A Rotary Project: Barley Twist Table

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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Rcnewcomb
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A Rotary Project: Barley Twist Table

Post by Rcnewcomb »

I'm delighted to see a project of the month for rotary: Barley Twist Table

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- Randall Newcomb
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Re: A Rotary Project: Barley Twist Table

Post by JoeBlow »

This is fantastic!

Just what I need to improve my rotary. I think I will cancel cable for the next month as I will be watching re-runs of this video for awhile :D

Thanks Vectric!

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Re: A Rotary Project: Barley Twist Table

Post by JMD »

Been looking for something like this for a long time. Thank you. Please post more like this. I, for one, need the help. :D :D

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Re: A Rotary Project: Barley Twist Table

Post by chri879 »

Thanks for developing this project and video. It is very helpful. Would enjoy seeing more rotary projects in the future.

-Chris.

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Re: A Rotary Project: Barley Twist Table

Post by scubanimal »

IMG_2717.jpg
IMG_2716.jpg
I'm having trouble with this. I've tried twice and its failing. One odd thing, I'm not sure if its the file or the machine. I swapped the X-Y as my stinger has the longitudinal along the Y.
But I noticed that after running the finish toolpath for about 8 hours when the blank was oriented about 7 degrees off. I checked that that chuck was tight, the blank was mounted firmly (tailstock tightly in). Belt is tight on the the gears driving the A axis. So I ran a quick test of running A36000 and it lined up perfect, then A -36000 and it was back to perfect. The two attempts though did not fail the same, First one failed on the 1/16th finish, the second on the 1/8tth finish.
The difference between the two runs is I reset A0 in front of each of those 2 runs that failed. As I mark the wood for 0 I know its not 90 degrees off. So I'm really perplexed as to what is causing this.

I can upload the Aspire file or toolpaths if that would be helpful. As not sure of my rotary skills, I'm not sure if this is a machine or file issue...

Any ideas on what to test or look at?

thank you,
Ian

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Re: A Rotary Project: Barley Twist Table

Post by SteveNelson46 »

I have a Stinger 1 also and attempting to make a project that is similar to the Barley Twist Table and learning a lot along the way. On my first try I had similar problems when using the same settings as the example so I changed the roughing toolpath strategy to "Raster along Y", changed the bit to a 1/4" EM, slowed the feed rate to 100 ipm and the plunge rate to 45 ipm. On the finishing toolpath I still used the 1/8" BN but I changed the raster angle to 90 degrees, the feed to 75 ipm and the plunge rate to 25 ipm. I think what caused the project to lose steps was the raster angle and the chatter caused by too aggressive feeds and speeds settings. Also, be sure to make your blank long enough to allow sufficient space at the ends for the boundary offset.
Steve

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Re: A Rotary Project: Barley Twist Table

Post by scubanimal »

Steve,
Thank you, I'll change the raster angle, and slow the speed down even more. My .25 EM seemed to do fine on both runs, but your idea makes sense as to why it could be getting off. I'll give it another try using your feeds & speeds!

Despite taking Gary's training, I still had to learn the hardway a bit; plenty of extra length, triple check that I have the material origin set right and that it matches the files, a proper safe Z, make sure the tail center and chuck center and X 0 are all exactly inline, don't forget the

I really liked your tool tray so did my own Sunday as I gave up on that Barley. Need to put some finish on it, thank you for the idea, it really looks like it will fit nicely on the control box.

thank you!!!

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Re: A Rotary Project: Barley Twist Table

Post by scubanimal »

Another attempt, and its way off again. For the 1/8 BN " runs I dropped the feed to 59 ipm X,Y, and 9ipm Z, and after 11 hours it's about 90 degrees off in A axis. So I'm really perplexed.
This is such a long toolpath, I don't know of anyway to break it up.

Can't figure out what is causing the A axis to get so far off, The Stinger is a good machine, the belt is tight, it feels pretty solid if I try to rotate it by hand once the machine is powered on.

Sure hope someone can help with this...

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Re: A Rotary Project: Barley Twist Table

Post by TReischl »

About the only thing I can think of is that you are either having an interference (noise) issue or you have a motor that is going bad or is just too weak to turn the mass.

Ahh, one other thing, I know nothing about the stingers but is it possible you have the accels/decels set too high?
"If you see a good fight, get in it." Dr. Vernon Jones

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Re: A Rotary Project: Barley Twist Table

Post by Mark's Wood Chips »

Greetings,
I started a discussion on the General Aspire forum about this project and I'm moving it over here because it may be related. My original post is as follows:

"I'm trying to make David's Barley Twist Table (In the labs with David project) and I'm creating my own file by watching the video. When I add the 3D circular tab that defines the gentle taper of the twist, David instructs to set the model height property to -0.6 and at that point strange things happen. Multiple attempts finally get things looking right except when I look at the 3D tab properties, it reverts to positive 0.6, yet it looks correct on the 3D screen. Next, I downloaded the [project] file from my V&CO account, took a look at the component and guess what, it is also a positive value, yet it is clearly a negative appearing tab. What the heck is going on?"

I haven't tried toolpathing this yet but, like Ian, I have a rotary in the Y direction as well so I took that into consideration when constructing my Aspire project file. When I was following along with David's video tutorial and got to the part where he adds the tab to give the barley twist it's gentle arc, strange things appeared on the 3D screen that didn't look anything like the video. After a few attempts, it looked like the video EXCEPT for the negative/positive value of the model height property. I would be interested to know if the negative height "stuck" when you changed it? Could this be related to Ian's issue because of "strange math"?
Attachments
Notice the shape height is a positive value, the instructional video shows it as negative.
Notice the shape height is a positive value, the instructional video shows it as negative.

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Re: A Rotary Project: Barley Twist Table

Post by gregk »

Dear Mark,

The height, by definition, cannot be negative. That's why it is displayed as a positive in the component properties. The David used a trick with specifying a negative height to effectively invert the component. This have to be done only once, unless you want to invert component back again.

Suppose that there is a dome component with height of 0.8". If you type -0.5 in the component height, the component will become a dish with height of 0.5". if you now decided that it should have a height of 0.4", you should place 0.4 in the shape height box.
Using -0.4 would make it a dome again, with height of 0.4"

In case of rotary projects, when dealing with negative components (created with David's trick or subtracted) it is best to switch off the wrapped view and use flat view instead. The rotary view does not show negative z-values correctly. As the taper initially descends below the zero plane in flat view, it would most likely not look right when in wrapped view. After the shape base height is adjusted, the taper component is effectively lifted and does not go below the zero plane. At this point wrapped view should be correct.

It is important to clarify that the shape height behaviour cannot explain the problems with machining. When changing rotary axis from X to Y, it is important to also remember to adjust relevant machining strategies. In this project roughing involves raster along X axis, which means along rotary axis. After changing orientation of the project in Job Setup form, one should also switch the roughing raster to work along Y axis. The same will apply to finish toolpaths.

Greg K

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Re: A Rotary Project: Barley Twist Table

Post by scubanimal »

TReischl wrote:About the only thing I can think of is that you are either having an interference (noise) issue or you have a motor that is going bad or is just too weak to turn the mass.

Ahh, one other thing, I know nothing about the stingers but is it possible you have the accels/decels set too high?
Ted, thank you for the thought. Given the speeds & feeds, I'm sure I'm not over taxing them machine, the CAMaster is a pretty strong machine, and at 59 ipm/9Z my wimpy Shark could do that...
I'm way too new to Rotary, to know if my accels/decels are off, so I'm contacting CAMaster to find out. Thank you!

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Re: A Rotary Project: Barley Twist Table

Post by Mark's Wood Chips »

gregk wrote: The height, by definition, cannot be negative. That's why it is displayed as a positive in the component properties. The David used a trick with specifying a negative height to effectively invert the component. This have to be done only once, unless you want to invert component back again.
Greg K
Thanks for your clarification. None of this is obvious and I'm very pleased with your response.

Mark

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Re: A Rotary Project: Barley Twist Table

Post by SteveNelson46 »

I thought of this as odd behavior also. I also thought it odd that the shape height slider in the properties of the component worked backwards even though the height was a positive number. So, I changed it to "merged inverted" and it had exactly the same effect. I wonder if Dave could have just used "merged inverted" from the start instead of using a negative number and forcing Aspire/V-Carve to override it? I don't completely understand how this works until I study it some more so I may be completely off base here.
Steve

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