Big Ol' CNC, by Awesomenesser

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Re: Big Ol' CNC, by Awesomenesser

Postby mikegrundvig » Sun Sep 30, 2012 3:52 pm

I use SynCool to cut aluminum all day long and it works great. As for flow, that's tricky - one of the biggest issues you will have with that spindle is chip welding. This occurs when you can't clear the chips fast enough and things get hot. This also makes for a bad surface finish and kills the life of the end mills. Lots of people just use WD-40 to lubricate while cutting aluminum and compressed air to blow away chips. This works pretty well at slower cutting speeds. With my big mill, I use a cheap debris-capable sump pump from Harbor Freight in a 30 gallon Rubber Maid tote full of coolant. I then blow enough volume of coolant to remove the chips too. This keeps heat down to nothing, removes the chips, and gives me a good surface finish. One thing to note - it's going to spray coolant EVERYWHERE when it hits the end mill at high RPM. I had to build a full enclosure out of PVC and shower curtain. It's pretty ghetto but works great.

-Mike
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Re: Questions About Aluminum Milling

Postby Liberty4Ever » Mon Oct 01, 2012 2:29 am

awesomenesser wrote:Also do you guys think I will have issues cutting aluminum with my setup?

If you stick to smaller end mills and your goal is mostly oriented toward cutouts and engraving in aluminum sheet, if you restrict your cutting to slow feed rates, I think you'll be fine. If you want to hog out big chips of aluminum and do some serious machining of billet aluminum, you'll want a Bridgeport style milling machine or a vertical machining center. I have an inexpensive Grizzly G1006 benchtop milling machine that's paid for itself five times on the little work I've done on it. Almost every time I use it, I think about converting it to CNC, but then I come to my senses and plan to sell it and buy a used Bridgeport clone and convert it to CNC. Actually, I saw a very nice conversion of the Grizzly (also offered under many other names). Not much of the original remained , but it became a mini vertical machining center, which would be difficult to accomplish with a Bridgeport knee mill. It was fully enclosed in a cubical shape, with an integrated flood coolant system. The iron is probably suitable for a 1 HP or 1.5 HP spindle. Mine shipped with a 2 HP spindle, which is probably over powered for the rigidity of the cast iron.

awesomenesser wrote:I think the flood system will help out a lot (at least hopefully more than the mess it is going to create).

I'm trying by best to avoid flood cooling. My shop is in the basement, and I don't want the house to smell like a machine shop, and most of that smell is the coolant. There are low odor coolants, but they still stink too much for a basement, IMO. If you're machining in your garage, that probably wouldn't be a problem. But you still have the problem of coolant flying everywhere. Shoot a stream of coolant at an end mill spinning at 10,000 RPM and see where it goes! If I was converting to flood cooling, I'd put the entire machine in a big box, and I'd probably interlock it so the spindle and flood coolant are disabled unless the door is closed. I'm planning on short run production on my lathe once I convert it to CNC, and I'll be turning steel parts, and I'm going to try to get by with compressed air for coolant and carbide tooling (that I expect to replace much more often because I'm running without coolant). We'll see. For occasional hobby use or even small scale manufacturing, I think conventional coolant systems are probably more trouble than they're worth.



awesomenesser wrote:Here are a couple pictures of my progress.

Totally awesomenesser! Very nice job. Much better than the original, I'm sure.



awesomenesser wrote:I guess I had one other quick question how much cooling do these Chinese spindles need? I was thinking of installing a dual 120mm radiator and pump loop, is that too much or too little?

I just designed the cooling system for my 80W laser tube, and the water cooled spindles and water cooled laser tubes typically use very similar setups. In the case of my laser tube, I guessed I'd need to remove 800W of heat. I used a 120mm X 240mm radiator. With a good fan, a 120mm X 120mm radiator would have probably worked. I think your spindle will have considerably less waste heat. Electric motors are much more efficient than laser tubes. You may only have 200W or 300W of waste heat. That's a complete guess. The manufacturer should provide that spec. But for hobby CNC machine conversion, most people don't go to great extents to quantify and calculate everything. It's more TLAR engineering (that looks about right). Err on the more cooling side and call it done.

I did notice that the little submersible pump shown in the Automation Technology video demonstrating the coolant setup on their comparable gantry router (from your earlier link) was tiny and pathetic compared to the manly coolant pump that I selected for my laser cooling. That small pump implies that not much cooling is needed. The delta T of the water is pretty much fixed by the room temperature on one end and the maximum motor temperature (or the boiling point of water!) on the other end, so the amount of cooling is purely a function of flow rate, assuming the radiator and cooling fan is large enough. That tiny pump isn't moving a lot of water, so it's not sinking a lot of heat. The 120mm radiator should be more than enough. BTW - If your muffin fan isn't pushing enough air through your radiator, you can always upgrade it in the same form factor. I went hog wild and bought a pair of the very nice looking fans from LightObject.com when I ordered the radiator. I checked after placing the order, and they were cheaper than the eBay prices for the same blower. That was true for a lot of LightObject components.

http://www.lightobject.com/Ultra-Strong-12cm-DC12V-Cooling-fan-200CFM-P605.aspx

In fact, you might benefit from browsing their entire selection of cooling components.

http://www.lightobject.com/Cooling-C52.aspx?s=OrderBy%20ASC&c=52&p=1

In addition to low prices and fast shipping, Marco was extremely pleasant. He's very customer oriented.

Water cooled lasers always use a flow switch to ensure that the coolant is actually flowing, as opposed to simply turning on the pump and hoping it's flowing. The laser power supply is not enabled if the water isn't flowing. I'd do the same thing for a water cooled spindle. I'd have the flow switch wired to an enable pin on the VFD. Barring that, I'd have the flow switch operate a relay that supplied power to the VFD that powers the spindle.

http://www.lightobject.com/Search.aspx?k=flow

As to your question about too much or too little cooling... for hobby CNC machines, I'm inclined to agree with Robert Smith's advice in a song by The Cure. "Too much is never enough." :)
Apparently, I didn't build that! :-)
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Re: Questions About Aluminum Milling

Postby awesomenesser » Mon Oct 01, 2012 3:48 am

Liberty4Ever,

I went with a really nice pc liquid cooling system for the laser and paid a pretty good amount of money for it and I want to avoid that if possible. I like closed loop systems so I will be avoiding the submersible pumps and will go with some kind of inline pump, hopefully a cheap ebay rip off one and not the swiftech I have in my laser. I will probably get one of the new swiftech radiators with the reservoir build in, I just need to decide how large it should be.

I know the flood system is going to be a huge mess but since the table surface is 2'x3' and I will most likely be working with small pieces I will be able to setup some kind of shield to contain the liquid to the table itself (once it is going I will see what I can come up with). I have seen machines with plastic brushes or plastic sheet that hangs down around the mill bit to keep the liquid contained.

Bart, if you happen to read this what kind of cooling do you use on your spindle/what would you recommend?
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Re: Questions About Aluminum Milling

Postby Liberty4Ever » Mon Oct 01, 2012 4:31 am

awesomenesser wrote:I went with a really nice pc liquid cooling system for the laser and paid a pretty good amount of money for it and I want to avoid that if possible.

I paid about $100 for the entire cooling system for my laser project and that seemed reasonable and appropriate. I think it's gonna be vurra vurra nice. You could probably do very well with the same setup, but only one blower instead of two, and the 120mm X 120mm radiator instead of the 120mm X 240mm that I used, for around $70.

I'm all about doin' it on the cheap, and for one off projects, my favorite is lightly used high quality stuff on eBay for cheap, but reasonably priced new stuff of high quality is almost as nice. Including convenient one stop shopping instead of an eBay & Craig's List scavenger hunt to save $20, buying new looks like a pretty good idea... particularly when that time could be better spent designing or building, which I enjoy a lot more than shopping.
Apparently, I didn't build that! :-)
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Re: Big Ol' CNC, by Awesomenesser

Postby awesomenesser » Fri Oct 05, 2012 4:03 am

I decided the light switch on the side looked pretty stupid so I decided to replace it with a AB disconnect switch. I found it on ebay for $14 so I couldn't pass it up. I also got my USB port installed. I found these waterproof twist connect cables and panel mounts on digikey. I didn't really need the waterproof feature of the twist lock will be very nice. Here is a link to the series info on the usb cables here digikey carries almost everything in this pdf.

P1030663.JPG
The new disconnect switch and usb port with cover.


P1030668.JPG
This cable is going to be a very nice feature.


P1030672.JPG
The panel adaptor just has a female inside so I can use a standard A to B cable.
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