Messages

1211

General Mach Discussion / Re: Using a 3 axis router as a lathe - oddball question

« on: April 23, 2009, 09:48:00 PM »

A strange idea popped into my head as I was drifting off to sleep last night. I'd been thinking of making some dollhouse decorations for a 2 year old and wondering how I could turn miniature baluster without a lathe. A picture formed of my router holding a dowel in the 1/4" collet and a tool bolted to the table and the router was moving in two axis to cut the baluster - a vertical lathe where the work moves instead of the tool.

Has anyone ever tried this? I was trying to figure out how to set up my axis to accomplish this but nothing is sticking to my aged neurons. I can't imagine it would be all that difficult to accomplish. Of course, being supported only at one end means long workpieces are verboten but since I only have 5" travel on my Z that temptation is moot

Any ideas?

I've done exactly that on my knee mill.  I once used it to turn a 12" diameter disc for a disc sander I made.  Works great!

Regards,
Ray L.

1212

General Mach Discussion / Re: Hotkeys for buttons on screen...

« on: April 22, 2009, 07:45:00 PM »

How would I set up a hotkey to zero the x and y axis values?

I want to be able to zero the DRO for X axis, by pressing "x" and the same for "y". How would I do this?

Download screen4, the screen designer tool.  It will allow you to assign hotkeys for any on-screen buttons.

Regards,
Ray L.

1213

General Mach Discussion / Re: What size motors?

« on: April 18, 2009, 08:29:26 PM »

Ha ha, good term: "inflection"...

 So the next milling machine that I convert will have steam engines on it, but was wondering which to use - turbine or reciprocating? Doesn't really matter because I could snap a 4 inch end mill at will! And rapid travel....? I could over in to next week in a wink.  

A commercially available NC mill is using direct drive series 34 stepper motors and they give reasons why. http://www.cncmasters.com/CNCMasters_Supra_ProductGuide.pdf

We are seriously looking at purchasing one of these...

 Thanks once again,
Bill C.

Probably a nice machine, but 50 IPM is a *painfully* slow max speed for a machine that size.  That's almost as full minute to go end-to-end on the X axis, and almost 20 seconds on Y.  The basic machine is identical to mine - same castings, same paint even.  It is a very good basic machine.

Regards,
Ray L.

1214

General Mach Discussion / Re: What size motors?

« on: April 18, 2009, 11:30:22 AM »

There are benefits and pitfalls with both type drive motors. Servos are more powerful at higher speeds where steppers begin to decline but the most prevalent benefit to stepper motors is that they don't require tuning via their drive. Tuning can be a problem then it must be done at a later date with servo motors again - and again. I would direct drive that Bridgeport with about 1500 Oz In stepper motors with appropriate drives from Gecko and forget about -  tuning, belt adjustments and wear, and all the 'bracketry' required for servo motors and their belt reduction and adjustment fixtures. I converted a similar mill and used servo motors.....And BTW: servo motors are very much more expensive than equivalent stepper motors and servo motors require an encoder to give position feedback to the drive where steppers are where they are told to be. Use size 34's.



2.25 cents worth at least!

Bill C.

"servo motors are very much more expensive than equivalent stepper motors" - That is simply not true!  The difference is perhaps very, very, very worst case $100 more per axis, which is almost lost in the noise compared to the overall cost of a decent conversion on a knee mill.  And the difference in performance can be very significant indeed.  There are plenty of valid reasons for preferring steppers over servos in some applications, but cost is not one of them, unless you're really pinching pennies.

I used 850 oz-in servos from www.homeshopcnc.com, with 2.5:1 GT2 belt reducers, and Gecko G320s.  My machine can get up to 400 IPM rapids on X and Y, and it absolutely un-stoppable at machining speeds.  I've snapped off 1/2" endmills without losing position.  Try to get that kind of performance from steppers.

Regards,
Ray L.

1215

General Mach Discussion / Re: Can two 36v power supplies be used in series to get 72v?

« on: April 15, 2009, 02:30:07 PM »

Be VERY VERY careful. Unless the power supply is designed for series operation you will have problems. Many switch type power supplies tie the DC common to earth ground through a small resistor. Chaining two in series would be a bad idea. If a power supply can be put in series it will be stated so on the data sheet.

It's ***NOT*** a switching power supply! It's a plain, unregulated linear supply!  There is absolutely no risk of damage.

Regards,
Ray L.

1216

General Mach Discussion / Re: Routing Acrylic!!! Please Help!

« on: April 15, 2009, 12:02:22 PM »

I am trying to route a logo into .220 Clear Acrylic.  I am using an .125" End Mill bit and i'm only plunging .09375" into the material. Can anyone give me advice on what my feed rate, spindle speed, etc..etc.. should be in order for me to get a smooth cut? Ive been toying with it but it seems everything i try still comes out poor. The acrylic is basically melting and re hardening where i'm cutting. The edges are coming out not as smooth as I'd like. Acrylic isn't cheap- so I'd like to stop this shoddy work! Please help acrylic masters!

Thanks- Brian

If it's melting, then you need to reduce RPM, and/or increase feed.  But, to get the best finish, you want higher RPM and lower feed, so best results do really require coolant.  Just air might suffice.  It might also help to use a very high helix cutter.  You should be able to find tooling made for plastics.

If you're looking for a really smooth finish, do the best you can with the router, the flame polish to remove the machining marks, which will leave the cut surfaces clear and glossy, just like the unmachined surfaces.  You can do this with a cheap propane torch set on a pretty high flame.  Hit it *just* long enough for the surface to gloss over, then move on, before it catches fire.  Takes a little practice, but leaves a really ncie finish when done right.

Regards,
Ray L.

1217

General Mach Discussion / Re: Can two 36v power supplies be used in series to get 72v?

« on: April 15, 2009, 11:06:31 AM »

Thanks for the replies.

The power supply: (KL-320-36 36V/8.8 or 9.6A) http://www.kelinginc.net/SwitchingPowerSupply.html

 . . have 3 sets of terminals, but internally they are all connected together, so it is actually only one output from one rectifier/transformer. There are three caps, but again they are in parrallel and connected to the same trace on the output.

So, refining the question a bit; using two of these powere supplies, can I use a 36v terminal from each power supply to drive steppers @ 36v  and then also series wire a set of terminals to get the 72v for the servo motor?

Yes.  Wire the - side of one to the + side of the other.  For a 36V device, you can use the two terminals from either supply, and for a 72V device use the unconnected + and - terminals.  It would be best if you used the "low" side 36V supply for the 36V devices (the one whose + terminal is connected to the - terminal of the other supply), so both 36V and 72V devices have the same "ground" reference.  Otherwise, you'll need to be VERY aware of which devices are using which "ground" reference, to avoid shorts.  And make sure the - side of the "high" side supply is NOT tied through its case to your system ground.

Regards,
Ray L.

1218

General Mach Discussion / Re: Can two 36v power supplies be used in series to get 72v?

« on: April 14, 2009, 03:41:24 PM »

Some will work and some will not, you'll have to verify the spec of your power supply. Look for a PDF file from keling.

You can't use a step up transformer to crank up voltage from a DC source, you're looking for disaster, transformer only work for AC voltage

These are unregulated supplies - transformer, rectifier, filter caps.  There's no way it won't work....

Regards,
Ray L.

1219

General Mach Discussion / Re: Can two 36v power supplies be used in series to get 72v?

« on: April 14, 2009, 10:44:15 AM »

Connecting two supplies in series should work fine.

Regards,
Ray L.

1220

General Mach Discussion / Re: M01 Optional Stop

« on: April 14, 2009, 10:42:43 AM »

Thanks.  I did figure that out eventually.  Apparently the M1 toggle not working was some random Mach wierdness.  I re-started Mach, and it's now working OK.

Regards,
Ray L.