What's new
What's new

# Looking to buy a used 5 axis VMC, what should I watch for?

#### bryan_machine

##### Diamond
Don's point is fully valid, but not the whole story.

thesidetalker is discussing the same point I am trying to make (and try to make in lots of these threads) - totally true but also not the whole story.

Here's a summary of Bryan's Rules of 5 Axis Work Envelopes...

With a 3-axis machine, one's intuitions about how large a part can really be machined with that particular mill are pretty good. Everybody knows that to drill a 6" deep hole you will need 12" of Z travel. With a 5-axis machine, the "raw envelope" does not so easily convey how large a part the machine can work.

In part this is because problems rotate with the part. So you turned the part on its side to B90°, and suddenly the Z-height limit is a rotated X-limit, and tool+depth stack applies - sideways. It is because to get at the side of the part, you will often have to elevate it off the table so the head will clear - which takes up Z height at B0. It is because while you can rotate to any orientation, axis geometry limits still apply - so on a B-axis machine (table rotates around Y or head does same) the longest rectangle you can mill at 90° will be limited by the Y axis travel, X length and C rotation will not help you with that particular feature.

On the other hand, if you can elevate the part to clear the trunnion shoulders, you can indeed interpolate a circle that may be quite large. Likewise, if you can clear the rest of the cabinet, it may be possible to do end work in very large work pieces that would otherwise require an HBM or a machine with some enourmous Z travel.

So MAKE A MODEL OF THE MACHINE. CAD, paper, 3d printed plastic, whatever. Put in movement "mates" of some kind. Add in workholding + part + tooling.

And then open your mind to both the idea that "uh, well, my parts won't fit in that machine" **AND** "oh if I turn the part like this and do that, this part WILL fit in that machine."

#### thesidetalker

##### Hot Rolled
I can’t get a video to load but here is a pic going around a 27 x 27 block 2 inches Down
Don

Sent from my iPhone using Tapatalk Pro

Yep, that's great.

... and what happens when you need to drill some holes on the sides 26" apart?

#### D Nelson

##### Stainless
Yes there is a limit to what is possible but it helps to know a few tricks that can sure help. The stuff on the sides is more difficult but if it were on the top plane it surely would work outside the envelope. That is what I was trying to say
Don

Sent from my iPhone using Tapatalk Pro

#### boosted

##### Stainless
Yep, that's great.

... and what happens when you need to drill some holes on the sides 26" apart?

View attachment 346961

You just use a coolant driven right angle tool (so that you can use the spindle orient as an additional axis). The right combination of vectors would get you there inside that work envelope.

If you are really creative, 5 axis gives you the power to fuck up parts from any angle.

#### MaxPrairie

##### Hot Rolled
Don,

What is the story with that ModuleWorks you have on your screenshot? Is it just a simulator or is it cam and post processing also? Simulator looks similar to Camplete, but the toolbar looks cleaner to me...

#### D Nelson

##### Stainless
Don,

What is the story with that ModuleWorks you have on your screenshot? Is it just a simulator or is it cam and post processing also? Simulator looks similar to Camplete, but the toolbar looks cleaner to me...

It is from postability we bought with the umc post from master cam
Don

Sent from my iPhone using Tapatalk Pro

Replies
0
Views
251
Replies
11
Views
2K
Replies
61
Views
2K
Replies
2
Views
301
Replies
30
Views
759