Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Laughing Coyote on May 30, 2013, 11:16:36 PM
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I purchased a Taig CNC mill about 4 months ago and finally started messing with it. It's a pretty good little machine but i have one issue with it. The Z axis will not go to the desired depth when cutting. I'm using Cut2d software for the G code. I spoke with the CNC tech at Taig and he cant figure it out. The other two axis are working fine. They move to the proper locations in the program. If i use a dial indicator and zero it out, then step jog at .100 ot .010 it reads right on. I then leave the indicator in the spindle and zero out the axis and then run the program. The dial indicator will go the proper depth of cut every time. I can run the program over and over with out resetting my mach preferences. Once i put an end mill in the machine and get all my settings set. The Z axis will not dive to the right depth. The DRO reads that it went that far but the end mill is short on depth. If i let teh part cycle and run another after it the depth gets even less. It looses at least .010 or more per depth of cut. Not sure what is going on. I checked all the configurations of the machine and Mach3. It's just strange that it only does it when an end mill is in the machine. Also checked the gibs and the lead screw nut for slop and also switch it with the A axis port???? Any help would be appreciated.
Thanks
Martin
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Welcome to the forum Martin!
It sounds like you are either skipping steps or you have some sort of mechanical slip when under a load. Make sure the tool isn't slipping up, a coupling isn't slipping, and your aren't pushing it harder than it can go without loosing position.
Brett
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I put a mark on the Z motor coupling to see if it is slipping under load and it hasnt moved. I marked the tool to see if it is slipping also and it hasn't moved. I'm cutting aluminum with a .250 end mill and .100 depth and a feed rate of 9.00 inch per minute. Thats whats driving me nuts. The tech had me mess with the motor tuning and that helped but everytime i start a new program it losses depth. I do think it has something to do with with pressure but I cant think of anywhere else to check. Also tried it with backlash enabled and dis enabled and still the same.
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Can you make some test cuts so that you are not feeding in the z? Go to depth then feed in the x or y and check it? I'm guessing its just more than it can handle.
Brett
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I can manually set the depth and come in from the side and run it that way and see. I asked the tech about the depth of cut, material, feed rate and the end mill and he didnt act like it was a major issue or was causing the problem. Thanks again for the input.
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Hi LC, I see from you first thread you are using an end mill (4 cutting edges) for cutting. If you are plunging into the material with this tool you might have a problem as the centre of this cutter usually has a non cutting area or even a hole in the middle of it so if your plunging in at 9" per minute you will be pushing the cutter further into the holder. Try a slot drill (2 cutting edges and slow the Z feed rate down. I used to tell my students to use at least half the X Y feed rate when plunging in with a z axis cut for that very reason. Plus the fact that I was standing with them when they took the first cut with safety goggles, a hard hat and bicycle clips on (you work out the need for cycle clips). It also gives you time to hit the emergency stop if there's a serious problem with the clamping etc.
Keep trying if your like me you will quickly find CNC is great fun and a sense of achievement when all is working fine.
Jim
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Hi,
Just a thought. Have you checked that the endmill is not moving up into the collet?
Cheers,
Peter
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Also,
0.1" cut with a 1/4" endmill is a very big cut for a Taig, expecially if you are plunging at 9"/min.
Try doing the same cut in air and see if you still loose position.
Cheers,
Peter
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Hi LC, I see from you first thread you are using an end mill (4 cutting edges) for cutting. If you are plunging into the material with this tool you might have a problem as the centre of this cutter usually has a non cutting area or even a hole in the middle of it so if your plunging in at 9" per minute you will be pushing the cutter further into the holder. Try a slot drill (2 cutting edges and slow the Z feed rate down. I used to tell my students to use at least half the X Y feed rate when plunging in with a z axis cut for that very reason. Plus the fact that I was standing with them when they took the first cut with safety goggles, a hard hat and bicycle clips on (you work out the need for cycle clips). It also gives you time to hit the emergency stop if there's a serious problem with the clamping etc.
Keep trying if your like me you will quickly find CNC is great fun and a sense of achievement when all is working fine.
Jim
;D
Brett
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Thanks for all the input. Haven't had a chance to mess with it again. I will post the results after changing things up.
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I use my Taig mill a lot and get very good results with 1/4 inch end mills, but I do slow the plunge rate down a lot. The Taig doesn't really like anything much larger than 1/4. Have used 5/16 with some success, but a 3/8 will really bog it down.
Best results have been achieved using high helix center-cutting carbide tools. They cut 1/8 to 1/4 inch deep in one pass (6061 aluminum) without a problem at a speed of F5. Have not pushed any harder than that. Generally requires little or no polishing for a really good surface finish.
Bob@BobsShop
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Yawn, too early to be typing anything. Opps, forgot to say that I am using high-helix 3-flute end mills.
Bob - back to the bed.
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I will look at purchasing the higher helix end mills to move out the chips faster and see what I can do with it. It seems to be a pretty stout machine for its size. I'm also in the process of building a bigger gantry style machine with a 2' x 5' bed. Just have to get the time to start building the main frame. Have all the other goodies to make it work.
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Hello all,
Finally got around to designing and running a new program. Using a 1/4" 2 flute, high helix, center cut carbide end mill and took lighter cuts and it seemed to hold the Z depth. I guess I'm used to the old Bridgeport in the shop. Got to think light cuts and longer cutting times. Cant eat the cake all in one bite. Good thing becuase the Misses was about to take it to the scrap yard. :o Thanks for all the input on this post and I'm sure I will be posting more questions with issues when I start building the "Monster"" CNC table.
Thanks