PDMS Life Expectancy

Life expectancy of the PDMS layer has typically been give in terms of liters of resin being used, however that number is extremely vague and should not be the measuring stick we use.

I think it’s time to actually put some meaningful numbers behind this.

We all know that different resins have different curing/exposure rates which affect the PDMS, but we don’t know what the actual numbers are behind them other than the tough or castable is harsher than white or grey.

Layer resolution will have a great impact on the life expectancy. As a simple example. take a 100mm solid cube; it’s approximately 1 liter of resin. Printing this cube at 01.mm without supports will expose the PDMS 1000 time (1000 layers), but printing it at 0.025mm will expose it 4000 times. Or put in other terms the equivalent of 4 liters at the lower resolution.

I think it’s about time that we get a more accurate idea of what to expect out of a tank based on empirical data which FormLabs already has and can provide.

They only offer 2 types of tanks with 2 types of materials, PDMS and FEP or whatever they have on the new LT model. So the life expectancy should be attached to the resins, rather than the tank. For example:

Grey v.4 (RS-F2-GPGR-04):
PDMS = 10,000 exposures
FEP = 100,000 exposures

Tough v.5 (RS-F2-TOTL-05):
PDMS = 3,000 exposures
FEP = 25,000 exposures

Obviously my numbers are just a place holder, but the actual numbers exist. FormLabs has already done this testing and knows exactly how many times you can print each and every one of their resins on the various surfaces they’ve used.

This way, we will know exactly what we should expect from every resin and tank we buy. I understand that one’s mileage may vary, but these types of numbers are certainly more useful than “your tank will last about 2 liters of resin”.

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This isn’t as simple as you might think. We’re all printing parts of different sizes and shapes and in different areas of the build platform. Repeated printing in a single spot can blow out the PDMS way before 2L of resin. A bunch of smallish parts that are moved around every time will last well past 2L of resin.

There’s a lot of risk for Formlabs if they say a tank will last for “X” number of layers because some users will print in ways that kill the tank early and demand new ones. This is why you get an “about” in the statement of tank life.

I have a tank that’s on it’s 3rd liter of clear resin and still going strong.

This is the meat of it I think, and also why they don’t offer to display the number of layers or litters the tank has been through despite the fact that they probably record the data anyway.