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Topics - Tj256

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*****VIDEOS***** / MaxNC 15 Upgrades: Spindle Motor Replacement
« on: July 06, 2012, 09:49:11 AM »
The stock brushed 10,000 rpm Grainger motor on my MaxNC15 was insane. The brushes kept wearing out, flames occasionally shot out of the motor, and it was freaking loud. My solution was to replace the spindle motor with a servo drive from LeadShine. The video here shows my many upgrades, but focuses on the 400 watt servo motor spindle motor upgrade.

http://youtu.be/VYMddSNP058

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Hey guys!

I finally set up my MaxNC 4th axis. I noticed it had a severe amount of backlash, and trying to apply manual pressure to rotate the table compresses the black motor coupling and moves the table 10 degrees! I did play around with Mach's backlash settings but it's so bad that I probably won't be able to fix this one in software.

Since MaxNC is kauput and I can't ask them, Does anyone recognise this table? I am trying to locate any instructions for adjusting it. Surely there's got to be a way to adjust this thing. It does have 2 set screws in it but they don't seem to do much but cause things to bind when tightened.

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It seems that after searching through the intertubes, nobody seems to have posted any instructions for getting the most accuracy out of a MaxNC/MachIII setup. I'm talking about properly setting up backlash compensation and properly “aligning” the spindle on this machine (MaxNC15) so it is perfectly orthogonal to the X-Y table.  I guess I'm not surprised by the fact MaxNC has no such instructions, but surely others out there have run into accuracy issues over time. My journey began when I  crashed my Z axis, and suddenly woke up to the wonderful world of alignment issues.

In the end I went from roughly .01” of change for every inch of Z I plunged. Maybe this is acceptable to some, but for me it is NOT. I do crazy things like cut solder stencils with .005” apertures. I want the advertised accuracy out of my machine! After I did the calibration I'm about to describe, I can actually get the accuracy and repeatability claimed by the manufacturer of .00025"!!

First off, I wanted to get rid of backlash so this didn't mess me up through what I'm about to describe. MachIII has some nice dialogs for modifying these parameters, and unlike the naysaysers out there, I'll make the wild claim they actually work WELL. I take a value much higher than the actual expected backlash... say .01", plug that in, then go into JOG (tab) mode / 1% and hit left-right very briefly and alternately on that axis. I also use my favorite indicator setup so I can see how much the spindle has moved on the axis. If you have too much backlash configured, the needle jumps. I then lower the backlash value it until the needle doesn't move at all when you hit left/right. Repeat on the other axes and you've gotten some additional error fixed thanks to MachIII. Out of the box, my MaxNC15 had .003" of backlash on X and Y but now ZERO thanks to this feature. Note that I'm talking about pulsing left then right very briefly so the s/w only has enough time to take up the programmed backlash and nothing more. You'll see the steppers moving but the table won't.

The following are sources of error in the MaxNC mill as they relate to the tool:

1) Wobble from the tool (runout)
2) Misalignment between the tool's rotational axis and the axis of travel (Z).
3) Lack of orthogonality between the tool's rotational axis and the X-Y table.

You can't just lump these all together and fix them at once. EACH one must be accounted for seperately or you'll go mad (like me). I'll admit that I'm a n00b here, but what I'm about to describe worked for me. Maybe you have a simpler solution. If so, let me know!

n my machine, I noticed the issues when trying to use an edge finder to locate the center of bar stock. I would touch the edges on X divide by 2, set zero. Same for Y. Theoretically I now have zero. However I was always off. This drove me mad until I realized the three issues above. Esentially the edge finder was tilted relative to the table, finding the center at a skewed and incorrect location.

Here's how I addressed each issue:

1) Runout: Not much you can do about this. Make sure your collet is tight. I have the original TAIG style spindle with the ER adapter and runout is about 3 mills. I measure this by putting a longish 3/8” shank bit (has to be smooth!) in the collet and rotating it by hand.  I put a dial gauge anchored to the mill with its point on the bit, and rotated.  My machine has .003” - .002” runout/ depending on how well I did inserting the tool.

2) Misalignment of rotational axis vs Z movement axis: This can be measured on X and Y independently.  Using the dial gauge on an arm (affixed to either the table or the bench, doesn't matter) touch the front of the bit for Y changes, or the sides of the bit for X changes. When jogging the machine up and down, you'd ideally want to see ZERO change. Unfortunately you will see the #1 and #2 error sources, so you need to get rid of #1 (runout / tool not straight) and #2, actual misalignment. Rotate the tool and get the max or min deflection on the needle.  Then rotate 90 degrees. This will temporarily get rid of the #1 error for the measurement you're about to do. Why? Because the tip of the bit is basically offset (aka wobble/runout) and draws a circle as you rotate. 90 degrees from the max or min rotates that error so you don't see it. Then when you jog up or down you don't get the runout error since the runout is now pointing perpendicular to the measuring device. Now we can fix error source #2 without source #1 messing with us. So for #2, I found that this source of error was 0 in the Y direction most likely to the way the machine is constructed. X however had 5 mils per inch of delta. I fixed this by loosening the 4 screws  holding the spindle and applying some force as I re-tightened the screws. After doing this and re-measuring a few times, both X and Y were ZERO delta over a few inches. Perfect!

3) Lack of Z orthogonality: If all that weren't enough, I made the Z axis tilt relative to X and Y because I crashed once and popped the “Z fuse” so-to-speak.  Turns out since the Z axis sits on the Y axis FLAT, and because rotation of the Z axis along the long axis just adds a fixed offset, the only misalignment that matters is front-back movement. I fixed this by putting a dial gauge in an Indicol arm in the spindle and touching the side of a perfectly machined block on the table .  Make sure to touch the block pointing toward the back or the front of the machine so you get the tilt! Jogging up-down changed initially over .01” per inch. I loosened the screws and slightly moved the tilt of the Z axis slide (motor and all) forward or backward bit by bit while jogging up and down. Eventually I saw ZERO change. I tightened the screws down and retested. Perfect!

I hope this helps someone. I don't know why I can't find anyone else doing this with their MAXNC, nor do I understand why the instructions for aligning the machine weren't included. Maybe this is common knowledge?

I've attached an image of a solder stencil I cut.. the apertures are roughly .009" wide. All done on a maxNC15! The stencil was so accurate I was actually able to lay it over the circuit board, hear a click and it attached itself to the pads!

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Hi Guys,

I'm pulling my hair out over what seems like a simple issue. Very excited to finally have MachIII working on my MaxNC mill (I had to gut the stock controller) I've milled wood and foam up until now, and I'm in new territory with aluminum.  I've got a MaxNC15 which has a Taig collet system for holding endmills. No matter what I set my feed speed and RPM to, the endmills eventually decide to slip up or down wrecking either the endmill or the part. I've attached a photo of my lame attempts to route around a 1" square to show you what I mean. The bit I am using, as well as the holder is pictured. I've tried 10k rpm, 1"/min feed rate as well as a lower 1k rpm which started to produce larger pieces of aluminum shavings (a good thing?) but still started to crap out after a few minutes. I've also lowered the feed rate to an excruciating .25"/min and the same thing happens. I've tried both no coolant and oil. The oil actually seems to make things worse and speeds up the time until the bit slips. What could I be doing wrong?

Thanks for any help. This is indeed frustrating!

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General Mach Discussion / Possible to use encoders for limits?
« on: October 26, 2010, 11:04:38 PM »
I finally have my encoders showing up in the "settings" screen under encoder positions. The main reason I want to use encoders is for safety-- basically to shut down if I go out of limits or if my steppers get out of sync by too much.

Yes, I know there is supposedly a board to do this but seems silly to buy that to simply subtract 2 values and error if the result is higher than some threshold.

Ideally I'd love for the DRO to compare itself to the encoder positions and do just that.... kill the run if things don't match. If that isn't possible, I'd like to get limits working on the encoder position. Limits aren't useful to me if the motors aren't where mach thinks they are. I want the limits to be based on where they actually are... ie the encoder position.

I'm hoping this is possible?

Thanks in advance!

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General Mach Discussion / G540 charge pump pin 16 is 2v instead of 5!
« on: October 25, 2010, 11:16:25 PM »
It seems the G540 from GeckoDrive pulls down my nice 10 khz 5 volt signal on pin 16 down to 2 volts, and is not happy about it. Does anyone know if there is a solution to this? I think this is why many people try random parallel port cards until they find one that works. I'm hoping to find the reason behind this happening.

Thanks for any hints...

-Tj

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Maybe I missed some instructions somewhere, but my machine has been acting erratic and generally not working. A big clue was my PWM frequency not being correct. Turns out there's a setting in Vista under control panel, power management, advanced power settings. Expand the tree and find "Minimum processor state". Make sure this is set to 100%. Also do the same for maximum.

Once I did this, my PWM frequency is correct and things work better than ever!

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Mach3 under Vista / Has ANYONE gotten a MaxNC15 CL to work?
« on: October 08, 2010, 03:02:14 PM »
Sorry about the title, but I am beyond frustrated after dropping 6 grand and not getting any support from MaxNC on this issue.

So by work I mean reliably. I have 95% operation of my new machine, but every now and again an axis just stops. Sometimes it humms, sometimes it pops the fuse on the controller. But this is happening with no load on the machine and no tool, and the motors running slowly with minimal acceleration.

What I think is happening is that the feedback loop in the controller is getting confused about where the motor is, and getting it wrong. It then gives the wrong stepping signals to the motor. When the motor doesn't move, it assumes it's stuck and gives up.

Now how it gets into this state is the question. I am suspecting that it has to do with the "busy" pin. The controller says "Don't send me any more quadrature!" but for whatever reason I am getting a step or two. Then the controller gets confused. At least, this is my current theory.

Anyone else having issues like this? Any suggestions? I am starting to regret ever purchasing a MaxNC product.. >:(

Thanks!

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I'm running Mach3 under vista, and I randomly have one of my axes give up and stop moving while running programs. I'm not sure exactly how MAXNC closes their loops with the encoders/steppers. If the PC is in the loop, then one theory is that somehow the software loses sync due to a lost interrupt and the wrong coils are energized, and the motor can't move anymore.  Sometimes I hear a hum from the offending motor, and usually after 30 or so seconds the fuse pops on the controller.

Anyone else see this issue? I can fix it by hitting reset and it comes back to life. When the axis is out, programs will run normally but the dead axis stays put. Jogging does the same. I can't jog the dead axis.  The DRO will increment / decrement as if it's moving.

Any help is greatly appreciated. I can't believe I'm the only one with this problem.  I'm hoping it's just a timing issue and some settings will fix me. I believe it's a design flaw or misconfiguration issue because resetting clears the problem. (ie, not a hardware failure)

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