sign with embossed letters

Cut yourself a female die and use rubber to do the forming.

Plan B. Since this is a sign, you are only going for a look. Make a positive male pattern and then vacuum form the sign from plastic. You could bond this to a chunk of sheet metal if it was free hanging and then use paint to give yourself the look of the original. This should be no problem for a good sign painter.

Plan B would be a lot cheaper and easier to fabricate the mold.

How much pressure would you estimate it would take to press a letter 5"H X

2.5"W? Would the rubber need to be contained in a sleeve? I have a CNC plasma cutting table so the female letter die wouldn't be a problem. Just trying to get a few ideas before I start experimenting.

Thanks, Steve

The word is "urethane" it comes in different durometers (hardness) and is used for pressing metal all the time. I'm not an expert, just enough knowledge on the subject to be dangerous?

Lane

Steve- Actually what you need is urethane, not rubber. Check out Bonny Doon engineering- he makes small hydraulic presses for jewelers to do this kind of stuff on a small scale, but he also sells the urethane, books about how to do the process, etc.

Basically all you need is a slightly oversize female die, and a sheet of urethane. Not sure how much tonnage you will need for that gauge of steel- probably at least 30, though. ries

I think Dar S knows all about this stuff, if he's lurking.

Best regards, Spehro Pefhany

Thanks Guys. This is what I have been looking for. I will give you an update as this learning experience progresses! Steve Peterson Kettle River Ironworks

Bonny Doon are fine folks but this is a very low-tech product, you can DIY it no problem. We actually bought the whole outfit from them for my wife's work - a fabricated press frame, a leaky 20 ton Chinese bottle jack that they drilled out to add a gauge to (with a conversion chart because they didn't change the scale) and various containment rings for the urethane. In hindsight I would have done a nicer job myself.

Bob

Gee I'm kind of surprise to hear that. I was under the assumption that Lee made good products.

Lane

Normally so from what I know, I have been in his shop. He does have people working for him and he has been in the past on the road teaching classes.

I know there has been a lot of general pressure to compete with the harbor type equipment. Maybe some models were that grade.

Martin

I wasnt suggesting steve buy one of those little pump setups- they are tiny, and meant for jewelers. But it sounded like he already has a big hydraulic press, and wanted info on how to do it. bonny doon is good for that- their book explains the process, and they sell urethane. If you are going to copy something, copy something that works- and bonny doon has figured out how to do it.

Here's my $.02 on this job.

As others have said pressing with a urethane or rubber pad is a way to do this. Rubber works as well as urethane, it just doesn't stand up over the long haul as well as urethane.

This method would be considered embossing. Since you're working with a relatively light gauge material and a large panel size you want the embossed letters to be created by stretching (thinning) of the material as opposed to drawing in from the surrounding area. Stretching will keep the panel flat, drawing will cause warpage. How firmly the panel is clamped by the pad in the area around the embossing determines whether you get stretching or drawing.

The amount of clamping to a large extent will be determined by the hardness (durometer) of the urethane or rubber. 80 to 85a durometer should assure the material is firmly clamped enough that you'll have pure stretching. Using really soft urethane/rubber gives less clamping action increasing the likelyhood of the material being drawn in causing warpage.

The "sharpness" of the embossing has to do with pad durometer. A soft pad gives a deeper more rounded embossing. Harder gives a sharp edge with not so much depth.

Tonnage required will go up almost exponentially as the durometer of the pad increases. With a 85a durometer pad I'd guess about 30+ tons. A major percentage of the required force goes into deforming the pad. Some estimates of pad tonnage say it requires approx ten times or more force than would be required with a set of hard dies.

Good luck and keep us informed on your progress.

Thank you for taking time to reply. I will keep you gents updated on my progress. Steve