A Beginner’s Guide to CNC with the SainSmart 3018-PRO
Introduction
In this article, I will share my experience working with the SainSmart Genmitsu CNC Router 3018-PRO. I will also help you get started on your first CNC job by explaining the basics of CNC. Hopefully this will make your experience go smoothly, even if you are a total beginner.
Overview
If you are a beginner looking to get into CNC machining, the SainSmart Genmitsu CNC Router 3018-PRO DIY Kit might be the best starter device on the market. This desktop CNC is only $250 and getting started is relatively easy.
After a month with this machine, I am thoroughly impressed by its capabilities. The text engravings with the basic v-bits turn out well (after a bit of sanding) and the overall build quality of the device is astonishing given its price point. All pieces fit together well and the device feels sturdy.
Here’s a list of device specifications:
- Effective Engraving Area: 300 x 180 x 45 mm(11.8 x 7.1 x 1.8”)
- Frame Size: 400 x 330 x 240 mm(15.7 x 13.0 x 9.4")
- Frame Material: Aluminum
- Spindle: 775 motor, 12V, 3000 RPM; 24V, 7000 RPM; 36V, 9000 RPM
- Rated Power: 60W; Maximum Power: 120W
- Step Motor: 1.3 A, 12V, 0.25 Nm torque (2.2 in lb)
Assembly
Explaining the assembly process in an article is difficult, so I do encourage you to check out my YouTube video above, which includes a time lapse of the process.
Nevertheless, I will try my best to summarize.
I performed this assembly without any prior research on my own and it ended up taking about 2 hours or so. That’s including time to film, so without those shots, it may have taken a bit less.
I would describe the instruction manual as “helpful enough”. It was not super detailed with step-by-step instructions for every twist of a nut or bolt, but the pictures really helped demonstrate how the pieces would go together.
Honestly, I actually enjoyed not having long and detailed instructions because most of the pieces went together intuitively and making the manual any longer would have just consumed more of my time.
The entire assembly went smoothly for me, with the exception of the mounting of the spindle. The instructions wanted me to pry the plastic piece and I was definitely being too gentle with it, but I obviously did not want to break anything. After about 5 minutes of working it, I finally got the spindle to fit. This was unfortunate, but I didn’t break anything so it was obviously not a deal breaker.
If you absolutely do not want to assemble it yourself, you can also purchase the more recent model shown below, which has much less to assemble (30 min vs. 2 hours).
Software
The Sainsmart 3018-Pro DIY kit comes with software on a flash drive that you can use to make your carvings. This software is called GRBL control (Candle).
This software is only good for executing g-code, so you still need other CAD software when making designs (like Carbide Create, which is also free).
Easel is a paid software that allows you to create designs and run carvings on the same platform. I will walk you through both Candle and Easel.
Candle
Once you follow the software installation steps in the instruction manual, you need to connect your CNC router to your computer using the USB port. Then, in Candle, you need to go to ‘Service’, then ‘Settings’, and enter the COM port number that the CNC router is using.
On Windows, you can find the COM port by going to ‘Device Manager’ and looking under ports. Once you have the COM number, return to Candle. This process is also outlined in the instruction manual.
Once connected, you can open the test engraving file, which is provided to you by SainSmart on the flash drive.
The final thing to make sure to do is to zero your device. You need to move the bit to the desired starting location using the jog keys on the right hand side of the screen.
Once the bit is in the correct location and touching the surface of your wood piece, zero the x, y and z axes.
Finally, you are ready to send the design to the router. Before doing so, make sure you follow proper safety precautions, as outlined later in this article.
Easel
Easel is a software that lets you design and run carves all in a single place. You can add text, shapes and images (in the form of SVGs). Easel also helps you preview your design and simulate how long it will take. One of the most useful features is how it provides automatic speed and feed recommendations based on the information of the material and bit you provide.
The first thing you need to do is to set up your machine. You will need to manually enter the correct COM port, just like you did in the Candle example. Here are the proper settings for the SainSmart 3018-PRO:
Next, you need to create your design and specify the dimensions of wood you are using. Then, enter information about the tool you are using. Simulate your design and make appropriate changes if necessary. Once you are satisfied, you can press carve. Follow the prompts to ensure your device is set up properly. Similar to the Candle software, you must zero your device before starting your carve.
If you ever need to stop the carve, you can cancel it in Easel or press the power button on the back of the Arduino on the CNC router. Personally, I press the power button to immediately stop the spindle. Then, I will move to my computer to cancel the carve. It is worth noting that you can also decrease the feed rate if it seems too fast.
CNC Basics
Making the best carvings in as little time as possible is a learned skill. You need to understand the fundamentals of machining to get the most out of your machine.
Without understanding the correct settings for your machine, you may break your bits, damage your machine, or make poor carvings. To begin avoiding these issues, I will walk you through an example. This example will help you get into the mindset of a CNC machinist.
Example
Let’s say I want to carve out a simple slot. I want the slot to be 1 inch deep and 1/8" wide. I will select a 1/8" endmill to perform this carve.
Naturally, I want the carve to take as little as possible, so should I tell the device to remove 1" of depth per pass? No, this would likely cause the endmill to break (chip load would be too large). You cannot remove as much material as you want instantly. The maximum amount of material you can remove is based on how quickly the spindle is moving (cutting speed) and how fast the bit is moving translationally (feed rate).
There are formulas that machinists use to calculate the maximum amount you can remove. Machinists need to estimate this maximum because if they operate too conservatively, the process will take too much time. In addition, as outlined in this guide, having too low of feed rate relative to your spindle speed can cause your bit to get very hot due to rubbing, which will decrease the life of your bit drastically.
Let’s say instead of trying to take out 1"of depth in a single pass, we instead only try to take off 1/64" per pass. Would this work under most circumstances? Yes, likely it would, but it would take 64 passes to remove the full inch, which means you would be standing at the machine for a long time.
Hopefully this gives you a sense of how the machine settings are important. Unfortunately, since these settings depend on the carve, type of bit and material you are using, it does not make sense to discuss the equations until you understand more about the types of bits you can use.
Types of Bits
There are many types of bits, but I will be focusing on the two main ones you will be using the most as a beginner.
The two most common bits you will use are v-bits and endmills.
- V-bits
V-bits are specialized for very detailed, shallow cuts and cannot cut flat slots.
One important characteristic of v-bits is the angle. The v-bits that are included in the 3018-Pro kit are 20 degrees. Larger angles will be more wider and shallow, while smaller angles will cut deeper and thinner. The image below shows how the angle determines the groove size.
The tip diameter is another important characteristic of v-bits. The v-bits that are included in the 3018-Pro are 0.1 mm. The tip diameter and angle together determine how detailed of carvings you can perform.
2. Endmills
These bits can be used for slotting, cutting out shapes, and other carves that require more material removal.
Endmills can be flathead or rounded. As the names imply, one can cut flat slots while the other cuts round-bottom slots. You should be aware that both of these endmills cannot produce a perfectly square corner, since the bit is circular.
The number of flutes is another specification of endmills. These are the number of pathways the material is removed from the workpiece.
The blades can be straight cut or spiral cut. In addition, depending on the orientation of the blades for spiral cut endmills, the material can be removed upwards (up-cut) or downwards (down-cut).
The advantages and disadvantages or each type of bit will not be discussed here, for the sake of time. As a beginner, you will likely start with a 2-flute, flathead, spiral up-cut endmill, as shown in the image above.
Feeds & Speeds
A single article cannot possibly provide you with every single piece of information needed to understand your machine settings under all circumstances. If it was so simple, CNC machinists would not be paid so handsomely. However, that does not mean you cannot learn enough to get started with a bit of research.
Do not be too scared if calculations are not your thing, there are plenty of resources that can help do the analysis for you. Most software, like Easel, come with built-in help for determining the speeds and feeds you should run at for any given carve.
So what are feeds and speeds?
Feeds and speeds refer to the cutting speed and the feed rate. They are combined into one term because you must analyze both to determine the effect on the cutting process.
The cutting speed is the difference in speed between the cutting tool and workpiece. Since the cutting tool is attached to the spindle and the workpiece is stationary during milling, the cutting speed is the same as the spindle speed.
The feed rate is the rate at which the cutting tool moves into the workpiece (translationally).
If you have a really fast spindle speed, you can have a faster feed rate, because the cutting tool can remove material fast. Likewise, if you have a low spindle speed, you cannot have a fast feed rate or else you may break your bit.
The key to setting these parameters is to do research based on the material and bit you are using. The more you learn, the easier it becomes.
This is another reason it is great to experiment with such a cheap device, that way you do not make expensive mistakes in industry. Make sure to have a good enough grasp of these concepts before attempting your first carve, to ensure your own safety.
I’m hesitant to provide any recommendations for settings because there’s so many factors based on what you are making. Instead, I have provided resources that can help you make those decisions. These resources below are the exact resources that I used as I learned what was best for my carves.
You can learn about the equations to calculate reasonable speeds and feeds in resources like these:
- Understanding Feeds and Speeds Sweet Spots
- Guide to Types of Bits
- Feeds and Speeds Calculations
- Chip Load Chart
Recommendations
Having a vacuum makes cleaning up shavings much simpler. The kit does come with a small brush, but it’s a pain to use every time.
The $250 DIY kit only comes with the basic v-bits, which are great for small text and other detailed carvings, but not great for removing large amounts of materials. Getting a greater variety of bits gives you more flexibility.
If you are interested in adding wood-burned etches to your designs, you can purchase the laser module attachment. You switch out this module for the spindle. Other than that, controlling the device works the same.
Safety Considerations
The goal of this section is not to scare you, but rather make you aware of the various hazards associated with CNC machine operation. Here is a list (albeit uncomprehensive) of some good precautions to take as well as some hazards to be aware of.
1. Safety Goggles
This should be obvious, but a spindle spinning at 9000 rpm can send metal or wood pieces flying. You absolutely do not want those pieces to hurt your eyes. Like in any shop, wearing safety goggles is a must at all times of operation.
2. Watch your fingers!
You might be tempted to brush off the wood shavings with your hand or brush, but you can misjudge where the spindle is going next and create a dangerous situation. The bits are extremely sharp and can devastate your fingers when spinning.
3. Tie up long hair!
This is another standard machining practice. You do not want to get hair tangled in the machine. It can rip out your hair, or worse, pull your head into the machine or blade.
4. Make sure the workpiece is clamped securely.
Make sure you clamp down the wood piece securely and that the clamps are out of the tools path. You do not want a blade spinning fast to crash into your metal clamps. If your workpiece is loose, the piece will almost certainly move under the stress of the blade, and your carve will be ruined.
5. Double check all workpiece dimensions and toolpaths.
You do not want the spindle colliding with anything it should not hit and can’t cut. This could damage the machine, break the bit and send pieces flying. So, make sure you have the told the machine the correct material dimensions and thickness.
6. Watch out for overheating.
This typically applies only for aluminum or acrylic. The aluminum can get very hot and you often need to add cooling lubricant. If you are using acrylic, you may have the wrong speed settings and the acrylic can melt. This will ruin your carve.
7. Monitor All Carves
You should never leave a machine unattended. Unforeseen issues may arise, and you should always be prepared to shut off the device.
Bonus Tips and Tricks
1. Zeroing the Z-axis
The easiest way to accurately zero the spindle in the z-axis is by placing a piece of paper between the bit and workpiece. As you jog the machine down, the paper will get stuck between the tool and workpiece. Then, you know the bit is at the correct vertical height.
2. Research Rules of Thumb
There are often rules of thumb to follow when machining, which were created by experienced machinists. For example, one rule of thumb for endmills is that you should not have a depth per pass of more than 1/2 the cutting bit diameter when cutting through soft wood. I’ve personally found doing less than this is recommended to have cleaner surface finishes. At the end of the day, it depends on what you value the most.
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