Sliding Table Versus Gantry

Pros discuss which type of CNC equipment is better, units with a sliding table or units with a moving gantry. July 21, 2006

I would really appreciate your collective views on sliding table versus gantry. We are in the specialized cabinet business in South Africa and have looked at Multicam, Thermwood and SCM.

Forum Responses
(CNC Forum)
From contributor P:
Sliding gantry - less stable, a lot of weight moving around. Having said that, the model 70 Thermwood with its moving gantry is more stable than the Model 67 counterpart that has a moving table. This was achieved through a bigger and heavier gantry. The maintenance would most likely be more for a moving gantry simply because of the amount of weight that will have to be moved. There is a new machine that Thermwood may have already released called the Model 90 that incorporated a heavy duty gantry and a moving table, the best of both worlds. Talk to a Thermwood rep.

From contributor M:
Given the choice of the three mentioned, I'd go with SCM. I think they are still using Num controls, which have served me well. I prefer moving tables with a fixed gantry. Next step down is moving gantry fixed table. Lastly open frame (C) and fixed table.

From contributor A:
Another thing to look at is how much floor space you have to put a machine in. A moving gantry machine has a considerably smaller footprint than a machine with a moving table.

From contributor J:
We have a Weeke with fixed table. No problems with whip in the drive on x-axis. Drive is digital encoders on both sides driving off long racks. Smaller footprint than sliding table. If you ask me, the gantry has less mass than a 5x12 table flying around. For the above reasons, I think fixed gantry is on the way out, at least for panel processing.

From contributor B:
How does the price of the moving gantry compare to the moving table? I'd think that there would be less engineering involved in developing a moving table system that is solid and stable than the same with the heavy bridge whipping back and forth on a moving gantry. That should, at least theoretically, make for a lower price. I'd really be curious to hear what others have to say about that.

Floor space, as stated above, is also a key issue. If you have it, then you have a choice... And since you are contemplating the two options, I would assume you do.

From contributor J:
If you look at new flat table nesting machines, like Komo, Weeke and others - they are fixed table, and the reason is they are cheaper to build. The rack drive with digital encoders on both sides is extremely accurate and easily handles the weight of the gantry, and is superior to ball screw over a 12' span. What will attract most to this design is the footprint, even if you have the space. Why waste it if you don't have to?

From contributor E:
A fixed table moving gantry that is driven from the center under the table with a spinning ball nut is the best of both worlds. Eliminates the rack, and skew of the gantry, and no whip of the screw since it is fixed.

From contributor T:
You're looking at some good machines. Perhaps the most important aspect of your decision will be some combination of how the machine will be serviced, and how you will program the machine with software.

I think you will find that some manufacturers will sell only what they make as the best approach, while other manufacturers who build all types of machines can give you more education on the best aspects of each type.

From contributor O:
I have worked with both types of machines. I found the fixed table models to perform better than the sliding table machines. I have always preferred to move my tooling around the material, not the material around the tool. It is important not to have any backlash on your machine. Purchase quality machinery. Talk to Homag.

From contributor S:
We use a CR Onsrud Panel Pro. It is a gantry, it is fast, perfect, simple, and a workhorse. It cuts, drills, dadoes, and labels 30 to 70 sheets a day.

From contributor L:
We've had both moving gantry and moving table. Seems like, if well designed for the mass they have to move, either is fine. I've never had a cantilever arm type and they always bothered me, but I know of those machines that have been running for years perfectly fine. Is anyone else amazed at the acceleration rates on the new machines? Seems like the stresses would be huge. We only run at 900"/min. and that looks plenty fast, but I've watched machines run at twice that and still hold good tolerances. Rate of wear?