[Newbie] CNC conversion or chinese "mills"

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LewisF714

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Hey guys been lurking here for quite a while. Finally thinking about actually buying a mill sometime.

My main uses for a mill would be mostly one off aluminum or plastic parts. Project that come to mind is something like a keyboard case or PC case part. I'm not looking for something that will turn out production parts.

Would going with something like a PM30 or PM932 conversion be a good fit for my uses? I am thinking I'll need higher RPM for aluminum than the stock spindle offers, so the brand new spindle motor would basically go unused. Would fitting one of those cheap 2.2kw 24k rpm water cooled spindles be good for aluminum?

I also been looking at different mills from china and there are some that are basically a cast iron frame with a router spindle mounted on top. Their price would be around the price of doing a conversion but the information on them is really limited. Does anyone here have experience with "LY group" cnc mills?
 
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LewisF714 said:
Hey guys been lurking here for quite a while. Finally thinking about actually buying a mill sometime.

My main uses for a mill would be mostly one off aluminum or plastic parts. Project that come to mind is something like a keyboard case or PC case part. I'm not looking for something that will turn out production parts.

Would going with something like a PM30 or PM932 conversion be a good fit for my uses? I am thinking I'll need higher RPM for aluminum than the stock spindle offers, so the brand new spindle motor would basically go unused. Would fitting one of those cheap 2.2kw 24k rpm water cooled spindles be good for aluminum?

I also been looking at different mills from china and there are some that are basically a cast iron frame with a router spindle mounted on top. Their price would be around the price of doing a conversion but the information on them is really limited. Does anyone here have experience with "LY group" cnc mills?
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Hi Lewis,

You didn’t say how thick of aluminum you want to work with but if it’s thin sheet a decent router motor will work fine. Lots of folks building DIY CNC routers use small Dewalt wood routers very effectively.

I ran a Teknomotor spindle on my CNC mill drill project and it was too fast for thick stuff. Would have been fine for sheet metal.

I don’t have any info on the LY group products but you will probably get a better bang for your buck building your own gantry type machine.

John
 
Hey John thank you for the reply. The stock will probably no more than 1 inch thick, and needs to have profiles cut into it. I have attached an example.

I was under the impression that gantry type machines are not rigid enough, which is why I've been looking at column type machines. Also gantry machines don't have a lot of Z travel. I wouldn't want to limit the stuff I can work on to flat stocks.

Would one of those spindles work for this kind of stock? I'll probably have to take a lot of step downs to remove all that material since you said it's too fast for thick cuts.
 

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Plastic would probably work, 1" thick aluminum not a chance.

You're probably looking at a bench mill conversion but will need to make sure whatever you start with has enough travel. Check speed/feed charts to find out what limits you'll have for different materials.

If you have the space I'd look into used production machines as they can be had pretty cheap sometimes. Tormach also makes units that fall into your requirements, not cheap but a known supplier with decent support.

What I'd avoid is something from China that nobody here has ever worked with.


John
 
I’d go with the conversion any day. The china routers are just flimsy.

If you only consider plastics than why don’t you take the 3D printer route?


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You can fit a 2nd spindle to a mill - add one of those high-RPM water cooled spindles for doing the aluminum. They generally clamp on to the spindle nose, so you get to keep your low-RPM spindle for steel or other harder material. The downside is that you lose effective travel with an offset 2nd spindle.

img_2718.jpg

Gantry machines are not necessarily flimsy, but the aluminum ones all over ebay are noodles. The only rigid gantry machines I've seen are DIY things or very expensive and very large.

Figure out the largest part you want to make and that will dictate the machine you need to get. You may be surprised at how large of a machine you need to do some parts. The PM940 appears to me to have the largest travels of the 'benchtop' (not really) type bed mills available at a fairly low price.

You can do just about anything you want to modify a machine, but extending its travels more than a tiny bit is not generally cost-effective.

Frankly, if you have the space for it, an old-style bed mill can be converted easily and provides massive travel and the flexibility of a tiliting head. They are heavy, but generally uncomplicated. Much easier to convert than a bridgeport, though slightly less flexible (no ram).

Below is obvioulsy a new (expensive) one, but similar mills have been made for years by many different manufacturers. You might find something used to be less expensive than a new 'hobby' mill.

trak-dpm-sx5p-three-quarter-view-zoom.jpg
 
It looks like a PM30 or PM940 would be the direction I should look in. The belt drive of the PM30 looks pretty attractive if I just wanted to leave the spindle alone, so I'm slightly leaning towards that direction.
 
Would a knee mill be good for cnc conversion? I was reading some stuff that said a quill wouldn't be the most rigid
 
LewisF714 said:
Would a knee mill be good for cnc conversion? I was reading some stuff that said a quill wouldn't be the most rigid
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A full sized knee mill (BP or clone) is fine for a CNC, but don't expect the same performance as you would get from a real VMC. I don't run larger than a 1/2'' endmill on mine. You just set up to keep the quill extension at the minimum for the job.
 
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