Problem with de-laminating shells

[Bjarte_Almklow]

Hello people. I am new to 3dhubs, so this will be my first question.

I am using a Makerbot Replicator 2X where I work, making polyurethane casting moulds and so far it is working fairly well, but I do have a small issue.

The shells are de-laminating at some points and I can’t seem to do anything about it. So far I have tried to increase nozzle temperature and I am now printing white ABS at 242°C with the print bed at 110°C. I have also tightened the X and Z belts, and lowered print speed from 90mm/s to 80mm/s.

Overall print quality is fairly good and I am mostly happy with the results, I just wish I could get this shell challenge fixed also.

Does anyone have some tips on what I can try from here?

[Richard_20]

Be sure the printer is not near overhead venting.

Try to use different layer height, .2 vs .15mm

Try a different spool of filament.

[Maciej_3]

Try to angle the model lets say 5dg i Z axe.

The easies thing to do is to fill the holes with the mixture of acetone and ABS.

[Openforge]

Do you spray anything inside tour mold prior your 2 parts injection ? Like something that ease when releasing.

I’d like to see you’re results if you don’t mind posting some more pictures.

Thank you, David

[augusta3d]

I’ve found filament to be very fickle at best, from spool to spool you can get different results.
You could us a mix of acetone and abs and make that into a slurry and paint it on. This will leave a visible mark that will show up in your cast pieces after molding. Often what we do is after we 3D print a part we do a lot of finishing work on it before making a mold, this includes lots of wet sanding, sometimes bondo or other pit fillers, heavy build primers, etc. It’s very time-consuming, but it works. I guess my point is that I’ve never had a single print come out perfect, there always seems to be something that needs fixing.

[rdibisch]

It looks like you might be under extruding. Measure the width of your filament and enter that into your settings. Made a world of difference for me.

[Bjarte_Almklow]

Thanks, I will give that a go before my next print.

[Bjarte_Almklow]

Hi.
We use a silicone based release agent before moulding. This is a shoreA75 polyurethane to water seal cable connectors and cable joints.

I don’t do much after work on the mould before we use them, so its not 100% smooth, but I will see if I can take some pictures on monday and post it here.

It works fairly well and is a huge cost and time saver for us, but I do have some issues with the ABS bubbling slightly during preheat to 70°C. I will try a new material at some point to see if I can combat this. But this might just be a result of the shells being delaminated, also.

[Bjarte_Almklow]

Thanks for tips Might try some of them, but if it becomes to much of a time consuming thing, then its not worth it and we might as well machine them in aluminium or rubber.

[Bjarte_Almklow]

I’ve on my third spool atm with the same issues, but I will try the layer height tip… Thanks

[Bjarte_Almklow]

might try that if I can’t fix it any other way, but I would like to find the root cause, since this might become something we do a lot of and I don’t handle things I don’t understand very well.

[rdibisch]

Looking at your print again, I definitely believe it’s under-extruding, but your build-plate level will also affect this. Filament is rarely exactly 1.75mm in width. I find the range to be between about 1.68 up to 1.80. By measuring the width of your filament with a caliper and entering that into the makerbot software, it adjusts the extrusion speed to ensure that you are delivering the correct amount of filament to the extruder.

The print bed on the M2X is notoriously warped at temperature. I switched to a heated glass bed for mine and that problem has gone away forever. If the build plate is too low, then the first level will not “smoosh” together correctly. Your photo shows the top side, so this would not come into play. But the fact that there are gaps and ridges on the top side shows that there is not enough filament coming out of the extruder.

[Bjarte_Almklow]

Thanks friend on Monday I will see what the caliper says and do some tests. Any tips for a good test print? A really difficult one?

[KrazyJim]

A couple of points. Well maybe more than a couple.

1) If the ABS filament has been open for a while, it may have absorbed moisture. Place in an oven at 165 deg F. The specifications for drying ABS say it may take up to 7 hours to dry. I periodically put it in for 2-3 hours. Much over 165 deg F will melt the spool which usually is Polystyrene, which has a much lower melting temperature. Ask me how I know.

2) Store ABS in sealed freezer bags. Squeeze as much air out as you can and seal the bag. Place in a second bag and again squeeze out the air.

3) Reduce the number of shells to 1. Try that. It looks like you are using 4 shells. The Makerbot slicer seems to be a little off when multiple shells are being used.

4) Increase the infill percentage when you reduce the shell count.

5) Increase the thickness of top and bottom surfaces. It is under Settings | Custom | Model Properties | Roof Thickness and Floor thickness. Increasing this value improves surface finish of top face.

6) Don’t go much over 243 - 245 C for extrusion temperature. Some plastics change their behaviour when extrusion temperatures are too high.

7) The belt gripper on the 2X head carriage does not have enough pinch. Remove both heads and nozzles. Slide belt fully into the gripper. Drill through the gripper and belt with a 1-1.5mm drill and use a 1 - 1.5mm bolt and lock nut to pinch the belt tight. Before starting this, you can prove this is a problem by pinching together the carriage left - right drive belt about 50 mm away from print heads. This locks the belt from moving. With the belt locked, now when you push the print heads left and right, you will see that they move and the belt does not. The play you see is in the belt gripper. The drill and bolt fix it. Make sure the belt is fully seated in the gripper and drill through the centre line of the belt.

8) The heated bed rises up in the centre of the platform as it heats up. This gets worse as the bed heat-soaks. So I set the bed level when it is cold. Then when I heat-soak it by preheating for 30 minutes, I then use the bed leveling utility and lower the bed evenly on all three adjusters until the gap in the very centre of the bed is just right. Now all the gap checks at the edges of the heated bed are too high, but the one in the centre is just right. A high temperature glass bed is next on my shopping list.

9) Tighten the left right carriage belt tension. Pluck the belts like a guitar string. They should all have similar tones or pitch. The deep tones are the loose ones.

10) The short vertical belt on the right rear is hard to tighten. Make sure it is very tight. Loosen both bolts holding the motor. they should be so loose the nuts almost fall off. Pull down on the motor. Tighten the upper nut first all the way. Then tighten the bottom nut. Pluck the belt to gauge the tension. I found it was best to remove the front door and side panel to do this. It takes a few minutes but is quicker than fighting your way through and around the front door and reaching in from the top.

11 ) High Speed printing is not your friend. You can easily go too fast. You seldom can go too slow.

Let us know how you make out.

Jim H

[Sra1]

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