Author Topic: 3D printer Ender 3 pro oval hole problem  (Read 1598 times)

Offline picclock

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3D printer Ender 3 pro oval hole problem
« on: April 12, 2020, 08:38:26 AM »
Ender 3 pro oval hole problem

Hi
I'm struggling with this. The holes I make are ovalled and diagonally offset  - see picture. Internet help seems pretty useless as the advice boils down to tighten the belts or square the frame - neither of which are applicable. A

The printer frame is square and the xyz dimensions calibrated. If I print a square it comes out square with equal dimensions across the diagonals, and the desired size within 0.1mm.

Yet the holes are all over the place. The test piece has holes 1 to 15mm, is 100mm long and 25mm wide.
The major axis of the oval is around 340 degrees. On the 11mm hole the diameter at approx 340 degrees (top view) is 11.04mm, at 0 degrees (y direction) its 10.89mm, at 90 degrees (X direction) its 10.53mm, which is typical.

I've tried an earlier version Cura slicer, 3.41, which always produced good results on my now defunct Prusa, and the results were the same. I'm beginning to think it might be a mainboard problem. Its a Creality 1.1.4 motherboard, using ATMega 1284P processor.

I have a new SKR V1.3 card on the way with 2209 drivers and a touch screen, so if it is this its not going to be an issue for long.

Any other ideas very much appreciated.

Best Regards

picclock
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Offline Joules

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #1 on: April 12, 2020, 08:51:28 AM »
If everything is OK when printing square parts, it looks like your bed is moving on the springs somehow.   It certainly exhibits drag I would associate with belt stretch or binding, or a hotend rocking as the top and bottom of the holes have very similar displacement regardless of size.  Check the hotend assembly is tight and you canít rock it side to side with your fingers.
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Offline Joules

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #2 on: April 12, 2020, 08:56:43 AM »
Just try printing some cubes again, but rotate them 45 degree to see if the sides distort.
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Offline picclock

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #3 on: April 12, 2020, 09:35:14 AM »
Hi Joules

Thanks for the springs idea, its something I hadn't  thought of. I've just compressed them well up, but now I will have to butcher the Z endstop (microswitch) holder for head adjustment. I'm not too worried about it as I've a 3d touch levelling sensor on order.

I have already checked the head for tightness, although I would imagine this would show up with unsquare prints if there was an issue like this.

I am impressed by the sturdiness of the frame and generally good engineering for a pretty low cost printer.
Do you have one and does yours print round holes ??  :lol:

I'll post my results when done.

Best Regards

picclock

 
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Offline Joules

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #4 on: April 12, 2020, 09:42:12 AM »
No Ender 3 here, I think I posted in the past my test prints for checking holes.  In extreme cases I will print a test ring, then draw an eliptical hole to compensate.   My worse case for out of round components was due to a ballrace going bad at the rear of my printer, the drag from that caused racking and lots of head scratching till I found it.
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Offline picclock

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #5 on: April 12, 2020, 11:51:40 AM »
@ Joules
I am just testing it now, but it looks very much better. I have nearly halved the spring length which gives much improved stability. I would have taken it further but the bed will foul a cable support bracket.

The height of the bed is fixed with the z sensor, and the software is locked to prevent alteration of any offsets. New board will run Marlin 2.0. Amazing price of £11-45 inc del. plus drivers at £14.

Thank you very much for your assistance. Hope I can return the favour some day.

Will post picture of latest print tomorrow.

Happy Easter

Best Regards

picclock
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Offline Joules

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #6 on: April 12, 2020, 12:27:43 PM »
Do you mind adding a few more details for the record.

What material being printed.
What temperature the hot end
What speed in mm/s you are printing at.

Add some spacers to compress the springs further without fouling the cables.
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Offline beeshed

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #7 on: April 12, 2020, 05:15:14 PM »
Is it anything to do with the shape of the test piece and asymmetrical shrinkage affected by the other hoes. I have had no noticeable problem with the hole in the middle of my gears but they are of course all round, and a round boss I printed fitted perfectly into the round gear hole so negative hole symmetry ok too.

Offline Will_D

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #8 on: April 12, 2020, 05:37:59 PM »
Ender 3 pro oval hole problem

Hi
I'm struggling with this. The holes I make are ovalled and diagonally offset  - see picture. Internet help seems pretty useless as the advice boils down to tighten the belts or square the frame - neither of which are applicable. A


Can you append the stl file (as in ...stl.txt) so I can run it on my Ender 3?
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Offline picclock

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #9 on: April 13, 2020, 02:23:39 AM »
Looks like its sorted.
Measurement of 11mm test hole gives 10.95 x 11.07, which for plastic is pretty good. The 13mm hole is spot on, and as seen in the other picture, I can push the bearing into it without any adjustment and its a good firm fit. The hole test was to make up an error correction chart but I don't think I'm going to need it. :thumbup:

Before I bought this printer I noticed lots of people selling or recommending upgraded springs, and I think this must be the reason. The assembly is such that the spring compression relies on a large number of manufacturing tolerances which stack up. If your unlucky enough to get a slack one the wobble is the result. I assume that squares are not affected as the motion is in one direction.

@ Joules PLA, 210, 50mm / sec.
@ Will_D - amended, unzip, rename.

Many thanks

Best Regards

picclock

PS the bearing is part of a home made extruder for solder paste used in smt assembly.
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Offline Will_D

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #10 on: April 13, 2020, 06:02:57 AM »
That's good to hear. I am still printing it though.

One thing to check is that after the first hour or 2 the belts may need adjusting. A bit of backlash in one of the axes would lead to oval holes,

I check my bed for level quite often using the attached gcode file. You may want to edit it to set your temperatures. It also leaves the heaters on!
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Offline Joules

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #11 on: April 13, 2020, 06:15:29 AM »
Thanks Picclock, those are the values I would use, those springs must have come from an old mattress if they drag about that much LOL   Glad you are getting the results you hoped for.
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Offline mc

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #12 on: April 13, 2020, 08:03:10 AM »
The spring upgrade is one of the first things recommended for an Ender 3, however despite buying them, my silicon buffer kit is still sat in the bag they came in, as I've never felt the need to upgrade
I do however run the stock springs pretty compressed, which is probably the big problem with anybody running the stock springs.

I'm also using a glass bed, so my Z switch sits a bit higher that normal, but even with the standard bed, you could just cut the locating tab off, and move it lower to get more compression on the springs.

The other option is adding a BL touch, which is something I keep considering, but I keep seeing mixed reviews about them. Plus there is a huge variation in prices depending on brand/source, and nobody seems to know how much they vary in quality/repeatability.


I upgraded mine last week to the SKR Mini E3 board (I opted for the integrated driver version), and the BigTreeTech 3.5 TFT.
The noisiest thing now are the cooling fans, with only a slight hum of the steppers at certain speeds. It's bizarre not hearing it home until you hear a switch click!

I wasn't that impressed with the TFT, but now I've updated it to the latest firmware with the unified graphics, it's far better. I do like how you can switch it between touchscreen and LCD mode, you just need to make sure you connect all the cables.
The E3 board is still running whatever firmware it shipped with (I really can't be bothered going down the software compiling rabbit hole just now to change something that's working fine!).


My next upgrade is a MicroSwiss extruder/hotend, which is currently in the post somewhere between the USA and here...

Offline picclock

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #13 on: April 13, 2020, 09:02:57 AM »
@mc
>>I'm also using a glass bed, so my Z switch sits a bit higher that normal, but even with the standard bed, you could just cut the locating tab off, and move it lower to get more compression on the springs.

That's exactly what I did. The springs also contact the heater element with just a piece of film between - looks like an accident waiting to happen.

@Joules - the springs are about a fith of the diameter off mattress springs, even thought of making some. I may junk them altogether when I fit a touch sensor and a mains powered silicone pad heater, and just set it up with nuts locked to the support plate. My scrap Prusa had this setup and I never looked back.

@Will_D
Frame squareness, bearings, belt tightness were all checked before I posted here. My big mistake was not to consider the bed springs. For some reason I just assumed they would be OK as supplied. I quite like the magnetic bed for ease of print removal, And will likely order some spring steel ones for smooth surface. The great advantage of a touch sensor is that you can swap the build surface without doing any adjustments, making it a much less fiddly. Hopefully this will last as long as my Prusa did. May even use the Prusa E3D head on it if I have to do very high temperature stuff.

Happy Easter :wave:

Best Regards

picclock
 
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Offline Will_D

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #14 on: April 17, 2020, 05:21:37 AM »
Measurement of 11mm test hole gives 10.95 x 11.07, which for plastic is pretty good.

My results are in:

The 11mm hole measured 10.70 - 10.74. Now I have noticed this with other holes and female threads  They are all undersized.

As another check I measure X, Y and Z dimensions. I assume you designed it as 100 x 25 x 6

I got 99.81 - 99.84, 25.07 25.10, 5.94 - 5.97

Cheers Will

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Offline Joules

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #15 on: April 17, 2020, 06:53:14 AM »
Remember "blob" size, speed, direction of travel and clearance.   Outside edges, slightly under extrude so your corners and retractions don't have massive blobs.  Inside edges, especially on smaller detail have the blob dragged towards the centre of the hole, so nearly always come in undersized/distorted.  Trial parts, make allowance in your model, it gets more critical as you reduce nozzle size (or wear in the nozzle) and chase those finer detailed prints.

Be amazed it works at all....

Oooh Will you jammy bugger, nice plasma cutter....
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Offline Brass_Machine

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #16 on: April 17, 2020, 09:28:14 AM »
...
The other option is adding a BL touch, which is something I keep considering, but I keep seeing mixed reviews about them. Plus there is a huge variation in prices depending on brand/source, and nobody seems to know how much they vary in quality/repeatability.


I upgraded mine last week to the SKR Mini E3 board (I opted for the integrated driver version), and the BigTreeTech 3.5 TFT.
The noisiest thing now are the cooling fans, with only a slight hum of the steppers at certain speeds. It's bizarre not hearing it home until you hear a switch click!

I wasn't that impressed with the TFT, but now I've updated it to the latest firmware with the unified graphics, it's far better. I do like how you can switch it between touchscreen and LCD mode, you just need to make sure you connect all the cables.
The E3 board is still running whatever firmware it shipped with (I really can't be bothered going down the software compiling rabbit hole just now to change something that's working fine!).


My next upgrade is a MicroSwiss extruder/hotend, which is currently in the post somewhere between the USA and here...

I have the BLTouch. Works well for me... even with having one, you still should upgrade the bed springs.

The SKR mini E3 and the 3.5 TFT are 2 of the best mods to date. So quiet!

I almost went with a MicroSwiss... but GulfCoast Robotics has an all metal hot end for much cheaper. I ended up getting that, works fantastic.

Eric
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Offline mc

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #17 on: April 17, 2020, 11:46:16 AM »
I have the BLTouch. Works well for me... even with having one, you still should upgrade the bed springs.

The SKR mini E3 and the 3.5 TFT are 2 of the best mods to date. So quiet!

I almost went with a MicroSwiss... but GulfCoast Robotics has an all metal hot end for much cheaper. I ended up getting that, works fantastic.

Eric

Have you got a genuine BLTouch, or a copy?

I opted for MicroSwiss as it happened to be in stock when I ordered, but it's still stuck in the USPS system :-/
I hope it turns up soon, as I'm wanting to try printing some TPU.

The other option I considered was the Triangle labs copy, as a mate uses one, but I thought I'd support the original version.

Offline Brass_Machine

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #18 on: April 17, 2020, 01:51:40 PM »

Have you got a genuine BLTouch, or a copy?

I opted for MicroSwiss as it happened to be in stock when I ordered, but it's still stuck in the USPS system :-/
I hope it turns up soon, as I'm wanting to try printing some TPU.

The other option I considered was the Triangle labs copy, as a mate uses one, but I thought I'd support the original version.

I assume it is genuine. I got it from Creality with the metal bracket for the ender 3 and the jumper for the cable. With the mini E3, there is no need for the jumper.

Will be adding linear rails and a second Z axis stepper/leadscrew in the next couple of weeks
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Offline picclock

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Re: 3D printer Ender 3 pro oval hole problem
« Reply #19 on: April 20, 2020, 09:18:05 AM »
@Will_D
The hole size issue is a tricky one - hence the stl to allow compensation for the small sizes in design.
The bottom layer (possibly 2) is likely to be inaccurate due to the head height adjustment. In order to get it to stick to the build plate these layers are often overextruded, so when measuring size its important to ignore these (see elephants foot).
It could also be that the filament extrusion is set too high. Easy to do a quick check by marking the filament with a pen about 120mm from the extruder, then extruding 100mm, and measure how much over.
The way you measure the hole size is also relevent. Generally I use some telescopic gauges for sizes 6mm and above. For sizes below that some ground rod will give an idea.
FWIW my sizes were good to 5mm, but below that they will all need adjustment. And if you look at the picture you will see the 1mm hole was just a solid.

Good luck with your calibration. FWIW, I think these are excellent printers and really good value for money.

I'm currently printing a mount for my E3D v6 head so I can hope to do higher temperature filaments. In reality the bed heater is nbg for anything over 120C, hence the need for a silicon pad heater. I've ordered a 500W mains powered version which should sort out any issues.

Best Regards

picclock

PS just read your post in another thread about destroyed prints. As was mentioned cables snagging the frame are a very good candidate, but I have had this happen when the filament gets snagged, normally trapped under a layer on the reel. I saw a print for an anti snagging device on thingiverse.
 
 
« Last Edit: April 20, 2020, 09:43:00 AM by picclock »
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