Todd...
I tried my best to avoid this thread. You did PM me and since I have not owned either of the machines in question, I did not comment. When he asked about a previous negative comment, I would simply stand by those comments. I don't know if you have figured it out yet, but we (other CNC users) cannot give you the answers that you request. That would involve us making a decision for you. Think about it.... it's the freakin internet!
If you want to know my opinion, read the thread I wrote on the CAMheads forum in the FAQ section titled "Buying a CNC? Do your homework!"
In my opinion, most of the assumptions you make are not the ones that I would make. Also, following the lead set by most pre purchase CNC wannabees, the vast majority of things that concern you now, will not be the things that concern you once you gain experience. Many of your questions (to me) are similar to " are brand A apples better than brand B oranges?" In other posts you answer most of your own questions with other questions. That said there are few questions that I can answer.
An air counterbalance allows a faster response from the Z axis be "counterbalancing" the weight of the Z assembly. Noticeably faster 3D cutting, if you do that sort of cutting and allows faster retracts without loosing steps. The Z axis still has to fight mass and inertia, but not gravity.
Steel vs aluminum: Equally sized steel is cheaper and stronger. Steel costs more to machine than aluminum, virtually eliminating any savings. So the real questions are: Are they equal sized? Do they have similar machining? Are the surfaces for the rails machined and set to datums? Do you actually think either of these companies would produce a gantry that visually deflects and still be in business?
Gantry height: All things being equal increasing the gantry height will always increase deflection. That deflection will seldom be in the gantry beam, it will usually be in the side plates. That's why stronger gussets are usually provided. In most cases the collet nut will travel to the factory table, as there is a couple inches of unused travel on the shorter heights .
Spring loaded tool measure switches are always better than the flat plate conductive type.
If you have questions about the control components find an online picture or have your sales guy provide one. You will want to know if they are using good products and methods.
It does not matter if they mount the rails on the top of the frame, bottom or side. What matters is how rigid are the connections, are they precision machined and how strong are the components.
In reality, most of us do not know the answers to most of your questions, as they don't matter much. Take linear bearing blocks for example. The maintenance you perform will have a much greater effect on their service life than the brand. Only a companies salesperson will tell you that brand A is better than B. In most cases we cant. Like Mark says, most here are biased towards the brand they purchased, just like he is.
Like most before you, you are suffering from "paralysis from analysis" Find a machine you like from a company you can trust, and order a machine!
Last edited by Gary Campbell; 03-09-2018 at 11:52 PM.
Gary Campbell
CNC Replacement & Upgrade Controllers
Custom 9012 Centroid ATC