3D printed powder cup weight gain while curing?

[VSP968]

So while I’m waiting for my Ingenuity Precision powder cup to get here from Oklahoma, I decided I’d try a couple of different powder cups to reduce powder bounce from my from my new IP trickler mount.

I’ve always had some powder bounce with the aluminum 419 cup and the IP trickler, even with the original mount.

But the Area 419 cup failed in a big way with the latest mount, bouncing powder everywhere. So I ordered the IP cup.

In the mean time I got an MK Machine 3D printed powder cup to try out and it was a failure, as far as powder bounce goes, too.

While I Iwas waiting for the next powder cup to get here I noticed something weird.

The MK Machine cup that weighed 245.08 grains when I got it now weighed 245.18 grains two days later. It currently weighs 245.22 as of this morning.

Way back since the ChargeMaster and later the Sartorious days, I’ve been writing my powder cup’s weight on the cup.

The Area 419 cup’s weight hasn’t changed.

Next up was this really nice Dead Drop cup I got last Saturday.

It weighed 924.56 grains when I got it.
This morning it weighs 925.66.

I realize the DD cup is a ceramic; the handle is printed.

The 419 cup’s weight has not changed.

Scale is calibrated and grounded, has a recently replaced power plug/ wall wart transformer and is connected to a line conditioner.

I have no doubt the scale is correct, because the 419 cup’s weight is a constant.

Humidity in this room is pretty consistent year round between 50-60%.

Anyone else experienced this? Do 3D prints gain weight while curing?

 

[jthor]

3D printed plastics are hydroscopic, they absorb water in the air depending on the humidity. If you wipe it off with isopropyl alcohol it will loose the weight for a bit.

 

[RegionRat]

Setting a really good null (zero) and gain (full scale cal weight) is a good way to know if the changes are real or just drift and static.

If you have check weights and those are reading true, then you know your issue isn't noise.

Many polymers will go up and down with the humidity levels or cure levels, so it could be real or it could be the challenge of keeping a scale calibrated and quiet.

 

[DairyDictator]

I'm seeing fluctuation with the IP cups as well. My theory is the handle is absorbing moisture from my hands, as it does drift a touch over the course of a couple hours, but my cal weights always read correct.

 

[RegionRat]

Another comment... If you have a concern with the kinds of small changes in weight we are discussing here, i.e., the kind that come from water content changes in (or on) polymers...

To avoid being confused by the potential for the auto-null to induce changes, track the total weight of the cup rather than zeroing the scale on it. That way, the potential auto-null issue isn't part of the measurement.

In other words, get a stable zero and then weigh the cup and record the weight, don't tare on the cup weight and tack the null changes since the auto-null could be playing with you.

In physics labs, we use $very$ good scales to track things down below a milligram, and while these A&D FX120i scales are great for the money, they are not the equivalent of a laboratory scale used for tracking small differences of big values.

That said, it doesn't mean your observations are not potentially real. Many common polymers do change with humidity.

Hopefully, your polymer cups don't change so fast that they ruin your work. As long as you occasionally watch the tare weight of the cup and the zero, you should be able to keep loading. Pick some interval during long loading sessions and force yourself to watch the tare weight of the cup. As long as you are careful to keep the zero, you should be able to keep your powder charges under control.

Nylons and similar polymers are notorious for absorbing and giving off water. Other polymers don't. It all depends on the chemistry and form of the polymer. Nylon, ABS, acrylic, PET, PBT, polyurethane, and polycarbonate, will all vary enough with humidity for you to notice.

The only polymer with zero water absorption is PTFE, but it can bring a severe static problem. Plastics with very low water absorption are polymers such as PEEK, PPS, PSU, PPSU, PEI, PVDF, PET, PP, and PE. All of these have their pros and cons. YMMV

 

[VSP968]

Another comment... If you have a concern with the kinds of small changes in weight we are discussing here, i.e., the kind that come from water content changes in (or on) polymers...

To avoid being confused by the potential for the auto-null to induce changes, track the total weight of the cup rather than zeroing the scale on it. That way, the potential auto-null issue isn't part of the measurement.

In other words, get a stable zero and then weigh the cup and record the weight, don't tare on the cup weight and tack the null changes since the auto-null could be playing with you.

In physics labs, we use $very$ good scales to track things down below a milligram, and while these A&D FX120i scales are great for the money, they are not the equivalent of a laboratory scale used for tracking small differences of big values.

That said, it doesn't mean your observations are not potentially real. Many common polymers do change with humidity.

Hopefully, your polymer cups don't change so fast that they ruin your work. As long as you occasionally watch the tare weight of the cup and the zero, you should be able to keep loading. Pick some interval during long loading sessions and force yourself to watch the tare weight of the cup. As long as you are careful to keep the zero, you should be able to keep your powder charges under control.

Nylons and similar polymers are notorious for absorbing and giving off water. Other polymers don't. It all depends on the chemistry and form of the polymer. Nylon, ABS, acrylic, PET, PBT, polyurethane, and polycarbonate, will all vary enough with humidity for you to notice.

The only polymer with zero water absorption is PTFE, but it can bring a severe static problem. Plastics with very low water absorption are polymers such as PEEK, PPS, PSU, PPSU, PEI, PVDF, PET, PP, and PE. All of these have their pros and cons. YMMV

That’s kinda’ what I’ve been doing all along with my aluminum 419 cup with the weight written on it. It’s an easy way to see that the scale is still zeroed during a session.

This all went out the window when I started trying printed polymer cups because of the powder bounce I was experiencing with the new style IP trickler mount.

Finally got my IP cup today. Calibrated the scale and weighed it. I’ll post my findings in a few days and see if the weight changes.

 

[Rich04]

Also a good idea to use a conductive filament to print the cup, I’ve drawn up a snail shell type for my V4 with ASA but I’ve found it a pain to get nice prints, acetone dip after helps but seems to make the powder stick worse initially.

 

[KnowNothing256]

Static can be an issue, but I was too cheap to buy a fancy cup. I found some glass espresso shot glasses that eliminate powder bounce, at least when I start with a manual drop.

I’ll reevaluate if I can ever snag an autodrop.