Routing sheet metal

[Molo1818]

Hi Guys,
Could someone please help me. I’m rather new to cnc, and only have worked with wood .
I picked up what I believe is 24”x36” x .0179 zinc plated sheet metal at lowes. I wish to cut out
A deco pattern for wall art that would be normally cut with a plasma. My questions are
1) Can I use a 1/8” HSS 4 flute spiral end mill to cut out the sheet metal ?
2) If yes, how much material should I remove each pass and how fast should it move?

I’m cutting with a cnc router parts pro machine with 35 steppers and a 3hp PC router .

Thanks Lou

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[RCaffin]

That must be one of the hardest things to machine. The sheet metal is going to flap all over the place. You cannot hold it down without a vacuum table, and even then it would still be difficult.
Go back to plasma.

Cheers
Roger

[KH0UJ]

If it`s only 0.4mm I think it`s just a piece of cake on a 4 flute HSS, on my experience I can even cut 1mm thick stainless steel sheet, by just using a 1/8 carbide bit single flute at feedrate 400 and plunge rate of 80 on 5 passes, sometimes 7 passes, depending on the sharpness of my installed tool bit, it gets dull in time after a couple of cuts, so in the beginning I make a CAM for 5 passes and for 7 passes, after 20 cuts I change the code for 7 passes to continue working and after a couple of cuts that`s the time I re sharpen hehe, sometimes laziness made me think further just to minimize the tool change make sure to have a sacrificial plywood to avoid accidentally scraping your CNC table and to easily clamp your holding tabs in place.

[RCaffin]

Hi KHOUJ

That fine for a little thing like you show, but OP is talking about 24" x 36"!

But I just had a great idea! Thick flat plywood or chip board, contact cement, glue the sheet metal down HARD and all over, then machine it to 2 mm deep.
Then dunk the whole thing in solvent to float the metal off.
Yeah - MESSY!

Cheers
Roger

[KH0UJ]

Hi KHOUJ

That fine for a little thing like you show, but OP is talking about 24" x 36"!

But I just had a great idea! Thick flat plywood or chip board, contact cement, glue the sheet metal down HARD and all over, then machine it to 2 mm deep.
Then dunk the whole thing in solvent to float the metal off.
Yeah - MESSY!

Cheers
Roger

ohh I was thinking it`s a 24mm by 36mm hahaha sorry my bad, your idea is not bad too, contact cement can hold steadily the floating parts enough not to fly and be kicked by the rotating spindle .

[Molo1818]

That must be one of the hardest things to machine. The sheet metal is going to flap all over the place. You cannot hold it down without a vacuum table, and even then it would still be difficult.
Go back to plasma.

Cheers
Roger

Hi Roger
I should have been more specific sorry.
I will be screwing down the perimeter and use double sided tape in the center. Here is a snapshot of what I want to cut from the sheet and make it as large as the sheet will allow.

[Molo1818]

If it`s only 0.4mm I think it`s just a piece of cake on a 4 flute HSS, on my experience I can even cut 1mm thick stainless steel sheet, by just using a 1/8 carbide bit single flute at feedrate 400 and plunge rate of 80 on 5 passes, sometimes 7 passes, depending on the sharpness of my installed tool bit, it gets dull in time after a couple of cuts, so in the beginning I make a CAM for 5 passes and for 7 passes, after 20 cuts I change the code for 7 passes to continue working and after a couple of cuts that`s the time I re sharpen hehe, sometimes laziness made me think further just to minimize the tool change make sure to have a sacrificial plywood to avoid accidentally scraping your CNC table and to easily clamp your holding tabs in place.

Hi KH,
When you say 400 /80 are you referring to mm , cm, or inches?
Here is what I want to cut.

[alan_3301]

I'm guessing your router is fixed at 20k rpms or so?
Get a 3/32" short 2 flute carbide end mill and cut full depth at 20k rpms and 10 ipm.

Your HSS bit will just burn up at router speeds.

[mactec54]

If it`s only 0.4mm I think it`s just a piece of cake on a 4 flute HSS, on my experience I can even cut 1mm thick stainless steel sheet, by just using a 1/8 carbide bit single flute at feedrate 400 and plunge rate of 80 on 5 passes, sometimes 7 passes, depending on the sharpness of my installed tool bit, it gets dull in time after a couple of cuts, so in the beginning I make a CAM for 5 passes and for 7 passes, after 20 cuts I change the code for 7 passes to continue working and after a couple of cuts that`s the time I re sharpen hehe, sometimes laziness made me think further just to minimize the tool change make sure to have a sacrificial plywood to avoid accidentally scraping your CNC table and to easily clamp your holding tabs in place.

You are not cutting steel, he wants to cut steel, which won't be possible for his spindle to run slow enough to do it

[nick952]

Also using a "DownCut" milling cutter helps a lot on thin material.

I know these are listed for wood, but I've used similar here in the UK on steel before without any problems.

2 Flute Downcut Bit, 1/8 Dia, 1/2 Cut Length, 1/4 Shank, Whiteside RD1600


Nick.

[RCaffin]

Have to be carbide for sure at those spindle speeds. A tiny downcut cutter is not a bad idea. Even so, I would suggest buying several at the start as one or two are bound to get snapped while getting the conditions right.

Double-sided tape for thin sheet metal? Hum ... I have some reservations. But - experiment. Try using a press to really get the adhesion everywhere. The downcut spiral will help to maintain the bond, and is a good idea for this.

Depth - full depth, right through the sheet metal. If you try to do it in several layers you will get a lot of rubbing on the underside of the cutter, but at full depth you will be cutting with the side of the flute which will be a lot cooler.

Cheers
Roger

[dharmic]

I've used contact cement with a small carbide bit on a router on 1.2mm gal sheeting before. The glue worked well, no solvent required, a bit of gentle persuasion lifted the metal off then just polish down the residue with paint thinners. Double sided tape seems a bit dubious to me, too, I think you may find small details being lifted unless it's particularly special tape.

Agreed on getting multiple cutters. Two to snap, two to burn through and one to finish the job

[KH0UJ]

Can you post a bigger picture on you work? also you preferred dimensions of your drawing, there`s no autoCAM software that can route your drawing in 0.2mm steps, you need to cut the inside parts first before cutting the outside outline, let me code it for you if you want

[RCaffin]

Two to snap, two to burn through and one to finish the job
Sigh
Sob

One ends up with a good collection of 6 mm carbide shanks after a while...

Cheers
Roger

[Molo1818]

Can you post a bigger picture on you work? also you preferred dimensions of your drawing, there`s no autoCAM software that can route your drawing in 0.2mm steps, you need to cut the inside parts first before cutting the outside outline, let me code it for you if you want

Thanks KH,
I have it made in fusion 360 already, it about 32”x 22”. The 1/8th bit clears all the books and crannies!!! Lol
Learned a lot yesterday but still learning mm vs in.
Thanks

[Molo1818]

Two to snap, two to burn through and one to finish the job
Sigh
Sob

One ends up with a good collection of 6 mm carbide shanks after a while...

Cheers
Roger

Hi Roger,
Thanks, as I was learning yesterday, I had an early visit from Santa!!!
Well at least from rudolf and his glowing red nose!!!!
😂 Up on the cnc roof I heard a chatter, and when I looked I was blinded by a super red glow!!! And with a puff of smoke my bit was toast !! Hahahaha
I had set my cnc to run at 200ipm and a depth cut of .005”. Needless to say the first bit snapped. So I slowed the feed to 60ipm and got a lot of it cut until that bit wore out. Same with second bit but it went faster due to the fact that the wd40 started soaking into the mdf that I spray glued the sheet toand swelled up causing the bit to dig in to deep.
I don’t think the bits I have can take a single pass cut.

[Molo1818]

Can you post a bigger picture on you work? also you preferred dimensions of your drawing, there`s no autoCAM software that can route your drawing in 0.2mm steps, you need to cut the inside parts first before cutting the outside outline, let me code it for you if you want

Hey KH,
So I was thinking about what you said as far as steps. I guess I’m not sure what you mean by that? Here are the specs of my machine. And as I said in last post lm using fusion 360 to design and cam. I usually work with wood but I always enjoy learning.

[mactec54]

Hi Roger,
Thanks, as I was learning yesterday, I had an early visit from Santa!!!
Well at least from rudolf and his glowing red nose!!!!
�� Up on the cnc roof I heard a chatter, and when I looked I was blinded by a super red glow!!! And with a puff of smoke my bit was toast !! Hahahaha
I had set my cnc to run at 200ipm and a depth cut of .005”. Needless to say the first bit snapped. So I slowed the feed to 60ipm and got a lot of it cut until that bit wore out. Same with second bit but it went faster due to the fact that the wd40 started soaking into the mdf that I spray glued the sheet toand swelled up causing the bit to dig in to deep.
I don’t think the bits I have can take a single pass cut.

"200IPM" that would of been good to see, what RPM was the Spindle running at??

Other posts said you will just burn up the cutters, WD40 is not a cutting fluid for cutting steel sheet like this, it won't help your cutters at all, try some better real cutting fluid and a max of 7000RPM and 10 IPM

[Molo1818]

"200IPM" that would of been good to see, what RPM was the Spindle running at??

Other posts said you will just burn up the cutters, WD40 is not a cutting fluid for cutting steel sheet like this, it won't help your cutters at all, try some better real cutting fluid and a max of 7000RPM and 10 IPM

Lol, ok, I did say I was learning !!!! Hahaha
It wasn’t much of a sight, only got a 1/4” before it snapped.
The slowest I can get with this router is 10000. My old router only had one speed so I used a speed control but I’ve been told not to use it with this one because of the variable speed controller on the new one doesn’t play well with it .
I’m assuming at 10ipm your saying I should try to do a full depth cut and use the side of the bit instead of the tip ?
Here’s a pic of the bits I’m using....
Thanks again

[Molo1818]

"200IPM" that would of been good to see, what RPM was the Spindle running at??

Other posts said you will just burn up the cutters, WD40 is not a cutting fluid for cutting steel sheet like this, it won't help your cutters at all, try some better real cutting fluid and a max of 7000RPM and 10 IPM

Oh, also, do you know of a home brew lube for cutting ?