Machining small fonts using CNC

[suspension]

Hi all

I wish to create a front panel for my device and trying various options available to print the artwork on it. I already know a bit about screen-printing, toner transfer, etc but having tried some of these for PCB, I am not sure if I will be able to get the high quality finish with small fonts used in my art work. I own a CNC machine so may be there are better ways to do this.
I already tried to mill a thin plastic sheet with this art work using a .2mm micro end mill cutter to create a mould. I tried various plastic sheets NOT designed for this type of work ranging from transparencies to an ice-cream container cup with no success. I ran spindle at 24000 RPM and tried various feed speeds, but in all cases the plastic sheet does not give me a clean cut. Is there a better purpose made plastic sheet that I can try? Or are there any other options available for me with the CNC? I know about engraving, but I want my artwork to be black and not sure how to get that finish. The front plate is made of aluminium.

Thank you
S

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[RCaffin]

If you want a really small font, you will have to get the top surface of the Al front panel really flat and square to the spindle.
Then engrave the artwork directly into the aluminium. Then fill the grooves with black enamel paint - Hobby paint for model aeroplanes is fine. Try to keep the paint inside the grooves - you won't succeed 100%, but try.
Let the paint cure for a couple of days, then very gently and lightly polish the excess paint off from around the letters.
It works.

Failing that, use stick-on letters. Not available real small though.

Cheers
Roger

[louieatienza]

Hi all

I wish to create a front panel for my device and trying various options available to print the artwork on it. I already know a bit about screen-printing, toner transfer, etc but having tried some of these for PCB, I am not sure if I will be able to get the high quality finish with small fonts used in my art work. I own a CNC machine so may be there are better ways to do this.
I already tried to mill a thin plastic sheet with this art work using a .2mm micro end mill cutter to create a mould. I tried various plastic sheets NOT designed for this type of work ranging from transparencies to an ice-cream container cup with no success. I ran spindle at 24000 RPM and tried various feed speeds, but in all cases the plastic sheet does not give me a clean cut. Is there a better purpose made plastic sheet that I can try? Or are there any other options available for me with the CNC? I know about engraving, but I want my artwork to be black and not sure how to get that finish. The front plate is made of aluminium.

Thank you
S

You can get engraving plastic from companies like Rowmark and Gravograph. The way the engraving machines work, they have s spindle that's "floated" on a spring, and a depth stop collar, which also is a vacuum nose. That's how they achieve uniform depth.

For aluminum, you may try purchasing a spring-loaded engraving attachment for your CNC, and either 1) get diamond-drag engraving tools and grave the fonts with the spindle NOT running, or 2) get carbide engraving burnishers. They are used with a spinning spindle, and usually to remove the enamel layer off sheet brass and sheet aluminum engraving stock, and even work on anodized aluminum as well.

Also, use single-edge engraving tools, not end mills. You could buy them from Gravograph, but I believe LMT/Onsrud sells some. Amana also sells some engraving tools as well.

I actually worked for Crown Trophy for three years, headed the engraving department for the mail-order side and franchise training, about 18 years ago...

[louieatienza]

If you want a really small font, you will have to get the top surface of the Al front panel really flat and square to the spindle.
Then engrave the artwork directly into the aluminium. Then fill the grooves with black enamel paint - Hobby paint for model aeroplanes is fine. Try to keep the paint inside the grooves - you won't succeed 100%, but try.
Let the paint cure for a couple of days, then very gently and lightly polish the excess paint off from around the letters.
It works.

Failing that, use stick-on letters. Not available real small though.

Cheers
Roger

When I had to engrave aluminum, I would use pre-coated aluminum sheet; I believe it was either lacquer or epoxy coated. To get a design visible, I'd use a burnishing tool to wear off the coating and part of the metal, then use an oxidizing solution to darken the graved areas. The untouched areas of course stayed pristine...

[suspension]

If you want a really small font, you will have to get the top surface of the Al front panel really flat and square to the spindle.
Then engrave the artwork directly into the aluminium. Then fill the grooves with black enamel paint - Hobby paint for model aeroplanes is fine. Try to keep the paint inside the grooves - you won't succeed 100%, but try.
Let the paint cure for a couple of days, then very gently and lightly polish the excess paint off from around the letters.
It works.

Failing that, use stick-on letters. Not available real small though.

Cheers
Roger

Thanks Roger. Have you got any links to pictures that show the finishing of this method? I actually thought about this, but was not convinced that I will be able to fill groves with paint. The width of these groves is less than .3mm.

[suspension]

When I had to engrave aluminum, I would use pre-coated aluminum sheet; I believe it was either lacquer or epoxy coated. To get a design visible, I'd use a burnishing tool to wear off the coating and part of the metal, then use an oxidizing solution to darken the graved areas. The untouched areas of course stayed pristine...

Unfortunately I already have aluminium plates for the purpose but they are not pre-coated.

[suspension]

You can get engraving plastic from companies like Rowmark and Gravograph. The way the engraving machines work, they have s spindle that's "floated" on a spring, and a depth stop collar, which also is a vacuum nose. That's how they achieve uniform depth.

For aluminum, you may try purchasing a spring-loaded engraving attachment for your CNC, and either 1) get diamond-drag engraving tools and grave the fonts with the spindle NOT running, or 2) get carbide engraving burnishers. They are used with a spinning spindle, and usually to remove the enamel layer off sheet brass and sheet aluminum engraving stock, and even work on anodized aluminum as well.

Also, use single-edge engraving tools, not end mills. You could buy them from Gravograph, but I believe LMT/Onsrud sells some. Amana also sells some engraving tools as well.

I actually worked for Crown Trophy for three years, headed the engraving department for the mail-order side and franchise training, about 18 years ago...

I never knew about sprint loaded engraving bit. Thank you for that. Any idea where I can but these in UK?

[louieatienza]

I never knew about sprint loaded engraving bit. Thank you for that. Any idea where I can but these in UK?

Not sure, but you can try eBay.... also you can sometimesfind a New Hermes floating spindle assembly online. Vision sells CNC routers/engravers. They have an assembly as well, but I'm not sure if it's sold separately.