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Author Topic: Success! Mini Machining Center under Mach3 control - Video link  (Read 331555 times)

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Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #110 on: January 27, 2010, 09:43:30 AM »
IF you have no need for using your 4th axis as a lathe spindle, then it is a perfect application that takes advantage of a stepper motor's strengths, which have been discussed numerous times.

Flying Scott: You mentioned 'small' servo motor, but a direct comparison between stepper and servo power cannot be made based on published specs because they are not measured in the same way. Sort of like comparing Gallons to Feet.

Steppers are very good at holding (big steppers, that is). That is where the torque spec is measured and they do not dither or vibrate or have any 'slack zone'.

You need to also consider the drive mechanism involved. Many 4th axis are worm gear driven. I would speculate that this would swing the advantage back to the servo motor, where the vibrations would not be an issue, and the far higher speed of the servo motor would be a great benefit.

Hood: If we may refer to the drives that I reviewed as 'hobby level', then there are none that can have their amp output commanded in real time with Mach3 software. I'm not saying it is impossible, as there may be some method that I am not aware of, but I did investigate 'real time' reconfiguration via Mach3 at the time of the review and I know of none. CNCdrives is adding the capability and I don't know yet exactly how it will be implemented, but it will thru a macro for sure and will use  the currently unused 'aux' connector on the drive. . 

Offline Hood

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #111 on: January 27, 2010, 10:15:03 AM »
Hood: If we may refer to the drives that I reviewed as 'hobby level', then there are none that can have their amp output commanded in real time with Mach3 software. I'm not saying it is impossible, as there may be some method that I am not aware of, but I did investigate 'real time' reconfiguration via Mach3 at the time of the review and I know of none. CNCdrives is adding the capability and I don't know yet exactly how it will be implemented, but it will thru a macro for sure and will use  the currently unused 'aux' connector on the drive. . 


If this is with reference to my last post then I was meaning disable the drives, I would imagine most servo drives require an enable signal, but maybe not?
Hood
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #112 on: January 27, 2010, 11:42:01 AM »
Very cool axis brake.

Let me just make sure I understand:

You've got a disc brake off a motorcycle or somewhere. 

Instead of operating it via brake fluid, you've threaded a rod into the caliper that directly acts on the puck when your air cylinder rotates it?

I'm also curious about the dithering concern with servos.  Yes, they dither, but are you seeing some effects in your work without the brake, or are you just concerned there might be?  The reason I ask is that the dither is pretty darned small, should be no more than a step or two.  I still would understand the desire for a brake to hold still for indexing.

RE stepper vs servo, stepper sure has a lot less resolution than an encoder.  If you've only got a timing pulley reduction, it's kind of hard to get good resolution with a stepper.  You can compare these resolutions versus various gear ratios in a spreadsheet I did for my own 4th axis design project:

http://www.cnccookbook.com/CCMillCNC4thAxis.htm

Cheers,

BW
Try G-Wizard Machinist's Calculator for free:

http://www.cnccookbook.com/CCGWizard.html
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #113 on: January 27, 2010, 12:16:21 PM »
Very cool axis brake.

Let me just make sure I understand:

You've got a disc brake off a motorcycle or somewhere. 

Instead of operating it via brake fluid, you've threaded a rod into the caliper that directly acts on the puck when your air cylinder rotates it?

Cheers,

BW

Bob,

The disc brake is off a bicycle, or mini-bike.  They are typically cable-operated.  This is a GREAT application for those!  I've considered putting a spindle brake on my mill, and one of those woudl be just the ticket.

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #114 on: January 27, 2010, 12:21:57 PM »
The disk brake caliper is mechanical from the git-go.  These are small calipers for bicycles, ATV's, mini bikes, etc. I purchased several varieties and the one featured on the 4th axis happens to be for what is called a 'pocket bike', which is a ridiculously tiny motorcycle. They all have similar internal cam arrangements.

I found the quality of the calipers to be unacceptable, so I had to extensively modify it. So much so that in the future, I plan to use the brake pads, but fabricate the caliper from scratch.

The disk is cut from 2024 of 7075 aluminium sheet. I must emphasize that this is a consideration for mass and these disks are not intended, nor capable of acting as brakes to slow a load. The disk on the milling machine spindle is another 'pocket bike' item. It simply needed a small hole for the sensors and have its mounting hub removed. It is the smallest pre made disk I could find at 5.5" OD

The servo motor will *try* to maintain one count on an encoder, but that is not going to happen if the load is too great and the amps too little. I have 35amps available and I can force the motor off center by hand with less than a 12" lever. The normal dithering is tiny with my 1800 line encoder (7200 with quadrature), but 'tiny' is relative. Cutting the teeth on the GT3 timing pulley was done with a tiny 4 flute ball end mil ll at 28,000 RPM. If you have a chip load of .0002, even a .001 oscillation is significant.

My 'anticipated' issue is off center drilling of fairly large holes in stainless or tool steel. The force needed for that would be greater than it takes me to move the spindle off hold.  This is a heavy unit intended for 24/7 production, so it needs to be able to handle tough jobs. 

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #115 on: January 27, 2010, 12:38:41 PM »
Hood: If we may refer to the drives that I reviewed as 'hobby level', then there are none that can have their amp output commanded in real time with Mach3 software. I'm not saying it is impossible, as there may be some method that I am not aware of, but I did investigate 'real time' reconfiguration via Mach3 at the time of the review and I know of none. CNCdrives is adding the capability and I don't know yet exactly how it will be implemented, but it will thru a macro for sure and will use  the currently unused 'aux' connector on the drive. . 


If this is with reference to my last post then I was meaning disable the drives, I would imagine most servo drives require an enable signal, but maybe not?
Hood

Some can be stopped with an external signal, but if I remember correctly, restarting any of them requires a reset and they loose reference. None of them track the encoder during a fault, so even if you could restart them, results would be unpredictable. methinks.

If I recall correctly, you have high end stuff and it may have a more sophisticated capability in this regard. I do know that some drives continue to track the encoder even when they are faulted . . . totally logical . . . and totally missing from the low end. Of the hobby level drives I tested, only the CNCdrive product was acceptable and it can be stopped, but must be reset to start up again. Unlike others, at least the CNCdrive products can be reset without powering down the whole system and waiting for all the CAPs to bleed off.

Offline Hood

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #116 on: January 27, 2010, 03:07:28 PM »
Yes my drives are Industrial type and do track the encoder in all states, I just presumed even the cheaper drives would need an enable signal which you would use to allow movement but could also take that signal away and the drive would stop holding the motor. If that was the case and you were using a brake then the motor couldnt move anyway so as long as you enabled just prior to releasing the brake it should not lose position.
 From what you say though it looks like that is not the way the hobby drives work and if you need to power down before re-enabling its not very good and obviously what I was thinking will not work..
Hood
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #117 on: March 12, 2010, 07:54:30 PM »
I have looked far and wide throughout this thread and more .
I cant find how its  achieved running
both spindles togeather without the axis swap.

Iam after a solution like the very first post,ie
controlling A axis as a continuous spindle (lathe mode) and also using a router spindle
at the same time.


Any info would be great.

Regards
Whatda

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #118 on: March 13, 2010, 03:01:39 AM »
You can run a router and use the 4th axis in 'lathe' mode now unless you want to use Mach to control the router speed.

This project is alive and moving forward. The current 4th axis version will become a standard part of a new commercial machine and I am currently building a new 'Super Duty' version with double reduction and a robust steel disk brake. I am pursuing a couple of different options for controlling the spindle without using the swapaxis function.

One possibility is a solid state device which will switch the servo motor's controller from a servo drive to a speed controller.

The second involves another modification of an existing servo drive to perform the speed control function internally and outside of Mach, but using an output of Mach to engage the 'lathe' mode.

A third is to use a pulse generator to create the pulse stream for 'lathe' mode and only switch the encoder output between Mach and the pulse generator for 'indexer' mode and 'lathe' mode respsectively.

There are advantages and challenges with each method.  It is an interesting challenge  Anyone who wishes to share some creative ideas on this challenge is certainly welcome to do so.
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #119 on: March 13, 2010, 03:53:48 PM »
Thanks for the info.

".......You can run a router and use the 4th axis in 'lathe' mode now unless you want to use Mach to control the router speed."

How is this Achieved. ????

Regards
Whatda