jpender wrote::-)
If you're right then a paper filter that has a big hole in the middle should work as well for you.

Very nice deductive reasoning! Betcha experiments are already underway (or certainly will occur tomorrow morning).

I know that people have experimented with paper both above and below the puck and found improvements in flow. So maybe that's what's happening here. Or maybe leaks around the screen are being blocked. It seems worth trying to figure out which, if possible.

I use Aeropress filters as I happened to have a bunch and no more Aeropress - I gave it to a friend. I don't actually remember the difference on extraction but I like it a lot as the screen holds tightly and the water stays very clean.

I'm working on a paper filter cutter with the Robot basket dimensions. It's a good practice for modeling and printing a tight tolerance part with a 3D printer. Also thinking about designing a deep leveler for Robot, OCD style. After sanding down the layers and applying a food safe coating should be fine.

you could copy this for the cutter. Also I designed and 3d printed a leveler, but I didn't like using it since I find raking the surface with a WDT tool to be effective without requiring adjustment depending on dose and bean density. Also some tests on the Decent Espresso Diaspora indicated raking maybe produce more consistency.

That looks like a great idea as well. I was going for a cookie cutter type with razor blades stuck in to keep a consistent look with the tamper leveler and distribution tool. Thank you!

Completely new to espresso at home, lever machines, with new beans new grinder, day 4 in and I got a decent shot today!
Reiterating how well made the robot is, and seemingly a really forgiving a machine in terms of technical skills required.

I didn't get the version with pressure gauge and had a feeling the earlier bad shots (somehow both sour AND bitter) were due to pressure rather than any of the more often addressed variables. Thankfully there was the weight/pressure graph in the cafelat instructions online, pulled out my weighing scale and turns out I was using like 3 bars of pressure...
Grinding a notch finer today, put all my weight into it to pull about 6 bars of pressure, resulting shot = a world of difference in taste! Still need to dial in the beans a little more, but am so excited I'm finally getting the hang of it!

For those without the pressure gauge, you might find it helpful to refer to weight/pressure graph too!

I figured out the easiest, quickest way to pre-heat the portafilter:

I was placing it on top of my kettle to steam, which took time and left you with a hot handle to manage once you're ready to put the coffee-filled basket in it and lock it into the Robot.

Now, after filling the coffee-filled basket with its ~60 grams of hot water, I simply pour hot water over the portafilter. The metal heats up instantly, only takes a few seconds and the handle doesn't get hot. I then drop the basket in, lock it into the Robot and I'm ready to extract seconds later, with no heat loss.

Obviously you need to be working next to a sink, but it makes pre-heating instantaneous with no hot fingers!

My handle doesn't get hot when I place the basket/portafilter on top of my kettle on the stove to pre-heat, but my kettle is cone shaped and the base fits the heating element well which may help keep the heat from the handle.

I gave myself a second degree burn one morning pouring hot water over the PF/basket. A little bit ran down the handle to my fingers leaving me with a nice blister.

I experimented some with the overflow method, measuring the water temperature profile during the pull. The overflow pour is a close cousin to the method you're using. I found that it was less repeatable than heating the PF on the stove, at least for me. I guess I just couldn't pour the same amount of water each time or the dwell time was varying. I don't know. On the stovetop it probably reaches some equilibrium temperature and that's it.

I insulated my handle so no hot fingers for me either.