Finally Getting Started

Topics related to wrapped rotary machining in Aspire or VCarve Pro

Finally Getting Started

Postby TReischl » Sat Apr 25, 2015 1:23 am

I wanted to get a rotary going on my machine over a year ago. Then came the big move. . . . ah well, lots of other things to do than build a rotary axis.

But I finally got started.

20150424_155159.jpg


20150424_155207.jpg


20150424_155222.jpg


I am using a 1 - 8 threaded shaft so that it will be able to use my standard lathe chucks. A jam nut sits behind the chuck to keep the chuck from unscrewing when running in reverse.

The aluminum it is mounted to may or may not be in the final assembly. Right now I am just using it to mount things.

The stepper motor is on order from CNC Router Parts since that is what matches the rest of my system. I am also waiting on the small timing pulley that goes on the stepper.

Later on I may modify this whole setup to become more compact, but right now I am not picturing cutting anything longer than about 36 inches.

This is getting downright exciting!

One of my ideas is to rough out turned vase shapes on my lathe, then move them over to the rotary for carving. Why use the lathe first rather than doing it all on the rotary? Speed. I can rough turn a piece much faster on a standard lathe than on a rotary. I also need to finish the inside anyhow, so while I am there, might as well get it ready.
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Re: Finally Getting Started

Postby 4DThinker » Sat Apr 25, 2015 3:31 am

Looks like a great start. Just today I figured out how to RUN the 4th axis we've had for a year on our Probotix CNC. Monday we'll do our first cuts with it.

Since you are building yours from scratch just go ahead and come up with a way to CNC out the inside of your vases. ;)
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Re: Finally Getting Started

Postby TReischl » Thu Apr 30, 2015 10:14 pm

I have made progress.

The small timing pulley arrived. Interesting how the Chinese folks have no problem shipping something that is not quite what was ordered. It was supposed to be .25 bore with a tapped set screw hole. Nope. So I did that and got it all assembled.

Next was working my way through the Mach setup. Here is where Gerry (ger21) gets a huge thanks. I have used his screenset for several years and have happily forgotten about how the Mach screens work. Gerry sent me over the directions to set up his screen set with a gentle reminder that all the info is in the pdf file. My only problem was that I forgot there was a pdf file in the directory! See what age does to ya, ya young whipper snappers?

Got it running. Am a bit mystified about feeds and how that is all going to work out. The rotary seems to need really high "feed" rates, and well, I will just program something up and see what is what. Have all the units set correctly, steps, etc.

Next, I got most of the tailstock built up, all it needs is a base plate to mount it to the machine.

So, tomorrow is gonna be a big day, finish the tailstock then actually program something and see how it all works.

A note to all you guys who have posted in this area: THANKS! The posts have been a tremendous help, in fact, I don't see how I would have got this going without them.
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Re: Finally Getting Started

Postby TReischl » Fri May 01, 2015 7:57 pm

It is working.

Feedrates look good, the only problem I have is that it is cutting a taper. About .030 over 13 inches. Smaller on the tail stock end.

If my aged memory serves me correctly that means the tail stock is either too high, or too low. Being a bit off center should not affect the diameter too much.

I programmed a 2.00 dia cylinder. I am getting 2.05 on the headstock end and 2.02 on the tailstock end. I zeroed the bit to the top of the tailstock (the only flat surface I have, none on the headstock). The overall size discrepancy could be because I am not truly set to zero on the centerline of the spindle (eyeballed the Z zero). Taper is a different story.

Soooo, what I am going to do is ship the tailstock up to see if I make the problem worse or better. About .015 (three sheets of paper) should do it.
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Re: Finally Getting Started

Postby roy_okc » Sat May 02, 2015 6:09 pm

TReischl,

Watching your progress/design. I understand the thought behind turning rough on the lathe, but can you generate gcode that takes advantage of that? I'm just curious if you'd be cutting a lot of air if you were doing, for instance, a vase and you rough turned a vase shape. Or would you just be doing a simple cylinder on the lathe?

I've been considering modifying a midi wood lathe for rotary use. I have several inches of overhang on my X axis and could build a lower platform to place the lathe, I've figured out most of the puzzle pieces of how to adapt to use a stepper system to turn it. I'll probably do a proof of concept using my Jet 1220 with the motor drive belt loosened and if it works try to find either a used lathe with dead motor/otherwise cheap (with MT2 and 1"x8TPI bits to use the chucks/other stuff that I have) or buy the $160 after discounts Harbor Freight 10x18 and leave the motor off. My last thought puzzle is to figure out how and where to mount a stepper and idler; I'd need to have enough idler movement so that I can easily add/remove the drive mechanism. A project for one of these days...
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Re: Finally Getting Started

Postby TReischl » Sat May 02, 2015 10:21 pm

roy_okc wrote:TReischl,

Watching your progress/design. I understand the thought behind turning rough on the lathe, but can you generate gcode that takes advantage of that? I'm just curious if you'd be cutting a lot of air if you were doing, for instance, a vase and you rough turned a vase shape. Or would you just be doing a simple cylinder on the lathe?


I am going to use it for segmented turning. One of the tools I use is the Segmented Project Planner. It has this output:

Capture.JPG


It is a simple matter to capture that image, enlarge it to scale and then trace out the required vector. Once I have that generating the g code is easy. Since it is segmented turning, and the shape has been roughed down to where the corners meet I should be able to offset that vector a small amount and take a cut without wasting a lot of time roughing.

I am not an anal retentive turner, since segmented shapes are not used for anything practical I just basically clean up the inside getting rid of the corners. I do not spend any amount of time worrying about how smooth the inside is or whether my wall thicknesses are perfect. Unlike solid wood there is no movement problems with segmented works.

There may be another trip back to the lathe for final sanding, not sure about that yet. I can spin the rotary fast enough that it would be practical to sand while it is still on the cnc machine.
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Re: Finally Getting Started

Postby PaulRowntree » Sat May 02, 2015 10:38 pm

TReischl wrote: Smaller on the tail stock end.

If my aged memory serves me correctly that means the tail stock is either too high, or too low.

I programmed a 2.00 dia cylinder. I am getting 2.05 on the headstock end and 2.02 on the tailstock end. I zeroed the bit to the top of the tailstock (the only flat surface I have, none on the headstock). The overall size discrepancy could be because I am not truly set to zero on the centerline of the spindle (eyeballed the Z zero). Taper is a different story.

Soooo, what I am going to do is ship the tailstock up to see if I make the problem worse or better. About .015 (three sheets of paper) should do it.



If the tailstock end is a bit smaller, then the tailstock is a bit higher than the headstock IF the other axes are aligned properly. If the rotation axis isn't parallel to X (or Y), then all bets are off.
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Re: Finally Getting Started

Postby TReischl » Sun May 03, 2015 1:26 am

Thanks Paul, I was having a hard time wrapping my brain around the tapered, whether too high or too low. Once you posted that, DING! Too high cause the bit is up there. . . .

BTW, the pun above was fully intentional. . .brain being wrapped. . .
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Re: Finally Getting Started

Postby TReischl » Wed May 06, 2015 10:09 pm

Have done a bit of test cutting.

The first item was a huge hex bolt with some lettering and a model:

20150502_165001.jpg


It came out pretty darn good. No complaints. Some minor programming gaffs but that is how I learn.

Next was to look at the process of cutting segmented bowls:

20150506_094128.jpg


20150506_143835 1.jpg


This went sort of "ok".

For some odd reason my Z axis decided to start losing steps. Adjusted the motor settings and ran some tests, looking better now. That is strange cause it was set up a long time ago and never had any issues.

With the Z axis acting up I am not sure if the lousy finish was caused by it or not.

All in all though I am fairly certain the idea carving segmented bowls is going to work out nicely.
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