Non-Alpha Indexer Capability Questions

[gerryv]

Hi,

I have a standard BT-32 with the table dropped giving me 10" of Z. I'd like to mount a removable Shopbot non-alpha indexer and am wondering if the SB indexer routines allow for continuous rotation and what my max. RPM would be. I'm looking at doing some simple lathe work on plastics. time is not an issue for me.

Also, is the SB indexer software very user-friendly, being that it not a part of Partworks or, hopefully, can it be used "through" the Partworks and/or Aspire programs GUI?

[Brady Watson]

Gerald,
You cannot setup an indexer at this time using a stepper for continuous rotation. You can however, buy a wood lathe and run it's motor at whatever RPM it will allow. If you are just doing turnings, then you do not need a stepper motor at all. You only need a stepper to drive the 4th axis if you need to incrementally index for decorative 3D carving or to incrementally index for 2D operations. With a wood lathe on the bed of the table, you can essentially have a CNC lathe of sorts, using the router as the cutting tool. XZ or YZ moves can easily be created using the Indexer virtual tool - which will allow you to do basic 2D lathe operations. You can couple a stepper to a lathe for times when you need indexing capability.

Currently there are no provisions specifically available for indexer work in the software you listed. You can, as previously mentioned, do lathe work using any CAD/CAM package and the SB3 Virtual Indexer Tools. Have a look in SB3 and read up on what it does. Once you get into 3D relief work on the indexer, things get increasingly more complex and expensive - as the software required to do what you REALLY want to do costs money.

-B

[myxpykalix]

I'll answer what i can here. The indexer allows for continuous rotation however you cannot move other axis' at the same time. So you can't rotate the indexer and manually move the X axis at the same time for example.

The indexer routines are accessed within the control software in the form of "wizards" that spit out a .sbp file based on your choices. Go to the control software and (TI) and go thru the choices you see.
If partworks3d is like millwizard you can take a 3d file like a .stl and create a toolpath for a 2 or 4 sided carving toolpath.
I don't think those programs make 4th axis toolpaths from a model but i don't know.

There is a way to increase the rotation speed and i believe i saw Jay Wyant do that on his indexer and it is a setting within the control software but i forget where it was and what the settings were.
You talk about doing "simple lathe work" by that do you mean just cutting down diameters or doing typical bead and cove work?
You can do shapes from the "carve the blank to a shape using a partwizard profile" to do that type of work. If you want to make spirals like this:
http://www.youtube.com/watch?v=jSy8PGj2eDU
let me know i can make you some toolpaths to try out.

[rnels]

When I round my logs or do profiles I have a routine that continually rotates the log (dedicated B axis) as the X (my indexer is in the X axis) moves down the log so it is possible (Doesn't SB3 Virtual Indexer Tool do this also in it's profiles?).

The command I think Jack is looking for is the VS command as you can set Bmovespeed with that(It is something to experiment with till you get the speed you are looking for - It seems to be more than fast enough when you are looking at feed speeds for your router/spindle. Remember instead of the router/spindle moving along the material at say 2 IPS - the material is moving at the router/spindle at a certain number of RPM's) . The stepover in what I do controls the number of rotations in the length of your blank.

You should be able to set up profiles in the Partworks software and use the Virtual Indexer Tool.

You should be able to buy or have custom made 3D reliefs set up for your specific blank size and get .sbp files made without owning the expensive 3D software. Once you have these .sbp files I believe the ShopbBot Virtual Indexer Tools software with wrap these for you.

[Brady Watson]

It is not possible at this time to independently move the B axis and have it remain spinning by itself AND do an X,Y or Z move independently from it. Simply setting the indexer spinning without any other type of axis movement is practically worthless, unless you want to use it for sanding, or use hand tools to carve, which I don't recommend doing. If your tool peels the skin off of logs and moves the X or Y while spinning, it is doing an XB or YB move, which are coordinated or 'indexed' in movement.

The easiest, and perhaps the cheapest, way to have a free-spinning indexer would be to use a cheap wood lathe that sits on your table and runs independently from the rest of the machine. Now you can spin your heart out and use the arrow keys or XYZ program to do basic lathe operations. This is not a new idea. Several people have done this & a few have even coupled a stepper to the lathe (that can be disconnected for lathe spinning) for times when they needed to index with the stepper.

You can setup basic 2D lathe operations via the Indexer Virtual Tool in SB3. The Virtual Tools does not deal with 3D relief-type work at all. You can also setup simple toolpaths for doing barely twists, spirals and rope molding by combining a simple 2D toolpath along with a shaped cutter.

The max RPM of a PRT/PRS Standard motor is around 300 RPM, depending on gear ratio & communication speed.

It is possible to convert your B axis from a rotary (steps per degree) to a linear axis (steps per inch) and 'wrap' a 3D relief toolpath to your blank. This requires some simple math and proper setup of your model & toolpath to do correctly. This method is certainly nothing new. This method works with files that are already 'unwrapped', and it is limited in the type of file that you can cut. You could cut a Tower of Pisa, but not a full 360° skull for instance, using this method.

If you wanted to do a 2-sided or 4-sided part, you could just use the indexer as an automated table turning axis and just use it to accurately rotate the part either 90° or 180° in between each of your 3-axis XYZ 3D relief toolpaths done in PartWorks3D. Most full 3D (360°) parts can be done this way with a minimum of undercuts. This eliminates the need for incremental stepover indexing (indexer steps over X° per pass as it rasters back and forth) and it also eliminates the need for expensive software. In fact, if you were crafty enough, you could cut multi-sided parts using nothing more than MillWizard and a few table turns of the indexer...

-B

[gerryv]

I suspect there may be others getting as much as I am out of this discussion and I'm thankful to all for the level of detail.

Based on Brady's last clarifications, what intrigues me is whether it could be perhaps a simpler but still great step forward to upgrade the existing SB software to allow for say 8 or perhaps 16 "positions" rather than 4 to allow for much greater undercutting and detailing without the need to go to very expensive (and hard to learn) true 3D software. would this also require Vectric to do a major rewrite I wonder?

[Brady Watson]

Gerald,
"N-sided" machining is something that already exists via DeskProto, and it is relatively affordable CAM-only software @ $1300 USD. However, it is possible to do your own N-sided milling of sorts if you center your model and rotate it in the software, with the side to be finished sticking straight up. A 16-sided model could be done by rotating the model 22.5° on center, and then just do a 3-axis toolpath on that focused area. This all depends on whether the software uses an overall rectangular or cylindrical bounding box of the entire model for rotation, or the silhouette of the model itself, as there can be some deviations in model positions when rotated, such that adjacent 'sides' may not line up, if the model doesn't rotate as you would expect it to. This is something best left to your R&D dept as it will take some time to proof out the concept for your particular CAM software. Personally, the $1300 isn't too bad if you use your rig to make money...now you'll be making $$$ and a return on the software if you can now do things that you couldn't do before.

PS - You can test drive DeskProto for 30 days for free.

-B

[rnels]

Brady, I stand corrected on the B movement. Thought Gerald was refering to an indexer stepper motor. Guess my movements are XB combination.

Brady have you ever tried my program to convert a flat 3D relief .sbp file to degrees? I do a 360 degree conversion not inch conversion. The .sbp file needs to be in Shopbot (inch)(*.sbp) format. I take flat files out of ArtCAM all the time and convert them to 360 degrees - would appreciate knowing if it doesn't work for others. Granted there are pieces of my software that may not work like everyone likes but the main conversion program for converting .sbp files should work. I also do N-sided machining using flat files. The computer I use to run my software is my design computer and is more powerful than my Shopbot computer. PS: the price is right.

[Brady Watson]

Randy,
I haven't tried your program. I'll check it out if you want to email it to me. It sounds very interesting & a great solution for those on a tight budget.

Thanks!
-B