PhireFase

Ok then tell me your address

Common misconception with cement.  Cement doesn't dry, it cures.  When it does this, it heats up which in turns evaporates the water.  It's a chemical process and will happen even if it is moving.  Eventually it will harden albeit not very strong due to many factors.

Yeah the problem was just the different double sided tape gummed up the endmill and then the chips couldn't get removed. Screws didn't work because the aluminum was getting pulled up off the table while being cut.  Now have a single flute carbide cutter that does wonders along with a FogBuster.  Very aware of speeds/feeds, I did several classes on CAM in university and have a license for GWizard.
Believe it or not I've actually done several classes on machining already, this was just some growing pains and not having the right work holding on hand.  We are getting a lathe, but I have spent hundreds of hours on one already with an instructor in the room and don't plan on letting anyone else use it until they have taken a course on proper use.

I agree with what @Thermosman says. You guys/ @AlexTheGreatish should really do more research into using more heavy duty equipment. These tools are not something that you can just wing and expect good results. I remember Alex asking about a welder and a metal lathe in an earlier video, and if you are to get those, I would STRONGLY recommend talking to a metal shop or someone with experience using heavy-duty equipment (even talking with a local school's metal shop teacher will be better than nothing). If you are to buy more heavy duty machines and not improve the way you handle them/ how much research you do beforehand, someone WILL get seriously hurt. I do not know the safety training that Linus Media has (you seem to be good about hand tools/machines), but there is a big difference between machines that you can hold, and machines that weigh 10 times as much as you. If you have any questions about "maker" related projects, feel free to DM me. I am ecstatic that you guys are doing more projects and really like the videos, it just makes me worry.
/rant

Also, you were using your router very wrong. While I cant see it very well due to 360p, It looks like you have severe chip welding in the aluminum, and I would advise aganist using double sided tape for workholding. Instead, I would drill holes and use screws to attach the part to the scrap board. When you are cutting a complete piece out, you can either put screws in it to hold it down once it is completely detached, or utilize tabs around the perimeter, a setting available in many CAM programs such as Fusion 360, which can be removed using a saw or angle grinder and filed down to remove the part. Also, remove the plastic protective sheet from the aluminum. Again, I can't tell much about the endmill from the video, but it looks like a ~1/2 inch 2 flute titanium nitride coated high speed steel endmill, which you are getting major chip welding from both on the endmill and on the edge of the slotting. Instead of this, i would go with a 1/4 inch or even an 1/8 inch carbide 1 or 2 flute endmill. To figure your your RPM and feedrate, commonly referred to as "feeds and speeds" there are many calculators online. You should reduce your depth of cut and take multiple passes, as slotting, the operation used here, is the hardest you can push any endmill, and you are going full depth in what appears to be 1/8th inch aluminum sheet. Rather than doing this, you should take several shallow passes which will take longer but will produce a much better cut than full depth slotting, which simply doesn't work in aluminum. The chip welding is caused by heat from friction between the tool and the material, as aluminum is a relatively gummy material. While a flood coolant system isn't practical in this case, an attached airblast system, ideally with an oil mister would greatly improve this.
There is much more information that you can find online about aluminum cutting on routers, there is absolutely no reason to just guess at it.
 

Students need discounts on entertainment too or else we'd go insane.
 
It's hard enough trying to pay for tuition fees and not being able to afford luxuries. 

Linus literally answers your first question in the intro to the video. No, they probably don't need it, but it makes building things significantly easier. I think its great that they are branching out into different topics and giving people an easy to understand video about other tech areas, rather than just computers (they are called LinusTechTips not LinusComputerTips).

I worked with a router for 2 ish years and I've got a couple "upgrades" you guys could use in the future that we used on ours. 
1: Use a vacuum table for securing parts instead of double sided tape (if you want to use tape, use this instead). We used 2 sheets of MDF glued together to create a vacuum for material to stick to instead of using double stick tape. The bottom sheet had channels cut into it in a square pattern so that the vacuum can be distributed more. The top sheet of MDF was considered a sacrificial layer so that if the material wasn't the thickness that is advertised or the bed isn't perfectly level, it isn't a big deal if the bed gets cut into. This also allows for the bed to be re-leveled by taking a wide bit and going over the whole bed to smooth it out. Now for the actual vacuum setup, we split the vacuum into 4 quadrants of the table, because if the whole table isn't covered then the parts won't stick as well. We used PVC splitters and manual valves to control which sections had the vacuum applied.
2: For picking up chips, we used a "boot" that clamped around the cutting motor and had a industrial vacuum attached to it. This had it follow the cutter without needing any human interaction. We also would use bristles around the motor to keep the chips in and allow the vacuum to still work at higher z-positions, while the bristles would just collapse when the bit lowers. Our current one is made using 2 plex pieces that have a channel cut into them so the vacuum can be attached next to the bit, but the channel transfers it to right under the bit. We also used 2 pieces so that when we cut aluminum (which you could probably do on your router, just be careful) we would take the bottom piece off, which was just held using magnets.
3: Cool your bits using compressed air. We use something similar to this and sent compressed air through it so that we could move chips in whatever direction we want and keep the bits sharper longer. You will need this if you want to do anything with aluminum, as it will destroy bits.
4: Put your control computer (not a laptop) in a cabinet under the table and have only the monitor, keyboard, and mouse in the blast zone of chips.
5: Label the wrenches that you use to change the bit, because they will walk away if you don't.
 
Overall fun video to watch and convinced me to make an LTT account for this comment. Also when you get a TIG welder make sure you get the correct tungsten and gas for the metals you plan to weld.

Linus literally answers your first question in the intro to the video. No, they probably don't need it, but it makes building things significantly easier. I think its great that they are branching out into different topics and giving people an easy to understand video about other tech areas, rather than just computers (they are called LinusTechTips not LinusComputerTips).

I worked with a router for 2 ish years and I've got a couple "upgrades" you guys could use in the future that we used on ours. 
1: Use a vacuum table for securing parts instead of double sided tape (if you want to use tape, use this instead). We used 2 sheets of MDF glued together to create a vacuum for material to stick to instead of using double stick tape. The bottom sheet had channels cut into it in a square pattern so that the vacuum can be distributed more. The top sheet of MDF was considered a sacrificial layer so that if the material wasn't the thickness that is advertised or the bed isn't perfectly level, it isn't a big deal if the bed gets cut into. This also allows for the bed to be re-leveled by taking a wide bit and going over the whole bed to smooth it out. Now for the actual vacuum setup, we split the vacuum into 4 quadrants of the table, because if the whole table isn't covered then the parts won't stick as well. We used PVC splitters and manual valves to control which sections had the vacuum applied.
2: For picking up chips, we used a "boot" that clamped around the cutting motor and had a industrial vacuum attached to it. This had it follow the cutter without needing any human interaction. We also would use bristles around the motor to keep the chips in and allow the vacuum to still work at higher z-positions, while the bristles would just collapse when the bit lowers. Our current one is made using 2 plex pieces that have a channel cut into them so the vacuum can be attached next to the bit, but the channel transfers it to right under the bit. We also used 2 pieces so that when we cut aluminum (which you could probably do on your router, just be careful) we would take the bottom piece off, which was just held using magnets.
3: Cool your bits using compressed air. We use something similar to this and sent compressed air through it so that we could move chips in whatever direction we want and keep the bits sharper longer. You will need this if you want to do anything with aluminum, as it will destroy bits.
4: Put your control computer (not a laptop) in a cabinet under the table and have only the monitor, keyboard, and mouse in the blast zone of chips.
5: Label the wrenches that you use to change the bit, because they will walk away if you don't.
 
Overall fun video to watch and convinced me to make an LTT account for this comment. Also when you get a TIG welder make sure you get the correct tungsten and gas for the metals you plan to weld.