From Manual to CNC - Sherlines

[kvom]

That would work as long as the stock will fit through the chuck and you can accurately re-establish Z0.  I doubt the finish would be as nice as I'd expect some degree of mismatch between the two halves.

[crueby]

That would work as long as the stock will fit through the chuck and you can accurately re-establish Z0.  I doubt the finish would be as nice as I'd expect some degree of mismatch between the two halves.

I read his post to suggest one chucking, but to do the cuts at the outer half first, so there was not a narrow section near the base when cutting at the outer end. Would that help?

[Jasonb]

I was thinking of leaving it all sticking out, still not ideal but at least it will not have that narrow waist that is more likely to flex than the full stock diameter.

Also don't really see the need to have that narrow waist near the chuck, better to just round the bottom corner and leave a decent diameter and follow up with  a parting off cut.

EDIt Chris got it

[zeeprogrammer]

Thanks all.

Yeah, it's not a great example with the stock so far out of the chuck.
A bowling pin is something I had in my mind from years and years ago (when all I could do was dream of machining much less CNC).
I couldn't get it out of my mind. Ah well.

Chris mentioned a miniature pin setter and I must admit I had an idea for a miniature bowling alley several years ago.
Getting pins up to the shark switch, the sweep, and lowering/raising the pin table is 'easy' enough. Distributing the pins into the pin table is the challenge.

Also don't really see the need to have that narrow waist near the chuck, better to just round the bottom corner and leave a decent diameter and follow up with  a parting off cut.

The only reason I did that was to make parting a little easier. I've always struggled with parting solid material.
The stock is 1" diameter. The base of the pin is about 3/8" and the widest part of the body is about .8".
With the little waist, I can bring the parting tool up to touch off the bottom of the bowling pin.

[zeeprogrammer]

Did a little sanding and then parted.
For parting I didn't use CNC. I don't know the jog system well enough and was a bit worried after my disaster yesterday.
So I unplugged the motors and used a handwheel on the back of the motors.
Then I used a dremel to take off the nipple on the bottom.

The finish could be better. Something else I need to improve.

[kvom]

I suggest nine-pin pins for easy of turning.   

[zeeprogrammer]

I'm calling this done until I get the mill converted to CNC (which may be a while).

To recap...

I wanted to have a go at CNC but didn't want to modify my lathe and mill. So I got a Sherline lathe and mill and converted the lathe.
I chose a bowling pin as my test. It's a poor choice as it required the stock to stick too far out but I'd had this dream for years before I knew anything about machining.

Attached picture shows the control board:
1) 48V supply for the motors
2) 5V supply for the motion control board
3) ESS Smoothstepper motion control board
4) Gecko G540 stepper motor driver
5) Mains switch

The emergency stop is next to the lathe.

I used CubifyDesign for CAD. I've used this for a number of years.
I used CamBam for CAM. I found this very difficult to learn but finally came across a video that allowed me to figure out how to generate toolpaths and g-code.
I used Mach3 for motion control. I found this also difficult but had had some familiarity with the controls from when I worked for a company making table-top robots.
I got licenses for all 3 programs.

I had wanted to provide step-by-step instructions in hopes that others would find this useful but it's just too much for me.

Thanks again to everyone who helped. I think I would have given up had it not been for the members on this forum being so helpful and supportive.

[crueby]

I don't think the bowling pin was a bad choice, you did learn more because of it.  Looking forward to the next step on this journey!   

[zeeprogrammer]

Took another run at making a maiden post for the spinning wheel I'm thinking about.
This was mainly about learning/experimenting with CamBam and Mach3.
It's supposed to have a threaded hole at either end...which I skipped for this experiment.
I used the wrong cutter too in that it interfered with the bigger bead.

I have a couple of questions.

1st picture shows the post during turning.
2nd picture shows the 'completed' post.

I had considered at least drilling the one end that has the live center (all I did was center drill). I don't think I would have tapped it prior to turning as the live center (I would expect) would damage the threads. I'm not sure how I would do the other end that was in the chuck. Ideas? Perhaps use a follower? The part is too thick to go through the headstock.

The bigger issue was the noise. See video. As the cut begins, there's a whole lot of noise (I assume chatter) which went away after some distance. The finish looked excellent though.
I noticed that as the part got turned down, the chattering would continue for slightly larger and larger distances.
The finish look great up until the very last finish cut (of two). Then it crapped up. (The rings you see was after applying some WD-40 before the next cut.)

Noise happened for every pass. This happened the other day as well on my first attempt.

.005 depth of cut and 3 ipm feedrate. It was slow. Took a little over an hour to complete.

What's the cause of the noise and what can I do? Spindle speed too high? (Dummy me didn't think to adjust it to see if it helped.) The spindle was running about 2200 rpm instead of the 1000 rpm that the feed/speed had said.

Thanks.

<a href="https://www.youtube.com/watch?v=Lb4BmWAChMw" target="_blank">http://www.youtube.com/watch?v=Lb4BmWAChMw</a>

[kvom]

Chatter is resonance, so you could try varying both RPMs and feed rate.  You should make only 1 finish pass as the second is likely just rubbing.

[Jasonb]

What's the revs as can't tell how much you are cutting with just a feed rate.

Tool does not look to have much top rake which aluminium likes, is it cutting dry

Does CAMBAM not have a simulator that would show the tool cutting where it is not meant to?

That long extended ctr won't help with rigidity, same with tailstock extension, reduce it if you can and maybe even think about using a solid tool post which will not put the tool so far over to the left and therefore the carrage won't go so far right to hit the tailstock base.

[awake]

I don't know the capabilities of a Sherline, but based on that video, I would be inclined to say rpm too high and feed too slow.

[zeeprogrammer]

Thanks all.

I'll try varying the rpm. I think the feedrate was a tad slow but perhaps not by much. Need to buy some more material.

What's the revs as can't tell how much you are cutting with just a feed rate.
Around 2200. I'm thinking it should have been half that. (I don't have a means to measure yet.)
Tool does not look to have much top rake which aluminium likes, is it cutting dry
HSS tool. Doesn't look like there's any rake. I need to go shopping.
Does CAMBAM not have a simulator that would show the tool cutting where it is not meant to?
CamBam shows the tool paths but only the tip. I don't believe there's a way to model the shape of the cutter.
I wasn't surprised the cutter interfered on the sides.

That long extended ctr won't help with rigidity, same with tailstock extension, reduce it if you can and maybe even think about using a solid tool post which will not put the tool so far over to the left and therefore the carrage won't go so far right to hit the tailstock base.
I think the tool post can be moved to the Z+ side of the carriage. Have to check if the Z- side will hit the chuck before the cutter.

[crueby]

Zee, which alloy of aluminum are you using? Some machine better than others.

[zeeprogrammer]

Zee, which alloy of aluminum are you using? Some machine better than others.

6061 aluminum

My selection of material is small.

6061 aluminum
360 Brass
303 Stainless

I haven't done much with steel. Some 12L14 and some cold rolled that I don't remember (I think 1018).

I welcome suggestions for machinable metals.