FRC pocketing

[GeeTwo]

OK, now I'll take the opposite side:

Originally Posted by Cory

But the two points above make zero sense to me.

1) If the part is going on a CNC, the time it takes to pocket is trivial in most scenarios. Our gearbox plates would be run maybe 3-4 minutes quicker if they weren't pocketed. The time to setup the machine is the biggest sink, not the run time. I don't see what laziness even has to do with it. It requires more effort to manually mill any kind of gearbox plate than it does to CNC mill it.

Got no CNC. Got no manual mill. Got no plasma or laser cutter. Got no router. Got no sheet metal sponsor. Pocketing to us means a drill press or jig saw, or worse. Your 3-4 minutes would take us 3-4 days or more. You're on a different plane of existence from most of FRC.

Originally Posted by Cory

2) Your comment about "buying extra material just to throw it away" doesn't make any sense whatsoever. If my gearbox plate fits inside of a 6" long piece of .25" x 6" 6061 bar stock...how am I throwing material out? I'm certainly not pocketing material that is outside of the bounding box of the part. I'm pocketing material that is inside the perimeter of the part no matter what.

This "makes no sense whatsoever" makes no sense whatsoever. If all goes well, there never was meterial outside of the bounding box of the part. However, every bit of material that was originally inside the bounding box of the part but cut away (i.e. in a pocket) is thrown away (or hopefully recycled, especially if aluminum). I certainly hope you don't discount the material originally in the pockets from your BoM; that would have violated the last several years of rules!

Originally Posted by Cory

I'm glad that you think pocketing isn't necessary for your team, but 9/10 years 254 would not make weight without the heavy use of strategic pocketing.

As I said earlier, you're on a different level of play; birds vs mammals. The key item between pocketing as practiced by top level teams like 254 and most rookie teams is that 254 (please correct me if I'm wrong on this) planned the pocketing from the get-go and knew how much strength would remain, whereas rookie teams pocket out of desperation, without a good understanding of what is acceptable vice what is excessive. For us mid-level teams, it makes much more sense to select the proper strength members than to engineer them by buying over and pocketing down.

[Abhishek R]

Originally Posted by GeeTwo

This "makes no sense whatsoever" makes no sense whatsoever. If all goes well, there never was meterial outside of the bounding box of the part. However, every bit of material that was originally inside the bounding box of the part but cut away (i.e. in a pocket) is thrown away (or hopefully recycled, especially if aluminum). I certainly hope you don't discount the material originally in the pockets from your BoM; that would have violated the last several years of rules!

Say you have a gearbox plate. Whether it was pocketed or not, it will end up on the robot as part of the gearbox. The material that is eventually pocketed was likely not going to be used elsewhere on the robot, so the fact that the material is there or not becomes irrelevant. It then becomes advantageous to just remove it in order to save weight - why not take every advantage you can get, right? I understand it's not much and for most teams there are better things to spend time on and ways to prevent this from becoming a large factor (my team did not pocket most plating on our robots), but if you can do it, might as well.

[Cory]

Originally Posted by GeeTwo

Got no CNC. Got no manual mill. Got no plasma or laser cutter. Got no router. Got no sheet metal sponsor. Pocketing to us means a drill press or jig saw, or worse. Your 3-4 minutes would take us 3-4 days or more. You're on a different plane of existence from most of FRC.

Well you wouldn't be able to make a gearbox plate to pocket, without a mill, so this is kind of an apples and oranges comparison.

Originally Posted by GeeTwo

This "makes no sense whatsoever" makes no sense whatsoever. If all goes well, there never was meterial outside of the bounding box of the part. However, every bit of material that was originally inside the bounding box of the part but cut away (i.e. in a pocket) is thrown away (or hopefully recycled, especially if aluminum). I certainly hope you don't discount the material originally in the pockets from your BoM; that would have violated the last several years of rules!

Unless you only make plates with right angles you're going to have material outside the bounding box of the part. It's a very loaded statement to say "if all goes well, you have no material outside the bounding box". Maybe that's true if your team's goal is to never make a non orthogonal part. That is not the case for many teams in FRC.

You also may consider it semantics, but "contouring" is absolutely different than pocketing and contouring is not under discussion here. Furthermore, teams can and do just bandsaw/belt sand the outer contour of their gearbox to reduce weight or provide clearance for other features of the robot.

Yes, material inside the bounding box of the part that you pocket out is thrown out...but MrForbes is making it sound like it's "extra" material that you didn't have to buy and you could have purchased a smaller piece and saved money. It's metal you already bought. It's metal that cannot be used for anything else. His statement makes absolutely no sense in that context.

Your last point is seemingly irrelevant...unless you're suggesting that you think 254 might be violating the rules. We are well aware of how the BOM works.

[Greg Woelki]

Originally Posted by Cory

Yes, material inside the bounding box of the part that you pocket out is thrown out...but MrForbes is making it sound like it's "extra" material that you didn't have to buy and you could have purchased a smaller piece and saved money. It's metal you already bought. It's metal that cannot be used for anything else. His statement makes absolutely no sense in that context.

I think MrForbes is talking more about using thinner, unpocketed (or minimally pocketed) material when he's talking about paying for material that is "thrown away," since you are clearly right in the context that you considered his comment. It obviously depends on the situation, but I'm sure we can agree that the time and money savings often make thinner material worth considering, especially if whatever part in question is being made on a drill press or manual mill (or even on the very low end CNC mill that my school has).

[GeeTwo]

Originally Posted by Cory

Well you wouldn't be able to make a gearbox plate to pocket, without a mill, so this is kind of an apples and oranges comparison.

More like cherries and pumpkins, but it's good that you understand that the situation is so different as to defy reasonable comparison.

Originally Posted by Cory

Unless you only make plates with right angles you're going to have material outside the bounding box of the part. It's a very loaded statement to say "if all goes well, you have no material outside the bounding box". Maybe that's true if your team's goal is to never make a non orthogonal part. That is not the case for many teams in FRC.

You also may consider it semantics, but "contouring" is absolutely different than pocketing and contouring is not under discussion here. Furthermore, teams can and do just bandsaw/belt sand the outer contour of their gearbox to reduce weight or provide clearance for other features of the robot.

You completely lost me on both of these points. Please elaborate.

Originally Posted by Cory

Yes, material inside the bounding box of the part that you pocket out is thrown out...but MrForbes is making it sound like it's "extra" material that you didn't have to buy and you could have purchased a smaller piece and saved money. It's metal you already bought. It's metal that cannot be used for anything else. His statement makes absolutely no sense in that context.

As I read it, MrForbes' point is that you could have bought thinner material originally, and yes, saved money. The money for thicker stock would never have been spent, and this makes perfect sense in my context.

Originally Posted by Cory

Your last point is seemingly irrelevant...unless you're suggesting that you think 254 might be violating the rules. We are well aware of how the BOM works.

If you were referring to:

Originally Posted by GeeTwo

I certainly hope you don't discount the material originally in the pockets from your BoM; that would have violated the last several years of rules!

I certainly did not mean to imply that you were violating the rules, but rather to express confidence that you were not violating the rules.

[Andrew Schreiber]

Originally Posted by Cory

Well you wouldn't be able to make a gearbox plate to pocket, without a mill, so this is kind of an apples and oranges comparison.

I mean, you don't NEED a mill to make a gearbox. It helps but it's certainly doable on a drill press, I've seen it done. Of course, you could pocket with a drill if you REALLY wanted to as well and just make your bot look like swiss cheese.

The big question is, if you don't have these resources and you don't know how to pocket wouldn't the resources being consumed be better placed by leveraging COTs components during the build season? [1] With the low cost of various planetary boxes and the wide range of reductions available in off the shelf spur gear boxes I question why any team that didn't make Einstein last year would need to design custom boxes [2].


I'll go back to writing code and stop nitpicking.



[1] Obviously not a question directed at you/254, more a general thought.

[2] From a functional standpoint, many of teams have the resources and knowhow so it make sense to use it to save weight/money but for teams that DON'T have resources to do it easily, use COTs.

[Travis Covington]

Originally Posted by GeeTwo

As I said earlier, you're on a different level of play; birds vs mammals. The key item between pocketing as practiced by top level teams like 254 and most rookie teams is that 254 (please correct me if I'm wrong on this) planned the pocketing from the get-go and knew how much strength would remain, whereas rookie teams pocket out of desperation, without a good understanding of what is acceptable vice what is excessive. For us mid-level teams, it makes much more sense to select the proper strength members than to engineer them by buying over and pocketing down.

Selecting without knowing the engineering trade-offs and objective differences is simply guessing. Thinner material is also not the same as thicker material with pocketing/lightening/trussing/whatever you want to call it. Maintaining a larger cross-sectional area is extremely important, and pocketing can let you do some cool things to make parts stronger (in directions you care about) while also lighter than their thinner alternatives.