pic: 2228 Cougar cut on to sheetmetal (CAD)

[jamie_1930]

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[548swimmer]

I'm assuming the yellow part is the cut-out?
How thick are those thin parts supporting the center?
If they're too thin, the h2o jet might not cut them accurately enough and you end up with a really sweet outline.

[jamie_1930]

It's two pieces of 1/8" sheet metal, the black sheet on the front has the cougar cut out on it, and the yellow is just a solid sheet. The supports for the floating pieces are 1/32". I wasn't really planning on making this into a part, but how thick should they be for a water-jet to cut them? and would you be able to cut smaller with other means?

[548swimmer]

If you have access to a vinyl cutter, that would be the way to go for this. 1/32 seems a bit small, but I'm not really sure. We tend to keep our walls at least 1/4, though for these parts structural integrity is an issue too. As far as other methods, no. Water-jetting will give you the cleaner edge than plasma, and a more reliably straight cut. With plasma, the edges are jagged, and may accidentally cut through a 1/32 wall. I think the wall thickness may be dependent on the precision of your water-jet, so I'd look for those specs if you can find them.

[sgreco]

Originally Posted by 548swimmer

If you have access to a vinyl cutter, that would be the way to go for this. 1/32 seems a bit small, but I'm not really sure. We tend to keep our walls at least 1/4, though for these parts structural integrity is an issue too. As far as other methods, no. Water-jetting will give you the cleaner edge than plasma, and a more reliably straight cut. With plasma, the edges are jagged, and may accidentally cut through a 1/32 wall. I think the wall thickness may be dependent on the precision of your water-jet, so I'd look for those specs if you can find them.

1/4 inch is overkill. My team used quarter inch side plates this year. We had 4 of them spanning the whole side of the robot and they were 3.5 pounds each after being cut and wouldn't break no mater what you did to them. CAD analysis I've done says 1/8 (if properly mounted and secured) should survive all FIRST type collisions. 1/32 is thin, but if it's just a backing for decoration it's not a problem. My team made our shooter in 09 purely out of 1/32 inch sheetmetal. It was really light and we had no structural problems (it didn't take any impact either though). For cutting it depends on the machine. Some might break it by accident, good ones won't. Any real machine shouldn't if used properly. The abrasive sand in waterjet can vary in tolerance and even abrasiveness, but it shouldn't shouldn't break a 1/32 inch piece of aluminum by accident. It can also depend on the PSI, waterjets PSI can vary by a couple 10 thousands. It can easily be adjusted to suit the material and its thickness.

[548swimmer]

Originally Posted by sgreco

1/4 inch is overkill. My team used quarter inch side plates this year. We had 4 of them spanning the whole side of the robot and they were 3.5 pounds each after being cut and wouldn't break no mater what you did to them. CAD analysis I've done says 1/8 (if properly mounted and secured) should survive all FIRST type collisions. 1/32 is thin, but if it's just a backing for decoration it's not a problem. My team made our shooter in 09 purely out of 1/32 inch sheetmetal. It was really light and we had no structural problems (it didn't take any impact either though).

we use 1/8 thick for side plates and such, but for lightening grid patterns the cross supports were 1/4 wide. The issues here is trying to cut out two shapes in sheet metal with 1/32 between them, not cutting 1/32 thick metal.

[sgreco]

Originally Posted by 548swimmer

we use 1/8 thick for side plates and such, but for lightening grid patterns the cross supports were 1/4 wide. The issues here is trying to cut out two shapes in sheet metal with 1/32 between them, not cutting 1/32 thick metal.

I see, I misread, but even so, it depends on the machine whether it breaks or not and whether it is used properly. A typical waterjet should have a tolerance to cut much thinner than a 1/32 inch divide.

It's going to depend on where the impact is taken, where the pressure points are, and where the cuts are in relation to that. Until we know that I wouldn't say that it's safe to assume a certain thickness is too thin.

[548swimmer]

Originally Posted by sgreco

I see, I misread, but even so, it depends on the machine whether it breaks or not and whether it is used properly. A typical waterjet should have a tolerance to cut much thinner than a 1/32 inch divide.

It's going to depend on where the impact is taken, where the pressure points are, and where the cuts are in relation to that. Until we know that I wouldn't say that it's safe to assume a certain thickness is too thin.

Yeah, we just go with 1/4 inch as a minimum to be safe.

[sgreco]

Originally Posted by 548swimmer

Yeah, we just go with 1/4 inch as a minimum to be safe.

It is good to stay safe on thickness. I just figured it won't matter so much on a decoration so long as the machine can cut it.

[548swimmer]

Originally Posted by sgreco

It is good to stay safe on thickness. I just figured it won't matter so much on a decoration so long as the machine can cut it.

I think a vinyl cutter would be the best way to do it though.

[jamie_1930]

Just to reitterate real quick is the whole piece is two 12" x 12" sheets of 1/8" thick aluminum, and the supports that are holding the floating pieces, like the swirl on the cougars cheek, on the front plate are 1/32" wide channels. My opinion is that these are completely structural sound for their purpose, keep in mind that if we ever use this it would be for decoration and kept out of the areas that will be frequented by collisions.

Out of curiosity how much would you guys estimate it would cost to get this cut?

[548swimmer]

Originally Posted by jamie_1930

Just to reitterate real quick is the whole piece is two 12" x 12" sheets of 1/8" thick aluminum, and the supports that are holding the floating pieces, like the swirl on the cougars cheek, on the front plate are 1/32" wide channels. My opinion is that these are completely structural sound for their purpose, keep in mind that if we ever use this it would be for decoration and kept out of the areas that will be frequented by collisions.

Out of curiosity how much would you guys estimate it would cost to get this cut?

My only concern is getting it cut, not how strong it will be once it's cut. If it is an issue, just throw some thin lexan over it. If you're outsourcing it to be fabbed, I would really look into making the yellow pieces out of vinyl. Especially since you could then eliminate those structural supports altogether. I got a key chain custom cut with plasma, not water, from TMSmetalworks.com, and they were really nice to deal with, and reasonably priced. I'd stay away from plasma because of the wall thickness though, but that's just me. We do all of our cutting at GM, so I have no idea how much it would cost.

I'll say it one last time: go for vinyl!

EDIT:
http://www.customcutvinyl.com/graphics.html