Pricing help on bronze plaque

[cnc_works]

I'm being asked to bid a bronze plaque (1/8" thick), something like 48" X 48", about a third 1/2" text and maybe a quarter of it 3" high text. 3D engraving on serifed text, obviously the large text will have to be depth limited.

My clear problems are: Keeping the bronze flat enough to get uniform engraving, cutting bronze in general, and, last but not least, pricing.

I'm thinking of vacuum to hold it flat or clamping cauls across it and doing a section at a time.

Pricing, I just dunno, wild guess is something in the $1200 range. More if I have to put together a temp vacuum plenum.

The other thing that's scary is the responsibility of delivering a no mistakes job on satin metal with no imperfections allowed.

So, any suggestions, pointing out anything I'm not thinking about would be very welcome.

PRT96, PC890 router, by the way. (Spindle arriving this week I hope...oh boy!)

Donn

[rick_woodward]

First thing that jumps out at me is the high probablility of "eating" this job,time and materials.Everyones idea of "perfect" is different.Second is the satin finish. This may require buffing equipment/tools and or glass bead blasting. Or some other media.I dont work with metals but even in wood there are tooling marks every where.... 4" x 4' wow. smoothing out tooling marks around all the letters. To perfection. Hope your bed is perfectly flat.Others with metal/bronze experience in what your looking at , hopefully will join in with their knowledge and experience.Wouldnt even think of this without a spindle. Just my thoughts.

[rookie432]

My first thought is to mill this in another material then use sculpt nuveau bronze on it. Heck, you could mill a few and give them the best one as perfect. At least you would have more controll over the finish and it would be a real metal finish that could be buffed. I can't tell the difference between real bronze and the sculpt nuvea product in many cases.

2 cents
Bill

[joe]

I'd consider the Bronze surface material by "Sculpt Nouveau".

Pricing is easy. Look at the price a foundry would charge. Check with Gemini. www.signletters.com
J

[tim_whitcher]

A cast bronze plaque would be between $3000.00 and $4000.00, but would obviously be a completely different animal.

[cnc_works]

I appreciate all the responses. I did describe the Art Nouveau process to them, but as I expected, the architect's specs won. I plan to apply Gerber Mask II to both protect the surface and make painting (to be done by the client) easier.

I've cut a sample and had it approved by my client. I'm going to bid about double what my limited experience dictates would be a "no problem" job, (total $1875) then cross my fingers.

A follow-up question. I engraved the 7/16" letters with a 45deg v bit. I wonder if 60deg would give me clearer serifs?

For info, I engraved the sample at about 20K, .1 ips, two passes: one at .04" and one at full depth. I have since replaced my PC with a spindle, I suspect I'll probably drop the rpms and leave the feed speed the same. As usual, any comments appreciated.

Donn

[joe]

Donn,

How did that project turn out?

[cnc_works]

Hey Joe!

Well, I did the test with my router and they weren't really satisfied, as mentioned I just installed a spindle and that took enough of the chatter out of the edges of the letters that they accepted my bid of $2300 for the whole job. I had no idea how much play there was in router bearings until I did the side by side. They're serious, already got half.

I'm going to have them cover the whole blank with Gerber Mask II to protect it and to provide masking for the painting to be done by someone else.

My main worry is flatness of the bronze plaque, so I expect to flatten my table, then use curved clamping cauls to hold the plaque flat, doing only a few lines at a time between the cauls.

Next worry is a programming glitch so I'll run a test cut in 1/4" melamine at a slightly increased feed speed.

Still wondering about a 45deg vs a 60deg v bit for the smaller letters (about 1/2" high). Also wondering about any more suggestions as to feeds and speeds with a spindle in bronze.

Hope to get the whole thing going next week. I'll post results when I'm done. An obit if things don't go so well.

Donn

[rookie432]

Hey Don,

I'd kindof be interested in seeing that side by side of router cut verses spindle cut if you don't mind. Just curious as to how much chatter a spindle really reduices.

Thanks
Bill

[cnc_works]

Bill, I'll try to get pix of the test blank on the forum soon. I must say, no doubt I did a lot of quality work with the router, but I'm in love with the spindle. The smooth, quiet power, ahhhhhhhhhhh! Going back to the router would be as hard as going back to dial-up from broadband.

I'm so sold that I'm going to get a 1hp spindle for my smaller cnc.

Donn