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Author Topic: X Y axis switched 4th axis milling  (Read 2688 times)
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Dave Sage
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« on: November 08, 2014, 12:11:16 PM »

It's the first time I've tried the program out on a real gear so I wouldn't be surprised if I missed something somewhere .
I generated some Gcode using the 4-th axis option. It seems the X and Y axis' are switched in the Gcode. Is there something in the setup to switch them?

The majority of the motion which is supposed to be across the gear seems to be going parallel to the side of the gear. I edited the code and switched X and Y and then it looks proper in Mach3 when used as a simulator .

Sage
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ArtF
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« Reply #1 on: November 08, 2014, 01:15:37 PM »

Sage:

  Be very cautious. . Ive cut, and many others have cut many gears using the present code. In actual fact to do tangentia l shaving there is a great deal of
Y motion as the tool must move quite far in the Y to reach the tangent point for each tooth's shaving spots.

 Soon, likely within two weeks or so a new 4th axis code generator will be out that will show you graphical ly how it looks  as it cuts, so that will
make it clearer. The most common error people have found is their A axis rotating backwards to conventio n, but no-one has found an X,Y reversal.

  Try generatin g a center line "involute tool" path, if you see the X and Y are then proper. ( Y doesnt move at all in involute tool paths), then Id
put those letters back the way they were. Smiley

Art
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Dave Sage
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« Reply #2 on: November 08, 2014, 02:59:36 PM »

Hey - I have no doubt that the program is correct. I'm just wondering why I don't see it. This is why I simulate things with Mach3's tool path display.
With so many passes it's difficult to see what going on at best.  I'll take a better look at it.

But to be clear. It's a spur gear 1/4" thick and 1.3" diameter. If I orient the toolpath display so I'm looking down on the teeth and the gear is a rectangle 1/4" across and 1.3 verticall y the axle of the gear goes left to right. What I see is the tool path moving rhythmica lly up and down on the display 1/4" and a very slight movement left and right and occasiona l rotation of the gear and Z depth change.
 If I switch the X and Y by editing the code. I see the movement going left and right 1/4" (which would be along a tooth) with slight changes in vertical movement on the screen and depth as it apparentl y moves around making passes between the teeth.

The latter looks more likely as the way the tooth would be milled. But then what do I know.

I think I'm being mislead by my assumptio ns.

Sage
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Dave Sage
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« Reply #3 on: November 08, 2014, 03:43:57 PM »

Ok. I abandoned the simulatio n on the toolpath display and, as you suggested, I generated an involute cutter path which is much simpler.
Then I ran it on my actual machine. It can work but the orientati on of the pieces is crazy.
The involute cutter is in the spindle.
 I have to orient my rotary table on the right side of the spindle with the blank horizonta l and facing the back of the machine (so I'm looking at the back of the rotary table). It's pretty inconveni ent. The Gcode makes multiple passes in Y (toward and away from the operator), moves away from the blank in X (left), rotates the table and moves back in X (to the right) to start cutting again with passes (front to back) in Y.
 It's hard to get my head around but if the X and Y were switched then the blank would be horizonta l left and right and be behind the quill (or maybe in front) and passes would be made in X and rewinds in Y. That's how I would expect it to be set up.
 I don't know. It's bass-ackwards if you ask me.
 What the heck am I missing. It's not like I haven't been machining for 20 years. I will admit I'm not the best at twisting 3D things around in my head.

Sage
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Dave Sage
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« Reply #4 on: November 08, 2014, 03:58:01 PM »

Ok. The Gcode is most definitel y X and Y switched. I edit the Gcode and now I have the rotary on the left side with the gear blank horizonta l along the X axis behind the cutter. The code drives the cutter in X left and right along the blank, moving in Y in cut depth steps toward the blank. Then it rewinds by moving the cutter quickly away from the blank in Y, rotates the rotary and moves back in Y toward the blank.
This is how I would expect it to be.

Sage

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ArtF
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« Reply #5 on: November 08, 2014, 04:47:07 PM »

Sage:

  Sounds like you've found it. I truly meant it when I said to be cautious, I didnt  think you were necessesa rily wrong, its often a matter of where the 4th axis si positione d
on the table. The options allows you to select a position. Mine, for example, has the 4th axis in parallel to the X ++ axis, your sounds like perhaps its on the Y-- axis.
 Check your options menu, you can select various positions for the A axis... ( And its possible there may be a bug for the axis you do have selected, some of them are rarely
if ever used. Let me know if you do have the right one selected and the numbers are still reversed. . )

  In the new code Im going to try to make that be a post processor selection to make things easier. Preciate the heads up..

Art




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Dave Sage
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« Reply #6 on: November 08, 2014, 05:59:23 PM »

Ok. That was it. I figured you had it configura ble in there somewhere . Great work.

But I'll throw one more curve at you. I usually cut a stick of gear material while I'm at it and part off a few spares. So I would probably specify a really wide gear. The problem is you have the program doing bi-directional cutting so at the end of the cut in one direction it's not clear of the blank so the in-feed jams the cutter into the work by the cut depth before making the pass back. I haven't actually made chips but I assume at the other end the program moves the cutter clear of the work before in-feeding.
 Having said that I don't see any setting for the diameter of the involute cutter so I don't know how it would know how much to move off the end to be clear.
Also when bi-directional cutting does it take into account climb vs conventio nal milling and finish off with a particula r direction?


Sage
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Dave Sage
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« Reply #7 on: November 08, 2014, 06:58:48 PM »

BTW
One other thing. I noticed you have a pictorial of the rotary table configura tion behind the gear to be generated . At least I thought I saw it show up a couple of times. Then it seemed to stop appearing . I was going to analyze whether it was correct according to the X or Y option but it stopped showing up somewhere along the way. The gear is now shown flat on the table. (or some black object). Nice touch when it was working. I like visual confirmat ions.

Thanks

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ArtF
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« Reply #8 on: November 08, 2014, 07:59:17 PM »

Sage:

  Not sure why it disappear ed on you, it should show a 4th axis holder.. and it is ( at present) bidirecti onal. The Clearance box dictates how much it will clear the end before
plunging, ( the clearance is in % of too diam..). But you can also set the depth/thickness) to a larger number to make it pass each end by more than the actual thickness of your blank.

  Its not a very good way to portray it and it makes it hard to know what to expect, which is why in a coupel weeks it will be gone and replaced with a much more
advanced and easy to read method of coding. The new one will simulate so you can watch what it does prior to actually cutting a gear so you know what to expect.
The toolpath shown is actually quite informati ve as to what to expect but it takes some experienc e with it to understan d how to read it...anot her reason for the upcoming
simulatio n method.

  The new screens will have a finish pass as well as unidirect ional cutting as a selectabl e option. As of now the graphics are complete, the primary toolpath informati on is done,
so I'm working on its completio n and conversio n to Gcode paths, Im hoping two weeks or so till preliimin ary release.. .then Ill have to deal with post processor options for
various positions of a persons rotary axis..

Art


 
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Dave Sage
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« Reply #9 on: November 08, 2014, 08:47:01 PM »

Hi Art:

I figured out why the rotary table pictorial was disappear ing. I think the 4th axis selection is not being saved in the project file. I select it generate the code and do a save but next time I start the program and load the project file the 4th axis is not selected. I hadn't noticed it was returning to 2.5D configura tion. Maybe that's a feature?

This is a great program Art and I really appreciat e the effort you have put into it. Some great thought and amazing programmi ng has been put into it.
Sounds like it's about to get even better soon. Especiall y if you add the simulate mode to the cutting path. I really like to see what mistakes I've made before I commit to material.

Thanks

Dave Sage
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Ya-Nvr-No
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« Reply #10 on: November 08, 2014, 08:52:43 PM »

when you change orientati on for the 4th axis, technical ly don't you have to change from A axis to B axis?
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ArtF
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« Reply #11 on: November 08, 2014, 09:11:14 PM »

Thanks Sage:

   It will help greatly when you can see what the cut does. At first, it wont show material removed.. thats for later in developme nt, so I intend to have it show a gear encased in
a glass blank ( which represent s the blank your cutting from. ), when you select Simulate, the blank with the gear will rotate and the tool will make its passes at a speed
you select. Youll be able to rotate and look at the gear form many angles to see if the tool hits the gear at any point, instead of just the clear glass. I think this will aid 4th
axis users greatly in understan ding the toolpaths .

  I wont fix the 4th axis selection, Ill let it die a natural death when I remove it soon in favour of the new module.

YaNvrNo:  Its arguable what letters should be used. Most hobbiests use "A" no matter the orientati on, I think the real standard is A,B and C depending on the perpendic ular axis in relation to the tool, ... but Ill leave that up to people by having them set it in the post processor file. Smiley, now that I dont write controlle rs anymore, Ill leave esoterics like axis designato rs to the "experts" .... Ex - "used to be" . Spurts-"Several drips under pressure. ."   :-)

Art
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Dave Sage
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« Reply #12 on: November 08, 2014, 09:18:14 PM »

<edit> you were answering while I was typing - none the less...

Ya-Nvr-No:

I don't even know what a B-axis is so I'll leave that question up to Art.

But I've noticed something else that doesn't make sense to Me.
I went through the options selecting the X++ X-  Y++ and Y- options and then go back to look at the graphic and the resulting code.

When I select the Y- option the gear blank is oriented ACROSS a table slot and the axis of the rotary table is parallel to the slot. Table slots run along the X axis of the table. The teeth of the gear therefore also run parallel to the X axis. But when I look at the resulting Gcode the Y axis is doing all the moving and the X is doing the depth steps. I'm not sure what is meant by X+ X- etc. but certainly the Gcode and the graphic do not jive (I don't think).

(As before a spur gear 1/4" thick 1.25pitch diameter 4th axis selected Y- option selected. View angle bottom arrow so it appears you are looking down the length of the table from the right and you can see the table slots.)

What are your thoughts.

Sage
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