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IndustryArena Forum > CAM Software > BobCad-Cam > Simulation Pro - Setting up the Machine Definition
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  1. #1
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    Simulation Pro - Setting up the Machine Definition

    I'm going to try documenting my setup of a Haas VF2 with an HRT-160 in BobCAD. I may eventually get around to the machine base and the spindle but I'm starting with the basics of the table and the rotary. This picture shows the Haas machine geometry I am working with and how the Machine Coordinate System is laid out. Looking straight down on the table, all X and Y Work Offsets are in the negative region. The tool is at the "Home" position in the upper right hand corner:

    Attachment 207672

    The rotary is positioned in the center of the table. Relative to the Machine Coordinate System:

    G53 X-15.0000 Y-8.0000

    One of my first questions/decisions is where Machine Coordinate Z0 should be. Trying to keep everything as accurate as possible, my first try would be to set Z0 up high at the tool change position:

    Attachment 207674

    I'm thinking this may not be practical as I have yet to see any of the BobCAD examples defined that way. The 3 axis machines have the top surface of the table as Z0 and the 4 axis machines establish Z0 as the center of the rotary. But I do want to check limits on the machine, use real Work Offsets, and basically make it as close as possible to the real world. This machine has a Renishaw probe and the way tools are set and offsets established will be important (I think). So is this the proper way to start? I don't know, right now I have the table as Z0 instead of the rotary and maybe that will be my first error but that's where I'm going to start.

    Attachment 207676

  2. #2
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    Well,I certainly have no experience on a 4th,,,BUT,I have a lot of experience with all kinds of things that go round and round,ha.Just from everything I have ever done,my mind would always say the center of the Rotary is Z0.More advantageous than not,as for what I have done,usually.My .02 cents from a Manual Machinist view.

  3. #3
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    Ok, it seems like having the center of the rotary positioned somewhere other than X0 Y0 Z0 is not going to be a problem. You just have to tell BobCAD in the Machine Definition where the center of the A rotation is:

    Attachment 207682

    This matches the position where I have placed the rotary on the physical machine. My exact probe measurements were within 0.100 in XY and Z is exactly 5.000 inches off the table. Looking good so far:

    Click image for larger version. 

Name:	BCC-VF-2-ROTARY-4axis-Milling.jpg 
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  4. #4
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    Quote Originally Posted by jrmach View Post
    Well,I certainly have no experience on a 4th,,,BUT,I have a lot of experience with all kinds of things that go round and round,ha.Just from everything I have ever done,my mind would always say the center of the Rotary is Z0.More advantageous than not,as for what I have done,usually.My .02 cents from a Manual Machinist view.
    You are definitely thinking ahead! At first it seemed like a bad idea but then I found that I had to move the centerpoint definition for the A axis in the Machine Configuration. That basically makes the center of the rotary Z0 like it should be. That took me a bit to figure out.

    So basically it shouldn't matter where you establish Z0 when you save out your STLs. I chose to stick with Z0 at the table like it is for the 3 axis machines. That makes it easier for me to share simulation STLs between Machine Configurations. I can simply delete the 4th axis and make the regular 3 axis Haas mill configuration. Maybe add a vise in.

    If you do not save your STL with the center of the rotary at Z0, you can account for that in the A definition.

  5. #5
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    Quote Originally Posted by SBC Cycle View Post
    So basically it shouldn't matter where you establish Z0 when you save out your STLs. I chose to stick with Z0 at the table like it is for the 3 axis machines. That makes it easier for me to share simulation STLs between Machine Configurations. I can simply delete the 4th axis and make the regular 3 axis Haas mill configuration. Maybe add a vise in.

    If you do not save your STL with the center of the rotary at Z0, you can account for that in the A definition.
    I did forget to mention one thing. Now that I have messed with the "easy" setup. There is one more thing I'm going to have to do from now on when I need FULL machine simulation to look and act correctly. Without using "real" Work Offset values, the simulation looks a little screwy:

    Attachment 207690

    It simulates the stock just fine but when the Machine is visible it looks bad and part seems to jump around the screen.

    I have to correct everything by setting a Work Offset in Machine Setup 1 to match my setup (accounting for fixture in X):

    Attachment 207692

    Now everything looks like it does above.


  6. #6
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    Did you model your own 4'th or is this available from Bobcad ?

  7. #7
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    Quote Originally Posted by btomlinson View Post
    Did you model your own 4'th or is this available from Bobcad ?
    Actually my rotary originated with the files from this link: HAAS VF5/40 - SolidWorks, STEP / IGES, STL, Other - 3D CAD model - GrabCAD

    I reworked the SW parts so that they were configurable, then created a new configuration for the HRT-160 based off of my measurements of the actual rotary. So now I can move it around in SW or suppress the 4th axis and load a vise on there. Save the assembly out as ACIS (.sat) and open in BobCAD. I save out the individual pieces as STLs for the simulation. That's my current workflow anyway.

    Here is another one that I didn't download but looked good: CNC machine table - SolidWorks, Other - 3D CAD model - GrabCAD

  8. #8
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    Well you can see that I have a problem, the HRT-160 is only 5 inches from the table to the center of the rotary plate:

    Attachment 207792

    Obviously I'm going to have to raise it up but I want the simulation to catch this. I believe you MUST be in Kinematic mode to detect collisions but someone can correct me if I'm wrong about that.

    I'm going to open up the Machine Definition under Current Settings and add a Collision Check between my stock and the table. I would also like to figure out how to add fixtures and check those as well but the fixture I built is already small than the 5" swing of the rotary. Here's the CC I added:

    Attachment 207794

    And it looks like that did the job. The two colliding pieces light up in Red whenever there is an oops. Moving right along...

    Click image for larger version. 

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  9. #9
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    The swing of my part in the fixture is going to be just less than 6" so I need a 1" minimum spacer to clear the table. I made a 1.5" riser just so I don't have a heart attack watching it swing so close, lol.

    Attachment 207802Attachment 207804

    I created a new Machine Definition to use with the riser plate because I make this part often and other larger parts with light machine work. I shifted all of my rotary STLs up 1.500" and just sketched up a solid block in BobCAD to represent my riser block. I added that geometry to my machine definition and moved my rotary centerpoint up 1.500 to make it a total of 6.500" off the table:

    Attachment 207806

    Now I believe I have proper machine definition. I already ran these parts before I had the Pro Simulation and they were good, it's nice to actually be able to check my tool clearance heights. I also had to adjust my Work Offset Z to 6.500 for the simulation to come out perfect in Kinematic mode. The Work Offset only seems necessary for full limit checking and machine simulation. I want to use both so I don't mind setting them.

    Click image for larger version. 

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  10. #10
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    I love this! You are absolutely right about having to adjust the work offset value for the machine setup in order to position the part properly. You can define a different XYZ shift for each machine setup you create in case you need to flip the part in a fixture. That's the primary reason you found that the machine 0 is set up in the center of the table or the center of the rotary, because it's easier to think with when setting the work offset value for machine simulation. The value is always just the shift amount from machine zero (simulation machine which the machine zero may be different than the actual machine).

    The one thing I didn't see mentioned was adding collision pairs to the machine. In order for the simulation to flag collisions you must create a collision pair in the machine definition. Right click on the top level and add a collision pair. Then you just simply put the geometry you want to check for collisions in two different groups. For example with a 4 axis machine you probably want to have the tool, the holder, and the head of the machine in one group and put the components of the rotary axis in the other. Also perhaps another collision check of the workpiece and the table.

  11. #11
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    Thanks ChipMaker! I am just now getting around to adding collision pairs. If you see post #8, I added a CC between the stock and the table. If I want to collision check the tool and holder with the rotary, is that best done in a separate CC group?

  12. #12
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    I tried to upload the STLs to the forum last week but they were too large to upload. I figured if they were too big to upload, it was probably too detailed to use in simulation without eating up resources. My laptop handles it fine but my desktop choked. I finally got around to checking the settings in SW and instead of using BCC to create the STLs I exported them directly from SW as STL (I couldn't get BobCAD to reduce the number of triangles, it's probably me as I don't work with them often). I actually like the way it looks in simulation with less detailed STLs. It's a lot more "crisp" which is opposite of what I would expect.

    Anyway, here are all the files I believe are necessary to simulate a full 4th setup for a 2012 Haas VF-2 with HRT-160. I saved these out for a "standard" setup - the centerpoint of the rotary is at XYZ zero the same way Bob is set by default. I still like using my actual work offsets but that's too much work even for my guys. I favor precision, personally. Of course you can modify them anyway you wish.

    I just Zipped up my MachSim folder that had all the files, including the XML Machine Definition. I would NOT recommend just dropping the whole thing into the MachSim folder. It might work (I am very curious if it does) but I can't test it until my new computer comes in.

    A question for ChipMaker or Al (or anyone who knows): Can we trade Machine Definitions like that? It would be nice if I could define the whole setup, then just save it to a jump drive and drop it in the MachSim folder of another computer running BCC. I am very open to sharing my files and it would be nice to have a thread here where people can trade Machine Definitions if they choose.
    Attached Files Attached Files

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