Indexing head

[kubotaman]

I have purchased a 12" PRS Alpha and I have a few questions in regards to the indexer attachment. I have two questions. First, why is the indexer for the 12" "Z" axis so much more than the 6" "Z" axis? The difference in price is approximately $3000!. Don't both kits use the same stepper motors? Why can't a fella use the 6" "kit" for a 12" Z axis or am I missing something? The second question is: I understand with the program provided with Shopbot the indexer is capable of "wrapping" a carving around a cylinder. Is the program capable of wrapping around a square or multi sided object? If so how would one do it?

[myxpykalix]

Are you sure there is no miscommunication about the price? That doesn't make a lot of sense. I bought my indexer in 2006 for a 6" Z however if you see the table it has a gulley which lets the Z go down to about a 12". I would clarify this because i can't figure what would add to the cost. For that matter you could do research and build your own indexer for substantially less. What was the total cost you were quoted?

As far as wrapping around a square, although i have never done it it would seem like you could do a file like a 4 sided carving like i do in millwizard, or maybe a series of 4 files that intersect to look like it might be a continous pattern. Maybe if you post a picture we could get a better idea.


2891

[kubotaman]

I am not mistaken on the price. Check out the price on Shopbot's price list. I can't understand why the big difference between the 6" and the 12". As far as a picture I don't have one but I was just curious if it were possible!?

[jim_vv]

Daryl,

Cangrats on your purchase.

You can definitely use a 6" indexer with a 12" Z.

My 6" indexer measures 6" from the center of the chuck to the bottom of it's 1" thick base plate thus giving a 9"-10" diameter part capability.

The 12" indexer appears be on a taller housing bracket and have a different drive setup making it capable of swinging a larger, heavier part.

Carefully read the following quote from the ShopBot website.....

"Maximum turning diameter for the 6" jaw system is 9". Maximum turning diameter for the 12" jaw system is 18". These maximums are for round stock diameters; square stock is measured diagonally between the corners. Six inch systems are fitted with tapered-hob gearheads; 12" systems are fitted with planetary gearheads for reduced backlash on larger diameter turnings and to support heavier parts."

You'll need to consider what you want to be able to turn to decide what to buy.

You will also need to consider how you will incorporate the indexer into your machine's layout.

Regarding your wrapping question..Talk to ShopBot about what you intend to do with the indexer and they can direct you toward the right software. ArtCam Pro will do what you are talking about, but there may be a cheaper option out there.

Kind Regards,

JIM

[eaglesplsh]

I recently purchased an indexer motor to build a 4th axis and inquired about the difference...

My understanding is that the gearbox built into the 12" indexer motor is more precise/has less backlash than the 6" motor. Evidently, the added precision is desirable for cut quality on large (6"-12" diameter) parts. You should be able to use the 6" version to cut 6" diameter parts with your 12" Z-axis without any trouble. If you don't need the added precision for your parts, you might be able to modify the 6" version to run 12" diameter parts - you'll probably need to raise the chuck and tailstock off the table 3 additional inches to allow for the size of your stock.

I intend to use a belt drive on the indexer I'm building. This gives the option of changing gear ratios to achieve higher precision with the 6" motor/gearbox. But, achieving higher precision will reduce my max feed rate, so I haven't decided on what ratio I plan to go with.

Best of luck finding the right solution for your application.

[myxpykalix]

Taking into consideration Russ's comments re:added precision I think you need to visualize the things you will be making and whether you actually need that extra precision and whether its worth the extra money.

I have made 8' long, 10-12" wide columns and fluted, spiraled and 3d releif carved them (not the entire 8') and my quality is perfectly fine.
I don't think you need that extra precision to make fluted columns.

[kubotaman]

I didn't realize the difference was in the precision of the gears. I assumed the difference was the "size" of the units themselves. I don't ever plan in turning anything larger than say 8-10 inches. Therefore I would only need the 6" capacity. Where can I find out more on the differences other than the price list?

[eaglesplsh]

Jack has a good example concerning matching precision with your needs...

If the flutes of a column are off by a degree or two nobody is going to notice. If you're trying to cut 12" diameter parts that have to fit together with multiple other parts in a system or if you want the computer to do all the work and don't want to have to sand your parts after they come off the machine, then the added precision may be right for you.

As for getting more info on the differences between the two units, I'd call ShopBot tech support. They've been exceptionally good at answering my questions in an open/honest manor, without trying to sell me something that I didn't need.

[kubotaman]

So does anyone out there have the more precision 12" indexer? How bout first hand knowledge?

[jim_vv]

I think you are mistaken about the two indexers being the same size and the only difference being precision. I don't think that the 12" indexer is any more accurate than the 6" one. The 12" indexer is set up different to allow less backlash. Backlash is going to be more noticeable as the diameter of the part being turned gets larger. I think you really should talk to the people at ShopBot about this.