Need Advice - Which Machine ?

[Northwest_Pat]

Hi Everybody, I’m hoping I can get some advice. I plan on purchasing a new Shopbot machine in the near future as an early pre-retirement gift to myself. However, I’m having a hard time deciding exactly what machine to purchase and I’m hoping I can get some help from the Shopbot forum…

First of all, let me say I’m am completely impressed with the Shopbot community. I've been pouring through this forum. You guys combine technical knowledge, trade skill and artistry to a fascinating level. I’m constantly in awe of the beautiful projects that you are producing. I have a fair amount of woodworking experience, but I have a lot to learn to even come close to the people in this forum.

I have narrowed my choice of machines between the Shopbot Desktop Max (which was just announced to the people on the waiting list) or the PRS Standard 96-48 full size machine. I know a lot of people recommend going as big as you can afford – either machine is in the budget along with the peripheral equipment that I will need. The struggle I’m having is not price, but precision. I plan on using the machine for wood engravings/relief work, some plaques and maybe some smaller furniture. The larger size of the 96-48 would be nice for getting into larger work eventually (for fun, not so much for revenue). However, I’m concerned about what I will be losing with regard to the extra precision of the desktop unit. I considered the Buddy too, but I have room for the full size.

I’ve been a mechanical engineer for +30 years with CAD experience the whole time. So I get the difference in design between the desktop ball screw drives and the full size rack / pinion – and the corresponding effects on repeatability/accuracy. When I posed the question to Shopbot, I was told verbally there is a difference – the full size machine is good to 0.016” (not as good as the website says for some reason) and the desktop is 0.002”. The person I talked to said that the resulting engravings would be “rougher” on the full size and I would not be able to do lettering less than ½”. But I realize that feeds/speeds/tooling/maintenance has a role too.

I know this is incredibly difficult to articulate, but can anybody tell me some of the difference in quality I will get between the machines for producing plaques / engravings ? I see some incredibly detailed work coming off the Buddy’s and the Full Size machines – so I’m having trouble visualizing under what circumstances or projects the desktop might do better than the full size unit. To be honest, I really want to buy the full size for the extra capacity.

Sorry about the novel, thanks for any advice !

[coryatjohn]

I was in your position a number of years ago and I opted for the PRS Alpha. I didn't know it at the time how I would use the machine. I run jobs now that last for 12 hours and need to be the same precision repeatably over and over again.

I run 12 hour jobs for days on end and after that, the machine can still return to the same exact spot. I have a 1/8" hole at 1"x1" that I use to index the machine. I never have to reset. If that's the kind of repeatability you're interested in, get an Alpha.

[steve_g]

Pat…
Consider the medium… Wood isn’t precise! It moves with temperature and humidity, has grain, pores and voids bigger than some of the tolerances you’re talking about! That said, there’s a lot you can do to mitigate some of the issues that are concerning you, like choice of font. Many of us run our Bots in environments with poorly controlled temperature and humidity, it would be a shame for you to buy a machine that you expected high levels of repeatability from just to find that many other issues come into play!
I own an Alpha but routinely run a friends PRS standard, either machine can be equally as precise, but the Alpha is more forgiving. If I were buying a new machine today, knowing what I know now, I’d buy the biggest Alpha I could afford! You never know which direction this new adventure is going to turn… it’s sure inconvenient to get a job that requires 5’ X 5’ Baltic Birch when you own a 4X4 or a 4X8!
Welcome to the community!
SG

[myxpykalix]

The first thing i would say is....you're not building rocket ships, so i doubt you will need that level of precision. I have a 5'X10' PRT Alpha with an indexer and I can lay a 4x8 sheet of plywood down and cut it and turn a 12" wide X 8' long column if needed. I bought the biggest and best at the time and have had it for almost 10 years and have had relatively few problems.
You will kick yourself if you don't get a full size machine, trust me on that. It will limit you in the things you can build by not getting a full size machine. Having said that however I confess that probably 75% of the things i make are done on 25% of the table space.
It will open you up to many more different types of projects that you can't even imagine you would want to do, let alone others asking to to make things for them.

[jerry_stanek]

I have a PRS standard and do lithos and 3d carving some of the runs are 10 hours or more. I also have the ability to cut cabinets or large signs that a smaller unit can't. I would get the spindle also.

[Bob T]

I am relatively new, 18 months, window shopped for a few years. I didnt/don't know exactly what I wanted to do with it, I have many interests. Did not want to be fenced in with small table and, if making cabinets, did not want to move sheets of Plywood more than necessary. I have a 48x96 standard, and enjoy it. Things I might splurge on if I was in (assuming here) your position are nice dust collection, vacuum table, and maybe the spindle, or really nice ear protection.

[joe]

Looks like this is a hobby venture. And we don't know what or if he plans on doing. Not sure there's a way to be specific as to what's needed. I'll dust off the magic ball and see if there's any hint there.

[coryatjohn]

>> Having said that however I confess that probably 75% of the things i make are done on 25% of the table space.

I totally agree there. It's the 5% of the jobs that take 100% of the table that makes having a larger machine more useful.

[joe]

Cory,

I looked up your profile to see some of the work you are doing on those long runs. I'm sure Pat and everyone would enjoy seeing some of your work.

Joe

[Northwest_Pat]

Appreciate the advice guys... The full size machines are very precise and you guys produce amazing work on them. Steve_G/myxpykalix: Good points. I spent a career dealing with tight tolerances on machined components, so I can get carried away. Having said that, the full size Shopbot machine repeatability are pretty close to the waterjet machines we buy at work that are several hundred thousand bucks ! And they don't have to deal with cutting forces.