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View Full Version : Shopbot vs the rest?



Jerry Mah
11-09-2007, 2:00 AM
My brief experiences with CNC routers have been with the following manufacturers: Larken, Denford, and Techno Isel. How do the Shopbots fair against the competition? What are some of the pros and cons?

Tom Galzin
11-26-2007, 11:35 PM
Every machine maker has an idea of where, on the price performance curve, they want to target. All machine builders today are reputable so it is a matter of trying to seperate the sales talk from the fact. Start by a gereral comparison of construction methods and components. This is a very non partisan way to grade machines, and the service life. First compare the frame, steel or aluminium. All the upscale machines, and I'm talking 150K and north are steel. Steel is more temperature stable than aluminium and is a better at vibration dampening (from cutting). The downside, for the machine builder, is that the equipment for cutting steel frames is more expensive, and slower that aluminium cutting machines. Tooling up

Next point of comparison is how is the frame assembled... bolted together or welded into a single piece. Welded is prefered because the stiffness is greater and accuracy is machined into the frame. Things like squareness and parallelism are locked in at the factory.

Look at the linear guide system. An ability to preload the bearings is key. "Profiled rails" use an interference fit. Think of it as your grip on your hand held router. If your want a nice cut you white knuckle the handles. A loose hold on the handles impacts your quality of cut. Again look upmarket, what do the most respected machine builders use?

Also compare spindles, and controls. I give you my thoughts on those if you'd like.

Full disclosure: I work in the industry for a company that offers CNC routers from around 20k to over 200k.

Keith Outten
12-12-2007, 10:11 AM
I have deleted a couple of posts in this thread because they were not on topic. The question is how ShopBot compares ot other CNC machines including pros and cons. This is not an open opportunity to link to manufacturers and sales web sites for the benefit of free advertising.

Keith Outten
12-12-2007, 10:23 AM
Jerry.

I can't offer much in the way of advice concerning a comparison between ShopBots and other manufacturers. I do own a ShopBot and I run another ShopBot at CNU so you can see I am a real fan. I know there are other manufacturers of quality CNC Routers and I hope people will chime in and provide some useful information.

It might be helpful if you could narrow the price range of the machine you are interested in, the prices of CNC machines can run from the basement to the sky these days. Are you looking for a machine for commercial work or something to run at home?

ShopBot concentrates mostly in the lower price range of CNC routers. They now ship more machines per month than any other manufacturer. Obviously, ShopBot is very popular with small commercial shops and even hobby shops now that they have introduced their "Buddy" line of routers. If there is a machine in their price range that is comparable in features, price and quality I would like to know more about it myself.

.

Neal Schlee
12-15-2007, 7:13 PM
How many do they ship per month? :)

Ed Lang
12-16-2007, 10:10 AM
How many do they ship per month? :)

I don't work for ShopBot and am only repeating what I was told by them to the best of my ability to remember something after I sleep:)

Oct 2007 = 30 machines

Nov 2007 = 32 machines.

Tom Galzin
12-16-2007, 2:32 PM
I have run CNC router spindles for about 30 years and the spindle is THE part of the machine that takes he most wear and tear. The MTBF (Mean Time Between Failure) is a good measure of expected durability. If you consider that a 24,000 rpm spindle is moving at 400 revolutions per second it easy to understand that the enemy is heat. To counter the effects of heat a better quality spindle will use a ceramic bearing. Ceramic ball bearings offer serveal benefits. First is it's much lighter than a steel ball, about 40% lighter. The lighter weight yields less centrifical force, and thereby less friction. Less friction = less wear. Next is thermal expansion, ceramic expands less as it heats up, much less than steel. Remember that the spindle bearings already have a preload, so keeping the preload constant, even at operating temperatures further reduces the running temperature. Lower temperature = longer life. Lastly is the hardness of ceramic, approaching that of diamond. The harder the bearings the less deflection under load, (technically it's called Youngs modulus of elasticity). Ceramic is 50% harder that steel. So a ceramic bearing spindle will outlast a steel bearing spindle by at least twice. The down side is $$$. It costs more.

Look at the average of a "hand router" motor. It's something like 200-300 hours. A "spindle" is good for something like 1000 hours.

There is one way to really extend the life, and that by adding an ACTIVE cooling system to the spindle. There is only one company that does this as a "standard" spindle. The company is CAM-WOOD. The active cooling is a "jacket" around the spindle. Then a pump recirculates coolant around the spindle. It is not unlike the system used in your car. A series of ports in your engine allows for coolant (antifreeze) to recirculate via your water pump. This spindle has a MTBF of 10,000 hours.

Steve knight
12-16-2007, 2:49 PM
it is a good machine for the price. it has more power then the other two brands I looked at like shop sabre. they have more speed to. all of the lower end cnc's that use screws for drives are pretty low and seem low on torque. being able to jog at 1200 ipm makes a big difference in time in cutting.
a welded table would be nice. but you can make the table accurate with effort. I notice too that most of the companies charge an extra grand for the same hsd spindle. you can buy a colombo for less then most sell the HSD.
but the biggest thing with a shopbot is the support and the forum. it is very easy to get the help you need fast . this is pretty important when you first start out. Plus it is easy to work on a shopbot parts are easy to get computers are easy to change.