PDA

View Full Version : Greetings & Punch Press Question



Skip Ellis
12-09-2010, 01:10 PM
Hi everyone - just joined up and am looking forward to learning a lot from you folks. I'm basically a woodworker and guitar builder but have gotten interested in doing some metal work and welding.

I'm also looking for suggestions on building a DIY "cheap" punch press for putting (6) - 3/16" holes in a 3" x 27" x 18ga galvanized mild steel sheet. I'm cutting the 27" pieces out of 3" x 10' stock with a 12" Northern Tool metal shear which is working fine, although it would be nice to cut and punch in one operation, but not sure if it's feasible. I will be making these on an ongoing basis. My present order is for 1400+/- pieces and I'm half way through by drilling 10 at a time in a jig with my drill press. Any suggestions on how this could be further automated on a budget?

Stepside
12-09-2010, 02:14 PM
We need a couple more bits of information to be of much help.

1) where are you? There are more options in a large city

2) accuracy and tolerance required for the size of hole and the location of holes

3) is the drilled hole good enough without removing a burr and is it round enough?

4) repeat job or once only?

Possibilities are a) let someone wear out their water jet cutter b) buy a 4 ton punch and make some fixtures to index and punch the holes. c) If not a repeat job and the quality is there, just finish the job d) find a shop with a CNC punch and have the parts done.

Ries
12-09-2010, 03:16 PM
Like the hot rodders used to say,
how fast you wanna go?
how much money you got?

And what direction will your work go in?

If you think it will stay with similar sized pieces of sheet metal
(ie, under 1/8" in thickness), then there are sheet metal punches and shears out there that will do this quickly and accurately.

A foot shear, and a bench punch, are relatively cheap, available used, since they have been made basically unchanged for 100 years, and easy to use, and resell if you dont need them anymore.

Available new from China, cheap.
http://grizzly.com/outlet/37-Foot-Shear/G9948
http://www.grizzly.com/products/Heavy-Duty-Hand-Punch-w-Stand/H7862

Or from the USA, not so cheap.
http://www.vansantent.com/sheet_metal_machines/tennsmith_shears.htm
http://www.amazon.com/Heinrich-Throat-Handle-Bench-Punch/dp/B000656AZ8

Unipunch makes punch and shear units that can be used in all kinds of presses.

http://www.unipunch.com/catalog/overview/aseries.asp?Unit=170&Page=20

But generally real "punch presses" are mass production machines that are not very flexible, and older, cheaper ones, are dangerous, and newer, safer ones, are expensive.

Press brakes are often used to bend, shear and punch, with unipunch style tooling, small thin stuff- press brakes are a different beast entirely than punch presses.



Or, if you are thinking of more heavy duty metal in the future, everything you are doing now can be done with an ironworker- and most will do the same thing in material up to 1/2" thick.
A nice little machine like this would do your job-
http://vancouver.en.craigslist.ca/pml/tls/2094963874.html
http://www.lislesurplus.com/misc/Mubea-21-ton-ironworker-1-phase-very-good/

Skip Ellis
12-10-2010, 11:19 AM
Thanks for the replies! The drilled 3/16" holes are fine and there are no burrs when using my jig as I have a thumb screw hold-down at each drilling location that keeps the sheets tight together. I just thought it would save time ($$) to punch the holes at the same time I cut each piece and do away with loading and unloading the jig. I guess I could build a punch and die set out of 1/2" plate and mount it in a frame with a 12T bottle jack. I believe it takes 0.7T to punch a single 3/16" dia hole in 18ga - a little less with an angled punch. I'd like to do multiples.

ADGO_Racing
12-10-2010, 11:47 AM
When we were open as a job shop, I had a customer that built a "special die system" It was a basic die set, designed to punch certain finished materials. It was completely self contained. Die set had a shaft through it, with an actuating cylinder on top. Since the cutting was limited, most used air cylinders to actuate them, some used for metals and heavier sections, used a hydraulic unit.

So rather than use a 12 ton bottle jack, which will take more time to pump, than loading/unloading a fixture, build the die set, use a hydraulic cylinder and a foot pedal. Either use multiple stops, punching two or four holes each stroke. Or, punch all of the holes in one stroke, just requires a larger die set. Punching usually doesn't like to have the material stacked. Due to the increased speed, you would still be getting the job finished much quicker.

TGTool
12-10-2010, 12:28 PM
Skip,

I think setting up to punch the holes would be a big, big step if you're wanting to increase the production rate. Right now you're drilling ten at a time, so the time for each is 1/10 the time to drill the stack. In a punch press you'll be doing one piece at a time, even if you punch ten holes in one hit, and then you have to add the load and unload time. As a production job it would probably be run from a coil of strip stock 3" wide with each cycle punching the holes and parting off the previous piece. (Stock is straightened on the path into the die.) You're probably doing about as well as you can expect for that volume with your drill jig.

Ries
12-10-2010, 01:21 PM
Punching multiple sheets at a time is fussy, and seldom works the way you think it should. Theoretically, it should work, but it seldom does, unless you have really good equipment.

Its usually faster to punch one at a time.
But not with a hand pumped bottle jack.

Buy a fifty dollar whitney hand punch with a bench mount- its faster than drilling.

A sheet metal punch, hand activated, is far far easier than a bottle jack or a drill press, and once you get in the rythym of it, you can knock em out in no time.

boslab
12-10-2010, 06:21 PM
whynot use a flypress? cheap and reliable
regards
mark

Ries
12-10-2010, 10:47 PM
In most of the USA, flypresses are very rare, and not cheap.
For some reason, they were pretty much isolated to the jewelry manufacturing industries here, which means you find them in Rhode Island, Connecticut, and Massachusets- but even there, the industry has been in decline for 40 years now, and they are mostly scrapped or shipped overseas.

They never caught on for general workshop use like the did in GB.

On the west coast, for example, I have never seen a used one for sale or at an auction. Its very rare to see one in industry.

In the last ten years, blacksmiths in the USA have started using, and buying, flypresses. Most of them we get here are NEW, from India, and cost a pretty penny. I know several blacksmiths near me that have flypresses, and have had to have them shipped approx 1000- 2000 miles to get them.

I doubt many in england or wales would use them, if you had to order them all from Turkey, and pay shipping.

That said, a flypress would work- but is a bit overkill for just punching holes.

x39
12-10-2010, 11:34 PM
But generally real "punch presses" ....are older, cheaper, dangerous...
Older, cheaper, dangerous... I'm getting all hot and bothered here.... :P

DR
12-11-2010, 10:00 AM
.................................................. .................................................. ....


My present order is for 1400+/- pieces and I'm half way through by drilling 10 at a time in a jig with my drill press. Any suggestions on how this could be further automated on a budget?


Your "present" order is for 1400? This implies you are anticipating more orders, right?

Be careful in investing money to speed things up.

My worry would be at some future point the customer will realize there are shops that can do this much less expensively with mega dollar equipment.

Have you considered getting the parts quoted from a shop with a CNC punching machine? You take a small markup and sell to your current customer.


I had a somewhat related scenario. We were marking parts for customer A who was taking a markup and selling to customer B.

Customer A retired. He connected me directly with customer B. Customer B's quantities increased substantially from approx twenty a month to a thousand. We adjusted price to reflect the increased production.

Customer B began giving me other work. The situation looked really good. Except for the fact the original part was done by us on a CNC in two operations in a method not as efficient as possible on a faster, more expensive machine. I warned the purchasing agent it could be done less expensively by someone with a specialized type of CNC lathe. The reply was, no, they had shopped around and my price was the best.

This went on for 9 months, until I get a call saying to stop all work on their parts and bill them for the work in progress. They had found a shop with the machine the parts should have been done on. I lost all work from that company because according to them I had been ripping them off on the original part. This happened in spite of the fact I had warned them several times the part could be done elsewhere for less.

In my opinion, you're setting yourself up for the same outcome.

fishfrnzy
12-11-2010, 10:53 AM
What DR says.

Check with a "Precision Sheet Metal" shop that has a CNC turret press. Those things will do 80-160 hits per minute ( 5 for your holes and probably 3-4 to part the thing off. Or they can punch all the holes in the sheet and just shear out the rectangles. They'll be accurate too. If you find a small shop they will often allow you to supply the metal if you want. If you are using lawn edging stock ( hardware store metal ) be aware that quality varies A LOT. It can be hard, undercoated, xtra soft you just don't know so its not consistant.

AlleyCat
12-11-2010, 02:17 PM
I use a Roper Whitney kick press for this type of work and it may work for this application as well. Another machine to look at would be the DiAcro stylus punch that operates from a template. It's not CNC but they work pretty good and can be bought for $1500 or so.

I had a customer who used one of these with long strips about five inches wide. The sheet metal strip was fed to a stop on the table, clamped, punched and then cut to the final length by nibbling with a rectangular punch. They produced thousands of parts per month with this setup.

Ries
12-11-2010, 11:10 PM
Older, cheaper, dangerous... I'm getting all hot and bothered here.... :P

I am talking about flywheel powered mechanical press brakes and punch presses.
OSHA doesnt like em, to be sure.

There are still mechanical punch presses in operation in OSHA approved shops- they require a fair amount of guards, and, usually, either a laser beam safety curtain, or two hand operation (so your hands are both always out of the way when the thing trips) or both.

These old mechanical presses cannot be stopped once they start a cycle- unlike newer, hydraulic presses, that can stop at any point in the operation, if the E Stop is hit.

So, yep, more dangerous. But often available quite cheaply. Heavy, though.
Even a relatively small tonnage machine- like say a 15 ton 4' model, which will only do 16 gage, weighs almost 3000lbs.

Punch presses must be used with dedicated tooling- if they hit past bottom dead center, they can destroy themselves, and the tooling, and send flying metal everywhere.

Press brakes are slower, and usually dont destroy their tooling the same way, and so are more flexible for fab shops, where you use the machine to do a variety of jobs.

Many, many of these machines have been scrapped and sent overseas, but they still turn up for a few thousand dollars in the midwest and east coasts, while a new, hydraulic machine of similar capacity might cost ten or twenty times as much.