ABS print sticks nicely to tape... the tape? Not so much.

Hello folks,

Has anyone had any issues with the Kapton tape sticking so well and the part warping so hard that it is lifing the tape from the bed? Any ideas on how to limit warping in this instance? I'm guessing that the HBP is softening the glue on the Kapton tape enough that it can pull away from the glass surface. I've tried lowering the bed temp, but then I have other ahesion issues.

I'm a total newb, tinkerer, and all around inexperienced with this whole 3d printing thing. About two years ago I built a gantry CNC machine all with the plan of retrofitting it into a 3d printer. I spent the last couple of years building an extruder (modifed Wades cut from 1/4" thick HDPE on the CNC), hot-end, purchasing a HBP, added an "A" axis for the extruder (aka. E axis for the CNC), etc...

The goal is to use this machine to print up parts for a standalone printer. I'm looking at the Rostock or some variant thereof. I designed and built my own Nozzle and HBP temperature controller based on an ATMega328p, some MOSFETs, MAX31855-KASA based thermocouple circuit (also built by me). Once I got the software nailed down, the controller is working very well and keeps the temps pretty solid.

The hardest part of the whole process so far was getting a proper hobbed bolt made. After about 8-10 ruined 8mm bolts, I finally got made one that will reliably feed the 3mm ABS filament I'm using. I've been able to print some pretty complicated things without any extruder jams or other hiccups.

I've researched and tried all the various HBP surface preparation techniques and finally settled on inexpensive 3mm(3/32") window glass from Home Depot. This is placed over the rather large 8 1/2" x 12 1/4" PCB bed heater. I'm using a dedicated 12v 30A supply for the bed and nozzle. On top of the glass I have covered it with 200mm wide kapton tape using the "wet method". I then skim the surface with an ABS slurry. Needless to say, the part being printed sticks to the tape/slurry surface very well... It also comes off nicely when cooled. So I really have no complaints at all using this technique.

Now for the problem... The kapton tape itself will begin to lift from the glass or form bubbles (I've actively dried the tape and left it overnight). In other words, the edges are still lifting, but they're taking the tape along with it! I've not seen or read about this happening anyplace I've looked. I've degreased the glass surface with everything from acetone, to ammonia based glass cleaner, to simple soap and water. I wear nitrile gloves while handling the glass so no finger oils contaminate the surface. Before the print there are no bubbles under the tape and it is very difficult to peel up cold. I'm tried printing with the HBP set to between 100C to 120C. I've reduced the temp to 100C after the first couple of layers. I'm printing with a wide brim, but it will still warp on taller prints (1.5-2cm+ high). Due to the construction of the gantry CNC there is some wobble, but is livable.

Sorry for the long winded post, but I wanted to make sure I've laid out exactly what I'm seeing and what I've done to correct the the problem. This is so that I can focus on things I've not tried, since I've done nearly all the "usual things" based on what I've been able to find. Is this a common issue or have I missed something?

Thanks,
Kylix.

"yes" and "yes and no".
That would be the short version for your first two questions.


Now, to elaborate.
Yes.
I've exprienced all you mentioned in your post.
And I suppose this apply for many of us.


How to find an all mighty solution...this is another issue.
There are many aspects and tons of discussions on forums but I believe few have made real scientific and systematic tests, trials and...so on.

I'll just point out some issues and my solution, if I found one.


Yes, I also have bubbles from time to time when I lift the printed part.
Solution:
-regarding the bubbles, first of all, i'm getting rid of them by making a tiny puncture in the Kapton and then squeeze the air out. This works, most of the time. And, the more prints I print on the same Kapton, the more bubbles I get. My believe is that the Kapton material handles heat far better then the sticky part of the capton
- regarding the bubble creation, they might appear during the print or at the object removal. For the first part, the solution is more complex and it is related mainly to ABS shrinkage. For the last part, remove the parts when the bed has cooled down, this will allow further shrinkage on the ABS part.



Yes, I also have troubles sometime lifting the parts from the bed (and creating bubbles)
Solution: as mentioned above, I believe it has to do with the aging of the Kapton's sticky part. So, change Kapton more often. Or glue it "wet only" without soap (this is a guess, I'm not 100% sure it'll work). Also, fine-tune the amount of ABS in the slurry.



I had incredible positive results on Hairspray on Glass.
Parts just pop-unstick at about 80-90 degrees.
But, it works only on small parts and it depends on other factors such: cold/ hot hairspray drying, how many prints on the same layer of hairspray...and many others.


Also, quite positive results on GlueStick on BlueTape.
But, same fiasco on big parts.


Another general solution is avoid part tension by design change. Break the tension by adding holes and bridges and stuff. (there's a video on Youtube, watch it, it's very educative and I tend to support his conclusion. )
https://www.youtube.com/watch?v=YhfrHo53K18


Also, there are some "magic" solutions on the market but .. I haven't tried them:
- some magic surfaces that resist better than Kapton but don't require slurry
- some magic glasses that... they say ABS sticks like crazy. Hm...
- NinjaFlex mat, sticks like crazy and you can bend it and ABS pops off.


My next "magic" solution will be an enclosure and... 50-60 degrees C inside.
I hope that will improve this issue with bubbled, first layer sticking, delamination and... all other related.


So, keep on tuning :-)
There is no single solution...that will work forever and regardless of the size and shape of your part.

alexella,

Thanks for the response! If I'm following what you're saying, this is, in fact, a common problem that many people encounter. That is odd since I find that most discussions are about getting the part to stick to the Kapton itself and not about keeping the Kapton sticking to the glass. Maybe because that is far and away the most common issue, whereas the bubbling and peeling of the Kapton tape itself is less likely on smaller prints?

I'm in the process of printing up the parts for a Rostock delta printer, some of which are fairly large like the motor mounts. While many folks tend to stick with PLA, I chose ABS because of it's durability and is less brittle. I also haven't yet got active cooling installed, which as I understand it, is required.

I did watch the youtube video you mentioned and that guy's approach is interesting. I will need to get a little more proficient in SCAD in order to tweak the part designs to incorporate the stress relief holes. There was also another thread on this forum that said extruding at really high temps worked as well. I've beed extruding at 256C recently moved down to a bed temp of 85C. Initial layer adhesion is still pretty good, but it's still warping as the part grows and is pulling up the Kapton still. I'm a little learly of going too much higher with the extruder. I, too, have found that a very small slit cut with a razor will allow the gas forming the bubbles to escape and re-adhere the tape once cool. I also take a thin credit card and burnish the tape back down to the surface.

My next step is to try a thicker piece of glass with either hairspray or a thicker slurry of ABS glue. Right now I'm using 3mm window glass, which will actually flex a little since the bed is rather large. I've also read about using some frosted glass with ABS slurry. The frosted glass has higher surface area and "grabs" the plastic better than a smooth surface.

Regardless of all these issues, I'm stilll having a blast tinkering and tuning with this machine. I suppose I'm old enough to really have the patience to spend enough time to get this all worked out... or it could be I'm a little OCD or both .

Well kylix, if you're having fun, that's all that matters.


Coming back to the print in ABS: remember that it's a feature not a bug.
This is how ABS WAS DESIGNED, to shrink so that it can be removed easy from the mold.
In the future, I tend to believe that somebody will tinker with the chemistry of the filament and come up with a "perfect" solution.
Till then...we'll have to design our parts taking into consideration the restrictions of the materials...


Regarding the design method from that video, I totally support it.
It's one of the things that can help.
Yes, it will stress more your printer due to less fluid printing but you'll have less tension in your part.
And yes, it requires additional work to build your part that way or to alter an existing part...

Also, there is a reading shomewhere in the reprap forums, something with a lot of formulae and calculations and...long story short: print ABS at 280C
This way, the upper layer will fuse propperly onto the one below.

And again, the bed temperature is also something to be considered.
As I mentioned before, higher temp might help for ABS sticking to the Kapton but.. the Kapton adhesive will unstick :-(
And again, the temperature is many times a .. shadow, if you don't calibrate somehow your thermistors with a thermocouple and/ or several other measuring devices.

In any case, in the near future I intend to make a systematic approach on this matter: printing the same test print over and over again, altering parameters and writing down the results.
Reverse engineering... in paralel with some theoretical readings on the Fuse Deposit Printing technology...
If I'll have the time :-)

alexella,

I did read that thread you mentioned about printing ABS at 280C... yikes, that seems hot. I may give that a twirl.

I've also read about folks turning off the HBP after about 5-10mm height. The theory being that since the lower layers are closer to the HBP, they are warmer and softer thus more suseptible to warping. Once you have enough of the part printed and the bead adhesion is established, the HBP can be safely turned off. . Makes some sense.

I printed another part today, and it turned out pretty decent with minimal warping. It's not a large as some of the other ones I printed. I also reapplied the Kapton to the glass because I accidentally tore the last piece as I was smoothing out the bubbles. This time I only used some soapy water instead of glass cleaner for the liquid-method. That seemed to adhere and smoother out better.

I'll keep reading and experimenting.

Thanks.

If you turn off the HPB with ABS then your part WILL pop off the bed. You have to keep the temp up to keep it sticking.

Hmmm... Then why do I still have to really work to get the part to pop off the bed once the print is finished and it's cooled? Once it starts coming off, it pulls away fine, but that initial tug is quite difficult. I've yet to have a part spontaneously pop off the bed without some coersion after it's cooled.

Nevertheless, you may certainly be correct...

After a print I power down the machine and wait till it pops. Depending on how cold the room is it might take about 20-30 minutes.

It just pops free all by itself? Interesting. I've never seen that on mine. I could come back the next day and will still have to coerce it free. I do make sure the first layer has a good "squish" to it and I have a decent coating of ABS slurry.

Hello Floyd,

I had my good share of "popping" only when I used hairspray.
Indeed, in that case, prints worked like miracle, and at around 80C, I heard a "pop" and the part was free.

With kapton, this never happened.

Maybe it's also to the ABS concentration in the slurry I'm using.
If it's too much, the part will stick really well.
If it's not enough...the part will unstick from the bed during the print.

I use kapton without problems.
Yes it degrades after a few prints. I get through two plates worth a week.

It doesnt pop off after printing. It sticks very well!
I keep the bed temp to the lowest i can get away with without the print lifting.
Small stuff 95c large stuff 110c sometimes with the printer covered.

I find a short sharp knock with the handle of a heavy screwdriver when the bed is cold removes the more stubborn prints from the bed.

Gordon

I never heard of Kapton tape lifting off the bed due to a part warping. I think that either the manufacturer had a problem with the adhesive on the tape or you're running the bed temperature much too high. The former seems most likely.
Have you checked the actual temperature of the bed with a thermocouple? The temperature reported by the printer's controller board is based on using a specific thermistor. If you don't use that specific thermistor the temperature might be pretty far away from what the controller reports. The same applies to the extruder temperature.

While 280C seems high for ABS, the Stratasys machines at the makerspace print at 270C.

I've never had degradation in the Kapton's grip. I only replace tape on my print bed if the tape gets damaged, typically once every few months. I use 2" wide strips on my 12" x 12.5" bed so I can replace just the damaged strips, usually just the two in the center of the bed.

I run bed temps at 85C with a custom thermocouple-based temperature controller. It's a custom made pcb with an Atmega328p, two max31855kasa thermocouple chips and uses large capacity MOSFETs for controlling both the extruder and bed along with a 4x16 lcd display and buttons for input. It also connects via a serial port for simple remote control using some python-scripted apps running with LinuxCNC as the controller. Since the bed is rather large, it's current requirements are around 16-17A cold, dropping to about 15A hot. Temp remains stable at +/- 1.5C. I've checked surface temps with a laser-targeted infared thermometer and the bed surface is around 75-80C.

Even with that, the Kapton tape will begin to pull away from the glass. I used to run bed temps at 100C and after reducing to 85C, the peeling has reduced, but it still happens. I apply the tape using the wet method. I also use a single piece 250mm wide so there are no seems. When the parts are removed, the surface of the tape is somewhat bubbly and I have to smooth them back down. Sometimes I even have to use a razor knife to slit the top of the bubbles for the trapped gas to escape then burnish the tape back down. I've been about to get around 5-7 prints before replacing the tape, even with it separating from the glass.

Since this is a converted homemade gantry-style CNC, there is no full enclosure. It prints out in the open. I wonder if the upper layers are cooling too quickly while the lower layers are continuously being heated from the bed? I do try and limit drafts and keep some "walls" around the bed.

Kylix

Was the bed clean before you stuck the tape to it? Are you printing on the tape while it is still wet? When there's water under the tape it won't stick well. I let it cook on the bed for a couple hours after I replace tape to drive out the moisture. I push the bubbles that form away from the center to the edges of the tape, and hopefully, out, though it can be tricky to get them all out.

75-80C is pretty low for ABS, but if it sticks it should be OK.

Dentist,

Yes, I clean the surface of the glass with glass cleaner, then some pure acetone. The acetone cleans off any lasting residue and doesn't leave any itself. I wear some nitrile gloves to keep from getting skin oils onto the glass. Once the tape is applied, I do allow it to dry overnight or just cook it on the heated bed. Using the wet-method, it's pretty easy to get all the bubbles out using the edge of a credit-card or one of those squeegee tools used to apply window tinting film. Forget trying to get a single 250mm wide piece of Kapton smooth using the dry-method .

For printing I also apply a thin layer of ABS slurry to aid in adhesion. Without that, the part doesn't stick nearly as well, if at all.

Kylix.

Try ditching the Kapton and applying the ABS slurry direct to the glass - that's how I and many other people print ABS. I find a surface temperature of around 100C works best, which typically means 110C to 120C thermistor reading because of the temperature drop across the glass.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

dc42,

I've tried that and have had serious adhesion issues (ie, part would detach mid print). Could it be that my ABS slurry isn't thick enough for going directly to glass, but is ok for the Kapton? I've seen some folks everything from thin and watery to thick and viscous.

Kylix.

After I rebuilt my Kossel recently with a new larger bed, I had problems getting the ABS slurry to stick to the new glass plate initially. To solve it, I cleaned the bed thoroughly, increased the bed temperature so that the top of the glass is about 100C (which means an indicated bed temperature of around 120C), and made the ABS slurry thicker. I think the main problem was too low a bed temperature.

Edited 2 time(s). Last edit at 04/19/2015 04:17PM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

@the digital dentist

Yes, at some points, my kapton is lifting off the bed.
Maybe the quality is not the best.
Or, maybe it has to do with the soapy solution I've used to fix the kapton.
I'll try next time only with water...but it's much harder to do.


@dc42

ABS slurry direct on glass works for small parts. For bigger parts, it will lift including the ABS slurry.
I've got better results with hairspray.
Even there, if parts are longer than 4-5cm, they will eventually lift.
I admit I didn't tried all combinations (Heated bed temperature, extruder temperature)

@alexella

I've tried to use straight water to attach the Kapton and failed miserably. I went through a couple of sheets of tape before I went back to soapy water. Straight water doesn't seem to "buffer" the adhesive enough to keep it from sticking back to itself or "grabbing" the glass. The soap, being a surfactant, tends to break the surface-tension of the water which makes it "flow" better between the tape adhesive and the glass. As you smooth out the bubbles most of the water and soap is pushed out from between the tape and glass.

I, too, have considered that what little soapy residue is left between the tape and glass is what is causing the tape to detach as the part tries to warp. I may try again with just water the next time I replace the tape.

I've not tried the hairspray trick yet so that may be another avenue to persue.

Kylix.

Quote
alexella
ABS slurry direct on glass works for small parts. For bigger parts, it will lift including the ABS slurry.

What do you think is the size limit for printing on ABS slurry on glass then?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
What do you think is the size limit for printing on ABS slurry on glass then?

Hm, it's hard to "think", that would mean to make complex adhesion calculations that I...don't know even where to start.
I'll try to remember...and if I remember well, I printed some printrbot parts (around 5 cm length) and all corners lifted up.

And what I remember clearly was the mess I did when I tried to clean the glass.
The fine sheets of ABS tend to get electrostatic charge and they stick to whatever, even to my fingers.
I think this was the moment I... divorced the "slurry on glass" solution.

The best memory I had was with hairspray but...same issue: the bigger the part, the greater the corner lift.

But, you convinced me: I will restart the tests. In a more systematic way :-)

Edited 1 time(s). Last edit at 04/20/2015 04:46PM by alexella.