Bob's Super Simple 4th Axis

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NewAgent45
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Joined: Sun Sep 08, 2013 8:29 am
Location: Edgewater, Florida, USA

Re: Bob's Super Simple 4th Axis

Post by NewAgent45 »

Bob or anyone else familiar with the use of the Array - Circular Copy tool in VCarve Pro 7.5 I need some help.

I’m building a variation of Bob’s Super Simple 4th Axis accessory for a CNC Shark HD Black Diamond. The version I’m building has the cross beam to allow for adjustable material length. I want to increase the allowable working material diameter a little bit. The rack can’t be raised anymore because of clearance with the cross beam.

I’m attaching two pictures of what I have built so far. Note in the pictures the rack is just sitting on temporary spacers to locate it where I plan to mount it. Also note I added alignment plates (white HDPE) which can be moved slightly up and down and also in and out so the shaft can be aligned. I haven drilled the plates yet.

I’m also attaching a CRV file so you can analyze my array copy problem. My CRV file includes several layers. I think my problem will be obvious if you view only (hidden) Layer 4. I have a copy of a single gear tooth and my attempt to array copy. I have tried copying different versions of the original gear from Layer 1 and still get undesirable results. This is my first attempt using circular array copy feature. What am I doing wrong?

Have a great weekend!

……… Rod
Pic 1
Pic 1
Pic 2
Pic 2
4th Axis Pinion Gear - Larger Gear.crv
Attempt to create larger gear
(2.17 MiB) Downloaded 540 times

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Bob
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Re: Bob's Super Simple 4th Axis

Post by Bob »

Rod,
Check your pm, and give me your email address. I'll send you a couple of gear versions. I would rather not post them publicly, because I have not tested them. Of course, you could publish if they work.
Bob
"Focus"
Antonie Van Leeuwenhoek (Developer of the microscope.)

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NewAgent45
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Re: Bob's Super Simple 4th Axis

Post by NewAgent45 »

I’m adding the post here to give you all and update on the “Simple” 4th Axis accessory I built for my CNC Shark HD – Black diamond edition. I only have praise for Bob’s Simple Design. I last posted an issue I was having with making the rack and pinion gear set. We went back to the drawing board on this and I’m happy to say the problems are resolved. We used FixitMike’s improved instructions for constructing the gear set. These instructions may be downloaded from Mike’s post on the Vectric Forum. We designed and cut a (58T-8DP-20PA) Rack and (27T-8DP-20PA) Pinion gear. We also decided to make a second matching set for the left-side of the 4th Axis accessory. We assembled everything taking care with the alignment. We mounted some oak stock on the fixture and did some test runs. I have to say everything is working well. With the current configuration I’m limited to material size of about 4 1/2 Dia. (max) X 25 inches long.

We tested three carving techniques using the 4th Axis accessory. (1) Rounding square stock using a pocket toolpath. We just drew a rectangle as the boundary for the pocket. Using a width (x) of about two inches shorter than the stock. We used a fixed y dimension of 10.6” (where, y=πPD for the Pinion. This also equals one revolution) (2) Secondly we cut a 1TPI spiral using a simple diagonal line drawing to create the simple toolpath profile. This worked well! I did forgot to invert the image to account for the gear and ended up with a left-handed spiral. I need to remember to reverse to image when using this setup. (3) Our third test was wrapping to 3D models around the cylinder. We used the pitch diameter for the gear and the diameter of the stock to calculate the size of the model and adjust the y for the gear.

I’m attaching some pictures and YouTube inks to some short videos showing the test runs and a drawing of the gear design.

Pictures:
Gear Design Drawing
Gear Design Drawing
Spiral carving test
Spiral carving test
3D Carving test
3D Carving test
Videos:
https://www.youtube.com/watch?v=DJ1yLLq ... e=youtu.be
https://www.youtube.com/watch?v=wegBE3H ... e=youtu.be
https://www.youtube.com/watch?v=5SPVSjy ... load_owner
(Note: I hope you are able to view these videos)

In my pictures and videos you will see I decided to use a matching rack and pinion on the left/freearm side. I feel this is a more robust setup and the T slots in my spoilboard allow the adjustment of the rack depending on the length of material. The other thing I added to Bob’s original design are left and right adjustment plates I slotted the mounting arms to allow for a little y and z adjustment to align the pivot shaft(s) for the setup. My pivot shafts are ¼ x ~ 3.5” polished rod and extend about ½ into the stock. I ground a notch for the set screw seat that you see in the picture. The set screws are temporary. I plan to replace them with the right type of screw. I used 1 ¼ brass flathead screws to attach the pinion gears to the stock.

Thanks to Bob’s “simple” design I have a working 4th Axis. I have some stock on-hand that I should be able to finish to about 3” dia. x 12”. I would like to try something larger in diameter next. I also want to try V-Carving on 2” Acrylic tubing.

Now I just have to come up with some unique fun projects that utilize the 4th Axis.

Have a great day!
Rod

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Bob
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Re: Bob's Super Simple 4th Axis

Post by Bob »

Rod,
Great job!
I like how you're keeping it simple.
I can't wait to see how you develop this.
Bob
"Focus"
Antonie Van Leeuwenhoek (Developer of the microscope.)

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NewAgent45
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Location: Edgewater, Florida, USA

Re: Bob's Super Simple 4th Axis

Post by NewAgent45 »

Ruhnau:

I'm interested in toolpath information regarding your post of 2/20/2013 http://www.cncsharktalk.com/viewtopic.p ... =70#p14027 I attempted to send a personal message earlier today but it looking like the message failed to send.

Now that I have my version of Bob's simple 4th Axis accessory up and running. I'm trying to learn how to create toolpaths specific to the accessory. So far I'm only using Cut3D

I have had successes as follows:
(1) Turning square stock to round using a simple pocket tool path.
(2) Turning a spiral of a given pitch X turns per inch using diagonal straight lines and profile tool path.
(3) Cut a 3D model imported from Cut3D to VCarve Pro. I successfully distorted the y dimension to account for the accessory.
(3) I'm playing with fluting tool paths with some success.

I'm wondering how you created the toolpath for that "football" spindle profile. My guess you are using another software package to generate a 3D model. I have been considering getting Sketchup for this kind of work. I found that Sketchup is a little rich for my blood and they no longer have a free version.

I'm interested in turning some spindles that could be turned on a wood lathe. But I don't have a lathe and I would like to be able to make exact duplicates.

Can you share how your doing this type of work?

Have a great day!

............ Rod

ruhnau
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Re: Bob's Super Simple 4th Axis

Post by ruhnau »

The football shape was created in V carve. It was just a x y curve machined as a profile. I then modified the G code in the toolpath data to cut in the xz plane instead of the xy plane. This was all manual editing I learned years ago as a CNC programmer. I think I have some posts under this thread somewhere

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NewAgent45
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Re: Bob's Super Simple 4th Axis

Post by NewAgent45 »

Ruhnau:

Sorry it took a little time to get back to the forum. That's interesting information. I have don't a little G-Code editing but not ate your skill level. It is handy to know a little bit about it. I use A text editor that has built in macro capability. (TextPad) I find it very useful for any editing that requires bulk replacement. This sounds like what you did.

Anyway I'm investigating using Sketchup to create some models. Sketchup Pro 2015 is available for a 30 day free trial period. At the end of the 30 days if you have not upgraded it reverts to the free version. Sketchup Pro's Export feature supports Several file formats compatible with Cut3D and VCarve Pro. I already s successfully imported a *.3DS file into Cut3d. The import/export features are one of the functions that aren't available in the free version. So I have 30 days to decide if it's worth up grading.

Stay tuned for a future post on my progress.

........ Rod

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NewAgent45
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Re: Bob's Super Simple 4th Axis

Post by NewAgent45 »

From my previous posts we built a simple 4th axis accessory for a CNC Shark HD/Black Diamond based on Bob’s design. This post is to serve as an update.

We stuck to Bob’s principle of “keep it simple”. We did add a couple features. Our version can handle material size up to about 4” OD and 25” length. I carved a pepper mill/grinder using a 3 ½” X 3 ½” X 15” Oak blank to be used to turn two pepper mills. I only turned one this first time.

4th Axis Accessory changes:

I decided to use the free arm design introduced by others. I wanted to have the adjustment for material length. I also decided to keep the two gear twin (right and left) rack and pinion. I’m glad I did as it does add stability and splits the turning torque by driving both ends of the material. We did not see any back-lash issues in our trials.

On a previous post I encountered issues making the larger rack and pinion set. The resolution for this is also discussed in the earlier post.
We added alignment plates to the support arms and this helps a lot to align the machine. The support arms have over sized slots to allow the axis shafts to be adjusted (y and z). We also discovered the right hand shaft axis was skewed. It looks like the Sharks right side gantry support arm is slightly skewed. We inserted a 0.025” piece of plastic shim stock at the top of the alignment plate between the plate and the support arm. This corrected the problem. Our shafts extent about ½ into the material center so alignment was needed to prevent binding. Keep this in mind if you make alignment plates. I drilled mine on a drill press to ensure the shaft would be perpendicular to the plate. The free arm may be adjusted so the shaft ends meet to make it easier to make alignment adjustments.

As for the pepper mill. We are using an Antique Style grinder mechanism available from WoodCraft for our first pepper mill. I should note this isn’t a real robust mechanism but has a nice antique character. We made a simple modification to the mechanism to improve its function. I added a simple set screw to the bevel gear on the vertical shaft. I won’t have any pictures showing this or the mechanism as I have not completed the turning yet. Since I don’t have a lathe I will bore the hole in the grinder on my drill press. I made a fixture and ordered a new forstner bit and extensions for this. Of course this would be easier to do on a lathe. I don’t have one!
We completed the pepper mill turning on the 4th Axis in three steps as follows:

1. Turned the blank to 3” using a simple pocket tool path. It is important to note in my particular machine setup and gear set that one revolution is 10.6”. I used 10.7” for the y dimension to insure a little overlap.

2. Turned the Pepper Mill profile. I designed the unwrapped 3D profile using Sketchup Pro. Note the 2015 version is available for a 30 day free trial. So you can try it before buying. After 30 day the software reverts to the free version and you will lose the export feature.

I used the same 10.7” dimension for y in my SketchUp model. We exported from SketchUp and imported to 3D Machinist because we found that XY were locked on Cut3D. Free 3D Machinist worked just fine for defining the profile tool path. Then we imported the vectors from 3D Machinist to VCarve Pro and made are final adjustments. You can import multiple instances, if you are turning more than one and combine the tool paths in VCarve Pro.

3. Then we Carved 3 instances of a 3D model wrapped around the top section of the Pepper Mill. I used a model from Vector Art 3D named BBQ Guy for my pepper mill. In this case I had to move the zero point or x to the center of the top section and zero on the cylindrical surface. We measured the diameter at this point with a caliper and used this to calculate the amount to resize the y dimension of the model in 3D Machinist.

Calculation notes:

Gear pitch circumference: πD = π x 3.360” = 10.603” where D is the pitch diameter of the gear. So one revolution will always be the same for this setup.

We use the circumference ratio of the material to the gear to calculate the y adjustment in the model. Note the ration is greater than 1 when the material diameter is less than the pitch diameter of the gear and less than one when the material diameter is greater than PD. Note this is the same as the diameter ratio. So you may simply divide PD by the material diameter to get the y adjustment factor for your model.

Y adjustment factor = PD/d = 3.375 / 2.360 = 1.430, in this case we are stretching

We scaled our model by entering the desired x value then multiply the displayed y value times the factor. Then unlock x:y and re-enter the corrected y.

Expect the imported model to appear distorted when displayed in VCarve Pro and position the model where desired after the import. In my case I imported three instants of the distorted model.

I’m attaching a link to a short video of the Pepper Mill profile turning/carve and a picture after the 3D models were carved. Note I left one end of the pepper mill waist uncut to facilitate boring the hole through the mill.

Video:
https://www.youtube.com/watch?v=R0DhoXh ... e=youtu.be

Picture:
4th Axis Pepper MIll turning.jpg
I trust this post is helpful for any of you that are trying Bob’s simple 4th Axis.

ruhnau
Posts: 59
Joined: Wed Nov 30, 2011 1:22 pm

Re: Bob's Super Simple 4th Axis

Post by ruhnau »

Great job on your 4th axis fixture and its modifications. I have the free arm for adjustments but am only using one drive gear which seems to be adequate. I don't see how you added the second drive gear, since the piece you are turning is attached to the free arm and one drive gear. using sketch up is the way to go for complex shapes like the pepper mill. It's a lot easier than modifying G codes as I have done in the past for simple shapes. Anyway again, great job.
I just watched your previous videos and saw how you have the rack on the free arm. Does this mean that you have to move the rack each time you change lengths on your turning piece?

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Bob
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Re: Bob's Super Simple 4th Axis

Post by Bob »

Real nice job Rod,
You and Kurt have taken this design and run with it.
It's fun to see how the idea grows when each person tries it.
Thank you for posting,
Bob
"Focus"
Antonie Van Leeuwenhoek (Developer of the microscope.)

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