3D model tweaking

With the advent of 3D printers, especially relatively cheaply - around the cost of a sound fitted loco, ok maybe not too cheap then, as a tool the 3D printer is becoming useful.

There are currently two main types available to us punters in the sub £500 market.

Fused Deposition Modelling FDM - uses a filament, heated then extruded through a nozzle on to a bed. The nozzle moves across the bed producing the finished model one layer at a time, each time a layer is completed, either the head is raised by the layer height or the bed is lowered by the layer height.

The new kids on the block are Resin printing, there are two version Stereolithography SLA & Digital Light Processing DLP. Both use light to cure the resin.
SLA uses a laser to cure the resin by drawing the image one layer at a time, much in the same way as the FDM print heads do.
DLP uses a HD lcd screen to act as a mask, and exposes the whole bed to UV light for a set time to cure the resin on the plate. One big advantage is it takes the same time to print 5 models as it does to print 1 (providing they will fit on the build platform), whereas with both SLA & FDM it will take 5 times longer to print 5 models than to print 1.

Quality wise the SLA is best, then DLP then FDM. However the cost of an SLA printer is approx 5 times that of a FDM or DLP printer.

OK so what has this to do with 3D model tweaking, well I have been asked to test a couple of 3D models on my Anycubic Photon DLP printer to see if the upgrade from FDM printing to DLP is worth the cost, and also with the spiraling cost of Shapeways 3D printing service, if these can produce a comparable product.

FDM printers normally on the finest settings print layers approx 0.1mm thick, the DLP printer on the standard setting prints at 0.05mm layer height, but this doesn't cover all the reason why the DLP prints look better, with FDM you are squeezing the filament out of the nozzle, which will ooze out of the side, it is also moving so this can also effect the thickness / outer edge of the layer.

Curves and low angle slopes can be really testing for print, as these will exacerbate layer changes.

As can be seen on the head code box roof, the side however are perfect.

To try and overcome this I am going to incline the model by 15 & 30 degrees


Also with the DLP printer I have found you need to lift the model off the build plate using supports and a raft.

Project sliced at 0.05mm layer height



Also the estimated print time is normally 50% over optimistic.

Time to load the printer with resin and give it a try.

Back in a few hours

Paul

 

Oh forgot to mention the layers at 0.05 mm thick on the head code could be felt with the finger nail, but were smooth to the touch with the finger.

Paul

 

While that's printing, there are many threads on tinternet regarding optimum or sweat spots for FDM layer height. Basic theory is the standard Z height is controlled by a lead screw, and the most common used has an 8mm pitch ( 1 rev = 8mm ), and the normal stepper has a 1.8 degree angle per step (200 steps per rev), so 8/200 = 0.04mm per step.
The logic is to use layer heights of multiples 0.04mm.

So.........

As the Makerbot software I have allows the height to be adjusted, I have used the 26 cab roof, tilted at 15 degrees, and created a 0.04, 0.08, 0.1 (std) and 0.12 mm sliced models, time to print and see if this theory holds any water.

Paul

 

Well the first FDM print has started - 0.04mm layer height (don't even know if the printer do that fine), and have reduced the print speed to 20mm/sec, and 40mm/sec for the movement (I normally print faster than this), PLA filament, 220c, 30% infill, 2 outer layers, the bed heated to 70c, and fingers crossed.

Paul

 

The models used was from a pair of STL files provided by Steve Beattie to test the quality of the Resin process. The STL files are smooth with no sign of faceting.

2h24m later and the Resin print has completed

Post printing process - clean down with IPA and a brush to remove any resin clinging on to the print - this is bath No 1, and uses the oldest IPA. Then released from the build plate and given a wash in the ultrasonic cleaner, again with IPA as the solvent.
Then as its the UK approx 4min under an ultraviolet lamp (sold for curing nail varnish).

And the results

Class 26

Normal print

15 degree tilt

30 degree tilt

Class 27

Normal print

15 degree tilt

30 degree tilt

Conclusion

The Class 27 fronts and roofs were printed first, and I did think I may have an issue with one of the axes, as the lines were all in one direction, but the Class 26 were at 90 degrees to them, so it was down to slope direction.

On the 26 at 15 derees facets can still be seen, and only just felt with the finger nail, at 30 degrees it's smooooooth, with no signs of faceting.

On the 27 at both 15 and 30 degrees all sign of faceting has disappeared.

Now just have to wait for the FDM printer to finish its first print - the 0.04 layer which should (if it works) be of a similar layer height to the DLP.

Paul

 

FDM - 4h2m to print one @ 0.04mm layer height

There is a texture feel to the print,

The support material is still in place on the front hood

And compared with the same file printed on the Resin printer

I'm impressed, not as good as the Resin print, but a smear of filler and a light sanding the result would be acceptable.

Interestingly, the facets show on the hood in exactly the same place on both models, so printing at 30 degrees would be good for both processes.

I have started the 0.08 print on the FDM, in theory should take 2h1m to print, we'll see.

Why bother I hear you ask, well I want to 3D print a boiler, so need to find away / settings required to get a near perfect result.

Paul

 

Andy

Regarding the cleaning, two schools of thought

1. Expose to uv before cleaning
2. Expose to uv after cleaning

Different approaches seem to be recommended in different areas, not sure if that is peer related or ambient temperature related.
I find quite a lot of resin still on the surface of the prints even after allowing to drain for a while, so I tend to be in group 2. Care has to be taken as the prints are soft, so I use a tub with IPA in, and a soft 1" paint brush to clean down the prints and print bed (on the Anycubic Photon the print bed detaches from the printer). Remove them from the print bed and then I give them 90 sec in the ultrasonic cleaner.

I would normally remove the supports before exposing to uv as they are softer, but for these tests I left the supports in place so I could tell them apart.

Paul

 

Not far off - 2h3m

FDM 0.08

The band showing may have been when I turned the additional fan on - I forgot to do it after the 3rd layer , and is probably the cause of some melting at the rear edge.

0.1 test piece now printing - the normal high quality setting.

Paul

 

I think it is horses for courses, I will try the FDM printer on brick courses once these tests are completed - may take a couple of days to print tho'

Paul

 

Final two prints completed

0.10 Layer height - default high quality setting 1hr 40m

0.12 layer height - 1hr 20m

Comparison 0.10 (left image) vs 0.12 (right image)

Final comparison

0.40 vs 0.10

Now these are nasty prints for a 3D printer especially an FDM printer the dome of the roof will stress test most printers.

My 3D printer is a CTC dual extruder 3D printer
the only upgrade was an additional cooler added to the nozzles to help cool the printed parts. The rest is out of the box standard.

Filament PrimaValue Dark Grey Filament approx £16 per kilo from Amazon

All printer settings were identical except the layer height.

Looks there may be some traction in the theory as the 0.12mm looks to be a better print than the 0.10 print, and the 0.04 print is impressive (for an FDM).

Andy Sollis has provided me some files to test as well, and as a further test I will try the 0.04mm layer height on the brick base unit. As the Resin version took 10hrs to print this one may take a while.

Paul

 

I've not needed to keep the heat in with PLA - ABS is another matter.

Issue with 0.2 nozzles they can tend to block - especially when using cheap filament, like what I do

Just made up the print file in makerbot for the base unit,

Temp 220c
Bed Temp 70c
3 outer layers
30% infill
0.04 layer height
Raft but no supports, so I will have an issue with the floor
Increased the extrusion speed to 40mm/s (against 20 mm/s on the test prints)
Movement speed increased top 60 mm/s from 40 mm/s on the test piece.

Just need to start the print off.

Paul