Getting Started for the Beginner

You’ve got everything ready for your CNC Router/Mill, Now what do I do?


Jogging: You may be staring at your computer screen for your router/mill and asking the question, “Now what do I do?” The answer is easy, jump in and get going! I like to start off by finding the jog commands and jogging the machine around to get a feel how the machine moves and how it sounds. In machining sound is very important, it usually lets you know when something isn’t right like spindle speeds, feed rate, oil, etc. You should have two or more speeds to jog in; high and low.

Cutting while Jogging: Next I would try out your cutting spindle manually. Secure a work piece to your table top and take some practice cuts while jogging your machine around. You will get an idea of what that sounds like and how much you can easily remove in a pass. I would start small at around .030 for your plastics and wood. If you try aluminum I would start at around.010”. Your standard jog rate should be slow enough to produce some good cuts in your material. Doing things like this will get you more comfortable with your machine and you can build some confidence from there.

Your First Program: Start with a very simple program maybe even one that was given as a sample file with your software. You need a baseline of what will work and what will not work when it comes to codes that the software recognizes. The most important parts of your program are the starting and ending code. The starting codes create the settings that the rest of the program will follow like absolute, incremental, metric units, English units, fixture offsets, etc, etc. It also specifies the safe starting position of your tool so that crashes do not occur. Your ending code is important as well because it turns off any thing that needs to be turned off (spindle, coolant, mist spray, etc.) and then sends the tool to a safe location for the end of the program. I will discuss CAM software later which helps with programming substantially.

Crashing Your Machine: Most people will crash or wreck their machines; it’s a fact of life. We are going to assume that we are using a table top sized machine and not some huge industrial CNC machine that will cost $30,000 to fix if it is crashed too hard. First things first, you must know where your program stop button is! On almost every PC based system I have used it is the ESCAPE button. When running a new program, always keep your finger above that button. Anytime you crash a machine you will need to redo your set-up (we’ll discuss set-ups later). Usually what happens in a crash is that you break your tool bit and cause your stepper motors to skip steps. Once that happens you will need to go back and retouch on your new tool bit and relocate your program start. If it is a bad crash you might have some repairs to make to your machine.

Home & Limit Switches: Do you need them? If you are a beginner I would say no. Limit switches are nice but unnecessary. You just have to know where you can cut and where you can’t cut without running out of room. These switches are needed on large machine with tool changers and encoders to help keep track of where everything is. When you run a program you run it from the program zero which is set on your work piece. When you create your workpiece zero, the program could care less where the Home location is. I would recommend them if you have a large machine where you have multiple fixtures and multiple set-ups for running different programs with different fixture offsets. Most hobbyists just don’t need the added expense and hassle of wiring limit and home switches into their driver boards or breakout boards and the setting them up in the software.

Part & Tool Set Up: Basic set ups are very easy. If you are cutting a circle, jog your machine to an area of your work piece that is clear to cut on. Make sure your work piece is securely fastened down with clamps, holding screws, double sided sticky tape, etc. All programs will start at the programmed zero point. You must know what this is before you get started. On a circle, the center of it is usually the zero point. For a simple set-up jog to a clear area that you know your circle will fit into without the spindle cutter hitting anything. You then go to your software and zero out the x and y axes. Next you slowly jog your z-axis down until you touch the top of your work piece with the tool tip. Do this very slowly so you don’t break the tool or ruin the material. Now zero out your z-axis in the software, move the spindle to a safe starting distance and hit start.

DXF’s, CAD, & CAM: You now are getting comfortable with your machine and you want to start cutting the things you need for your business. Hand programming should be dead by now. You can still do it but it just takes too long and making changes on the fly is a nightmare. Your PC has CNC control software on it that takes the G & M codes and converts it into motor code so that your motors cut what you want. If you don’t have CAM software you will definitely need it. Some CNC software comes with basic CAM software but having stand alone CAD/CAM software is the way to go. If you have a product you need to get a drawing of it if you don’t already. This will be your CAD file created on some sort of CAD software. You will save this file as a DXF file which can be imported into most CAM software. Your CAM software will then generate your G&M codes based on of this file and your inputs into the CAM software to generate the best path. You will then “post” your G & M code file and you take that to your machine and run it. CAM software is great because now you have a file for that part and your customer wants you to make it out of plastic instead of wood. Don’t start changing 1000 lines of codes by hand to fix your feed rates and depths. You will go back to your original CAM file. Perform a “file save as” and then make a few edits to the program. You will then verify the program with your software and repost the file and you are done. You let the software do the changes instead of yourself. Modular CNC is now selling Dolphin CAD/CAM Level 3 Software at a great low price to help with your software needs.

Value Design & Engineering

One of the main things that I pride myself in is that I was taught the great process of “Value Engineering” in a machine and tool design environment. The dictionary definition is very wordy and long winded so I will talk about my experience as a young designer. I had a great opportunity to start as an entry level detailer at an engineering company back in the Mid West. This was great because since everybody new I was entry level they were all willing to teach me all they could. I learned as much as I could, soaking everything in like a sponge.

In tool design, Value Engineering meant to design the best machine using the least expensive materials and components that didn’t require expensive processing. My favorite analogy came from the general manager of the company. He said, “Anybody can design a BMW. You take the best parts and components, put them in a car and the result are an $80,000 car that will run for 200,000 miles. You want to be like the Ford Escort designer that takes affordable parts and components, puts them in a car and the result are a $13,000 car that will run for 200,000 miles.”

I really related to that analogy and understood its meaning. A classic example is the oil impregnated bearing. The bronze/cast iron oil impregnated bearing has been around since the industrial revolution. Lathe spindles started off having bronze/babbitt bearings which helped fuel the industrial revolution. Its very easy to use the nice looking expensive fancy stuff but if you check the load ratings versus your application you can find a lot more affordable items that you can substitute in place of the $50.00 roller ball bearing.

Alot of my designs may not look very sleek and attractive but they work and they are strong. I try to verify that for everybody by taking videos of my machines cutting different materials. I like to show them taking large cuts through material because this shows the heavy duty capability of my machines.

New Product Release, CNC Mini Milling Machine!

It's been a little while but I was busy filling orders and doing some more R&D work. I just completed our newest product, the Modular CNC Mini Mill. Perfect for people that want a small machine to get started in CNC programming.

I am also working on a nice programming guide that will be great for the experienced and the beginners. I've gotta get to bed.

Andy

Why You Need to Learn CNC Now

When is the last time you had something quoted by one of your local CNC job shops?

Here in the Albuquerque, NM area, shop rates have risen to $60 - $100/per hour and I think that is being very conservative.

When I got my first job in manufacturing and design, shops rates and engineering rates were $40/hour in 1995.

I think we are only at the beginning of this phase. You must also remember that the baby boomers have started to retire and will continue to retire very quickly as we approach the next few years. I have worked with a lot of very talented boomer machinists. They are the ones that have taught me the most about precision set-up, speeds & feeds, and just all around common sense in the shop.

I am a generation X'er. I look around at my peers and they are not technical people. They went to school to be doctors, lawyers, teachers, accountants and high end engineers. Most of these guys/girls probably have never tapped a hole in their lives. This is what I have noticed and it is probably the norm from state to state.

Here is another factor to consider. The manufacturing industry in the USA has taken a beating, lots of jobs lost and moved out to China/Mexico. This means alot of people have lost their jobs and gone on to other careers or retirement.

Considering all of the information above I believe soon we will see the "Machine Shop Perfect Storm". This is when shop rates will rise even higher and lead times will become even longer. Good machinists will be in high demand which will drive up shops rates even higher. Now is the time to start learning CNC!!!

The best way to learn CNC machining is to stop your career/life and enroll in a 1 - 2 years long college or tech school program. Then follow that up by another 1 - 3 years as an apprentice at a shop.

Most of us are already in careers and have full time jobs. There are also alot of people that don't live close enough to a school to make this an option. What are you to do!

My suggestion is to buy or build your own cheap CNC router for learning. That will be the fastest way for someone to learn CNC programming, set-up and operation. This is not some long wind sales pitch, this has been my thinking about the industry for the past few years. The nice thing about learning this way is that you can do this on a shoestring budget and when you are done learning and are capable on not crashing on every your machine, you unbolt the motors from your starter machine and bolt them (along with the other electronics) onto your next size up or better material machine. Some peoples websites have said "Don't start with a starter or beginner machine, buy or build the right one the first time". That is a great statement but who wants to crash their really nice big machine the first time they hit the cycle start button. I would much rather plow my spindle into the top of my MDF top plate than into a large aluminum/steel plate. Learn your lessons with an affordable machine to repair and replace.

• Modular CNC MDF X-axis top plate, $25 replacement cost (you really just need to cut a piece from you own stash of MDF and match drill the holes and you just fixed your machine)
• Modular CNC Aluminum X-axis top plate, $95 replacement costs

Once you have your starter CNC router, software, electronics box, PC, and motors, I would spend about 4 - 8 hours just playing with your machine and software. Jog it around, manually cut something, click on all of the buttons int he software. Ask your boss if you can go out to the shop and do that with one of his machines. I am sure he'll say no and want that spindle cutting instead of sitting still (standard job shops).

Next up is programming. Go out to the web and download a copy of the standard G & M codes. HaasCNC.com has a nice free download of standard G & M codes. You must live them and love them, be one with the code. I tell people that you need to be like the people from the movie "The Matrix". When they look at the computer code they see "people, places, and things". That is how you need to be, instead of seeing G & M code, x..this y...that, you need to see the machine movement and know what your machine will be doing next. This is very helpful during initial progrma set-up and tryout. Once your program and set-up is proven you can just let your machine run.

Another programming tip is to make sure you get a cool CNC software like Mach3 that includes a CAM program like Lazy CAM. This program lets you upload DXF files to it which it then converts to G & M code automatically. Here is the really slick idea, go to eBay.com and do a search for DXF files. You can buy pre-made DXF files in bundles that have common themes like western, flowers, fishing, etc, etc. You take these files, upload one, covert to code, do a quick part zeroing and cut something. Here is how I have learned alot in CNC programming. Go back to that same program without removing your cut part and run in step block mode. This means that it will run one line of code at a time when you press the start button. This lets you see what each line does. I think this is very important because it lets you become very comfortable with the code, your software , and your machine.

This isn't going to be an overnight learning process. You still need to know about quick, fast, and accurate set-ups and most importantly Feeds & Speeds. A few quick tips: start slow with your feedrates, rough spindle speeds: wood 12,000 - 20,000 rpm, plastic 4,000 - 8,000 rpm, aluminum 2,000 - 7,000 rpm, steel 200 - 2,000 rpm. Those rpms vary depending on your cutter size and # of flutes. Remember when cutting, heat is our enemy, aluminum and plastic like to melt. Nothing melts them faster than too heavy of a cut at 10,000 rpm. If you have seen my aluminum cutting videos you will notice that when I cut aluminum, my rpms were very high due to the cheap spindle I was using but it cut because I was taking a light cut. In the MDF cutting video I take a very large cut of 7/16 deep and plow right through it like butter. That is because the wood likes the higher rpms.

This is all for now. I ahve to go to sleep.

Andy

Your Custom CNC Router

Modular CNC offers a nice and affordable standard line of products but don't be afraid to ask about a custom application that will fit your needs better. We have over 12 years of experience in designing and building custom machinery for people. Email us with anything you may need.

The "Other" Modular CNC

There is another small business with the name of Modular CNC on eBay. So far that is his only selling venue.

My eBay user ID is modular-cnc

We are not related in any way. I believe I got the domain name first and before I thought about it he got the eBay user ID of modularcnc.

He sells circuit boards and other related products and is located in Canada.

www.modularcnc.com is located in New Mexico USA and sells mechanical components for CNC routers and mills.

CNC Router Accuracy

This is a great topic because everybody wants to know how accurate of a machine that they are buying or building. Here is some helpful information to consider.

• Accuracy in any simple CNC machine boils down to one thing. The accuracy of your lead screw or ball screw. There are of course other factors but in the end this is the big one.
• There is also some softwares that allows you to "map" your ball screw so that you can adjust your machine to be more accurate. This is done by almost all CNC manufacturers out there.
• Servo driven machines are no different because they work with a rotary encoder that trusts the accuracy of the ballscrew.
• The other factors that aafect the accuracy of your machine are heat, moisture, wear, tightness of srive components, and backlash in the drive system.
• Here at Modular CNC we handle backlash using a double nut system and a little preload.

I hope this helps explain accuraccy during your machine build.

Thanks, Andy

Getting Started with CNC Routing

Here is a quick guide to getting started in CNC Routers. These are some of the main items you will need.

• Spindle: Harbor Freight 1/4" Laminate Trim Router (2.5" body diameter)
• Shaft Couplers: To couple the motors to the screw shafts look at I have them available on my website. You can also try http://www.mscdirect.com for shaft couplers. You can also find them on eBay as well.
• Electronics package: http://www.xylotex.com/ and others. The type of electronics package you get will depend on your level of electronics experience and what you want to do. I like Xylotex because you can buy a complete finished controller with motors or you can buy just the board and get the other items you need separately (motors, power supply, fan, enclosure, etc.).
• Software: You should use the software that works best with the electronics kit you choose. They will have recommendations.
• PC: You should use the type of computer that is recommended by the software. Some need an older computer that boots in DOS mode but there are others that can run on XP.
• Work Holding: This can be easily accomplished by using a "spoil board" piece or sacrifice piece. You bolt your work piece to the spoil board and then bolt the spoil board to the table top. This allows to cut through the work piece and into the spoil board without ruining the machine top plate.
• CNC Programs: You will need to generate G & M codes to operate your CNC Machine. This can be done in many ways. You can buy your programs form others on the internet, you can hand write code, you can purchase a CAM program that allows you to draw in there software and generate code from that, or draw in a separate CAD program and import it into you CAM program for CNC code generation.

There is tons of info out there on the web just Google CNC Router and Table Top CNC Router. I hope this helps.

Thanks,

Andy