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 CNC is Finally up and Running !

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Frisco
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PostSubject: CNC is Finally up and Running !   Sun Jan 16, 2011 8:41 am

Our CNC Mill has finally been updated and is running.......

I ran our first piece on it friday and seemed a little enlightened by the fact that it only took 3 years....

Everything that it needed, Myself and another teacher had to do ourselves....

Raise the funds, install the update, fix spindle, switch, new collet....

It took a while with absolutely no time for us to work on it but we managed to somehow pull it off...

I still have one homing switch giving me problems but I think I can fix it on Monday....

I ran a side rail out of wood for one of our bots and it came out perfect except for the arcs...

I used an 1/8 end mill so I guess that is why the arcs are kinda jagged a little...

looks like I have to find a 1/4 shank 1/16 end mill before too long...

Any idea on how to contour mill on an old Denford Compact 1000 ????

I think if I had that option it would run a decent arc and circle...

FRISCO
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rdubard
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PostSubject: Re: CNC is Finally up and Running !   Sun Jan 16, 2011 8:47 pm

Making arcs and circles is by far the greatest advantage of CNC. It will change your entire robotics experience.

Good work and good luck!
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jeeves_m_d
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PostSubject: Re: CNC is Finally up and Running !   Sun Jan 16, 2011 9:36 pm

We used to use a denford Micro Mill and Micro Router

I dont know how well built yours is, but ours was just not cut out for use with metal... plastic and wood only because it vibrates like hells and starts confusing all the switches and sensors and all those doodads. But yours may just be a rougher model, but still take it very very slow with EXtremely shallow passes.

The jagged arc finish may have something to do with the direction of the arc, if going counterclockwise and its jagged try clockwise. I thinks its a matter of switching between a g2 command and a g3 command, It really makes a world of difference and i have no idea why, it just does
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Frisco
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PostSubject: Re: CNC is Finally up and Running !   Sun Jan 16, 2011 9:45 pm

I have figured out that it was the way it rasterized the post processing.

I have been using rough and finish modeling when I need to use what they call a waterline finish rasterize..

I just need to find out tomorrow if we have the Pro version of their Quick Cam.....

The finish will save time with just a few passes of the manual mill and a little sanding of the arcs but I am hoping that we can have the pieces come out ready to assemble...

If not we might have to see what the cost is to upgrade to the Pro version...

BUT.... their website does say that they did away with the regular version and shipped all of the new Compact 1000 mills for F1 with the Pro version so maybe we do have it and I am just missing something that it needs to activate the other finishes for rastering...

I guess I will find out tomorrow.

FRISCO
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Stephen
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PostSubject: Re: CNC is Finally up and Running !   Sun Jan 16, 2011 11:39 pm

Can't wait to see that part u cut out
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Frisco
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PostSubject: Re: CNC is Finally up and Running !   Mon Jan 17, 2011 8:48 pm

Well...

Made the first pass on aluminum and things didnt go so well....

The processor cuts in both directions and either the spindle speed was too high or the clearance was not enough on a cut for boundary clearance..

The bit chattered on the first pass through the final cut then made a second pass and threw the x direction off and then ran into the edge of the left over aluminum and the bit broke....

It cut the whole thing out without a problem 5 passes total and on the last pass it happened..

I think the spindle speed was to high and the bit got hot??????

Looked good with the step over set at 10 percent.... Got the rough arcs out of there...

Then of course that happened...

Have to brainstorm tomorrow...

FRISCO

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rjw
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PostSubject: Re: CNC is Finally up and Running !   Tue Jan 18, 2011 10:16 am

a couple of things to try...

1) use a solid carbide 1/4" cutter

2) set spindle speed as low as possible

3) try very shallow cuts at moderate feed speeds (.02" @ 40 to 100 ipm)

4) perhaps get a cold air nozzle or soap or some kind of spray cutting fluid

5) post on rfl form...perhaps some there have experience with that machine

Being a stepper motor driven machine, almost anything will cause it to lose its position.

Being a router motor, spindle speeds will be way too fast for cutting metal, unless you use VERY good tooling. 1/16 and 1/8 toolsare probably too small...I would try to design around and use solid carbide 1/4" tooling....try Niagara micro carbides..not the cheapest tho.

One of the biggest problems will be keeping alu from welding itself to the tools...if you can't use coolant or spray, a cold air setup would be best, but they require a lot of compressed air.

Perhaps the machine has a lot of backlash, so experimenting with conventional/climb milling might help.

Again, try many small depth of cut passes , as opposed to fewer deep cuts, until you find where the machine is happiest.

Not a great machine to start with, so start with light cuts and see what happens.

Good luck with it




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Frisco
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PostSubject: Re: CNC is Finally up and Running !   Tue Jan 18, 2011 11:25 am

That is some good info there RJ...

I just got off the phone with Our Denford Rep and he had a bunch of that info for me..

Basically, I thought we could change the spindle speed through the programming and the fact is we cant..

That was really the problem that happened yesterday... Bit got too hot and molded...

He also suggested dish washing detergent between passes..

I used a 10 percent step over and .0625 bit depth per pass 85 IPM Feed and set the speed at 3500 RPM...

That should of and would os worked well on a machine that could adjust RPM but in the case that ours does not Spit happened...

So I guess I will switch up to a 10 percent Step over again with .030 to .050 bit depth per pass 15 IPM Feed and the RPM will stay at 20K..

That should take care of it ????

On to trial #2...

FRISCO
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rjw
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PostSubject: Re: CNC is Finally up and Running !   Tue Jan 18, 2011 12:13 pm

trying to cut dry at a high spindle speed will be a problem.

On my techno router, i cut alu with a solid micrograin 1/4" endmill at .03" depth and 200 ipm, 18000 rpm spindle speed, but I flood cool the bit.

They are not cheap, but you might want to look into the cold air venturi device that runs off of compressed air.

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Frisco
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PostSubject: Re: CNC is Finally up and Running !   Tue Jan 18, 2011 1:13 pm

Might be an addition for next year but we are going to have to wing it this year...
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rjw
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PostSubject: Re: CNC is Finally up and Running !   Tue Jan 18, 2011 1:18 pm

The i suggest taking very light depth of cut , see how things work out and take it from there.

hope things work out!!

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rdubard
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PostSubject: Re: CNC is Finally up and Running !   Wed Jan 19, 2011 9:32 pm

rjw--where do you get your table feeds from? Maybe I'm used to a high horsepower machine, HSS bits, mist coolant only, and large endmills, but by my calculations I would NEVER get more than 15ipm on the table.

Maybe it has something to do with your speeds? I run Al at 300fpm at the tooth. For a 1/4 inch diameter endmill, that gets me a spindle speed of 4600rpm. (my mill maxes out at 3500, and I like to keep it at 2500 max, but let's ignore that). If the mill is a 2 flute, and each tooth cuts 2 thousandths a pass, then I'm feeding 4 thousandsths per revolution (times 4600 revolutions per minute) gives me 18 ipm on the table. Let me restate that--spindle at 4600rpm, table at 18ipm.

You said to cut at eighteen thousand rpm (4x what I would ever do), which in my opinion, will undoubtedly make a dry bit hot enough to weld, and on top of that the incredible table speed of two hundred inches per minute (11x what I would do) would do one darn heavy chip thickness.

But hey, YOU are the machinist, so what the hell am I talking about? Am I missing some giant piece of information? Is the difference entirely accountable from using carbide and flood cooling?
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Frisco
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PostSubject: Re: CNC is Finally up and Running !   Wed Jan 19, 2011 10:00 pm

My machine is router based small machine that has no Spindle Speed Adjustments..

( DENFORD COMPACT 1000 )

Meaning it is way too fast at around 20K...

I will need to take the smaller passes just to avoid heat build up even though there is no way to prevent it...

I figured somewhere around a 30 IPM feed with 10 percent step over of the cutter per pass and a little dawn dish detergent every other pass..

That is what I am going to start at and go from there....

Each piece that comes out good, I will just throw 5 IPM and 5 Percent Step over per piece until it starts getting a little too hot..

Then I know it is time to back off a little..

If the times seem too long per part then I might try a foot control voltage variable and see what I can achieve with it..

I am a little afraid of loosing the Torque needed with the foot control though..

Should be testing on more Aluminum on Friday...

3 weeks to get it all cut out for NERC..... VERY ACHIEVEABLE...

RJ... Getting a 1/4 X1/4 mill tomorrow... Found out I need it for 4 pieces that are thicker...

Tested them tonight on some wood and the shank was hitting... Local Fastenal store has some...

FRISCO

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jeeves_m_d
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PostSubject: Re: CNC is Finally up and Running !   Wed Jan 19, 2011 10:33 pm

Frisco, your machine is almost identical to the one we have used for the past few years, we used a 1/4'' regular HSS end mill and a cut depth of 0.0625'', a feed of something like 5.5 IPM, and the 20k rpm.

Parts took forever to machine, but it was a pretty nice finish, We also had to play with the manual overide knobs until the cut sounded consistent.

We found that time wise it was easier to have the machine center drill all the holes for the part and then only partially cut out the profile. Just engrave it so you can clearly see the lines and then follow them with a bandsaw or something. OTHERWISE these denford machines will take FOREVER. Also please don't make the same mistake we did, never leave the machine unattended during operation.
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rdubard
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PostSubject: Re: CNC is Finally up and Running !   Thu Jan 20, 2011 6:54 am

I see how a spindle speed almost ten times my max would be a different animal altogether! I would expect it necessary to use something to cool and lubricate it. How much access do you have to the bit when the mill is running? Could you give it a squirt of non-volatile lube every 30 seconds or so?
We have a mist system, which requires compressed air (quite a high volume actually), and use Tri-Cool lube so a tiny spray of coolant is directed right at the bit continuously. Sometimes the chips come out hot enough to sting a bit if they hit you, but no welding or discoloration. One gallon of lube will last a year or more, because so little is used. The setup and lube is a bit of an investment ($300, not including the air compressor), but it makes using the mill a workable proposition.


You could get a small system for about half that price, it seems--Relatively Cheap Kit (including lube!)
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