how I avoid fail print and lines (especially on b9emerald)

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nzfinescale
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Joined: Fri Apr 22, 2016 5:13 am

Re: how I avoid fail print and lines (especially on b9emerald)

Postby nzfinescale » Mon Dec 04, 2017 6:31 am

Hey Carl

I am quite happy to post settings but that rather misses the point - which is that the ideal setting will depend on your specific circumstances.

For example when my bulb was new I found that I needed much shorter than recommended exposure as the recommended numbers caused light bleed with over sized details and undersized apertures. As the bulb has aged so my exposures have crept upwards towards the recommended.

Likewise I recently finished my bottle of Emerald and the new bottle didn't work at all at the old settings (either the batch was different or more likely my previous 18 month old bottle had aged). Parts that had previously printed well broke. A bit more exposure fixed the problem and I'm getting better results than ever.

I changed the film today as I was getting some surface artifacts in the same place every run, and a small amount of flashing. Problem solved.

The important thing is to analyse any problem and change variables as required to get a solution. Admittedly, that is not always easy, but that is what the forum is for!

L
OpedHead
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Location: Melbourne, Australia

Re: how I avoid fail print and lines (especially on b9emerald)

Postby OpedHead » Thu Feb 01, 2018 5:40 am

First off Thankyou GREATLY Weaver for taking the time to create this thread!!!!This is one of the best threads I've read.

nzfinescale wrote:For example when my bulb was new I found that I needed much shorter than recommended exposure as the recommended numbers caused light bleed with over sized details and undersized apertures. As the bulb has aged so my exposures have crept upwards towards the recommended.

Likewise I recently finished my bottle of Emerald and the new bottle didn't work at all at the old settings (either the batch was different or more likely my previous 18 month old bottle had aged). Parts that had previously printed well broke. A bit more exposure fixed the problem and I'm getting better results than ever.

I changed the film today as I was getting some surface artifacts in the same place every run, and a small amount of flashing. Problem solved.

The important thing is to analyse any problem and change variables as required to get a solution. Admittedly, that is not always easy, but that is what the forum is for!

L


May I ask what are the indications that the exposure is too short or long?

I think I've deduced that too long will give light bleed (flat thin cured 'splashes' coming off prints), and does the rest mean oversized printed areas and shrunken recesses?

What may be the indications of too short of an exposure?

Also were the spacers you were refer to in your other post related to calibrating the build head and not the film on the VAT?

Thankyou
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nzfinescale
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Re: how I avoid fail print and lines (especially on b9emerald)

Postby nzfinescale » Tue Mar 06, 2018 8:47 pm

Exposure is obviously important.

Underexposed and the prints will be soft and lack mechanical strength (which can lead to breakage and/or distortion during printing). Fine wires and detail may not form.

Over exposure can lead to softening of detail, overthick wires and under size apertures. On the other hand it generates a stronger print, which can sometimes be used to reduce the number of supports.

The light output of the projector is not entirely even either so actual exposure in the corners of the build plate will be less than the 'centre'. 'Correct' exposure may need a bit of trade off between performance at the edge of the build plate and dimensional accuracy in the centre.

Note also that resin age impacts on this. I run both proto and Emerald and I tend to leave them in the vat. If the resin has been sitting around for a week or more it is fine to use but its performance will be different with respect to exposure.

As a model builder I am interested in small details and fit of parts, which means I am interested in accurate dimensions which may not be such an issue for other uses.

To calibrate exposure, I print a small test block with wires and holes ranging in size from 1mm down to 0.1mm. This is printed with an example in each corner and centre of the build plate.

Things to measure:
1. The size of the block overall - obviously this should match the file.
2. Size of the wires, and whether they have printed. If the wires measure different from the file (but the overall block is correct) then the exposure is off. Obviously the block size will also be affected by exposure, but the impact on a 10mm block is relatively small compared to a fine wire.
3. Size of the holes. Fine holes are a challenge, but again it is easy to see the impact of exposure.

Initial layers are deliberately over-exposed to ensure good adhesion to the build plate and to address any unevenness between the build plate and the film on layer 1. If, as I often do, you want a usable layer 1 then tuning this is required. If the initial layers are just supports then just leave them over exposed and accept a little flash.

Spacers/Film tension/build plate calibration.

Currently I am getting the best prints I have ever had. Here's what I have done:

Film tension. Basically I set up the film flat, off the machine. When I fit the vat I tighten the thumb screws until I take up the slack and then just a quarter turn or so more. I have longer thumbscrews than standard (actually the standard ones with 2mm turned off the plastic head). As the film ages (stretches?) the screws need to be tightened.

Build plate calibration. As noted in this thread I have used build plate spacers up to 0.7mm. Currently 0.05mm. The key thing is that if you print a block 1mm high in Z directly on the build plate, then it should be 1mm. If it is less, then a thicker build plate calibration spacer is needed. I have not got to the bottom of why this varies - but for me it does. Consistent once my film/build plate set up remains the same though.

I fitted the new square tilt motor kit. The tilt plate drop is controlled by the spring, and its return to vertical driven by the motor. My tilt plate was sometimes dropping with a loud snap. This was both unnerving and contributing to layering in the prints (I think). I uprated the return spring (with something in the junk box - so don't ask!). The snap is effectively gone and peeling is now far smoother and the prints improved. The issue of build plate spacers MAY have disappeared with fitting the new tilt motor. It is too soon to tell.

Lawrence
petertruong07
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Re: how I avoid fail print and lines (especially on b9emerald)

Postby petertruong07 » Thu Nov 01, 2018 4:12 am

thanks for sharing

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