Poor 3d cut quality

[fsrdoug]

I have a PRS 9648,2 years old and I have always had poor cut quality in 3d. The top surface is great but the sides are very rough and uneven. In the past I have just sanded the sides but now I have a project where that is not an option and it seems to be getting worse. I use a PC router and have tried several, even a new one, always with the same results. From the top looking down the edge looks like a saw blade.
Thanks for any help

[myxpykalix]

It sounds like maybe your stepover is too big and leave material between each line of cut? If the sides look like that then the top would too. What does the top look like? Maybe a picture or two might help diagnose your problem.

[jimmya]

I also have a PRS 96x48 and mine does the same thing.

[ken_rychlik]

Is your bit tapered? If so the sides of the taper are cutting when the program does not think it is.

Kenneth

[fsrdoug]

Jack, the stepover is at .01" and the top quality is great, just bad sides.
Kenneth, the bit is tapered 1 degree. For cuts on the x or y axis there is no problem but just a slight bit off and I start having problems even if the depth of cut is .25" on a round over.
Will try to post a picture tomorrow.

[ken_rychlik]

I think if you run a straight bit with no taper, the problem will be gone. All the program sees is the tip of the bit, so to speak. The taper is cutting and the program is not taking this taper into account. I have had the same issue on deep carvings. I have to step up to a 1/8 bit and no taper. My stepover is normally .005, but that won't help with the taper of the bit issue.

[rcnewcomb]

Can you post a photo?

[butch]

Doug
Try using a ball nose bit. I use a 1/8" ball nose and the sides are fairly clean. I do this with a .01 stepover. I had similar problem using tapered bits, but fixed it by going to ball nose.

Also check the bit is sharp, and that the pinions are tight.
Butch

[curtiss]

I have a PRS 9648,2 years old and....

9,648.2 years old? wow...

[fsrdoug]

Curtis, Didn't think shopbot was around that long?
How do you think Noah built his ark?
lol

[fsrdoug]

To all who responded, even Curtis, thanks for the help. Changing to a straight bit.
Ken, this program has 1.4 million lines and over 18 hours at .01 stepover. I can't imagine .005 stepover.
Again ,Thanks to All
Doug

[myxpykalix]

No doug that is stardate 9648.2....
seriously tho.. you didn't say how big your carving is? I 3d carved a toybox lid that was roughly 24"X36" and both the roughing and finishing pass was around 14 hours combined and it had lots of 3d in it. I don't recall the bit/stepover info but i think Kenneth may have the answer by making sure its not a tapered bit because that sounds logical.

3880

[billp]

The bit which is used more often than any other for 3D carving on the 'Bot is a tapered ,1 degree ball nose bit. It's usually a 1/8"tip, but can be bought in sizes as small as 1/32". Most 3D CAM programs will "see"a ball nose bit geometry and program the tool path accordingly. The 1 degree taper actually aids the cutting process because it makes the transition from one level of depth to another smoother.
There are multiple sources for these bits, and they have been discussed, and reviewed, ad infinitum on this Forum many, many times...
3881

[mmccue29]

Are you adding a outside offset to your outside vector line that is 1/2 of your bit size?

[fsrdoug]

Michael
No I am not. How is that done.