Bob's Super Simple 4th Axis

[CountryWoodCrafts]

Bob . . . any updates? Is it still working as designed?

It's good to hear from you,
The guy who's taken this in all sorts of different places is Kurt. He is a frequent contributor to our Owner's group meetings in Milwaukee, and to this forum. He has made engraved cylindrical boxes, threaded projects, inlays, and many modifications to the original design.
So...That's my update. This thing is working beyond it's design expectations.
What have you been up to?
Bob

Major move and buying more sharks. . .

[NewAgent45]

Bob,
I have been studying your awesome simple design for your 4th axis accessory. Great work and thanks for sharing with the forum community.

I’m using VCarve Pro 7.5 and I have the Gear Maker gadget. Is this what you used to generate the tool paths for the rack and pinion gear. I have no experience with the gadget or making gears. I may want to make a different gear set to accommodate larger diameter stock. I realize I could alternately raise the rack up. Can you or anyone in the community provide some direction on gear making?

Have a great day!
…….. Rod

[Bob]

Rod,
I didn't have the gear gadget when I designed the 4th axis. I borrowed a tooth from a wooden clock gear, the copied it in a circular array. Then, in a linear path for the rack. The gear gadget is a lot easier to use though. Raising the rack sounds like a simple solution. I tried not to over think the gear making. I tried an easy idea...it worked...I used it.
Bob

[NewAgent45]

Bob,

Thanks for your advice! I think I'll stick with the KISS principle and raise the rack.

Right now I'm working on mounting arms for the HD. The gantry support arms are at a 15 deg. angle to the perpendicular. I also want to add a simple 1/4 plate (HDPE) on each end to engage the center shafts and allow for a little centering adjustment y and z. This seems a good idea because it might be difficult to get the accessory back in the same exact position every time you use it. I was just thinking of tapping mounting holes in the support arms and drilling oversize clearance holes in the plates to allow for a little adjustment when setting up the accessory. What are your thoughts on the adjustment?

.......... Rod

[EdThorne]

Hi Bob,
I really like the simplicity of your design. You did a wonderful job on this design. I have always been a little concerned about sawdust getting into the rack and pinion and causing problems. Have you devised a solution to this problem? I can envision an enclosure that incorporates a belt the rides over pulleys located at the end of travel. This belt keeps the enclosure actually closed during movements and keeps sawdust out of the gears. The pulleys may be fabricated from the same material used for the rest of the parts.

Your design offers a lot of bang for the buck!
Ed

[Bob]

Bob,

Thanks for your advice! I think I'll stick with the KISS principle and raise the rack.

Right now I'm working on mounting arms for the HD. The gantry support arms are at a 15 deg. angle to the perpendicular. I also want to add a simple 1/4 plate (HDPE) on each end to engage the center shafts and allow for a little centering adjustment y and z. This seems a good idea because it might be difficult to get the accessory back in the same exact position every time you use it. I was just thinking of tapping mounting holes in the support arms and drilling oversize clearance holes in the plates to allow for a little adjustment when setting up the accessory. What are your thoughts on the adjustment?

.......... Rod

The slanted gantry support arms place you in uncharted waters. I don't know if you're planning on drilling holes in the gantry. I decided on a clamp because I didn't want to have holes in the machine. As the machine gets older, I'm starting to re-think that. I'm going to mount a laser that projects a line down the center of the table. This is for making multiple setups on one long project. But, that's a story for another time.
Back to the topic...In order to make the gear support arms adjustable, it would seem easy to make a pair of vertical supports that attach to the slanted gantry arms. This way the axis could be moved up or down to accommodate different diameter workpieces.
This is still fun stuff.
Bob

[Bob]

Hi Bob,
I really like the simplicity of your design. You did a wonderful job on this design. I have always been a little concerned about sawdust getting into the rack and pinion and causing problems. Have you devised a solution to this problem? I can envision an enclosure that incorporates a belt the rides over pulleys located at the end of travel. This belt keeps the enclosure actually closed during movements and keeps sawdust out of the gears. The pulleys may be fabricated from the same material used for the rest of the parts.

Your design offers a lot of bang for the buck!
Ed

Ed,
I just use compressed air to poof out any dust that looks like it's getting too close.
The hardest job in any project is to keep things simple.
Your design looks like it would be fun to do. I just don't have time.
Bob

[EdThorne]

I can't object to simplicity!

[NewAgent45]

Hello Bob,

I’m having some fun building one of these for my CNC Shark HD (Black Diamond). I have redesigned some of the parts to fit my machine and the angled gantry supports. Everything fits well so far. I plan to post some pictures when I complete this project.

I do have some questions on carving the gear rack. This is my first time for working with HDPE material and gears. To be specific I’m not satisfied with the quality of the gear tooth carve. The cut is not nice a clean like it should be and like yours. I’m pretty sure the quality issue was caused by my choice of the bit used. A friend that used to be a machinist and also sell tools gave me the bit I used to cut the gear teeth. I don’t know everything about the bits given to me as the packaging is unmarked.

I do know the following:
- Tool steel not carbide
- Dia.: 3/32 (0.09375 inch
- Endmill 3 spiral flutes
- I ran this bit at a feed rate of 70 ipm and a pass depth of 0.0325”
- These bits were just barely long enough for the job. I had to cheat on mounting the bit in the chuck. I plan to buy a new bit for this job.

I’m thinking of getting a new 3/32 Endmill and possibly a 1/16 (0.0625 inch) Endmill for this work. What type of are you using? What would you recommend?

Thanks again for your simple design and assistance.
I can’t wait to cut something round!
Have a great day!
…… Rod

[Bob]

Rod,
It was made by Onsrud no: RBL-22613 and another set of numbers on it: 876740
Or, you could use a .125" carbide bit for all the gears like another builder did. The gears worked out very well for him.
I like using solid carbide bits because there is less flexing...more accurate cuts.
For cutting plastic, one flute works best, because it takes a bigger bite of plastic and ejects the bigger chip which removes more heat from the cut. I also use a lot of two flute bits for plastic. Slower router speed combined with a faster feed rate also produces bigger chips. You have to try different combinations of speed and feed to see what works best for you.
When you start making your projects with this axis, you should check Kurt's work (ruhnau). He has been making a huge variety of neat projects with his. Here's one: http://www.cncsharktalk.com/viewtopic.p ... 870#p21870
Bob