3020T- DJ CNC Users thread

[ruffrecords]

Looks promising?

That looks like the stuff.  That's a big tube of it. I find the small sticks more useful because you can get it right on the cutter easily.

Excellent. I just ordered some. I'll let you know what it is like when it arrives.

Cheers

ian

 

[dirtyhanfri]

I'm using paraffine oil for cutting, drilling and tapping (and for protecting anodized surfaces) - IKEA has that in ½L-bottles under the name "Skydd"

Jakob E.

For protect surfaces during work or using it as some kind of varnish to the finished piece?

Is that blue oil used for heaters?

 

[gyraf]

Protects anodized by making pencil marks and fingerprints non-permanent.

Not heater oil, it's meant for protecting kitchen wood surfaces in a food-grade way

Jakob E.

 

[dirtyhanfri]

Ok, now I know what parafine we're talking about.

Thanks

 

[ruffrecords]

Protects anodized by making pencil marks and fingerprints non-permanent.

Not heater oil, it's meant for protecting kitchen wood surfaces in a food-grade way

Jakob E.

My wife uses a mineral oil made by Catskill for her butcher's block and other wooden surfaces. Made in USA but readily available in UK:

http://www.catskillcraftsmen.com/care/0111.html

Would that do?

Cheers

Ian

 

[gyraf]

Yup, that's probably the exact same oil. But the IKEA is probably cheaper

Jakob E.

 

[ruffrecords]

Yup, that's probably the exact same oil. But the IKEA is probably cheaper

Jakob E.

Catskill is £6.95 for 8 fluid ozs which is about 225ml. Skydd is only £4.25 for 500ml but I would have to travel 50 miles to get it.

Cheers

Ian

 

[Andy Peters]

Yup, that's probably the exact same oil. But the IKEA is probably cheaper

Jakob E.

Catskill is £6.95 for 8 fluid ozs which is about 225ml. Skydd is only £4.25 for 500ml but I would have to travel 50 miles to get it.

You'll spend a LOT more for the Ikea oil.

A LOT.

-a

PS: I'm in Tucson, and the nearest Ikea is up in Tempe, which is a 106-mile drive. There is a very large U-Haul outlet right across the street from the Ikea. When we re-did the big bathroom, we rented a 4'x8' trailer from that U-Haul to shlep the stuff south. A one-way rental cost $28 for two days. The VW had no trouble towing the load.

The U-Haul guy asked, "So, what are you buying over there? (pointing to Ikea)" I asked him, "How many trailers a day do you rent out?" and he said, "Easily a dozen, and we'd do more if we had them." Even better was when I returned it (there is a U-Haul outlet a block from my house), where the guy processing the return said, "Oh, you got this from Tempe. What did you get at Ikea?"

 

[Gold]

Food grade mineral oil is called USP Mineral Oil here. I don't know what USP stands for. My workbenches are butcher block and I use it on that. I also give it to the dogs if they seem constipated. I coat knives with it that will be left in humid conditions unattended. I also use it with a sharpening stone for knives. Most "honing oil" is mineral oil.

I've tried other oils for cutting but not mineral oil. I like the wax because it doesn't splatter like the oils I've tried.

 

[ruffrecords]

Food grade mineral oil is called USP Mineral Oil here. I don't know what USP stands for. My workbenches are butcher block and I use it on that. I also give it to the dogs if they seem constipated. I coat knives with it that will be left in humid conditions unattended. I also use it with a sharpening stone for knives. Most "honing oil" is mineral oil.

I've tried other oils for cutting but not mineral oil. I like the wax because it doesn't splatter like the oils I've tried.

The teo sticks of wax arrived a couple of days ago. I will try them on my next cut.

Cheers

Ian

 

[ruffrecords]

I am still struggling trying to cut front panels. I tried the wax a lubricant but I still keep breaking drills. Only if I use feed rates as low as 50mm/min and stand over it with a bottle of lubricant does it work, and I don't want to spend hours standing over it. I am beginning to suspect it is my use of a 0.8mm diameter cutter. I think it is just too flimsy so I am going to try something bigger like 2.0mm. I don't want to use anything much bigger because then you have a lot of material to remove which in itslef limits feed rate. Some where between the 3.75mm maximum my macine will handle and the 0.8mm I have been using there ought to be a workable compromise.

In the meantime I had an idea for making holes for prototypes. I have a lot of blank 3U Fischer front panels that I use in my modules. I used to print the front panel design, stick it on the panel and then hand drill the holes. The problem is you cannot get the centre of the holes very accurately by this method. So I wrote a Python program to drill pilot holes in the correct positions on the blank panel; then you just drill out to the right size. I just tried this with the 3U Pultec front panel and it works a treat.

Cheers

Ian

 

[tonzauber]

Hi Ian,

have you checked the speed of your spindle? For fast feed rates you need a very high rotation speed,  if you want to be somehwat fast in aluminium you should not be below 40-60.000 rpm.
Usually the small china spindles are limited to 20.000rpm.
I have just modified my small china CNC to go with a large and strong spindle and going at around 55krpm, and now it is cutting through aluminium as if it was feeding a hot knife through butter.....

 

[ruffrecords]

@tonzauber

You are right, my little 200W spindle motor barely reaches 20K rpm flat out which is what I have it permanently set to. I think it is time to upgrade it. Do you have any recommendations? Cutting aluminium like a knife through hot butter is exactly what I am after!

Cheers

Ian

 

[Gold]

I am still struggling trying to cut front panels. I tried the wax a lubricant but I still keep breaking drills.

I hope I didn't give the impression it would fix that problem. It won't make you sick if you breathe it,  it doesn't run all over the place and cleans up fairly easily. Those are the advantages as I see them.

 

[ruffrecords]

I am still struggling trying to cut front panels. I tried the wax a lubricant but I still keep breaking drills.

I hope I didn't give the impression it would fix that problem. It won't make you sick if you breathe it,  it doesn't run all over the place and cleans up fairly easily. Those are the advantages as I see them.

No problem.  Those advantages were what I found attractive. I think the root of my problem lies elsewhere.

Cheers

Ian

 

[gyraf]

Cutting aluminium like a knife through hot butter

This is the Holy Grail of cnc'ing.

I've only had a cnc setup for 14years, and I haven't been anywhere near the grail yet. Granted, I mostly use for engraving, but.

A couple of things to consider, in no particular order. Just so I know that I mentioned it...

Breaking tools is 99% because of something cluttering the cutting edge, then your feed breaking the bit. As I understand it, caused by too much heat where the tool meet the workpiece.

The rpm/depth/feedrate must ensure the removal of somewhat coherent shavings, not fine-grained dust. This because the disappearing shavings are the one most important aspect of getting rid of built-up heat. Also ensures continuous cleaning of cutting edge. This aspect is probably why you want a relatively high-powered spindle motor.

Because the required RPM goes up with smaller tool dia, limitations on spindle RPM can force you into running larger dia tools - but these requires more feed, and thus more spindle power...

Compressed air is sometimes used as the only cooling medium when cutting alu - seen it done in a local shop, and it looks very convincing, both for sawing and routing.

Jakob E.

 

[Timothytitus88]

Hey Ian,

Getting the Ali to cut like butter is a very very sweet spot between many many things.

I do not think the power or speed of your spindle is the issue... but assuming the 200 watter is one of the DC ER11 spindles, they have much larger run-out than the 3 phase versions. And I believe this is your main problem. Run-out is where the bit does not spin around the central axis. As a rough guide from Ebay... the DC spindles typically say 0.03mm run-out (probably best case - they are just a chuck whacked on a cheap DC or brushless motor) where as the better three phase spindles (4 bearing) say better than 0.005mm run-out.

This is very important..... particularly cutting with such a small bit. Practically, your little 0.8mm bit is banging against your ali from a distance of 0.03mm every revolution.... imagine.

But power wise (and speed wise) 200W is a lot of power for a 0.8mm bit. 20000RPM or even less that that is fine as long as the feed rate is appropriate.... more sweet spot parameters.

Now onto the bit.... can you provide more information? what type and where from?

The smallest end mill I use for cutting aluminum is 1mm.... but even that is small and breakage is common. I would only describe it as butter cutting over 2mm diameter. only then does the bit have enough strength. But note that my run-out is closer to the 0.005mm......

Other things that play a large role in the sweet spot is the grade of ali.... the soft stuff is no good. it sticks to the cutting edge of even the best bit, then things rapidly go bad. Most Ali I cut is anodized, and therefore for good for engraving and cutting.

Material hold down...... particularly with thin stock.... very important. as soon as your stock begins to chatter, the sweet spot is gone.

Lubrication is a hot topic of this thread, and this helps greatly... especially if the grade is not perfect for machining. A little WD40, CRC, IKEA oil, or the all of the things that have been talked about earlier in the thread are good (i have no experience with the wax sticks but im curious....) And some compressed air to blow swarf away helps too.

But.... all the lube in the world will not help if you have bad spindle run-out... and ill bet you a nice little selection of bits in the post if this does not turn out to be your main problem.

Cheers,

Tim

 

[ruffrecords]

Thanks for the comprehensive insight Tim.  It seems whether run out or insufficient speed is my problem, the solution is a better spindle/motor. Any recommendations?

The 0.8mm bit is a carbide type by Union Tool of Japan. I bought a set of 10 and I have four left. I have two other selection packs of drills. One of carbide and the other titanium coated in sizes of 1.3mm to 3.175. Edit: BTW I bought them all from banggood.

Cheers

Ian

 

[Timothytitus88]

The 3 phase spindles start at 0.8kW, and one of those should be fine for your application. Look for the ones that boast of high quality with Japanese bearings (4xC7002), etc etc (Ebay = gamble...but you can often win). My current spindle is an air cooled 1.5kW Ebay purchase. Perhaps I got lucky, but I have never had any problems.

I am about to start on my next machine, and for that I plan to use the 0.8kW spindles (yes, more than one....)

But, you will see that they can come matched with a cheap VSD. I suggest not doing this, as I feel like the cheap VSD will be the thing to fail soon (capacitors going pop, etc....) I would get a single to three phase VSD from a more reputable supplier. Just make sure that it goes to 400Hz (or even more) to get the speed up there.

Also, with air vs water cooled: I went air cooled for simplicity, and have never regretted it.

Cheers,

T

 

[ruffrecords]

I am woderring if the qualuity of the end mills I have is an important factor. A 2.5mm end mill from banggood is just £1.73. A simillar end mill by Dormer from RS is over £12. It has four flutes to the two of the banggood one. That alone cannot justify the 7 times price increase.

Cheers

Ian