you see is done by hand. Wanted to test before putting to much time into it. I'll go back over it with a small orbital sander to get a better final finish, but it's not needed.

Whitewolf

Here is from the inside so you can see there were no bottom layers… No rafts, no glue, no tape no fuss, just print and forget the rest

Whitewolf

@TwoTone:

@okercho:

Whitewolf, are you using something like this, I guess? goo.gl/cXpKY3 (link to Amazon, not sure if it's ok, if not, just let me know and I will remove it).

Just a few questions about it, are you using it as it is, just over your bed surface? how do you attach it to the bed? clamps or double side adhesive? What about heating it? I'm just printing PLA and PETG, but for PETG I usually need to heat the bed to 70 degrees. Anything required to use it? (you mentioned sanding it, but I'm not sure if you sand it to maintain/remove the remains, or you had to do it in order to get good adhesion)

I'm really interested, as it's cheaper than buildtak (15Eur 3mm sheet) and seems to be more durable… What color should be the best for the IR Sensor? Those guys sells it in transparent, white, gray, black...

Regards

Edited: I just noticed that the link I've posted is for Acrylic plastic and not for Policarbonate... so I've changed the link

I'm using the black on my Rostock Max with IR probe. I bought the same sheet he linked.
I used 1400 grit paper on it. What you see is done by hand. Wanted to test before putting to much time into it. I'll go back over it with a small orbital sander to get a better final finish, but it's not needed.

http://i381.photobucket.com/albums/oo254/TheOriginalTwoTone/20170701_152934.jpg

I actually found parts to stick too well especially if you find yourself needing to remove before the print is large enough to pop off. that is why i use the 60 grit.

I started with 120 grit by hand and it gripped too well. The Fleks3d plate that i own is very rough not smooth for the same purpose. Also the bottom surface of the printed part looks nicer when you cannot see individual scrratches which are visible in a lightly sanded version

TwoTone

I can confirm ABS sticks no heat.

Whitewolf

Yeah, it stuck to the Flesk3d no problem… just wasnt sure without the fancy sand blasted surface good to hear cause this is a lot cheaper to have multiple plates on hand.

I will be testing all of Taulman series as well as some Igus Iglur and Acetal POM filaments which are considered by many impossible to print.... we'll see I have a couple rolls sitting on my desk waiting for their turn on the printer.