• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Help! Inaccurate 3D print sizes!

Turbojoe

Well-known member
#1
OK, this is about to become a one way ticket to the loony bin for me...... :mad:

Creality Ender 3. A year old. Absolutely love it! Only 1 1/4 spools through it. Glass build plate. I've been getting and still get great prints for things that don't require "precision" fit. Now that I'm getting better with TinkerCad (and just installed Microsoft 3D Builder last night) I'm designing parts that need to actually fit where I want them to go. I've spent hours upon hours upon hours ensuring bed level, extruder, X, Y, and Z e-steps are spot on based on a 1cm cube print. I can STILL get 1cm cubes to print at 10.0-10.02 on all three axis yet once I print larger items and one servo plate in particular I designed in TinkerCad is a 40mm x 51mm x 3mm plate with two 12mm x 24.5mm openings the as printed measurements are all over the place with no rhyme or reason. On both X and Y axis one of the two measurements is too large while the other on that very same axis is too small. I've updated Cura to 4.4. Uninstalled and reinstalled Cura 4.4 just because. Still no help.

I realize a 3D printer isn't going to give absolute precision prints like a laser cut but this is ridiculous. Something is wrong somewhere and I just don't know where. There are SO many (too many?) settings in Cura. I make very few changes in Cura and then only if a file I've downloaded suggests it. I don't know if the problem is with TinkerCad, Cura or the printer. Specified sizes should print at that specified size or hopefully very close. I've given up trying to get accurate hole sizes as that's obviously just not going to happen. Now I'd settle for fairly accurate basic flat plane prints. Printing cute little boats and other little toys come out great but they don't need to fit together with another printed item. There is apparently some compensation adjustment needed but I don't know what that may be. I took measurements from the last wrong print and input the difference into the next print and it came out VERY close to accurate. It's a one hour print. It's just plain stupid to have to spend all that time for a throw away print just so you can measure it to make changes to the next one hour print. I just know I'm missing something. This servo plate is just one item. The problem is with anything larger than 1cm square that I need reasonable accuracy on. Hoping someone can give me some pointers. I've got a lot of hair but at the rate I'm pulling it out I'll be bald soon.......

EDIT: Just added a poor quality picture of the servo plate I'm printing. The servo holes look different size but only because of picture angle.

Joe
 

Attachments

Last edited:

LitterBug

Troll Spammer
#2
I'd say check to see if your belts are loose, but I don't see anything in the picture of the print to suggest that is the issue. I can't speak for Cura as I use Simplyfy 3D. But it almost sounds like there is something in your Cura config that has the X and Y axis printing at different correction rates. So if you rotate a part, it is causing things to shift.

Cheers!
LitterBug
 

rockyboy

Skill Collector
Mentor
#3
I'd recommend doing the setup with a bigger square - I like this 100mm x 100mm one https://www.thingiverse.com/thing:25101

Also, check to see if there is any slop or backlash in your x and y axis mechanical setups - backlash could explain some of the difference in dimensions on the same axis. This print object and process could help with that https://www.thingiverse.com/thing:885066 - or at least confirm that's not the problem
 

Turbojoe

Well-known member
#4
We are currently working on some performance issues. Updates on our Twitter account: @Thingiverse. Thank you for your patience!

Thingiverse not working so well right now. I'll try again later to see what it's all about.

Joe
 

Piotrsko

Well-known member
#6
Not going to suggest much because I'm not really qualified except at desktop geek level, BUT, what are your encoders reading, or, is there some sort of factor to get clicks to the distance? Or the old: are your sensors clean and counting correctly?. The NC router I set up and got working had dirty as heck optics and a batch of wrong hacked conversion formulas
 

kilroy07

Well-known member
#7
First, I like @LitterBug 's idea of trying to first rotate the print 90 degrees...

If the parts STILL show issues in the same direction (in relation to the part), then I'd say it's software. If they show it in the same axis (related to the printer) as before I would point to hardware.

You mentioned the calibration cube came out nice, have you done one for wall thickness/extrusion?
While the outside of the cube might be fine, inside features might be thrown off by too much extrusion.

If you want, Send me your STLs, I'd be happy to try a test print here and help.

@Piotrsko unfortunately, the ender 3 does not come equipped with encoded steppers.... (Wish it did!, although the new 2209 drivers come close) We can set the number of steps per inch/CM but if that were off, I would expect his cube to be off as well.
 

Turbojoe

Well-known member
#8
Thanks for the new suggestions guys. I was out of town all day yesterday and didn't get to do anything more with the printer. Later in the day on the 20th I did spend significant time making certain the X axis rail was absolutely square to the uprights. I had to enlarge the right side roller plate mounting screw holes to allow adjustment. I replaced all of the roller wheels on the X and Y axis simply because I had a bag of new ones. Made sure the belts were good and tight. Re-leveled the bed to the newly adjusted X axis. Made many many, many, many, many step adjustments and got X and Y very close but Z axis is now a problem as it had little if any affect on Z print thickness.

10mm calibration cubes are simply OUT of the question for me. I have large hands and fingers and trying to fiddle with and measure these tiny little pieces is maddening! I printed out the 100x100x1mm cube and it's much easier for me. The 1mm thickness is a huge problem though as the cube is so flimsy that it's virtually impossible to accurately measure X and Y axis. I made my own 100x100 cube but I made it 3 mm thick and it's now much more useful. After several prints and step adjustments I was able to get X and Y close but Z axis is always pretty much the same no matter what step adjustments I make to the Z axis. ALSO and that's a HUGE also Z axis adjustments mainly change X and Y axis!
That I just don't understand. How could Z affect the other axis and not Z axis unless something is bent?

Problem #1: X and Y axis I'll eventually get to where I'm happy after a testing through a few rolls of filament. Z axis is what is driving me nuts now and WHY is it affecting X and Y axis?

Problem #2: Z axis on the 100x100x1mm cube was at .95 to .82 mm descending to the right side of X axis no matter how I changed E step for Z axis.

Problem # 3: Z axis on the 100x100x3mm cube was at 2.96 to 2.88 descending to the right side of X axis. Z axis E steps on Z axis STILL only affect X and Y steps. NOT Z thickness.

There's still a TON of stuff I need to learn about all this but until I can get the X, Y and Z axis usefully calibrated I feel I'm just pissing in the wind.

Normal prints that don't require any degree of accuracy come out great. It's only when I need something to print to fit a certain space that everything falls apart.

When I make a part that specifies 30mm x 50mm x 3mm I need it to print out close to those numbers. Am I asking too much or should I stick to printing only cute little figurines etc that don't have to be any where near accurate sizes?

I feel like I'm SO, SO close yet SO far away.......:confused:

Joe
 

rockyboy

Skill Collector
Mentor
#9
Depending on how much X and Y variation you're seeing when you mess with the Z axis, it could actually be caused by the feed rate - the amount of filament it's pushing through the nozzle. I found getting the feed rate set right was one of the most helpful things I did - it starts with making sure that 100mm of filament feed actually does feed 100mm through (instead of 107 or something like that). If the filament feed is coming out faster than expected, you can end up with a bead of hot plastic that's wider than the nozzle - and that can throw things off and be a real problem on holes or inside dimensions.

There's a good calibration walk through over here https://www.3dhubs.com/talk/t/howto-calibrate-tune-and-fine-tune-your-printer-and-filament/5695 that I have mostly followed in the past - although I do the very first feed rate calibration differently. Instead of taking off the hot end, I just measure up 120mm from the top of the feed tube and make a mark on the filament. Then feed in 100mm of filament letting it just be a pile of melted spagetti, and measure from the top of the feed tube to the mark. If it's 20mm, hooray! If not, time for mathy stuff and adjustments.

Another thing is I think your bed is either warped or angled just a tiny bit. When the layer height is different from one end of the bed to the other, but off by the same amount at different height blocks, then an off kilter bed is the only thing that makes sense to me. The "old school 3D printer way" of dealing with this if it can't be mechanically adjusted is to print on a raft. If you haven't heard of that before, it's a setting in the software that builds a 3 layer platform underneath the printed part, and the platform (or raft) peels off the bottom when it's all over.
 

Turbojoe

Well-known member
#10
Another thing is I think your bed is either warped or angled just a tiny bit.
Print bed is 1/8" plate glass so no warpage and within .002 inch right to left distance from bed to X axis rail. I'm quickly falling out of love with 3D printing and may have my daughter just come and get this thing. Maybe wait a year or two until they become more accurate without needing an engineering degree and unending patience to set them up and maybe then consider buying one.

Joe
 

Turbojoe

Well-known member
#11
If you want, Send me your STLs, I'd be happy to try a test print here and help.
Attached are files I created in TinkerCad .stl and Cura .gcode. 100mm x 100mm x 3mm x 3mm. I would LOVE to see what measurements you or anyone else get. I'm at the end of my rope and about ready to wash my hands of 3D printing if it can't print at least somewhat accurate.

Joe
 

Attachments

mach1 rc

Well-known member
#12
Attached are files I created in TinkerCad .stl and Cura .gcode. 100mm x 100mm x 3mm x 3mm. I would LOVE to see what measurements you or anyone else get. I'm at the end of my rope and about ready to wash my hands of 3D printing if it can't print at least somewhat accurate.

Joe
Cool I currently the public account of tinker cad by @mrjdstewart. Is that what you are using?
 

Turbojoe

Well-known member
#13
Cool I currently the public account of tinker cad by @mrjdstewart. Is that what you are using?
Originally I tried a 100mm x 100mm x 1mm cube that was too flimsy to be useful for me because of the 1mm thickness. I don't remember who it was posted by. The file I posted here was created by myself in TinkerCad. Please print it and post the measurements you got.

Joe
 

LitterBug

Troll Spammer
#14
Attached are files I created in TinkerCad .stl and Cura .gcode. 100mm x 100mm x 3mm x 3mm. I would LOVE to see what measurements you or anyone else get. I'm at the end of my rope and about ready to wash my hands of 3D printing if it can't print at least somewhat accurate.

Joe
I'm giving it a print now. Should have results in about 40 minutes....

Cheers!
LitterBug
 

LitterBug

Troll Spammer
#15
I'm giving it a print now. Should have results in about 40 minutes....

Cheers!
LitterBug
UPDATE:
Printed it on my Monoprice select mini V2 with a 120x120 bed. My bed is slightly out of level so Z was slightly off on one side +- .1ish. But consistently sloped right to left.
OD = 100x100
ID = rougly 94 in both x and y
 

Turbojoe

Well-known member
#16
UPDATE:
Printed it on my Monoprice select mini V2 with a 120x120 bed. My bed is slightly out of level so Z was slightly off on one side +- .1ish. But consistently sloped right to left.
OD = 100x100
ID = rougly 94 in both x and y
Thanks!

I'm getting 98.75 on Y axis and 98.81 on X axis O.D. I can get them closer to 100 no problem. 92.33 on Y axis and 92.53 on X axis. The "edges" should be 3 mm wide and I'm getting 3.2 mm. I'm finally getting close on Z axis at 2.89 mm and it should be 3 mm. Step adjustments that I make to Z axis affect X and Y MUCH more than Z axis and I don't understand why. Once I get Z semi close and go back to adjust X and Y again then Z axis goes back in the toilet becoming a vicious circle. It's like there is cross contamination affecting all 3 axis and it's driving me freaking nuts! I can either have X and Y but no Z or Z but no X and Y.

Joe
 

rockyboy

Skill Collector
Mentor
#17
Maybe wait a year or two until they become more accurate without needing an engineering degree and unending patience to set them up and maybe then consider buying one.
That's what I said back in 2013 when I got the first Printrbot kit. Things aren't much different now - still lots of individual tuning and tweaking for the vast majority of the machines. It can work - and it can work well - but it can drive you crazy too.
 

LitterBug

Troll Spammer
#18
Thanks!

I'm getting 98.75 on Y axis and 98.81 on X axis O.D. I can get them closer to 100 no problem. 92.33 on Y axis and 92.53 on X axis. The "edges" should be 3 mm wide and I'm getting 3.2 mm. I'm finally getting close on Z axis at 2.89 mm and it should be 3 mm. Step adjustments that I make to Z axis affect X and Y MUCH more than Z axis and I don't understand why. Once I get Z semi close and go back to adjust X and Y again then Z axis goes back in the toilet becoming a vicious circle. It's like there is cross contamination affecting all 3 axis and it's driving me freaking nuts! I can either have X and Y but no Z or Z but no X and Y.

Joe
Are you sure you don't have a loose hot-end? Seems like you have something shifting around....
 

Turbojoe

Well-known member
#20
Are you sure you don't have a loose hot-end? Seems like you have something shifting around....
Nope. I had everything off while I was getting the X rail squared up. Made certain the hot end was tight and square to the rail. I'm thinking something somewhere is bent. It just doesn't make any sense why Z adjustments are affecting X and Y so much and that's what is driving me absolutely bonkers.

Joe