Here are some frequently asked questions regarding this particular CNC machine guide:
Q: How difficult is it to assemble the machine?
A: I have done everything to make this process as easy as possible. If you follow my recommendations, you will need only those tools listed in the tools list. I think that everybody can use a screwdriver and a hex wrench. Assembling machine is not much more difficult than that. Squaring and aligning the machine is a bit more difficult and requires attention, but this is not something that cannot be done by a patient DIYer. Literally hundreds of high quality photos are there to help you with every step. I will also provide support via e-mail in case you are really stuck somewhere.
Q: How much would it cost me to build the machine?
A: According to my calculations, the basic price of this CNC machine is 1980$. This price does not include router motor, computer, software, fasteners and shipping. You can save approximately 210$ on machining if you can cut, drill and tap the extrusions yourself. You can also save some money if you buy, cut and drill steel rails yourself. You can save another 20-30$ if you choose to use unregulated linear power supply instead of switching one (I do not recommend it though). Assuming the 1980$ basic price (and depending on where you live) the full price will be around 2400-2500$ without a computer and 2900-3000 for an all-included version (in case you do not have an old PC to hook up to your machine). This may sound like a lot of money, but I assure you that you will find that the price of almost any commercially available machine with the same (or the like) specs starts from 4500$.
Q: Are there any modifications to the current design that can make the build cheaper than it is now?
A: Well, it is always possible to make something cheaper. The big question, however, is how much is compromised comparing to cost savings. You cannot really save on linear motion components because they are available from one supplier only. Thus, the most reasonable solution is to use less extrusion for machines frame. You can probably redesign the frame and use 1515 extrusion instead of 1530, gantry supports can be 1530 instead of 1545. You can also replace 3030 extrusion with 1530. However all decisions should be carefully justified - you can make machine less rigid and it will not be able to perform some tasks (as cutting metals with acceptable quality for example). Stripping milling machine of additional weight is not a good thing too. It may cause additional vibrations and even movement of the machine itself during operation. I suggest that you weight all decisions carefully before making any changes. There is always a risk of saving 200-300$ and building the machine that will not operate to the required specs. At that point, a big part of your money (hundreds or even thousands of dollars in parts and design time) will be wasted.
Q: Is it possible to use metric extrusion for the build?
A: Unfortunately, no. The particular linear motion components that were used in the machine, are designed for the 15-series extrusion made by 80/20 Inc. (imperial). There is no easy way to substitute this extrusion without considerable redesign of all linear motion parts.
Q: Do I need to perform any calculations while building the machine?
A: Being a musician (sound engineer) by trade I know how difficult it is to "get through" all this math and technical stuff. Fortunately, you will not find any of that kind in this guide. I am not saying that math and mechanics is not needed for CNC machine design, but I worked hard to leave all that "behind the scenes". If you want to know more about CNC milling machine designs I encourage you to dig through special literature and learn all the details yourself. Here you will not find anything too complicated that cannot be understood by a regular man or woman.
Q: I need my machine to move faster. Can I use double- or five-start ACME screws instead of single-start screws?
A: Yes, you can. Please note, however, that while you gain in speed (2x faster with double-starts or 5x faster with five-starts), you loose resolution (2x with double-starts and 5x with five-starts). Double-starts and five-starts require more torque from the motors as well. This may be not a big deal if you are doing woodwork and are not planning to machine metals. However, if precision is a concern, I highly recommend using single-starts. If you choose to use double-starts or five-starts, update the BOM accordingly (you will need appropriate ACME nuts, thread clamps and shaft couplers).
Q: I need my machine to have smaller/bigger working area. Do you have plans for my dimensions?
A: Unfortunately, no, I cannot provide plans for your particular dimensions. However, it is possible for you to adjust the dimensions of the machine to your needs yourself. This type of design is scalable and can be tweaked to your needs. The easiest part to "play" with is Z-axis and Z-axis to table clearance - you will need to adjust the gantry legs and slightly modify the head assembly. Now, X and Y-axes can be scaled down easily. The X-axis upper limit is 29" though (with stock components). Extending it further will require considerable modifications to the current design. I cannot tell you Y-axis upper limit right now. But at some point, it may require to incorporate additional support for the table. This can be accomplished by adding more linear carriages, moving the steel rails to the outer edges (instead of inner edges), and reviewing the gantry legs attachment. At some point, it may be wiser to switch over to the moving gantry design instead of moving table design. When scaling down you may want to strip the machine of some enforcing elements or even review the base and table design. This may be especially useful for light-duty machines (like PCB-drilling and routing machine and the like).
Q: I would like to use ballscrews instead of ACME screws. Is it possible?
A: Yes. In theory though. In order to use ballscrews you will probably have to revise all the bearing blocks, you will also have to redesign the mounts for ballnuts. This may lead to redesigning the bed and/or the table too. This is a lot of work but it can be done. You will probably need another CNC machine to produce all parts for your machine. Remember though, that the first goal of this design is to have no hard-to-get or hard-to-work-with components. If you have access to another CNC machine, you may adjust the design to your needs and incorporate your ballscrews into this design. However if it is your first attempt at DIY CNC machine, I suggest that you build the machine as is and then design another one that will use your ballscrews. You can then mill parts for your second CNC machine with this one.