5th axis stock dovetail stock preparation

[magloviti]

Hi all,
my first post here.
I would like to use 5th axis DM12 dovetail fixture for the 3+1 milling job that is coming my way.
Problem that I'm facing is that when I model stock according to dovetail stock preparation pdf which I found on 5th axis webpage stock is not centered in the middle of the fixture.
Is this supposed to be off-center or am I doing something wrong?
I did send an e-mail to the 5th axis some time ago but didn't get any reply from them.

 

[TrollTuner]

Have to measure, comp the dovetail cutter. We use thread wires works great.

Half of the 10.28 isn't the 5.12 in your sketch..
I always just subtracted the dovetail vice from the stock and extended my cuts.

 

[gkoenig]

It looks like your model in Fusion is a bit off as well? The dovetail on the left isn't mated - it looks about 0.05" out.

 

[Mtndew]

Is this supposed to be off-center or am I doing something wrong?

You are doing it wrong.
You drew it off center.

 

[magloviti]

@TrollTuner, I know that 5.12 is not half of 10.28, that is drawn like that because that is what the 5th-axis drawing says it should be.

@gkoenig @Mtndew, I placed it off-center because I thaught that part should be in the center of the fixed part of the fixture. This is obviously not correct.

Thanks for the clarification. It makes much more sense now.

 

[HAA_S]

 

[DSMWerks]

I sell 5th axis dovetail fixtures with the Moreside Fixtures that I make. I always send a solid model of the correct material prep because of just this reason. The locating pins, bolts and dovetail can get a little confusing when nothing is symmetrical.

 

[implmex]

Hi All:
I gotta ask...does it even matter?
It's a stock prep dovetail...you're going to mill it away eventually anyway.
So is there any benefit I'm not seeing, to getting anal about it?

Now I do not do 5 axis milling so I cannot say from experience, but I can't think of a good reason why I should care.
So long as the vise or fixture can grab the stock and I know where everything is before I start whacking away at it, all should be good, should it not?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[Mtndew]

I gotta ask...does it even matter?

It matters for initial part location.
For example we have a 3+2 Tsudakoma table, and we do NOT have TCPC. So our parts have to be dead center of rotation as drawn in Mastercam.
If they are off, then the parts could be scrap depending on how much they are off.

Think of a 3axis mill, and having the part not be against your vise stop in one or both directions.

 

[implmex]

Hi Mtndew:
Thanks for that explanation...makes sense.
Next question:
If you grab your raw stock by the dovetail, and it's not centered on the stock and you don't have Tool Center Point Control (yeah I had to Google it), may I assume you'll have less stock on one side of the part and more stock on the other than you planned when you spin the block around the B and C axes?

If that is so, you are still theoretically good, and your part will come out properly, it's just that you'll take a humungous extra bite on the one side when you first start roughing.
If you're way way off, you could rip the block right off the machine, but if you're only a little bit off, will the machine even notice?

Since the machining axes of the finished part can sit anywhere inside the raw stock depending on where you bolt it on the platter, so long as you have enough stock to still completely cover the part in the position you chose to place the block...the absence of TCPC shouldn't matter...should it?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[DSMWerks]

I gotta ask...does it even matter?

Not so much on 3 axis but on 4 axis or one of my 5 axis indexing fixtures I like to program with the part and the stock on center and not be eccentric. Also makes the Z retracts easier. Instead of higher on on side and lower on the other.

 

[Mtndew]

may I assume you'll have less stock on one side of the part and more stock on the other than you planned when you spin the block around the B and C axes?

If that is so, you are still theoretically good, and your part will come out properly, it's just that you'll take a humungous extra bite on the one side when you first start roughing.
If you're way way off, you could rip the block right off the machine, but if you're only a little bit off, will the machine even notice?

Correct.