Always a Newer and Better SHOPBOT!!!

[bwclark@centurytel.net]

Bitbreaker,

Couple of things....

First, the Gecko G340 would be a better choice for the servo drive. First since the SB is limited in how fast it can output steps per second the G340 with built-in pulse multiplier would work MUCH better. It is also only $30 more than the standard G320.

BTW, I can vouch for the DC servo drives. They ROCK! I have used them, but not on a ShopBot.

Second, while Dan Mauch's motors are very nice, you can often do a lot better by checking on such places as Ebay (use such search keys as "servo encoder", "dc encoder", "encoder motor"--these will turn up a LOT of good hits), local surplus houses (Marlin P. Jones, Electronic Goldmine, ect), or even your junk box/drawer--a lot of old printers and vinyl machines contain dc servos with quadrature encoders.

Last thing, the encoder that provides feedback is also the "weak" link, as they are VERY susceptable to contamination. Most quadrature encoders are HP, while very good, rely on the motor manufacturer to seal it from contamination. Well, most of the motors that I have seen/own would not seal out the kind of dust my Shopbot makes. So, in this aspect, steppers are better!

Just some thoughts...

Bruce Clark
bwclark@centurytel.net

[danhamm@abccom.bc.ca]

It seems awfully quite on the forum!
I have put a few pics. on my website "Bruce"
some thoughts on them? maybe we can get some action going for the weekend..

http://www.burningimpressions.ca/fixit

[bruce_clark]

Don,

Just some quick calculations...

To retrofit a 4 x 8 Shopbot with the LM rail with
built in rack (at the price you stated) would be
$7500 canadian. Kinda expensive, but otherwise
that is very kool.

Check on places like Ebay for rails and guides for
surpluse motion control parts. You could get your
whole machine "upgraded" for a lot less than just
the the price of the rails alone.

Bruce Clark

[danhamm]

I have no intention of upgrading my bot..other than the "Z" axis its the pr series..
My math is a little different than yours,
Rack and rail 312.00 x 5
LM stabilty rail 184.00 x 5
12 pads x 87.00
24in. "Z" axis screw.412.00
5ft 4x12 extruded box aluminum "X"axis"new"
2-2x12 channel aluminum vertical rise for"X" azis
don,t know prices on this..
vexta pk296 300.00 ?for "Z" axis
=$4236.00 + taxes
with agood base under it, would be as strong and
as accurate as the 1.2K machines..
I spent a day as a guest in the University of the north. they have 2 cnc's,I came home more impressed with the shopbot's simplicity.

Dan Hammerstron

[olivier]

Hello there,
Speaking about upgrading, I am considering going for the new shopbot with ball bearings and welded frame. Is there anybody out there who has upgraded from the carriage wheels and bolted frame ? Is there a real difference ?
Also, I read on a posting earlier, that the motor where being offered with direct drive, (no gearbox would mean no backslash and maybe a very different noise) , but that later on, because of supply problem we are back with the gearboxes . What is the situation now exactly as far as the backslash is concerned ?
And what about the noise? Is it still this kind of harmonic cranking cum vibration ? (I am about to buy a very silent Perske Engine that should enable me to hear it )
Also I read on the shopbot web site that the max cutting speed with force is 100"/min ie 1,66"/sec.
I personnally regularly cut at more than 2"/sec without problem. Is there a trade-off of speed for precision in the new tool ?
Comments from Shopbot would be welcome.
I think the three areas improved : rigidity of the frame, get rid of the wheels, and the backslach of the motor are the only limits I see in my tool today. That would make the new shopbot close to the perfect tool for the price then...
Olivier

[cmrtom]

The new photo of the shopbot on the website has a very nice looking router..........what is it, how much is it, and where can you get them?

[bwclark@centurytel.net]

Mr. Foster,

That is a Persky router. Not sure the exact HP but looks like a 2 or 3 hp unit. They suppose to be quieter and more heavy duty than most other off the shelf routers, but the downside is that they start about $2K, require 220V/3 phase power (depends on model and if you get a variable frequency drive unit--which electronically controls RPMs).

If you can live with the noise, it is still hard to beat a Porter-Cable 3.25 Hp router. Inexpensive to buy, service, and you can buy a new one when the old one gives up the ghost at most Home Labyrinth stores.

Bruce Clark
bwclark@centurytel.net

[olivier]

Hello there,

I am planning to set up a Perske 5,5 HP on my bot, Weights 16 Kg...
Will the z axis handle this weight ? Should I modify the compensation with the strings ?
Any experience welcome.

Olivier.