Annoyed with Machine Cut-Help?

[SpeedsCustom]

Finally was able to get some cutting done and my first real tests with the Gecko540.

So I have been cutting this one part that I make for about 8 months now (Don't have pictures) It's a small part, 17 mm wide, 15mm Y and 3.4 mm thick. I use a small 1.6mm cutter and have the spindle on the TAIG at 6500 RPM like today (sometimes 10,500). I usually cut the part at around 5 inches minute and pretty small DOC, roughly .40 mm. Tonight I did the cut and I changed some things around (Because I have the gecko540), I did climb milling tonight, I went from 5 IPM to 10 IPM and same DOC. The part had lots of shavings on it, near the edges, they never really flew off. So I had to debur them, essentially I'm less then satisfied with the cutting and it's to much "work" after a cnc job to finish it up. I expect it maybe need a small filing job, but not like this.


Am I cutting to fast? To deep??? It could be my tool because I have been running this two flute for about 8 months now. (On and off)



I also today cut the panel mounts for my Gecko540 and switches. It's from a cabinet I took from school, some pretty thin steal. It's 0.0385in thickness and I took a 3/16 TIn coated endmill: 1900 RPM, about 7 IPm and two passes to cut through. I'm less then satisfied and not sure if this is machine error or skipped steps or what?

From the pictures you can see how it poorly it cut, the lines are not straight and it like "wobbles" in certain areas. I did notice a lot of vibration on the machine, so much that the coolant flowing out was vibrating; It was sputtering and well...sputtering out. Maybe this made the sloppy cuts?


I actually had to run the file again because it did not cut all the way through, maybe in the process I also accidentally moved the machine in x or y slightly without knowing and reset everything to zero which when it cut the second time looked funky. ( I don't think so, like 99.99999 % sure)


What do you think? I feel that the speeds would be ok with a DOC of .40mm in aluminum and 1.00 mm in the steel








-Jason

[cadmonkey]

So I assume your only change was from a different stepper driver system (ala Xylotex, HobbyCNC, etc) to the G540 - correct? If I recall reading previous posts you are running Mach correct? Did you adjust the step timings to the proper settings? The kind of outpuit you're showing almost makes me think that if you were able to run the same speeds and feeds previously that either a) your pulse timings aren't set correctly or b) you're cables need better shielding. If you've only changed the driver then I'd investigate option A first.

If neither of those work then I'd start to question slop in the gibs or lost steps due to trying to ask too much of things - misaligned screws/nuts, incorrect/insufficient current limiting values, incorrect/insufficient voltage, etc.

HTH - take it one item at a time and make a note of how things change, it could be a combination of symptoms so if you try everything, setting it all how it was when you first started trouble shooting then go through and try different combinations. Perseverance (and a bit of luck) is the quintessential job skill

[EDIT] Rereading I see that you went for climb milling - had you done climb milling before? Climb milling will yield great results - IF you have a tight machine with no slop in the gibs/screws. You run a Taig right? I'm not familiar enough with them to give you much better insight, but since you did change processes from conventional to climb, try running it as a conventional milling operation and see how it compares. If things turn out ok then you can probably rule out the electrical issues I started off with and concentrate on mechanical. [/EDIT]

[SpeedsCustom]

I actually went from my old cnc drivers to a Xylotex that could not do anything. (Worst ever) and am happy with the 540. I'm actually using EMC and it seems to be ok, the step pulses seem to be ok. My everyday part came out find, just to rough (Maybe old cutter and to fast with old cutter). I'll def have to try some smaller feed rates, at least for now. It could also be from vibrations.

Oh and my rapid speed is 24 IPM.



Edit- Yes, I never really did climb milling. I actually changed all the files I cut tonight to climb milling (2 files) I'll revert back to conventional.

-Jason

[cadmonkey]

Well I don't know if it'll make a definitive difference, but I know the step timings for the G203Vs were different than the G201 and G202 so my drives did work, but the motors got warmer than they do now before I adjusted for the correct timings in EMC. I had used the default Gecko timings in EMC's Stepconf wizard. I am betting the other drive's had more limiting timing requirements, especially since I recall reading the 540 is essentially 4 203's stripped down but still essentially the same drives, though I wasn't able to find the step timings for the 540 in their PDF manual (tsk tsk tsk Marriss...) or the webpage for the G540 so if rapids and straight line moves are ok, you can hold off on that for the moment and get things running accurately THEN worry about eeking out the best performance.

Good luck!

[SpeedsCustom]

Thanks Cadmonkey, I will need a few days to set up things and keep testing. On a side note, the parts for the panel do fit. I mean, there pretty unseen because the components cover it up, but I would like to mill things nicely. Thats why Invested thousands....


-Jason

[TOTALLYRC]

Finally was able to get some cutting done and my first real tests with the Gecko540.

So I have been cutting this one part that I make for about 8 months now (Don't have pictures) It's a small part, 17 mm wide, 15mm Y and 3.4 mm thick. I use a small 1.6mm cutter and have the spindle on the TAIG at 6500 RPM like today (sometimes 10,500). I usually cut the part at around 5 inches minute and pretty small DOC, roughly .40 mm. Tonight I did the cut and I changed some things around (Because I have the gecko540), I did climb milling tonight, I went from 5 IPM to 10 IPM and same DOC. The part had lots of shavings on it, near the edges, they never really flew off. So I had to debur them, essentially I'm less then satisfied with the cutting and it's to much "work" after a cnc job to finish it up. I expect it maybe need a small filing job, but not like this.


Am I cutting to fast? To deep??? It could be my tool because I have been running this two flute for about 8 months now. (On and off)



I also today cut the panel mounts for my Gecko540 and switches. It's from a cabinet I took from school, some pretty thin steal. It's 0.0385in thickness and I took a 3/16 TIn coated endmill: 1900 RPM, about 7 IPm and two passes to cut through. I'm less then satisfied and not sure if this is machine error or skipped steps or what?

From the pictures you can see how it poorly it cut, the lines are not straight and it like "wobbles" in certain areas. I did notice a lot of vibration on the machine, so much that the coolant flowing out was vibrating; It was sputtering and well...sputtering out. Maybe this made the sloppy cuts?


I actually had to run the file again because it did not cut all the way through, maybe in the process I also accidentally moved the machine in x or y slightly without knowing and reset everything to zero which when it cut the second time looked funky. ( I don't think so, like 99.99999 % sure)


What do you think? I feel that the speeds would be ok with a DOC of .40mm in aluminum and 1.00 mm in the steel








-Jason

Hi Jason.
WhenI get the burrs on aluminum like you are, the first thing I do is use a new cutter and they go away.

On that aluminum part you changed a whole bunch in one shot. You doubled the feed rate without any increase in cutter speed. and then went from conv to climb.

Your depth of cut is 1/4 of your cutter diameter which should be good. A 1.6mm (.060") cutter at 6500 is way too slow especially at 10 ipm. I go 10 ipm with a .125" (3mm) cutter at 10k and the spindle sounds like I should be spinning a lot faster. I notice that when I close in on the proper speeds and feeds is that it really piles up chips in a hurry. It is very different than using a larger cutter where the chips are thick and fairly large. The small cutters at the right speed makes a whole bunch of slivers in a hurry. The small chips take the heat out of the cut along with the coolant and help prevent the cutter or part from getting hot.

If you routinely run that small of a cutter you may need to go with a higher speed spindle. I don't know how fast the stock spindle bearings will go but now that you can reliably run the table at 20 ipm while cutting, I would shoot for 20k rpm or so, with coolant of course. I am still learing but one thing I have learned is that going too slow is almost as bad as going too fast. Small cutters like to spin fast and take a light cut as in chip load per flute. The flip side is that when you spin the spindle fast you need to move the table fast but not too fast or too slow.

The speeds and feeds are one of the things I will be studying up on as soon as I am ready to make parts.

I know it is one of my week points.
But I am learing and reading and studying and reading and studying and learing and reading and trying to find everything I can. A good cutter suppler can get you set up on the maximun for their tooling but you will have to tone it down for each machine based on the speeds available and the rigidity.

8 ipm in steel on a Taig sounds like you were going way too fast for the machines capabilities. I am not sure about the proper settings for the cutter that you were using but I think you have your answer in your post. If the machine was vibrating so much that the coolant flow was affected you need to do it differently.

I hope this slightly clear than mud LOL.
Mike

[SpeedsCustom]

No it's good post. It makes sense, I did change a lot didn't I? I need to take the various steps in getting what I need at a slow pace. I changed way to much before I got to test anything. I guess I was eager, it's been weeks.


I really do think the cut in steel was due to chatter and all. I should also try finish passes to.


I don't think it was mechanical this time, to many changes at once.

I'll keep people informed


-Jason

[SCzEngrgGroup]

Jason,
The finish you're getting is a result of either a dull cutter, gummy material, heat buildup, or improper feed or RPM. Any of these can cause what you're seeing. First thing to do is start with a new endmill, to eliminate that as a cause. Set RPM strictly by SFPM - use 400 SFPM for aluminum. If your machine is not capable of reaching 400 SFPM, then you'll have to scale your feedrate accordingly. Start at a low feed rate, with the deepest depth of cut you can get away with - the tool diameter is a good starting point, except for the smallest endmills. Increase feed rate until you see the surface finish deteriorate, then back off about 10%. Often, those ragged edges will be the first thing to appear with small endmills. Coolant is essential! A mist system works very well, provided you have enough air flowing to keep the cutter absolutely free of chips. If you don't, it'll clog quickly.
Too low a feed rate will give a poor result, and dull the cutter quickly. Too high RPM will do the same. So, if necessary, reduce DOC and increase feedrate, but don't go too shallow, or you end up just wearing out the tip of the tool.

Regards,
Ray L.
Santa Cruz, CA

[SpeedsCustom]

Much better results back in Aluminum. 10,500RPM, .35mm Doc, Conventional milling and 9IPM. Good cuts, nice and smooth. Also used a new cutter.


-Jason

[Fixittt]

may I make a suggestion?
I know your using EMC but could you go back to mach maybe on another pc and use the sherline pulse mode and try the cut again in another piece of material similar to what you have there? I had all sorts of funk things going with the g540 until I went to sherline mode. maybe its all in the timing....

[MichaelHenry]

How were you holding the panel when you cut it? It almost looks like the panel was bowing up during the cut, as if it wasn't being held down flat.

Mike

[SpeedsCustom]

It wasn't down flat. It probably was for that reason, It was probably fluttering up and down, It was almost free floating expect being clamped down on the sides.


Fixitt- What number for the timing do you now have for the Sherline mode, what are your numbers even though I think i'm fine.


-Jason