Newbie looking for advice on SB selection

[Pennywood]

Greetings all,
I am in the lurking stage of buying a shopbot, and was hoping to get some advice about which machine to purchase.
Primarily I think it would be used for 3D relief work, but I'm new enough to the prospect that I don't know what it CAN do. Occasionally I build custom gun stocks, and while I haven't had any luck searching this site for others who do this, I'm sure the cnc would be indispensable for routing the receiver pocket.
My specific question is "could I carve a complete stock with a 6 inch Z?"
There are tons of other questions regarding models and features, but I think that's where I want to start. Please redirect me if that is not the thing I should be most concerned with at this point, and thank you in advance for helping me wade through the learning process

[scottp55]

Understand that I know ZIP about indexers and making gunstocks, but Nate at Shobot was playing with them a couple years ago;
http://www.talkshopbot.com/forum/sho...9522-gunstocks
And try Google search for pics;
https://www.google.com/search?q=shop...w=1366&bih=628
A couple Luthiers have managed a 9"Z for a Desktop, Look at Max's comments and video;
http://www.talkshopbot.com/forum/sho...is-upgrade-kit
Wish I could help more, but maybe the indexer big guys will chime in?
Welcome!
scott

[Pennywood]

Thank you Scott. Those links were very helpful. I can see how Weston's mod works, and it's impressive. I understand conceptually how the indexer works, and it would definitely make the shape easier to cut. Being able to rotate the whole stock gives the cutter access to the entire shape.
I've been looking at the different models trying to decide how to proceed. I haven't called shopbot yet to discuss the available z options, but I believe they offer a 12". There seems to be a cautionary tone in the forum regarding its merit, though. Am I mistaken in this?

[steve_g]

Pennywood…
I have a PRT with 12” Z and regular access to a PRS with 6”. Any “cautionary” concerns regarding the 12” are due to the additional leverage a bit has against the mechanics of the gantry, and ensuing less smooth cuts… An experienced operator can overcome this issue by carefully choosing his cut direction and using onionskin toolpath strategies. Sometimes you just must have the additional Z height!

If I could only have one machine, it would be the 12” one. One method that could be used if this became a real issue, is to have a temporary table “riser” that raised the bed for normal cuts by 6” and was removed for those times when more Z was needed.

IMHO the issue is more imagined or theoretical than real…
SG

[Pennywood]

Thanks Steve, that is reassuring. I am not, by any means, an experienced operator. I hope to someday become one
I'm assuming "onionskin" is what it sounds like, (I searched the forum, and the word is used a ton, but the context does not clarify exactly what it means) cutting close to the final dimensions with a rough cut, or bit, and making a final cut at a lower speed or load (or direction)?
If I understand your implication, the greater z axis capability does not inherently create additional lateral forces on the gantry, but the additional leverage is relevant only when at cutting at maximum axis setting. Since I'm currently thinking of a 48 x 48 machine a riser box should be viable, if necessary

[chiloquinruss]

"a riser box should be viable" If the primary thing you are getting a machine for is gun stocks then I would go the other way, that is instead of a rise how about a pit! Seriously imagine the 'log' is half buried in the machine with half above the surface and half below. The requirement for a higher 'Z' would not be necessary. Some on here have modified their tables by mounting their indexer crossways on the very end of their table or by having an opening in the table. I'm not sure that would work for a Desktop but it would work on my 48x96 table like the example below. Russ

[Pennywood]

Thank you, Russ, that certainly would make a stable mount!
The first operation in cutting a stock (at least using conventional methods) is to cut the receiver pocket, which means cutting through the deepest axis of the stock. It's the required bit length that makes me think the 6" z movement would complicate, if not prevent, the cnc from being able to do the job.
I'm committed to the prospect of expanding into the world of cnc, so I'm trying to anticipate which axis limitations would be least restrictive to the types of projects we are likely to take on. Honestly, the digital modeling of a stock seems impossibly complex to me, but someday I may learn to do it. Currently the checkering and "decorative" cutting actually takes more time than roughing the shape, and if I could somehow program that it would save many hours of eye strain. I see there are many fine examples of checkering on gun parts and signs, so apparently curved parts aren't a problem.
That being said, stocks currently make up a small percentage of the work we turn out, and I'm not sure acquiring a cnc will contribute to any change in that situation.

[Tim Lucas]

A little more to expand your possibilities - If you purchase a machine and the Aspire software you could pay someone for creating the tool paths needed for your complete gunstock and any other 3d item, at least until you can get familiar with the software and machine.

I would think for your interest you would want an indexer set low like in Russ picture either on a 48 x 48 or a 48 x 96 setup.

Just my opinion
Tim

[scottp55]

You may want to join the Vectric forum as well, as I came up with pages of thread references and they may explain why you need to get an accurate model of the stock before you can consider carving on it.
https://www.google.com/search?q=vect...w=1366&bih=628
You may very well consider upping to Aspire, as the gun stock model itself will not be a Vectric .v3m file format, and VCarvePro(VCP) will only allow one example of a non-native format per file(there are work arounds though), and although Design and Make(Vectric .v3m format available) has a lot of nice models, there are many other good 3D files that would probably be in other formats.
Checkering and VCarving could be done easily one you have the stock contour model by either probe or scan with the included VCP software.

Russ, He couldn't do a recessed area with the Desktop because of the Y screw under the deck in the center...Possibly with the MAX, but pretty sure the aluminum extrusions are across the 24" axis, which would be a pain to swap and recess. Even the RWS rifle I bought to use with my Match pistol Diana pellets for indoor and backyard shooting has a 3/4 stock 32.5" long, so that may throw out the MAX as well.

That's a shame as he plans to do small intricate stuff like mine a little anyways.
Probably working in Black Walnut, which is great, but still fairly often you have to do a second pass for clean up, and Desktop repeatability is exceptional. REALLY tough to sand any details when that small without losing some detail that you worked so hard to get.

Pennywood,
What sizes were you thinking in your head for 3D carvings?
Double sided models, or bas-relief?
Remember that you'll probably be making stuff you never thought about when you considered the machine
Jigging for all the other machines in the shop comes to mind!
scott

[scottp55]

Have you seen Gene's machine?
http://www.talkshopbot.com/forum/sho...or-Desktop-Max