Parts print slightly shrunk in the center  

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My Robox printers used to print perfectly until around the time of a recent firmware update.  Now all my prints are shrunken in the center with a flare out at the top last layer.  From the base and 8mm up, there is about 20% shrinkage... then it returns to normal with the uppermost finish layer extending half a mm past.

Any ideas on how to fix this?  Never did this before.

This topic was modified 4 months ago by gavincurtis
4 Answers
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@gavincurtis Can you post pictures? They will help identify what you are looking at so that we can try to see what is happening. 

What material are you using, and what print profile? Also, what infill % and if you have set up a custom setting, please note what you have changed in the event that one of the settings you have edited is leading to this behavior.

Please note what version of AutoMaker you are using and what firmware. AM 3.02.00 came out in September of 2017 so any firmware update was released at that time and is not recent.

I have seen this in the past with ABS where the top and bottom solid layers are fully filled and then layers with infill or open walls shrink due to the structure and the behavior of ABS. This is why pictures. print profile, and material are needed to diagnose the issue. If you can share the STL that may also help.

Hi Ben,
I am using AutoMaker 3.02.00 (when I check the version) and using Robox Black as Night ABS with 40% fill. The parts turn out flawless as usual, but oddly now they have this strange "necking" for the first 5mm of growth from the table. Whether I print a cube, cylinder, sphere.... there is always that necking at the bottom for about 5mm or so.
There are a couple of things that have changed. First, we moved to a new building. When setting up in the new location, the machine prompted a firmware update, which we let it do. Now we cannot get a part to print without this neck. We have tried this with other colors such as dynamite red and cornflower blue. Exact same anomaly.
So this could be an environmental issue vs firmware.
There are no corner edges pulling up or elephant footing.....it is a perfect print aside from this necking. The object printed in the photo should have perfectly straight edges. The very first layer appears to be correct size, but necks inwards...then back outwards once above 5mm and rest of the print is normal.

1554771822-bracket.jpg

Are you using the default Draft, Normal or Fine setting or a custom setting?
What firmware are you using? Preferences - Maintenance, bottom of the page.
Are you printing with the door open or closed?
What is the temperature in the room the printer is in?

Does the necking appear if you repeat the print immediately after?

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The "necking" you mention in the comments is shrinkage. I haven't seen this for along time and I think it is probably related to the ABS you are using. The older ABS we supplied had far more warp than the TitanX we love now.

If it was performing well before but is not now then it is likely the usual culprits:

  • Environmental. Keep the door closed for ABS and try to maintain a high temperature inside the box. If the room is cold or draughty it might effect this.
  • Moisture in the filament. It is possible that the first few rings of material have absorbed more moisture and are shrinking more with heat from the bed. Are there any popping sounds coming from the nozzles? This would indicate steam bubbles escaping. Ask a new question about drying filament. We have a new industrial dryer at CEL-UK and are having a great time refreshing old filament. It makes a huge difference.

For official support please create a support ticket using this link www.cel-robox.com/support/

Hi Pete,

I keep my spools in a vacuum oven which can be heated and pull a vacuum at the same time to dry things out. Other spools of ABS have this same necking effect. I have a sample of ABS filament I am making sure there is no moisture content and will try a sample print and let you know. I saw that industrial dryer. Very nice.

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@gavincurtis

Does it do it with say a 20mm test cube. Is it "necking" in one plane only, so say just the X or Y or both all the way around? I too think it is shrinkage, but related to the infill area vs strength. the larger areas of infill can exert more shrinkage on the perimeters. Out of curiosity, if you increased the perimeter shell count does it improve or reduce the infill percentage. If you have only noticed this from a firmware change, you can revert it back to an earlier version, if you want to do a back to back test. I've been told the firmware is normally matched to an AutoMaker release, but you can manipulate this, and BTW my robox_r765.bin file was modded in November 2018. There is a r766 too you can try. :)

I do not think that this is a firmware related issue - the changes to the firmware should not affect this behavior. We have had the 765 firmware out in the wild for several months and this is the first time this has been reported. I am inclined to investigate material or environment first, then a possible printer mechanical issue, possibly due to an assembly issue. The user has reported problems with Bowden tubes in the past, though has not made me aware of the final solution for that issue.
I also use ABS with the 765 firmware, though I use TitanX, and have not seen this behavior.

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@bhudson Neither do I :) I've had all flavours but the OP thought it happened from then on, so besides asking questions before to ascertain if there is a mechanical or model issue, and stating first I thought it was shrinkage related, I then suggested a way to revert the firmware back for his peace of mind. I don't use ABS or TitanX anymore.

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