Messages

1081

General Mach Discussion / Re: CNC screw cutting lathe advice

« on: June 30, 2009, 01:14:53 PM »

My little project is not ready for prime time . . just something I'm dinking around with for the fun of it. The capability of it is dependent to a very great degree on the mill it is sitting on.

You make a very good point.  MACH does seem to have problems threading, although not using Mach turn at all,  I am not the one to comment on the extent of that.

If all you are doing is the kind of item you posted, I'd have to really question how much time savings CNC will be to you, vs the cost of hardware, software and learning curve.

I am an engineer with many years experience in machining and designing prototypes of all mannet of machanisms and it has taken me months to get a simple CNC retrofit to perform adequately . .  and I'm not done by a stretch. Not intended to scare you off, but if you are busy running a successful business, I would not recommend you dive into your first CNC retrofit if you need any product off it in the coming months, or if you have other things to do besides becomming a full time student again   

Out of curiosity, what started you thinking about CNC in the first place?

1082

General Mach Discussion / Re: Anybody using Rutex servo drives?

« on: June 30, 2009, 12:30:50 PM »

With the notable exceptions of Gecko and Viper (just my luck, the two I tried so far), the rest of the drives all have graphing software interfaces for tuning.

Particularly nice for those of us who do not have an oscilloscope handy.

I'm anxious to see what I can do to talk to these drives from inside of Mach. For starters, I guess I'll just try to read something from the drive and display it.

Some of these drives monitor load, so the potential exists to have a macro (or a brain) monitor the drive and slow the feedrate if the load on the motors exceed a certain level, ore pick up the pace if the motor is kickin back on the beach sucking down a MeiTie.

Maybe a pipe dream, maybe not . . we shall see.

1083

General Mach Discussion / Re: Anybody using Rutex servo drives?

« on: June 30, 2009, 10:33:19 AM »

Update:

With Gecko and Viper out of the running, and some of the other alternatives shot down by volt/amp rating or input speed, I'm down to three possibilities (that I know of)

Rutex is $148 and the other two are over twice that, so today I ordered the Rutex. Fingers crossed.

I'll post back my results.

1084

General Mach Discussion / Re: Rotary Encoder as Spindle Index Pulse - Possible with Mach?

« on: June 30, 2009, 10:24:17 AM »

Rich,

If you have been following my progress on the 4th axis, you can see an encoder on the spindle seems to pretty much solve the threading issue, and it makes tapered threads a piece of cake.

I may be wrong on this, but it seems that MACH's single point threading is a simple plunge at the same place over and over . . . not the best way to cut threads anyway. Using an axis, it is easy to advance the threading tool in the classic way to cut only one side of the thread form. If MACH threading already does this, then disregard this paragraph.

If one is going to go thru the trouble of rigging and encoder on the lathe spindle, why not just use it as an encoder and run the spindle as another axis. Rather than 'swap axis', could not a new special purpose axis be created within MACH that is the 'spindle axis'. It could simply be a selection similar to choosing PWM or step for speed control, and it might even be automatically compatible with the popular smooth stepper.

The faciilities are already present in MACH and it seems that G-code compatibility could be accomplished with a macro.

Just random thoughts on the topic.

1085

General Mach Discussion / Re: CNC screw cutting lathe advice

« on: June 30, 2009, 07:27:02 AM »

Note that I am not endorsing any of the following, just FYI here is a link to lots of other links:
http://www.mendonet.com/cnclinks/index.html
An example of an outfit that puts all of the controls together for you into a functioning system:
http://www.lowcostcncretrofits.com/

If you need to do more than simple turning, you can follow my thread here on a 'mini machining center' that I am developing. Currently I am looking for the right sero drive and getting ready to start making the final new head:
http://www.youtube.com/watch?v=NzY-OqckqpI

1086

General Mach Discussion / Re: Has anyone used Viper Servo drivers?

« on: June 30, 2009, 06:26:18 AM »

keithmech,

I had a feeling you were using the bigger drives.

On the Viper web site, when you click to download the manual for the Viper75/95 what you actually get is the manual for the 100/200. Combining similar products into a single manual is not an unusual practice so even though the Viper75/95 was not specificaly mentioned in the manual I was not concerned about it. From the manual, the drive looked impressive and influenced my buying decision, but the Viper95 that I actually received is nothing like the 100, so the manual was not representitve of the product, nor was it useful in installing or tuning the drive.

1087

General Mach Discussion / Re: Rotary Encoder as Spindle Index Pulse - Possible with Mach?

« on: June 30, 2009, 05:53:19 AM »

You may also have to amplify it. The index pulse on my encoder is only 2V  . .  i.e. ignored by the BOB.

That seems unusual, well certainly from any encoders I have, are they 5v encoders? Does the spec say the index pulse is 2v or are you just measuring that?
Hood

http://www.usdigital.com/assets/general/90_e6_datasheet_0.pdf

These are all  '5V encoder' but that refers to the supply, not the output. Mine is the 1800 line with index. I can't use the encoder index due to reduction, but just to dink around with it, I hooked it up to the BOB . . . zip, NADA. I did not pursue interfacing it, although that would probably be simple. Changing the pulse width is outside my knowledge.

1088

General Mach Discussion / Re: CNC screw cutting lathe advice

« on: June 30, 2009, 05:36:05 AM »

Couple of thoughts:

There are lots of places that sell pre-converted asian mills and lathes. You are not restricted to Sherline for off-the-shelf small CNC machines.

If you are starting with hex stock, you should consider getting a lathe large enough to pass the stock thru the head, otherwise you are committing yourself to pre cutting each piece and the resulting waste in stainless material and manhours may cost more that the lathe itself.

Of you are willing to precut your stock and don't care if it can pass thru the spindle, you can consider doing the threading on your mill.

For many years I did extensive machining of all of the stainless grades including Inconel and Monel. I would wager that you will have zero success cutting anything except perhaps 303 on a Sherline in a production environment. Stainless work hardens pretty much instantly so you need enough power to keep cutting at ALL times. For this you will need not only the HP, but a very rigid machine, even for 12mm shafting. You are also goint to need flood cooling.

Single pointing 316 is one of the trickiest things I ever had to do. Unless there was an absolute need for single point (reverse thread, odd size or pitch, thread to a shoulder, etc ). I always used threading dies . . up to about 25mm, using a die holder in the tail stock. The low speed also eliminated the need for flood coolant. A squirt of threading oil was sufficient.

You make some beautiful parts, incidentally.  How are you cutting the hex pocket in the drain bolts?

 

1089

General Mach Discussion / Re: Rotary Encoder as Spindle Index Pulse - Possible with Mach?

« on: June 30, 2009, 05:14:58 AM »

You could use the Index pulse (Z) of the encoder for the Index to Mach BUT you would almost certainly have to electronically stretch it so its probably just as easy to fit an opto instead.
 If you are using the SmoothStepper then there is no problem at all as it can read the very short index pulse from an encoder.
Hood

You may also have to amplify it. The index pulse on my encoder is only 2V  . .  i.e. ignored by the BOB.

For a lathe, one would want to follow the development of the new threading functions in Mach. This is going to involve multiple count index. Last I peeked into that thread it seemed to be settling around 100 per rev, so an encoder index would not be adequate anyway to take advantage of the new lathe threading features.

Anyone working on a lathe index for use with Mach would be well advised to design something that can accommodate a multi slot wheel of some kind.


 

1090

Show"N"Tell ( Your Machines) / Re: What The World's Been Waiting For - Yet Another Power Drawbar Design

« on: June 30, 2009, 05:02:10 AM »

I just took a peak inside of the qc30 cavity and here is a method that could work using the existing parts and spindle without modifying the spindle. Just add in the claw mech and modify the tool holder a bit. It uses the upper part of the toolholder taper to run the claw(;-)

If you look back to the photos in Hood's reply #49, this is exactly how his power drawbar works.

Positive drive is the key whether by going with a new CAT spindle or modifying the R8. Either has product potential, methinks. The fast track solution would be a simple modification of the Tormach setup, but in the long run, of all the ideas presented, your spindle solution I think would offer the best perfrormance, and you only have to produce and/or modify one part. The rest are proven off-the-shelf items purpose built for the application.