problems with first layer

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problems with first layer

Postby friederich » 2016-Jan-Sat-14-Jan

I am new to 3d printing. I have a printrbot simple metal with a heated bed. I'm trying to print out a phone case and the first layer of this is essentially a big (slightly rounded) rectangle. I'm not happy with my first layer. Other layers are printing fine and I already have a passable phone case but I'd like to see if I can do any better.

As you can see from the pictures, the first layer is fine in places, but distorted in places. If the distortion occurs at the edge then I get adhesion issues. The distortion can occur with brims too.

I have tried several things but given that this is my first time I am not able to diagnose the problem and I'd appreciate some suggestions.

I have tried changing the nozzle temp (200 and 210, I'm using glow in the dark PLA), and recalibrating Z (M212 Z(blah) M500 etc), but in each case I am not even clear about whether I should be going up or down. I've also tried moving the print around the bed before slicing. I'm reluctant to start fiddling with the spanners to adjust the sensor height, unless someone convinces me that this is worth trying.

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problems with first layer

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Re: problems with first layer

Postby cacb » 2016-Jan-Sat-17-Jan

Very good pictures. I am not 100% certain, but it looks like a case of "bulldozing", too much extrusion causing the hot end to work like a bulldozer through previously laid plastic. If so, the fix is to reduce amount of extruded material. Did you measure the diameter of the filament? This is one important thing that can cause over extrusion. Fix that issue first and print small test cubes until ok.

For the Z-calibration, you need to see of the first layer is completely squashed (z too low) or if the filament are laid out as almost loose threads (z much too high). When it is correct, the filament should be somewhat compressed, but there should be no bulldozing.

For different behaviour in different places, are you running G29 autoleveling?

For adhesion it is very important to clean the kapton tape with alcohol often.

Btw. I have a Simple metal with heated bed also.
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Re: problems with first layer

Postby friederich » 2016-Jan-Sat-18-Jan

Many thanks for these ideas and comments; it's great to get some new directions. I have not cleaned the kapton once, so clearly I should start there. Everything else I think I've checked: I am using 1.75mm diam filament and it's set at 1.75 in cura, 100% flow, nozzle size 0.4mm. I've intentionally set Z both too low and too high by a few tenths of a millimetre to see what I'm supposed to be avoiding, and I think I have everything Ok now. I am running G29. I did wonder whether somehow it wasn't working properly but given that I seem to have more success in some areas of the bed than others I am now wondering whether my kapton needs cleaning.

Here is a completely ridiculous thought. I've not tried it yet -- too scared. My son has some small but quite strong magnets. If I see a brim part of which has not printed well and looks like it's beginning to peel off, I'm always tempted to just get one of his magnets and ram it onto the brim. It would certainly hold it down, assuming the bed is magnetic. I was also worried that it would really mess up the print head when it was nearby too :-) so will probably never try it.

If I have adhesion problems (which sometimes my poorly-printed brims lead to) then should I be thinking about printers tape? I've never used this at all, I've just used the kapton up until now. I had it in my head that auto-levelling might not be working because I was having better results in some parts of the bed than others, but the more I think about it the more I wonder whether you've hit the nail on the head with regards to cleaning the bed. I'll see if I can pick up some isopropanol alcohol (is that what I'm supposed to be using?) tomorrow...

Cheers.
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Re: problems with first layer

Postby ChefScott » 2016-Jan-Sat-19-Jan

friederich wrote: I am using 1.75mm diam filament and it's set at 1.75


You need to measure the filament with a micrometer at 90 degrees to each other in several places over a foot or two of filament several times and get the average diameter of the filament and plug that number in. Rarely is filament exactly (if ever) 1.75 mm in diameter.
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Re: problems with first layer

Postby thawkins » 2016-Jan-Sun-00-Jan

friederich wrote:Many thanks for these ideas and comments; it's great to get some new directions. I have not cleaned the kapton once, so clearly I should start there. Everything else I think I've checked: I am using 1.75mm diam filament and it's set at 1.75 in cura, 100% flow, nozzle size 0.4mm. I've intentionally set Z both too low and too high by a few tenths of a millimetre to see what I'm supposed to be avoiding, and I think I have everything Ok now. I am running G29. I did wonder whether somehow it wasn't working properly but given that I seem to have more success in some areas of the bed than others I am now wondering whether my kapton needs cleaning.

Here is a completely ridiculous thought. I've not tried it yet -- too scared. My son has some small but quite strong magnets. If I see a brim part of which has not printed well and looks like it's beginning to peel off, I'm always tempted to just get one of his magnets and ram it onto the brim. It would certainly hold it down, assuming the bed is magnetic. I was also worried that it would really mess up the print head when it was nearby too :-) so will probably never try it.

If I have adhesion problems (which sometimes my poorly-printed brims lead to) then should I be thinking about printers tape? I've never used this at all, I've just used the kapton up until now. I had it in my head that auto-levelling might not be working because I was having better results in some parts of the bed than others, but the more I think about it the more I wonder whether you've hit the nail on the head with regards to cleaning the bed. I'll see if I can pick up some isopropanol alcohol (is that what I'm supposed to be using?) tomorrow...

Cheers.


The secret to printing on kapton is clinical level cleanliness, the grease from a single finger print is enough to cause the print to detach. Make sure you wipe your bed with alcohole before each and every print.
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Re: problems with first layer

Postby Mooselake » 2016-Jan-Sun-09-Jan

Or just put some gluestick on it...

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Re: problems with first layer

Postby HerbsMix » 2016-Feb-Mon-08-Feb

I encountered a similar situation when trying to print larger parts. I had calibrated my printer using a small cube in the enter of the bed with good results but when printing a larger part the same problem resulted in areas of the print as you have experienced. The process of printing when the bed reached 60C and hot end 200C didn't work on large prints. After initializing the situation, I discovered warping of the aluminum hot bed during warm up. The solution was improved leveling by shimming and allowing 30 minutes of bed warm up time. I can now print large jobs.

In analyzing the problem I used a dial indicator mounted on the Y-axis. First leveling the bed when cold (added paper shims to accomplish this). I then monitored the bed during worm up and discovered that the corners where the leveling prob senses were reading +.010 inch above the center of the bed. After warm up the bed indicated +-.003 inch. I also sensed some twisting which cannot be resolved by shimming without stressing the rods and bearings.

Because of the warping I am considering using glass to get a flat surface. I would like to continue to use automatic leveling but haven't work that out yet. Suggestions are welcome.
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Re: problems with first layer

Postby cacb » 2016-Feb-Mon-10-Feb

HerbsMix wrote:I encountered a similar situation when trying to print larger parts. I had calibrated my printer using a small cube in the enter of the bed with good results but when printing a larger part the same problem resulted in areas of the print as you have experienced. The process of printing when the bed reached 60C and hot end 200C didn't work on large prints. After initializing the situation, I discovered warping of the aluminum hot bed during warm up. The solution was improved leveling by shimming and allowing 30 minutes of bed warm up time. I can now print large jobs.


Was this experience with a Simple Metal and stock heated bed and PB heat plate? If so, I find it hard to believe as the aluminium plate is quite thick relative to its other dimensions and I have never seen any warping of that plate, I usually print at 65C bed temperature, 200C hot end.
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Re: problems with first layer

Postby HerbsMix » 2016-Feb-Mon-11-Feb

This is experienced on my Simple Metal with extended Simple X-axis upgrade and heater. It makes sense when considering the expansion rate of aluminum and the thickness (¼ inch) of the bed. The heat is first applied to the bottom of the plate, by the heater, expanding it more than the top side resulting in th plate bowing down or warping down. After the temperature normalizes it should return close to its original straightness. Some bowing will remain because of the temperature difference between the bottom surface, next to the heater, and the top exposed surface to room temperatures and later cooling fan. The bowing is noticeable with a dial indicator and is evident, on my printer, when trying to do a large print before the temperature is normalized.
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Re: problems with first layer

Postby bbrown64 » 2016-Feb-Mon-14-Feb

I am curious as to why you would not want to make manual adjustment to the hotend and the Z-Probe? Printers are NOT plug-n-play. After all it is correct procedure to make all the initial settings manually. Then go into the software to make the Z-Probe offset more fine tuned. Always remember when making adjustments in the software. The initial setting would be at Z-.2. Then work your way down to some where around Z-1.2. According to Brooke and PB you have to move in .2 increments to be sure everything is correctly smuching the filament.
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Re: problems with first layer

Postby HerbsMix » 2016-Feb-Mon-17-Feb

I don't mind and have made many manual adjustments to calibrate the printer. My Z-axis is currently set to -1.85 which works great for small parts (Parts can be removed without destroying painters tape and gives excellent height accuracy). When printing large parts I use Z-axis offset of -1.90 to compensate for plate distortion and achieve first layer adhesion in all areas. With -1.9 offset part removal destroys the painters tape and when examining the bottom side of the part it becomes obvious where the high and low areas are on the bed.

This is why I am thinking of using glass to get a flat and smother surface and allow full utilization of the X-axis. I need to research this more.
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Re: problems with first layer

Postby RetireeJay » 2016-Feb-Mon-17-Feb

Glass is great. But it doesn't play well with probes. I think a lot of people put metallic tape on top of the glass, but that loses print area.

Just level your bed with the shims (as you have been doing) and find a substitute for the probe. Before the probe came out, most people were using microswitches just like the ones on X and Y; the microswitch actuation is based on motion of the Z carriage relative to the base of the machine, adjusted with a simple screw.

By the way, my "sandwich" is as follows, top to bottom:
Glass
Heater
Paper shims
Silicone mat for insulation
Plywood base of bed.
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Re: problems with first layer

Postby WaffleMan » 2016-Feb-Wed-11-Feb

It might be because your nozzle is wearing down with the glow in the dark pla you are using. Maybe try a plated nozzle instead. Here's a video explaining it.

https://youtu.be/YsEVUNoo9Zc
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Re: problems with first layer

Postby friederich » 2016-Feb-Mon-07-Feb

I'm the OP; for me things got a lot better when I bought some rubbing alcohol and gave the bed a good clean. I also continually tinkered with Z height using M212 and started using hairspray for bed adhesion. I still see occasional problems like the above but far less often. In answer to the person who asked why I wasn't making manual adjustments to the hot end and Z probe -- my printrbot simple came pre-assembled and I assumed they knew what they were doing. Recalibrating has worked so far for me. I have been moving Z in .1 increments and even this seems to make a difference for me. I print in a shed outside my house and the ambient temp can get as low as 10C, so I need to be careful sometimes; sometimes my printrbot prints slightly differently in the day and the night depending on how cold it is.
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Re: problems with first layer

Postby trathier » 2016-Mar-Wed-14-Mar

I'm seeing the same issue when printing large parts with the exception that I'm using a raft. I can print small to medium parts with no problem and they come out fine.

Maybe someone can tell me if this is bull dozing or what to adjust to correct it?

I have a Printerbot Metal Plus heated bed with a MatterTouch controller. I'm using MatterHacker Pro filament. I also print on blue painters tape, scuffed, and wiped with rubbing alcohol which gives me good adhesion for the raft.
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Re: problems with first layer

Postby trathier » 2016-Apr-Fri-12-Apr

I solved the problem by:
Setting the extruder temp to 215 degrees
Setting the bed temp to 80 degrees
Blasting the print with a 12" fan during the print.

When combined with the blue painters tape, scuffed with emery cloth and wiped with alcohol, the print no longer curls and prints perfectly flat. It also no longer comes off the table without a hammer and screwdriver :(
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Printrbot Metal Plus
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G2 processor
----------------------------------
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