DIY CNC Router cutting steel

Thought I'd post this follow-up in its own thread as its more about DIY steel cutting than actually building the machine..
but here are literally my first few cuts in mild and cold rolled steel.. screw-ups and all.

Before building / component selection I did some research but didn't find a whole heck of a lot of specifics, so maybe
this might help someone out / give them a better sense of what to expect.

I'm using a 1.5kW ebay air cooled spindle (came with Huanyang VFD).

6mm carbide, 5mm DOC, 7500 RPM, about 10 IPM -- details in the video.

The poor thing did better than I expected but I couldn't say how long it would last doing this kind of work.. probably not long?

Tips/comments/criticisms welcomed, as always.

-OldTony


https://youtu.be/jOvGv9aRKFs

that is pretty sweet. putting loctite on the screws then?

you know it Scott!

you can have low rpm spindle

Large Torque water cooled spindle motor 2.2Kw 1000rpm 8000rpm lower speed + 3.7Kw SUNFAR inverter + 85w water cooling pump-in Machine Tool Spindle from Industry & Business on Aliexpress.com | Alibaba Group

The ballscrew mounting hardware backed out during operation?

I would use some "permanent" loctite on those mounts/supports - and you just said that at the end of the video! I've pulled apart some parker stages before and man, they must use some serious loctite on their threads. I always think I'm going to strip out the hex key.

Great video man, I appreciate all the work you put into them.

You do make some excellent videos.

For a router type machine you are doing pretty good. You might want to try a 4 mm end mills to see if you can find a better speed and power solution but the reality is you are running very high RPM's for the type of machine you got already. The big problem with using these machines to mill steels is that you have to run very small end mills to achieve any sort of performance at all. That might not be bad for intricate work but makes the machines useless for more tradition milling tasks.

At least now people have a good video to reference to better understand what the limitations are when trying to machine harder materials.

As for Loctite that is a two way street. I would suggest trying the removable stuff first. Some of the stronger variants are a real pain when you come back to work on the machine later. Also don't be afraid to just torque stuff down tight, people have a tendency to be to gentle with cap screws. I believe at one time there was a US Army manual floating about with torque specification for standard cap screws, it was free but at the moment I don't have the link.

Agains I really like the video but might suggest one thing. This is simple close ups are good for awhile but once in a while it would be nice to see a larger view that encompasses all the machine. It gives people a context and also helps them understand what sort of machine you are working with here,

Excellent points Wizard, and I'll definitely keep them in mind.

thisoldtony

A very good video, what camera, and software did you use

Using a smaller cutter of the same type would not be a better idea,it will flex more than you would gain, the 6mm or 1/4 5 flute, is the best to try something like this, your bottom spindle bearings won't last very long though if you keep doing steel

Something for you to check,and then you will see why it's not a good idea to do steel with this spindle, by hand pull down on your spindle, you will have up to .020" of movement, so the high amount of noise you here when it starts to take a cut and cutting, is the spindle bearings being pulled from there correct seating position in the Bearing race, so what is happening is the Bearing is rattling around inside itself,like beating on it with a hammer

These Spindles are designed like this, because of the High Speed they normally run at, the top Bearing controls the preload on the ( 2 ) front Bearing with a wavy spring washer, I have adjusted some of them that I have rebuilt, so that they have less pulldown, but there has to be some, just the Design which is why they last as well as they do, when used as they should be

These better constructed machines are quite capable of cutting steel with the right spindle, I have been testing a Spindle for doing Steel & Aluminum, it has a Max of 8,000 RPM with full torque down to 1000 RPM this is only a prototype, but so far is working quite well

Quote:

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Originally Posted by thisoldtony

Excellent points Wizard, and I'll definitely keep them in mind.

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As a follow up, this site: ASSIST-QuickSearch Basic Search has all sorts of technical documents. If you select THDS in the FSC drop down box you will get two pages of documents related to threads, every type of thread you could imagine really. The ones I find useful are the "H28" Handbooks series and "Handbook 60". There is an H28 handbook for just about any thread you can imagine and Handbook 60 covers just about everything you could want to know about torquing bolts.

There is probably more information there than some people will want to know but the manuals are very handy in understanding how things should work. These are also where all those drill charts for taps come from.

I didn't want to leave you and the rest of the forum hanging after mentioning I forgot where to find this resource. These documents are very widely circulated, some even charging money for them, but this is a very good resource. (Your tax dollars at work). As it was it took awhile to find this site again. In any event if you have ever wondered how those drill charts for taps come up with their values there is information to explain it all here.

Quote:

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Originally Posted by wizard

As a follow up, this site: ASSIST-QuickSearch Basic Search has all sorts of technical documents. If you select THDS in the FSC drop down box you will get two pages of documents related to threads, every type of thread you could imagine really. The ones I find useful are the "H28" Handbooks series and "Handbook 60". There is an H28 handbook for just about any thread you can imagine and Handbook 60 covers just about everything you could want to know about torquing bolts

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You obviously have never had any experience with these Chinese machines, if you Torque the cap-screws to the correct torque requirements, two things are likely to happen either the cap-screw will break, or you will strip the thread this is pretty much the norm, if you replace the cap-screws with a quality brand, this will only help if they have good threads to screw into, the best is to replace the Cap-screws use a little Blue Loctite and do them up tight without pulling the threads out, before using the loctite clean the threads of any oil or chips

Must have missed something I thought this was a DIY router build. As for cap screws in aluminum or cast iron you certainly have a stripping problem there. That is the nature of the beast. As for the cheesy screws from China well that is why you replace them, in many cases they are at best use once and throw out screws.

Quote:

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Originally Posted by mactec54

You obviously have never had any experience with these Chinese machines, if you Torque the cap-screws to the correct torque requirements, two things are likely to happen either the cap-screw will break, or you will strip the thread this is pretty much the norm, if you replace the cap-screws with a quality brand, this will only help if they have good threads to screw into, the best is to replace the Cap-screws use a little Blue Loctite and do them up tight without pulling the threads out, before using the loctite clean the threads of any oil or chips

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Quote:

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Originally Posted by wizard

Must have missed something I thought this was a DIY router build. As for cap screws in aluminum or cast iron you certainly have a stripping problem there. That is the nature of the beast. As for the cheesy screws from China well that is why you replace them, in many cases they are at best use once and throw out screws.

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Yes I believe he did build the machine, as he said in the Video that he brought the cheapest Ballscrews he could find

Have a look at my diy cnc router cutting steel:

https://youtu.be/UboWO2BHDYQ

Almost any cnc router can cut steel. The question is how well, how quickly and for how long (before damaging your spindle or other components).

I wouldn't ignore "chatter noise" or any other unsavory sounds when cutting. It's a good indication that you are doing something that will damage your machine. I learnt this the hard way...

If it sounds wrong, shut it off immediately and check your feeds and speeds.

I highly recommend using GWizard for feeds and speeds when cutting (any) metal on a cnc router. It can save you destroying your machine through trial and error... It's a great tool IMO.

I also recommend filling those voids in the gantry. They amplify sound and vibration which is problematic when cutting metal.

Even filling it with a urethane foam would be better than a large void. Epoxy granite would be a better filler but it may add too much weight on a moving gantry machine with tiny steppers.

Rigid two-part foam is easy to apply and would also add some stiffness to a hollow tube or extrusion.

We cut up to 1/4" aluminum and even steel on our DIY router at work. It's been doing it apparently for about 8 years, no failures. Slow is still cutting and lasers aren't free, but the 1/8" single flutes practically are when 4-8 last almost a year of cutting for us. When your duty cycle is only an hour or so a day, then you don't need the speeds of laser. Plus we can manage up to 1/4" depth contouring in steel or 1/2" or deeper in aluminum with a 1/4" end mill.

I recently pushed them to stop slotting with a 0.050"/pass ramp and to use HSM+HEM approaches. The 1/8" endmill cuts even stainless with no chatter at 32ipm, 24krpm, and 0.01" RDOC. I use 1-1.25 diameter ADOC. This switch has reduced dulling on the tips of the endmills, they are all still sharp when the one currently on the mill was expected to have been dull by now.

Yes, the shallow cuts can feel like they take a lot more time given that slotting is now a lesson in patience as it trochoidally mills at 32ipm your whole part profile, but the bulk of the stress on the endmill is the helical bore mill to create an entry hole, which is still just seconds of time.

Previously they were slotting things like mild steel or free machining stainless at 8ipm and 6krpm. So even though the trochoidal milling takes like a billion little circular motions, at 32ipm is way faster in the end.

And again, the banshee has been quieted.