ShopBot Variant Reference

[achevrier]

Hi folks, I'd like to understand how stock ShopBot configurations have varied over time.

The "What kind of ShopBot is this?" wiki article is useful, but I was hoping for more detail; for example, motor makes/models, controllers, etc. Basically, what differentiates one system from another?

Can anybody point me to a reference?

While my searches haven't turned up much, it's possible I'm missing the proper key words, so my apologies in advance if I've overlooked something obvious.

[Brady Watson]

There have been too many variations over the years to pare down to a neat list. Google Image searches of the various models in that list will be helpful for identifying the chassis and gantry configurations.

The controllers are proprietary - so there's not much info available there, although this may change at some point in the future.

Aside from the paint color, nearly everything has changed over the years...

Not to be trite... Are you writing a book? Are you looking to purchase? What's your angle?

BTW...Welcome to the SBF

-B

[achevrier]

Brady,

I'm coming at this as a hobbyist with an obsessive streak who's logged a lot of hours on an alphastep PRT of indeterminate vintage at a makerspace and is looking at maybe getting his own shopbot.

Knowing more about how the tools have changed over time would help me understand the used market better. In particular, the relative merits of different machines. I've got a rough sense but I frequently find it difficult to judge the value of a used shopbot. Especially older ones.

Anyway, thanks for the welcome. Longtime lurker, first time poster. This is a great forum and I appreciate your response.

[Brady Watson]

I wouldn't consider purchasing any used tool older than a PRTAlpha with 7.2 motors on all axes, or a PRT Standard with the 4G control box. If you bought a PRTAlpha with direct drive AS911 motors, you could put a 3:1 belt reduction on it to get it up to 7.2 motor specs (even better actually).

The PRT rails are soft and wear. They need to be dressed with a file from time to time to keep them smooth. PRS tools, Standard or Alpha have hardened rails, I-beam gantry and a few other updates. If you buy a used 4x8 or larger tool, make sure it has at least 6 legs. The early PRS had 4 legs that caused a sag in the table. It is a problem on AL-extrusion sided 4G PRTs too. This is not a problem on an all-steel PRT. Early PRS (and early BT32) had a less than desirable Z axis configuration.

4G and RBK are very similar. These are found on the Standard tools to this day (RBK).

AS98AA-7.2 are on some PRTs and all PRS Alphas to this day (AR series)

I've owned all but the cable drive. It pretty much boils down to what you need/want. Accessories greatly increase the price of these tools.

-B

[barrowj]

Brady,

I have a used 2005 PRT Alpha with the AS911 motors, what is involved in upgrading to the 7.2? Always thinking about performance improvements and when I see someone such as yourself (with all the experience you have) recommending something I give it thought.

Joe

[Brady Watson]

There was a point in time (circa 2007 or so...I think) where SB offered a value priced upgrade where you would trade in your 1:1 motors and drives in exchange for 7.2s and drivers for around $1500. This included the motors for X & Y. There was an additional fee to include the Z axis for those that did a lot of 3D. That time has come and past - and the cost to upgrade is probably quite a bit higher. You'll have to contact SB directly for pricing.

Rather than switch out your original motors, it is possible to do a 3:1 belt drive to get your UV in the 3800 range, up from around 1270, while still maintaining fast rapids. This equates to 3X the torque and 3X the resolution, without really giving anything up. It is 1.5x finer resolution than the 7.2s. You'll get smooth cuts in plastics and dense materials and have limited to none, 'dime edge' parts. You can make your own (others have done this...and posted pics on the forum) or have someone make them for you. It will be like a new tool again...and you can run a 30T pinion, which will last WAY longer than those little 20s.

-B