More sheet metal tools

Chadfrom7226 · October 13, 2020, 1:45am

Our team is looking to expand our sheet metal capabilities. We have a CNC Router and a basic 48” brake (1/16” capacity)

We struggle with bends in the middle of parts, bends that are close together, and we would like to do some bead rolling. Currently, if we don’t use the brake, we use a vise and a hammer

Are there any machines you guys can recommend? We primarily do 1/16” 5052 but we also have 3/32 and 1/8. I don’t expect anything cheap to do anything thicker than 1/16”

Thanks!

Mike_Schreiber · October 13, 2020, 3:13am

We did all our sheet metal on 3538 this year (and there was a lot of it) with these two tools our of 1/16" 5052.

30" Super Cheap Harbor Freight Brake

This has been in the 3538 shop for years and didn’t get used much. We upped our sheet metal game this year by adding a backstop and some beefier clamps and we were able to get really consistent bends. We could not bend 1/16" 5052 full width on this if our flanges were less than an 7/8". We successfully did 24", but that was an effort. In general we just don’t design for parts that require that.

8" Vice Brake

This was necessary for some bends this year because of proximity to each other. Also makes it a lot easier to get precision bending compared to the harbor freight brake. This is probably your best (cheap) option for bends in the middle of parts or close together ones. Also worth noting this is a bit of a hazard for your toes. I recommend a cheater bar for the vice.

Not sure if your 48" brake is a finger brake or a cheap HF one that is all one piece on the clamping area, but the finger brakes where you can move the fingers enable a lot more functionality. If you want to do 1/8" you’ll likely end up needing some sort of press brake or a hydraulic press and some tooling that fits in it. Bead rollers sound cool, but I’ve never found it necessary in FRC - if you think of a part where a bead is better than bending I’d love to see it.

On 67 we didn’t use the press brake in the shop until 2019, before that all of the sheet metal stuff was done on a 48" finger brake - that should do just about anything you need for FRC.

A few tips for home brew sheet metal (these don’t all apply if you send your stuff out)

Design with a consistent flange length (I like 7/8", but you do you), this can’t be too short because you need material to grab when you bend. It also makes your robot look good if all the flanges are the same length.
Use a backstop, this means you don’t have to setup your brake every time you want to bend a part. This takes ~30 seconds to do and significantly improves the accuracy and consistency of bends. Set the backstop distance on a caliper. Use the caliper to space out a 30 thou thick piece of lexan and tape it down. It’s easy to adjust and remove. Double check the tape between parts, duct tape held fine for us.
If your bend needs to be within 10 thou for the part to work the design probably doesn’t work.
Don’t put precision holes on either sides of a bend in a part. They won’t end up the right distance apart. Clamp and match drill when you can get away with it (most of the time you can). Exception if you can get away with a slotted hole.
Two Cs that are designed to nest, will still nest if their flange lengths are all off by the same amount. This is why you should use a backstop and design them with the same flange lengths - the bends will all be the same even if they’re wrong, it won’t matter. This is the most of the reason the 67 sheet metal chassis went together.
Use geometry over thickness. Lightening holes don’t get you very far in 1/16" aluminum, but most of the time small brackets that were 1/8" can just be down sized and flanges can be added and then it’s way stiffer and lighter.
If it’s not stiff enough, you can tie the flanges together with a piece of angle or another bent sheet, this will give the part significant torsional rigidity.
Don’t put holes near bends.

Other cool things I’ve wanted to try but never got around to - 3d printed press brake tooling and 3d printed stamping dies. Also putting darts in parts sounds cool.

ahartnet · October 13, 2020, 4:14am

Do you happen to have a picture of how you did a backstop with the HF brake? Don’t you have to remove it or something if the backstop is only for the flanges, but not for other bends along the way?

Did yall use a router to score/mark along where the bends are supposed to be?

We’ve done pretty much no sheet metal, so these may be some silly questions

sanddrag · October 13, 2020, 5:14am

I researched this quite a bit about a year and a half ago. After reviewing pretty much every machine, because that’s how I shop, the determination I made is that unless you have some serious money to spend, most of the available options aren’t great. For something cheap, I had my eye on this thing from Grizzly. There’s also plenty of shop press brake attachments, that essentially of consists of putting a precision or non-precision punch and die into a standard hydraulic or air over hydraulic shop press. This is probably the way to get the most tonnage for the least money, but it doesn’t accommodate a back gauge without some custom fab work, and that’s kind of a big deal.

If you have the budget and are looking for something kind of nice, check out the Atek Bantam press brake. It’s air actuated, and seems like a neat little machine. It can get a fairly pricey with the accessories though.

If you can find one, the old DiAcro manual press brakes are cool. 971 uses one. But, they haven’t been made in many years, and are pretty hard to come by.

We tried doing some bead rolls and didn’t have a lot of luck getting them to turn out right. On the other hand, we had a blast with this dimple die set this year. Very high quality and an amazing price for what it is. https://www.eastwood.com/eastwood-dimple-die-hole-flares.html

Mike_Schreiber · October 13, 2020, 5:34am

The backstop we used all season was only a 5" x 2" piece of lexan. If we wanted to not use because we had longer flanges we’d either bend in a different part of the 30" long brake or just pull it off.

I used to mark the center of the bend line and cut a notch so it could be easily seen where to bend parts, this good for when you want to show where to line it up in the brake but you don’t have a backstop because the flange is too long or a weird shape. I stopped doing this when we went to the press brake on 67 out of laziness because I didn’t want to open AutoCAD (and time spent doing that delayed the CAM process) and couldn’t figure out an easy way to do this in Solidworks. I found it easier to either make a layout drawing with the flange dimensions or just sharpie the part than doing a bunch of line trimming in AutoCAD (if someone has a good way let me know).

@Allison_K may be able to scrounge up a picture. I did not take any and don’t go into the shop these days. (it probably feels like I tag you for pictures every time some one asks)

Chadfrom7226 · October 13, 2020, 3:11pm

My technique for accurate bends is to drill holes on the bend line with the CNC router. I place 3-5 holes (1/16") on the bend line and line the fingers up on that. Ever since we started doing that, we have had very accurate bends.

However, I’m gonna have to steal that backstop idea. That’s a good idea

coderkevin · October 13, 2020, 5:35pm

We ended up purchasing this finger brake that fits in a harbor freight hydraulic press. It does everything we could possibly want and comes out cheaper than anything else I’ve seen. We can even bend 1/8” aluminum to 90 degrees, no problem.

https://www.swagoffroad.com/SWAG-20-TON-Finger-Brake-Heavy-Duty-DIY-Builder-Kit_p_86.html

Allison_K · October 13, 2020, 8:30pm

Here’s a picture of the backstop. The backstop should be thinner than whatever material you are bending. The deep throat clamps were helpful, especially for very long flanges.

Edit: In the interest of full disclosure the one pictured is not the one we used in season but it’s been six months and who knows where that one went. It could safely be much shorter than it is as pictured.

JamesCH95 · October 15, 2020, 11:46pm

Two words: Swag Offroad

Stupid name, great products. They have budget-oriented sheet metal tools (among a lot of other stuff). I bought the 12-ton press brake kit when I was broke but needed to bend some things. Still works great many years later, and now they have much nicer finger-brake kits.

You will also need a press from Harbor Freight, get that with a 20-25% off coupon. And if you have shop air or a compressor, this air-over-hydraulic ram is REALLY worth the upgrade. It makes extremely short work of pressing hex broaches too!

Edit: since you have a router you have the option of perforating your bends if you think you can tolerate the strength loss (stiffness is still, generally, diminished a bit less). I’ve done this and then bent the pieces on a very light-duty pan and box brake or by hand.

philso · October 16, 2020, 2:27am

Swag Offroad also sells several versions of a table for portable bandsaws. Each of them fits a different model. The various models are basically the same except that each one is designed to fit different makes/models of saws. Over the years, I have seen several teams bring these to competitions.

Swag Offroad also sells their metalworking products through Amazon in case your school or team has to buy from approved vendors.

Chadfrom7226 · October 16, 2020, 3:17am

Our team actually has one of these. They are great! 10/10 would recommend

philso · October 16, 2020, 3:54am

I am considering getting one for myself.

They also have Dimple Die sets for stiffening large pieces of sheet metal.

JamesCH95 · October 16, 2020, 12:05pm

We have the Milwaukee portaband setup, which has made more than one appearance at an event’s ‘machine shop.’ I like it very much, and having a portaband in general is really nice. There are better, more expensive, stands that can operate a vertical and horizonal bandsaws… but now I’m off on a tangent.