[Brian Corwin]

SprutCAM America - Beginning Tutorial #5 - Defining the Workpiece Waterline Roughing - YouTube

In the above tutorial after he adds the extra material, G54 is still located at the top of the part and not a the top of the material. In my brain, it seems to me that you would want G54 to be located at the top of the material so that when you place the stock on your mill you can set zeros to the top surface of the stock. With G54 set at the top of the part and there being excess z material, how would you set your z zero on your machine?

Can anyone explain what I am not understanding?

thanks much
Brian

[Brian Corwin]

It may be clearer in this video at this time

SprutCAM America - Beginning Tutorial #2 - Importing and Orienting a Solid Model - YouTube

[wwendorf]

Hi Brian,

The primary reason to do this would be so that he get's a nice machined edge over the entire top of the part.

When I setup a part, I tend to use the lowest point of part on the upper left hand corner. I also use step jaws in my vise. I then indicate off the low point of the step as my z0. That way I know that when it goes up to z-1.25 (or whatever), I will get a true part that is 1.25" high. A lot of aluminum extrusion is a little thicker than they originally tell you that it is.

Wade

[Brian Corwin]

I guess it makes sense in this instance where you can indicate off the top of a step to set z0. Hadn't thought of that

But it seems like it would work equally well to set z0 off the top of the material, and then just make sure that you have the stock set in sprut so that it will take enough off to remove the variations in the material.

I guess theres multiple ways to do it.

Thanks!

B

[Brian Corwin]

I thought about it more. In the example above, lets assume I did it the way its done in the videos, where g54 is the top surface of the part. Not, as in the case described by wwendorf, where you set g54 on the bottom of the part so you can indicate off the step jaw. In the example with a solid block of material, how would you indicate z0? It seems like you would have to find the top, jog z down, then just set it there? Again, it seems like just setting it to the top of the material is easier...

[wwendorf]

Many ways actually.

1) Turn mill on very slowly about 500 rpm and jog down until the cutter makes a scrape in the material.
2) Put a piece of paper down, jog down till cutter nails the paper. Paper is a known thickness, move the cutter down that thickness, set zero.
3) Get a height setter - have one with a light on it. When the cutter comes down and touches it, it is exactly 2 inches over the zero point.
4) Get a dial height setter, they have them in 2" and 4" models. When the cutter comes down and touches it, it is exactly 2 or 4 inches over the zero point.

In types 2 and 4, if you are using a 2" height setter, you would come down, and then set the z height to 2". Now the cutter knows it's 2" above zero.

It works the same on the top of material as well as on a step.

One other thing on your original question, a lot of extrusions are fatter in the middle by sometimes 5 to 10 thousandths than they are on the sections closer to the edge. If you need an exact thickness, I would either set z0 on an edge, or use the step method I described in order to get a uniform thickness.

Wade

[Brian Corwin]

Hrm I guess my question wasn't clear. I understand how to find z0, i've run manual mills for quite some time. However if z0 is not at the top of the material, say it is in the center of the material as in the videos you cannot touch off directly on the surface that g54 is on you must touch off somewhere else and then jog down to the known offset. In either case I emailed sprut and they said that they do it the way the tutorial indicates so that in the simulation you see material being removed but in actual usage they normally do it how I describe and that if you were to actually run it like the tutorial, when you touch of the Z you would just jog it down .01 to offset it

[wwendorf]

Sorry. I took it a bit different.

I don't think Tormach normally sets up parts that way. I think it was just done that way in that particular demo so they could show adding extra material.

Wade

[LRF]

My advice, from a guy who has been machining since 1977:
It does not matter significantly where you place the "0" location for X, Y, and Z; however never put them on something that is going to be milled away, like stock material, because once its gone its gone and you will not be able to know where it is or was and you can't use it again to locate the part; as in setting it up for further processing.

[tbaker2500]

How I prefer to do it most of the time, when using step jaws:
Zero Z to the flat of the step jaws using a indicator. In my case, a tormach dial indicator as tool 1. All other tools are referenced to this.
In Sprut, make G54 (or whatever co-ord system you are using) placed at the bottom of your stock. All Z moves will now be in the + direction, unless you are cutting below your stock.

[mountaindew]

How I prefer to do it most of the time, when using step jaws:
Zero Z to the flat of the step jaws using a indicator. In my case, a tormach dial indicator as tool 1. All other tools are referenced to this.
In Sprut, make G54 (or whatever co-ord system you are using) placed at the bottom of your stock. All Z moves will now be in the + direction, unless you are cutting below your stock.

I have been trying a number of different methods and strategies for this and find no clear or standard.
LRG has good advice for older methods. From my limited experience I complete all required operations before new coordinate system is set and having constant surface un-milled is not always required.

I like tbakers method of a fixed point z set at top of a step jaw. Then a user coordinate system in sprutcam at bottom of part. this sounds kind of logical, still looking for a normal or standard.
Also Tbaker , sprut must work completely different on setup of machine operations ?
Are you still using this method?
Most book examples, I find they set ucs at top of part and of course you can keep your g54 offset at jaws or almost any place you want to touch off in the machine envelope.

I have years of future work and designs to be based on these methods and would like to find something I can share with others and they can use it.
And Use one system for most work
md

[tbaker2500]

I'm not sure I understand your question about sprut, let me try this answer. I create a new CS for each part flip. So if I'm doing two sides, I'll make a g56 CS which is zero'd to the step jaw. Then I'll place a new g57 CS rotated around the y axis, placed at the correct depth for the size the part will be after all g56 ops are done. When flipping around the y axis, it's important to follow the same edge, since stock is not always perfect size. So if on g56 I'm zeroing to top-left bottom of part, after flipping the part around the y-axis (not IN the y-axis, but around the y-axis), my g57 zero should be the top-right.

[mountaindew]

ok lets not talk g54-g69!
lets just talk u.c.s. in sprut and where on the part you set them!

I use the top of the part as my normal cs in sprut.
Sprut even defaults to this when I load a part model into the tree and go to cs dialog box to set it.

You are setting your cs to BOTTOM of part model or stock right?
Do you keep this method of defining or setting each Z cs to BOTTOM of part model or stock,
For example you flip part in sprut and define new cs , do you set that one at bottom of part or stock?
Or are you now going of the top-right as you noted above?
md

[mountaindew]

Follow up
Tbaker!
I Went back and used your system of setting the usc at part/stock base for each of 4 different sides to a part on sprutcam.
Found this to work predictable and the resulting gcode is also readable.
I might use this for a while, see if I like it.
What Im asking is what is normal or standard for all this ?
where did you read or decide the bottom was best?
They all work, and from what I can tell you can do it hundreds of different ways.
Unless there is some limit in the post processor and the gcode format it generates.
tbaker : Thanks for reply
md

[tbaker2500]

The clearly isn't a "right" way to do it, unless you ask somebody who is opinionated. I zero off the bottom of the part whenever possible, for a few basic reasons.
1. The vise jaws aren't going to shift on me in the z axis much. However, when clamping material, the material will shift in height most of the time by as much as several thousandths, depending on how much you tighten the vise. Something like plastic can change a lot. There is as much argument to do it the other way, this just feels better to me.
2. I always start with raw stock and do a surface as my first op in the program. If I'm running multiple parts, the stock is often slightly different dimensions. Zeroing to the bottom gives me the exact same resulting size part each time. I can then flip the part and take off the remaining rough on that was on the bottom in the next op, having an exactly sized part.

Just how I do it, not saying it's right.