Surface Texture Differential

This forum is for general discussion about Cut3D
Post Reply
User avatar
ScaleAero
Posts: 5
Joined: Mon Feb 23, 2015 6:51 pm
Model of CNC Machine: BlackToe
Location: Houston
Contact:

Surface Texture Differential

Post by ScaleAero »

Using Cut3D as a CAD editor with respect to Nurbs healing...and defining mill path.

We are milling large radio control aircraft fuselage components. We have 95% of our CAD
finished. We have a BlackToe and finding it excellent dssdfor what we need. However the
experience knowledge base is presenting a few questions I know everyone here doing
something similar will have had to see their way through.

1/4" ball mill stepping...

Our initial test was of the oval cap cover at the very nose of the aircraft. I have observed differential
in the surface smoothness during the final pass. We are at 10k milling Styrofoam Hi-Load 60.

The tip of the nose is tuned vertical so we are milling down and away or milling up and across down
the opposite half.

I have noticed a surface texture differential between milling down and away to the base down the Z
compared to milling in the opposite direction. Milling from base up yields a really nice smooth finish. I
think this is due to the Styrofoam being reconstituted as a smoother layer than when milling down.

Any thoughts?
Last edited by ScaleAero on Fri Feb 27, 2015 10:29 pm, edited 2 times in total.

User avatar
ScaleAero
Posts: 5
Joined: Mon Feb 23, 2015 6:51 pm
Model of CNC Machine: BlackToe
Location: Houston
Contact:

Re: Surface Texture Differential

Post by ScaleAero »

10k was chosen as a starting point to provide a longer life for bearings and router motor. Styrofoam Hi-Load 60
presents no resistance to the mill progress. Yes, we are vaccuming waste with a purpose designed system.

I will be coating portions of the milled surface with Polyurea Resin, a self leveling endothermic surface sealant.
The smoother the substrait, the smoother the resin coated piece with fewer applications of resin to achieve. I
perfer not sanding our surface.

Application of Polyurea provides the ultimate Flite-Metal prepared substrait. Flite-Metal is an adhesive backed
aluminum which provides the proper replication of aluminum to the model surface..

Thanks in advance for your input.

Ed

farmertom
Vectric Craftsman
Posts: 101
Joined: Thu Apr 07, 2011 5:40 pm
Model of CNC Machine: DIY
Location: Taft, Tennessee
Contact:

Re: Surface Texture Differential

Post by farmertom »

Hi,
I have seen wood have the same problems. I think the difference is which part of the bull nose bit come in contact with the surface it is cutting. The up cutting portion of the tool path the bit makes contact at a higher position on the bit that on the down cutting side. If that makes sense. Would like to see some of your RC airplanes. I use Aspire to cut RC airplane parts too.

P.S. Too bad about Dr. Spock. He will be missed. :cry:

User avatar
ScaleAero
Posts: 5
Joined: Mon Feb 23, 2015 6:51 pm
Model of CNC Machine: BlackToe
Location: Houston
Contact:

Re: Surface Texture Differential

Post by ScaleAero »

If I wanted to mill with the same result on both halves I imagine I will have to
rename and save the file after mirroring it so I can cut both halves with same
result.... :)

Glad to see someone else here flying RC.

For the most part its milled left and right halves except here and on the opposite
end when I mill the rear turret exterior.

This is a 158" w/s Boeing B-47 Stratojet with a pair of Dynamax bifurcated inside
nacelles with individual 90mm edf in each of the outboard nacelles.
Image
Attachments
B-47 Nose.jpg
NoseCap1.jpg

farmertom
Vectric Craftsman
Posts: 101
Joined: Thu Apr 07, 2011 5:40 pm
Model of CNC Machine: DIY
Location: Taft, Tennessee
Contact:

Re: Surface Texture Differential

Post by farmertom »

Wow, That is a big piece of foam. I have been thinking about your problem. Other things to try: If you slice your model, the second slice has an area on the top surface where no cutting is done. The bit just cuts the edges of your model moving in an up and down direction next to each other. At least the texture would be the same all around. As far as to top/end slice of the model, you could put a small circle in the center to force the bit just to cut the edges, similar to the other slices. Another thought is go use a fourth axis/ indexer. Your foam would be placed horizontal and your bit would run back and forth. The indexer would rotate the foam one unit over. This would allow for larger sections to be cut also.

Tell me more about your RC building. How big is that model going to be?
Check out my RC Airplanes. farmertomsrcairplanes.weebly.com/
Good luck

User avatar
ScaleAero
Posts: 5
Joined: Mon Feb 23, 2015 6:51 pm
Model of CNC Machine: BlackToe
Location: Houston
Contact:

Re: Surface Texture Differential

Post by ScaleAero »

Image

These are the 16 sections comprising the inboard nacelle so we can mill down
and out. Sections are reassembled after internal foam has been hot wired to
accomodate our air inlet and exhaust path.
Image
A center blade slides into a box receiver in center of the inboard pylon. Our
batteries, electric ducted fan, speed controller, and outrigger retractable gear
are placed in cavities hot wired out of the solid foam interior. Access is exactly
as it was on the 1:1 jet...through hinged panels.
Image
Our 1:8.7669 scale B-47's have 158" wingspans.

User avatar
ScaleAero
Posts: 5
Joined: Mon Feb 23, 2015 6:51 pm
Model of CNC Machine: BlackToe
Location: Houston
Contact:

Re: Surface Texture Differential

Post by ScaleAero »

I just called Sam in the shop to see where he was in remilling the endcap. Finishing up rough cut so its 2 hours
at our chosen speed and stepover to keep the nose of the plane as smooth as possible prior to coating with a
polyurea resin to harden it.

User avatar
mikeacg
Vectric Wizard
Posts: 659
Joined: Sun Nov 02, 2008 10:53 pm
Model of CNC Machine: Camaster Stinger, Sidewinder, SB 4x4
Location: Newberry, MI
Contact:

Re: Surface Texture Differential

Post by mikeacg »

I am impressed by the size of these planes! I hope you will continue to share your progress. I'm also interested in the coating resin. I will be researching that but any brand names or links would be appreciated!

Mike

User avatar
mikeacg
Vectric Wizard
Posts: 659
Joined: Sun Nov 02, 2008 10:53 pm
Model of CNC Machine: Camaster Stinger, Sidewinder, SB 4x4
Location: Newberry, MI
Contact:

Re: Surface Texture Differential

Post by mikeacg »

Found your YouTube site!

https://www.youtube.com/user/ScaleAero/videos

Thanks!

Mike

steina81
Posts: 8
Joined: Sat Aug 30, 2014 9:01 pm
Model of CNC Machine: Stinger
Location: SC

Re: Surface Texture Differential

Post by steina81 »

Have you fixed the problem?
I think you may be seeing a section of the cell wall not cutting.

Did you try rough cutting and then coating? Prior to the finish cut?

Post Reply