So you've made the decision to build your own CNC machine. Congratulations. The remaining chapters in this book will provide you with the information to do just that. But before we begin, let's take some time to talk about this project because, frankly, it's a big one! The authors of this book have gone through this process (and in some instances, more than once), and there's a lot of lessons that have been learned-often from mistakes!
This chapter is going to provide you with tips, advice, and some much-needed encouragement. The completed CNC machine can be a bit overwhelming the first time you see a picture of it, but keep in mind that the CNC machine you'll be building is nothing but a large assembly consisting of smaller assemblies (and just a few of those to boot). Like the old joke "How do you eat an elephant?" you're going to see that the solution to building a CNC machine is in "small bites."
We highly encourage you to refer back to this chapter as you build your CNC machine. Those of us who have already built this machine have had moments of frustration. We've also made mistakes (and we'll tell you where in later chapters so you don't make the same ones). But we've also learned a few secrets and figured out a few helpful tips that we're happy to share with you so you, too, can have one of these great little machines to call your own.
In later chapters, you're going to be measuring and cutting a lot of parts. One thing we don't want to do in every chapter and in every paragraph is annoy you by repeating ourselves over and over. Only when we feel it's important that something be repeated or emphasized will we possibly assume the role of teacher and hammer in some concept again and again.
So, now that we've gotten that out of the way, we want to go ahead and give you the first bit of advice that you've probably heard numerous times in your life but applies so aptly here:
Your CNC machine will be made of MDF, a material that is very strong and easy to cut, drill into, and paint. But one thing you most certainly cannot do with MDF is join two pieces back together that have been cut apart incorrectly.
Tip
My editor politely reminded me to add an addendum to the "measure twice, cut once" rule-don't cut when distracted. It's too easy to make mistakes when your mind is on one thing and you're doing another.
The same goes for drilling holes. Many of the holes you'll be drilling into the MDF will allow for a little inaccuracy-but not much. If the holes require that you to drill 1" from the left edge and 3/4" from the top edge, there's not much you can do if you end up drilling 3/4" from the left edge and 1" from the top edge. It's likely that your only option will be to cut a new piece of MDF and drill again.
We'll remind you in the specific chapters when certain cuts need to be accurately measured. All cuts are important, but you'll find later that some parts require a bit more precision than others. Again, don't worry-we'll alert you to parts where you need to pay special attention to measuring and cutting.
So, just to be clear, when cutting and drilling the MDF for your CNC machine, remember:
Whether you'll be using a table saw or a handsaw, or a drill press or a small portable hand drill, it pays to always be diligent when working with tools. The authors of this book assume no responsibility for your eyes, fingers, and other body parts that are exposed as you cut and drill. Always read the instructions for any power tools you use, especially the safety information.
Note
Just as your CNC machine will be using a router to do its work, you'll be using a router to do some work on the CNC machine parts (see Chapter 7). A router is a powerful and versatile power tool, but it can also be dangerous. Read the instructions, but also consider having someone demonstrate its use at a nearby hardware store if you can. You can even make this a requirement for purchasing your router; tell the salesperson you won't purchase unless someone can go over its operation and safety.
Safety glasses are another absolute requirement (see Figure 3-1). They come in a variety of shapes and tints; buy a pair that feel comfortable since you'll be wearing them a lot. Don't concern yourself about how good they look on you, however. Some of the strongest, most protective safety glasses are the most ridiculous looking when worn. When you consider that drills can fling off material (wood, metal, or other) at super-high velocities, take no chances with your vision; buy a pair of safety glasses and get in the habit of putting them on every time you enter your work area.
MDF is a great material to build with-it's strong, easy to cut, doesn't splinter easily like plywood, and has a smooth surface that's great for cutting and painting. But when MDF is cut or drilled, it puts out a lot of dust. And that dust is not good for your lungs. Some MDF sheets contain minute quantities of formaldehyde! You don't want to be breathing that stuff into your lungs.
Purchase a couple of breathing masks (see Figure 3-2) from your local hardware store-they're not expensive-and wear one when you're cutting or drilling MDF. They can sometimes get hot or be a little uncomfortable, but you're not going to be wearing them for long periods of time.
Tip
If possible, buy the kind of mask that comes with a small piece of bendable metal that you pinch over you nose. It will prevent your breath from exiting the top of the mask and fogging up your safety goggles. You might also consider a mask that comes with a small valve on the front, which will also prevent fogging of your safety glasses.
You might find it of interest to know that there are many organizations and groups that are pushing formaldehyde-free MDF. It can be a bit difficult to find, but if this is a major concern for you, we encourage you to do some research and locate a vendor who can provide you with formaldehyde-free MDF material.
Take a look at Figure 3-3. This figure shows all the MDF pieces for the CNC machine except for the two sheets of 2'×4' MDF that will make up the CNC's tabletop (x-axis).
You can see that each piece of MDF has been given a letter. It's a little difficult to tell from the photo, but the letter is written on the front and back of each piece on opposite corners. (If you should accidentally trim a piece along any one edge, the piece should still be labeled in one other location.)
Note
In later chapters, we'll use letters to reference parts, instead of their actual names. You'll find the assigned letters in the Part Letter(s) column of the CNC machine spreadsheet and on each of the parts in the Parts Layout PDF files. Both of these files are available for download at www.buildyourcnc.com/book.aspx
Don't stop there, however. You're going to find as you build your CNC machine that it also helps to label the front and back of each piece (F and B, written somewhere obvious). This will come in handy once you start assembling your CNC machine and can't remember which side of a piece of MDF faces outward or inward; sometimes it doesn't matter and sometimes it does.
When you go to buy your MDF for your CNC machine, you'll likely find the MDF sold in 4'×8' sheets (3/4" thick). (To make things even more confusing, some MDF sheets are a little oversized, so you may find the measurements are closer to 49"×97"-an extra 1" on each side.)
The CNC machine you'll be building calls for using four sheets of 2'×4' MDF. You have two options here:
Buy a single 4'×8' sheet and trim it yourself into four 2'×4' sheets.
Ask the seller to cut the 4'×8' sheet into four 2'×4' sheets.
Most hardware/lumber stores do not like to cut MDF due to the dust it creates, but some will-it never hurts to ask. But make certain to ask them to trim them to 2'×4' sizes, especially if the single sheets come with a little extra material on the edges.
You may luck out and find a seller that sells quarter-size MDF sheets, precut to the 2'×4' size (see Figure 3-4). You may pay a little more per quarter-sheet, however. Trust us-it's probably worth the extra dollar or so per quarter-sheet, and the cuts will likely be extremely accurate and easier to carry (MDF is heavy).
The quarter-sheets in Figure 3-4 were priced at $7.95 per sheet when the photo was taken. Multiply that by four sheets and you get approximately $32.00. Compare that to a single 4'×8' sheet sold at the same location for $26.00. Not having to carry and cut that big heavy sheet: Priceless. OK, maybe not-but definitely at least worth the extra $6.00 if you can find the quarter-sheets. Also, keep in mind that pricing will very likely fluctuate from location to location; the prices we quote in the book may not match exactly what you pay.
Take a look at Figure 3-5. It shows a listing of the parts you'll be cutting along with their dimensions. Notice that some of the parts have identical measurements-either in width or length.
You can download the entire listing in spreadsheet format at www.buildyourcnc.com/book.aspx
Figure 3-6 shows one of the two PDF files that contain the measurements and part layouts for two of the 2'×4' MDF sheets. These part layouts are designed to help you make fewer cuts, as well as to help make certain that paired parts (such as the two gantry side pieces) are identical in size because they're cut together along one or more edges.
You can download the part layout files at www.buildyourcnc.com/book.aspx
This may not make sense now, but trust us-try and cut only the parts you need, when you need them. Look back at Figure 3-6. The two parts in the lower-left corner are the Y-Axis Rail Support and the Gantry Bottom Support. These two parts need to be identical in length, but this length won't really be known until you reach the point where you'll assemble the Y-Axis Gantry. See the dotted line running vertically to the right of these two parts? That cut can be made to separate these two parts from the rest of the MDF sheet, but it's not the final cut that's indicated by the solid line on the right side of both parts.
Download and examine carefully the part layout files mentioned in the previous section. You should see that each 2'×4' sheet is further divided into sections that can be set aside until the parts they will provide are needed.
Tip
If you follow our advice from Chapter 2 and read through the entire book, especially those chapters focused on the cutting and assembly of the CNC machine, you should be able to locate the parts you'll need first-the Z-Axis Rail Support and Z-Axis Bearing Supports, for example. Those parts are conveniently located in the part layout sheets for first cuts.
But we hear you yelling "Hey, Figure 3-3 shows all the parts already cut out!" Yes, it does. But what you can't see in Figure 3-3 is the frustration we encountered when we figured out (later, after this photo was taken) that we really shouldn't have cut out the Y-Axis Rail Support and Gantry Bottom Support until we needed them!
We'd also like to share with you another one of our big mistakes in the hopes that you avoid it. You'll be using two 2'×4' sheets of MDF to make the CNC machine tabletop. These two pieces will be chamfered (see Chapter 7) and bolted together, and should be flush along all the edges. Well, in our eagerness to get ahead, we chamfered both sheets, measured and drilled the top sheet, squared it up, clamped it along the left and right sides of the bottom sheet, and drilled the holes. And guess what happened? The bottom sheet, which we assumed was exactly 2'×4', was actually 1/4" wider than the top sheet, but we didn't notice that until we bolted the two sheets together-the chamfered edges didn't match up! (Not a huge mistake, but it slowed us down since we had to unbolt the sheets, trim the bottom sheet, rechamfer it, etc.)
The lesson to be learned here is to measure all your parts and make certain they match up with the dimensions found in the actual CNC machine plans.
It never hurts to double or even triple-check your measurements against the part layout sheets and the actual CNC machine plans!
You can do it! OK, maybe you need a little more than that. If so, go back and watch the videos of Patrick at www.buildyourcnc.com
Don't view this project as a bunch of hurdles to overcome. And don't treat it as a race. Take your time. When you get tired, take a break. When you get frustrated, take a break. Just remember that others have built this thing and so can you!
But let's be realistic for a moment and talk about some of the bumps you're likely to encounter on this trip. Did you cut a piece incorrectly? Don't freak out. First, take a short break and then come back. Take a look at the part layout sheets and you're likely to see almost half of a single 2'×4' MDF sheet unused. This isn't waste material-it's extra MDF for when you make a mistake. And you will-we're not going to lie to you. Whether you cut or drill a piece wrong, just keep in mind that you've got some extra MDF there. The only thing your mistake has cost you is a little bit of time. (And if you use up all your spare MDF, just remember that MDF isn't that expensive in the big picture.)
Did you drill a piece in the wrong spot? Again, don't get angry. You may find that you can drill the correct hole without any problems other than having that "bad" hole visible on your CNC machine. If you're a perfectionist, go cut another piece if it's going to bother you. If you don't care if your CNC machine has an extra hole in a part here or there, then just roll with it and try to be more careful measuring and drilling the next piece.
Do the pieces not "square up" properly or match exactly the way they need to? Take a step back and examine the problem. Did you accidentally flip a part, and maybe the drilled holes aren't lining up because you've got the back of the piece facing outward instead of the front? Can you loosen up some of the bolts you've already attached and fix the problem before tightening down all the nuts? We promise you this-if you've cut the parts to the correct dimensions and drilled the holes properly, you're likely facing something simple and easily fixed.
Throughout the project, be patient. Give yourself three strikes per work period-if you make a mistake, slow down and fix it before moving forward. If you make a second mistake, it's time to really pay attention to your work. If you find you make a third mistake, it's time to call it quits for the day and come back later. Trust us-your CNC machine isn't going anywhere.
Chapter 4 will provide you with some of the information on how your CNC machine will actually move and cut parts. It's not done using any extremely complicated devices. If you thought your CNC machine would be using complex hardware to move forward, backward, side to side, and up and down, you're in for a pleasant surprise when you see the simple solution you'll be building and implementing on your own machine.