How fast do you cut in 3D?

[blackhawk]

Hello All - Here is a piece that I just machined out of Mahogany. (My customer calls it mahogany, but I expect that it is Sapele.) I cut this on my PRT Alpha (7.2 upgrade) and PC router at 2.5 IPS on X and Y and 1.8 IPS on Z, 19,000 rpm. I have optimized my VR sheet based on Brady's article. I am happy with the results, just wonder if I could go faster. This piece was about 12" tall and 40" wide and took about 3-1/2 hours with an 1/8" ball nose.

With this type of 3D work, I think that you are going to reach a point where the speed is limited by your ramping and Z moves.

[steve_g]

Nice work! I suspect that you have already maxed out the speed you're going to get due to ramping... It won't hurt to try ridiculous speeds and see if any time improvement is realized...

SG

[dlcw]

I 3D carve on my PRSAlpha at about 3-4ips. Any higher and I think you just beat the snot out of your machine. This seems to be the sweet spot for my carving. I cut plywood at around 6-7ips.

[blackhawk]

I just cut out two identical panels tonight. I ran the first one with all the same settings above except I had my X,Y speed at 2.6 IPS. It took 2:15:45 to run. I cut the second one at 2.8 IPS (about 7.5% faster). The second one cut at 2:15:10. I only gained 35 seconds or about 0.4%.

It probably makes a bigger difference if you have a lot of open areas with no Z moves.

[cowboy1296]

I am always looking for a way to speed up my 3-d. Currently I am at 3 ips feed rate and 2.5 on a plunge. I use a 7% step over and my rpm is 10k. I cut primarily black walnut and alder.

[Brady Watson]

She'll go as fast as she'll let you go...Every relief is different & tweaking ramps will let you gain some speed, but not gobs more.

Three areas are going to influence your 3D cutting more than anything else:

1. Slow Corner Speed; simply explained, the percentage of your move speed that sets how fast it will go around a corner, in XY OR YZ OR XZ (and XYZ) - so if your SCS is at 30, it will slowly climb over details. Jack it back up to the stock 65 setting, unless you are getting rough movement or 'banging' - think of SCS as a cushion. The higher it is, the harder it is.

2. 3D Ramp Rate, this reduces the sensitivity of ramping in the Z axis. Stock is 100, I like 150 for most things, up to 300 is useful, more than this is a diminishing return. If Z bangs, pull it back.

3. Often overlooked, one of the most important things is machining at a 'good speed'. The XY to Z speed ratio is important, so go check out the speeds I posted in the article and try running at one of those. On that relief, it isn't that detailed, so you should be able to run maybe 3,2 or 3,3. I don't like running the Z faster than 3 because it will result in a poor finish...it is asking an awful lot from the Z motor to move that fast while lifting a 20-35 pound gyroscope. Running at the speeds I recommended will make tuning the other 2 settings easier.

-B

[hespj]

Are you guys not worried about breaking your 1/8" bit at too high a speed?

Brady, where can I read your article?

John

[jerry_stanek]

After the first cut you are only taking just small bites

[Brady Watson]

http://www.shopbotblog.com/index.php...bradys-tricks/

[hespj]

Thanks Jerry, Brady.

John