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Offline kolias

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Questions 1st Aluminum Cut Sample
« on: November 11, 2012, 05:03:02 PM »
Finally I cut my 1st Aluminum sample and have some questions. The sample is on a piece 5.5”x4”x1/8” thick and the square I cut on it is 2”x2”. Before this cut I did another sample on MDF and all the cuts on MDF look good (see attached pic)

1. The tool I use for the square cut is 1/4" Drill Point 2 Flute Endmill and the start of the cut is at the top left corner. The speed of the tool is about 6000RPM and the feed rate is 20"/min. As you can see on the attached pic. the cut at the start is not the same as the rest, its deeper and wider. What may cause this?

2. I was expecting the cut to be more sharp and clean but have no experience with Aluminum cuts so is this normal? Perhaps I use the wrong bit?

2.  The thickness of the aluminum is 1/8" and I did the square cut with 2 passes of 1/16" each pass but the tool did not go thru. What is wrong here? I set the depth with a zero touch plate so I know that the Z is set properly at 0 on top of the material

3. This is not a question about the cut but I guess the pump I have for the cooling liquid is not big enough to pump the thin oil I use. I control the pump with a momentary switch and when I press the switch the oil just trickles out of the nozzle. Can you recommend a better pump? 


Nicolas

Offline Fastest1

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Re: Questions 1st Aluminum Cut Sample
« Reply #1 on: November 11, 2012, 08:27:21 PM »
Others with more experience will chime in. I dont think I would have used a drill pointed (chamfer?) end mill to plunge if that is what you used. I would have used a center cutting 2 or  4 flute end mill which is what it appears you used on the MDF. Are you trying to outline that square or was the intent to cut thru? Depending on the machine and its rigidity the depth of cut might or might not be too much. Did you calculate the chipload, rpms and feedrate or just guess? Dont be embarassed if excitement took over and you just wanted to see something happen! I have broken way too many tools and parts in this journey. MDF looks good. Also dont expect the letters to turn out very well unless it is engraved. They can be much better than what you experienced so far. As you can see wood and metal are 2 different materials. Actually if you were trying to remove the center piece. I would have done a circular or helical ramp into the inside of the line then proceeded. Straight plunges seem to wobble too much for me.
« Last Edit: November 11, 2012, 08:30:36 PM by Fastest1 »
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Offline kolias

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Re: Questions 1st Aluminum Cut Sample
« Reply #2 on: November 11, 2012, 09:16:01 PM »
Hey Fastest1, thanks for the comments

No experience here, I just used a drill point end mill because I thought it will be the best to straight plunge into aluminum and yes you are right on the MDF I used a 2 flute center cutting endmill.

The intent was to cut thru the square and I didn’t calculate any parameters, I just used what I have gathered from others on the web.

I don’t understand what you mean by "Also don't expect the letters to turn out very well unless it is engraved". I did use a 60deg V bit and although the letters turned out good, I was expecting better.

Also I don’t understand what you mean by "I would have done a circular or helical ramp into the inside of the line"
Nicolas

Offline Fastest1

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Re: Questions 1st Aluminum Cut Sample
« Reply #3 on: November 11, 2012, 09:55:39 PM »
   How did you generate the code? Were you just using wizards? Which CAD program are you using? If you used a Cad program generally there are a variety of ways to have your tool enter and exit the stock. You could plunge, ramp, helical (like a corkscrew) and tangential (which I dont understand yet). These different techniques place different stresses and or allow the tool to achieve its depth before following a path to minimize the deflection as you experienced where the top groove was wider than expected. Or maybe they create a place of the chips to be evacuated at the start of a cut. Or a dimple or ridge at a start point of a bore. You also want to overlap if boring a hole or circle to minimize the entry points mark.

  That is what I am guessing happened though it could be a few things. So much of this stuff has been counterintuitive to me. Rarely has higher rpm helped me and many times it has overheated the tool, the part etc.

  If I am seeing it correctly there are plenty of chatter marks in your letters. This could be caused by many things, fonts, feedrates, gummed up flutes. There is much to learn and engraving will bring new challenges of which I dont have much experince but have made similar errors to you.

  Also if the tip of the tool could go all the way thru the material so it uses the side of the tool to cut you would get a better finish on the final cut outs walls. Try doing the cutout with the 2 flute end mill. Also direction of cut is important. Climb milling has produced better results for me though I am getting better at both.
« Last Edit: November 11, 2012, 10:00:32 PM by Fastest1 »
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline kolias

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Re: Questions 1st Aluminum Cut Sample
« Reply #4 on: November 11, 2012, 10:41:24 PM »
I used MastercamX5 but remember I have no too much experience. I don’t want to use Lead-in because the samples I do now are to eventually help me cut the openings / letters for my control panel (8.5"x21"x1/8") and I don’t have a space for Lead-in.

Yes I also see the chatter marks and I think it's because of the wrong type end mill I use. This is the 1st time I do a cut in aluminum and next time I will try a 2 flute end mill as you suggested
Nicolas

Offline Fastest1

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Re: Questions 1st Aluminum Cut Sample
« Reply #5 on: November 11, 2012, 11:01:18 PM »
  I meant a lead in for cutting the openings not letters. Do you have a center drill? I was just reading in the "show and tell" section here and there is a thread "bike part" where he uses a center drill for the engraving and has very good results. He didnt think so but i did. The shorter and more rigid the tool, least amount of stickout and w secure workholding will give the best results.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline kolias

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Re: Questions 1st Aluminum Cut Sample
« Reply #6 on: November 12, 2012, 12:51:38 AM »
Yes the"bike part" post is pretty good, if I can do something close to it I will be very happy, lol

I do have a 2 flute center cutting end mill and will give it a try soon to cut the 2"x2" square. For the engraving I will use again the 1/16" V end mill I have but reduce the RPM perhaps to 2K to 3K and the feed rate down to 15
Nicolas

Offline Fastest1

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Questions 1st Aluminum Cut Sample
« Reply #7 on: November 12, 2012, 07:09:53 AM »
Btw, I too get great results in MDF only to experience some frustration after moving over to aluminum. I also can cut real fast and deep in the wood. But it isn't quite so impressive (it is to me) in metals.

On the engraving hopefully someone else will chime in. I have always understood it is a high rpm tool. At .06125 diameter it should be fast. IIRC engraving is generally a single pass but I could be wrong.

  Personally I would take a piece of scrap aluminum. Choose 1 letter. Fix the rpm at 6000. Cut the letter (shallow depth of cut, single pass) at a feed rate you know won't break your tool. Then look at the results. Move over an inch. Reset my X and Y coordinates to 0. Use the feed rate over ride button and reduce the feed rate say 25% and rerun the letter. Does it get better or worse? I am betting this v tool you are referring to ( if it is an engraving tool) is a single flute.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline kolias

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Re: Questions 1st Aluminum Cut Sample
« Reply #8 on: November 12, 2012, 08:15:37 AM »
The V tool I use is a 1/16" engraving 60 degrees end mill and cuts on both sides of the "V". I know that I have to play with the feed rate and RPM to get a good cut on Aluminum and hopefully I will get there sometimes this week
Nicolas

Offline Fastest1

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Questions 1st Aluminum Cut Sample
« Reply #9 on: November 12, 2012, 08:35:52 AM »
Just for clarification which tool.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)