3D Machining Gone Wrong - Odd Striations in Vectric3D Model carving

[Hutchie1]

Everyone!

I need some expertise. I am relatively new CNC work and the procedures I have followed before are not working. I have been trying to mill the following rosette for over a week now and I cannot get a smooth carving. I have attached two images of an example carving where all of my attempts look basically the same.

I am trying to carve the following from Vectric 3D website: Pattern 58037a (Square Panel 6A)

Here is what I have:
BT32
Porter Cable 7518 router attached
Shopbot Control software - latest version
Shopbot Controller Firmware - latest version
Vcarve Pro Shopbot Edition v8.024 software

Here is what I have attempted:
- Router RPM - 19k & 21k (via Chip Load Calc)
- Feed Rate - 2 in/sec to 7 in/sec (via Chip Load Calc)
- Plunge Rate - 2X bit diameter
- Area Machine Strategy - Normal Offset & 30deg & 45deg Raster (images are 45deg raster)
- Amana Bits - 1/16" (brand new) & 1/8" diameter ballnose (4 flutes each)
- Cutting Parameter: Stepover - 2, 3, 4, 5, 7, & 10%
- Cutting Parameter: Clearance Pass Stepover - 2, 3, 4, 5, 7, & 10%
- 3 different types of wood - Cherry, Pine, & Baltic Birch Plywood
- Collets: Porter Cable Manufactured & Precise Bits High Precision collet for Porter Cable 7518 router
- With & without the dust skirt

Any ideas? You will notice that the striations are not uniform and consistent. I have never had this problem before. Everything I have tried is producing the same issue.

Let me know.

Thanks!

Hutchie

[steve_g]

Erick…
Tell me about your substrate, properly dry top to bottom? How long are the cut times? I’m wondering if you are getting some part movement either from temperature or moisture variation during the cut…
SG

[Brady Watson]

What was the model size in inches or mm and model resolution in VCP set to?

What is the model depth? The model you show is very shallow. Double click on the component in the Component Tree and tell us the Shape Height.

You will get the best results finish machining at MS,2,1 rastering at 0 deg parallel to the grain, and 18k RPM. The roughing doesn't matter...just hog it out.

-B

[Gary Campbell]

You may want to use a piece of 1 by 2 under the collet nut and check the backlash in the Z axis. Another item to check are the rollers that control the X axis. Make sure there is no vertical play as the X works back and forth.

[Hutchie1]

SG-

I have a 3/4" MDF block carved out to be 1/4" deep to completely encompass the blank wood on the sides. The substrate is always 1/2" thick. I even screw the substrate to the MDF to hold it down. Everything is dry throughout.

The cut times range from ~2 to 4:40 hours.

[Hutchie1]

Brady-

I thought that too. I have varied the shape height from 0.18" to 0.26". The model shape height is 0.15".

The model size is 6 inches square.

Thanks.

[Hutchie1]

Gary-

I checked the Z play. It is solid. I will check the X axis.

Thanks!

[Brady Watson]

I think you are just cutting it too fast. Try at least a small section with these settings:

3D raster @ 10% stepover, 0 deg angle, MS,1.5,1, 18k RPM

Just draw a circle (say 2" round) and use that as your vector boundary for the 3D toolpath. No need to cut the whole thing. No need for roughing.

Try it and report back.

-B

[Hutchie1]

Ok. I admit that it has been a while for me to respond.

I have taken all of your suggestions and tried several more things to no avail.

Here is what I have done:
- 1) I have used the settings that Brady suggested and it didn't work. I even slowed it down further (aka ~24 hours to mill) and it still showed the same strations
- 2) Downgraded the firmware to 3.8.26 and this seemed to work a bit better. The cut was smoother and less jagged, but the strations are still present using Brady's recommended settings above.
- 3) I switched patterns to a Moose scene and milled using the same mill conditions. It came out perfect. Moose1a.jpg

I have since upgraded the ShopBot BT32 firmware back to the newest version. I believe the issue lies with the Vectric3D Art itself. It appears to be a function of how the VCarve Pro v8.024 and the ShopBot Control software interpret the image. In VCarvePro, the carving always looks fantastic. However, when the control software gets a hold of it, it all goes downhill. The depth never looks right (model depth is ~0.19") and the detail never looks visually good even though I have been milling it with a 1/16" bit with a 2-5% stepover at a really slow mill rate.

Any ideas on how to test the artwork to see if the file is just corrupted?

[Brady Watson]

If it shows up good in the preview, then it should be good. It's odd that it isn't machining properly and another file is.

Is it possible that the material is not setup properly in Aspire/VCP? Sometimes this can mess with you. Be aware that there is a material slider block in the Material Setup in the toolpath tab. Your 3D relief will move up and down as you slide it in the material column. Have a look at this and make sure it isn't jacked up.

I would first start with a fresh session and import the relief again with new toolpaths. I would then create a vector (say a circle) and put it around the worst part of the relief - say the back most antlers. Then use this as your machining boundary. That way you can test it out and not have to wait a long time to test your results.

-B