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Author Topic: Success! Mini Machining Center under Mach3 control - Video link  (Read 331553 times)

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Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #260 on: December 03, 2014, 01:26:51 PM »
Do you have the part number for your sealed AC 45mm ID Bearings?  I read through the thread but didnt see it. All I can find is non-sealed versions.

If your question is directed at me (the OP), I don't understand what you are asking exactly, and you did not specify the application you have for the bearings.

You are probably not going to find sealed AC bearings, nor sealed tapered rollers. There are DUAL row AC bearings that are sealed. These are typically 5000 series although the numbering system has changed a couple of times.

Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #261 on: December 06, 2014, 01:24:01 AM »
I was directing it at you. I am going to build a somewhat similar setup for myself using a spin index spindle. In several of your pictures you show what appears to be a sealed angular contact bearings. Are these not angular contact then? Or maybe you are using two dual rows? If not, what are they, deep groove?
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #262 on: December 06, 2014, 02:38:31 AM »
After doing a little bit more reading on another thread you participated in I see you are using 6000 series SKF Deep Grooves (on the first few prototypes anyway, the new ABEC 7 one sounds sweet btw!). I ordered up some 6209's just now. Was gonna go with the 6309's, but I wanted the higher RPM rating for some of the turning i do. One other question I had for you, in some of your pics it shows you line boring the bearing bores in the aluminum housing. It was my understanding that in order to preload these bearings, the outer races would have to be seated against something (horizontally). In other words, I would have assumed that you would have had to counter bore the bearing holes and leave a bit of a backing for the outer race to sit on rather than boring the hole straight through. Is the friction of the bearing fit enough to hold the outer races for the preload?

If my question doesn't make sense let me know and ill whip up a CAD model to show what im trying to explain.

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #263 on: December 06, 2014, 07:43:44 AM »
Al of the 4th axis that I have made use sealed beep groove ball bearings. Ball bearings can be side loaded and that is part of the spec. Early on I spoke to the SKF application engineers and they have no problem with pre=loading the deep grove balls provided the side loading spec is not exceeded. Because the spindle is hollow, it is very large in diameter and therefor takes a very large bearing. In fact, far larger than would be needed even in seriously abusing these machines. These big bearings have such high side loading numbers, that angular contact bearings are not needed in this application.

You can pre load a dual row AC bearing also, but doing so would result in only utilizing one of the rows. The side loading spec would be unaffected, but I would half the radial load spec. in that arrangement.

Good catch on the line boring!. The rear bearing is retained by three large socket caps with hardened washers. I later replaced this with an internal snap ring in the bearing bore. I have acquired a surface grinder and that changes the process considerably. It would take too long to explain here, but I am currently doing a video series on the new InTurn™ ULTRA model and, by request, focusing more on the design aspects than the machining of parts. There is a lot of information on bearings and the seals associated with AC or tapered rollers. The top-of-the-line ULTRA-T model features Tapered rollers which require 4 separate shaft seals.

The video series begins with a slide show and progresses to live narration video (again by popular demand) here: https://www.youtube.com/watch?v=TdU2VD3UdVw
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #264 on: December 08, 2014, 03:44:27 AM »
Wow! From what you started with in the first page of this thread to what you are building now is SERIOUSLY impressive. My hat is off to you. I really appreciate your help with my questions.

I'm going to be building something similar to your first aluminum framed prototype. Ill be using a spin index spindle, SKF 6209 bearings, and probably this Servo (http://tinyurl.com/nh6j2bo). I'm planning on gearing it to 3:1 only, for simplicity. I'm thinking that should give me enough torque and hopefully get me around the 1400 RPM max speed range. I will be using it to machine mainly 6061/7075 and 1018/1020, nothing too crazy. Most parts will be a couple inches in diameter or less. Anything that is bigger will only be indexing.

- I'm unsure on the calculations needed to get the rotational accuracy I should expect.

- For small diameter (3 inches or less) work pieces, and 2550 oz in of torque (850 oz in peak * 3), will I absolutely need a brake?

- I really love the Gecko products, and all of my builds have Gecko drives. I know you said the G340 didn't meet your requirements, but based on what I'm building, do you think the new G320x will accomplish what I'm after (bearing in mind that my 4th axis will not be anywhere near the Mega and Ultra stuff you are building now, but more so inline with your first aluminum house prototype)

« Last Edit: December 08, 2014, 03:47:41 AM by mikemaat »

Offline simpson36

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #265 on: December 08, 2014, 06:33:17 AM »
. . . I really appreciate your help with my questions.

Your questions have become component specific and I am not inclined to spec a machine for you over a forum, however, I will answer conceptual questions that are useful to the majority or people reading the thread. For example, unless you need to weld, 1018 is a poor choice of material for a low powered machine. You will fare much better with a 'free machining' steel like 12L14. That is my advice. You can answer 'why is it better' yourself by doing some research on materials.
 
Gecko makes fine products, but for a 4th axis that spins, you will want a drive that has  enable/disable capabilities and as far as I know, Gecko does not. For DC servos, I recommend Copley AccelNet drives. These can be purchased used for about what a new Gecko would cost.

http://www.ebay.com/itm/Copley-Controls-Accelnet-ACP-090-36-Servo-Drive-CNC-High-Current-with-Warranty-/261684304231?pt=LH_DefaultDomain_0&hash=item3ced999967

Here again, this is my advice, but do not ask me to spec the exact drive you need. Visit the Copley site. Learn about the drives. Do your homework.

Instead of endorsing a specific motor, I will tell you that Torque is a static measurement that does not define available power. 'Power' (Horse Power for example) is work done over time.  Without the time component, torque is a useless number unless you are tightening bolts.  The formula for calculating horsepower is easy to find.

CNC cookbook has a speed and feed calculator that will tell you how much power you need to make pretty much any cut in any material.

Yes, you will need a brake. There is no way your servo motor will be able to hold the spindle still for machining operations with a 3:1 reduction. However, you can use a simple band brake like I use in the Tail Stock II. A design goal for the Tail Stock is  to make the machine as compact as possible so a big rotor is not an option. The band brake is intended as a 'damper' an not a powerful precision spindle lock, but it will do a good job for light duty general-precision work.


« Last Edit: December 08, 2014, 06:36:27 AM by simpson36 »

Offline jeep534

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #266 on: December 08, 2014, 08:22:59 AM »
Simpson,
   Thank You for your time and energy wisdom you have shared with us. all of this info is special. and much appreciated by myself for one and I am sure many others.

Happy Hunting
archie

P.S. I have a pile of parts including a D-4 camlock spindle waiting in the wings.
Facebook archies machine
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #267 on: December 08, 2014, 10:35:28 AM »
^ Agreed, thanks again for all the help!

Offline nava

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Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #268 on: January 09, 2015, 03:22:47 PM »
I am in the middle of refurbishing an old lathe headstock to use on my bf20l/grizzly to be my 4th axis/  So far the mechanical side of things is pretty easy going with a few replacement bearings for the headstock and probably a 6:1 or 8:1 timing pully setup. 

I've been wondering how you might think a nema34 stepper would go instead of a servo drive?  Simply the price is the attraction not to mention I can get one with about 11NM of torque.  I cant seem to find any servos anywhere near the price range of around 200 USD that the stepper would be(including the driver and power supply). 

I actually thought about using a MTB disk brake with a small ball screw to  adjust the drag/brake.

Anyway these are things I am mulling over now perhaps let me know if you think there are obvious problems I may be over looking.
Ive given the link to the specific parts im looking at on ebay at the moment anda  pic of the headstock to make this more interesting



http://www.ebay.co.uk/itm/201217825668?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

http://www.ebay.co.uk/itm/261449060712?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Re: Success! Mini Machining Center under Mach3 control - Video link
« Reply #269 on: January 09, 2015, 03:41:56 PM »
6:1 or 8:1 with a stepper will have good holding power, but it may not have the resolution you are after.

With a 1:1 ratio, each step of the motor is 1.8 degrees. With a 6:1 ratio, each step will be 0.3 degreess. With an 8:1 ratio, each step will be 0.225 degrees. With half steps, those degree numbers half. With microstepping further the same occurs.

If you assume full steps, and a 3" diameter work piece, each step would be:

- 0.047 inches of circumference travel per step if 1:1
- 0.007 inches of circumference travel per step if 7:1
- 0.005 inches of circumference travel per step if 8:1

Again, those number shrink if you half/microstep, but you will also lose torque. I decided to go with a harmonic drive coupled with a pulley ratio to get 66:1 which should give me awesome resolution regardless of workpiece size. For reference, i believe HAAS' 4th axis is 88:1. Also keep in mind that with a stepper you probably wont be able to spin it anywhere near fast enough to do any spindle work like Simpson is doing with his Servo setup. Lastly, 8:1 may be difficult to accomplish within a specific given space. You will probably need to have a multiple pulley setup which can potentially introduce more backlash.


A servo will allow you to get much higher resolution with much lower of a pulley ratio, and will also allow you to spin it up fairly fast. The downside is servo's dont have much holding power, which is why Simpson introduced a brake when doing 4th axis work vs lathe work.
« Last Edit: January 09, 2015, 03:43:39 PM by mikemaat »