Monday, April 10, 2017

CNC router adjustment

The new puzzle that Juno is making now is a secret puzzle box. Since he has started making the secret puzzle boxes, he has been using the CNC router with high frequency. Then he noticed that the CNC router didn't make accurate cuts as he expected.

Making puzzles, as for the machine, high precision is required. The miniature furniture that I (Yukari) have made didn't need such high accuracy, even if the shapes were slightly out, they could be used for display for a dollhouse but puzzles need accuracy.

The CNC router that Juno uses is a cheap Chinese product which has been on the market widely, and he has to obey the rules of "you get what you pay for." Occurring small issues were expected and he has solved some problems already. One of the issues that he solved was the wrong wiring of the stepper motor driver board and he had to swap terminals to the right position. Another issue was also the inappropriate position of safety limiter switches.

There is a question for you, can your CNC router cut a perfect circle?
The CNC router is a machine that is controlled by a computer, therefore we tend to think that a CNC router can be perfect. However, it's not perfect if it's not set and adjusted correctly. Even though you had intended to cut a circle, it might be an ellipse.

To begin with adjusting the CNC router, Juno milled out two grooves of rectangles 20mm x 10mm. On the computer screen of CAM software, he drew two 20mm x 10mm rectangles at intervals of 200mm and processed it with the CNC router. He repeated the same procedure for X axis and Y axis, then compared two of them. When comparing two rectangles, it is important to check the length of two sides, inside and outside of the rectangles.



If the length of X axis and Y axis don't match, you need to adjust the computer software and try it again. Juno tested it again and again and noticed that every time he did it the results were slightly inconsistent. In this case, it can be ascertained that there was backlash of the machine that led to the inaccuracy.



Juno inspected each moving part of the CNC router. What he found was the linear slider unit which was connected with a ball screw was not secure. Having a backlash of the liner slider, the work table of the CNC router was also not stable and X axis travel became shorter than he expected.




He checked several parts and found that the screws which fixed the linear slider and the aluminium block were loose. When he bought the CNC router, he had checked and tightened some of the screws, in addition, he adjusted some parts to be placed at right-angles but the linear slider unit was not checked because of the difficulty of access.


He re-tightened the screws, fixed the sealed cap which had come off, and re-fixed the work table, then the backlash issue has gone!



After finishing the inspection work, he milled a square shaped groove. As shown in the picture below is the comparison of before re-screwing and after re-screwing. Take a look at the square on the left hand side, as you can see the bottom of the groove is burnt because of the backlash.




He examined the length of the squares' grooves and compared the length of X axis and Y axis, whose lengths were slightly different. The difference of 150mm square was about 0.1mm. The square supposed to be 150mm x 150mm became 150mm x 149.9mm. It means the spindle motor of the CNC router moved only 149.9mm along the Y axis, 0.1mm shorter than the expected measurement. So the travel of the Y axis has to be adjusted.




The finer tuning of 0.1mm can be done by CNC software. The CNC software we use is Mach3 which is very popular and common. Under the "Config" menu, select "Motor Tuning" and then click the "Y Axis" button on the right hand side.




The "Steps per" value would be suggested by the manufacturer of CNC routers. Our value was 320. Based on the original value of "Steps per" (320), the theoretical measurement (150mm) and the actual measurement (149.9mm), we can calculate new "Steps per" value like the following:
320 x 150 / 149.9 = 320.21347565043362241494329553035.

He entered the calculated value to "Steps per" and clicked the "SAVE AXIS SETTINGS" button.

He clicked "OK" and closed the dialog and then chose the "Config" menu and selected "Save Settings."

Just to make sure, it's good to double check the value of "Config - Motor - Tuning" settings because we often forget to press the "SAVE AXIS SETTINGS" button. After he finished the above mentioned adjustment he milled a square shaped groove again. It's important to measure both axis and sides: inside of X axis, outside of X axis, inside of Y axis, and outside of Y axis.




The picture as shown below is the MDF sacrifice board that was dismantled from the work table. The outside lengths of the square were 150mm, and the inside lengths were 130mm. The difference of the outside and inside measurement was just 20mm; Juno has finally got a satisfying result.





If you have got a result, for example 150mm and 130mm for X axis, 150mm and 130.5mm for Y axis, the discrepancy might be caused by backlash of the CNC router. In this case, a pocket can be milled accurately but the outside milling would be inaccurate. What if the measurement of X and Y axis are both 149.9mm and 131.1mm? Various factors can be imagined, but it might be not so serious as having a discrepancy to X and Y axis.
The following are the reasons that we can think of:

* The diameter of the milling bit is smaller than expected or worn off.
* The milling bit is extended too much and it causes it to bend.
* Too fast feed rate or too much milling depth.
* The backlash of the spindle motor. (It can be fixed replacing the spindle motor in the worst case scenario.)

Well, today's blog became long but we hope that if you find your CNC router inaccurate, our blog would be helpful.

See you then.

Yukari

Tuesday, March 28, 2017

CNC router and dust collection system

I have written about lots of machinery at our workplace: the table saws, the jointer, the router, the disc sanders and the belt sander. The next subject is the CNC router and the dust extractors. I have mentioned the topic of the CNC router before, just a little but this time I will show you the details that Juno has done.


First of all, he considered what type of CNC router is the best for our work. Gantry type CNC routers seem to be common in the market. The CNC router we bought is a column type, and one of the major differences between the gantry type and the column type is the travel range of the Z-axis, up and down. The column type routers have a wider travel height of the Z-axis, that means you can process thicker or taller objects on the work table. It also gives room for sacrifice boards, various jigs and clamping vices. As you know, we produce three dimensional wooden puzzles and those puzzles or puzzle pieces sometimes have significant length to X, Y and Z-axis.

Juno is now using the CNC router to make new secret box puzzles. I'll write about his new puzzle later someday, I can just say his secret box puzzle is a very unique design. Oops, let's get back on track.

Commonly, a CNC router is connected to a desktop computer with a parallel cable. However, he wanted to use a laptop computer with a USB cable. One of the reasons is new OSs doesn't support a parallel port. Old computers which have parallel ports sometimes don't have enough performance to run 3D CAD and CAM software. In addition, the other devices like a monitor, keyboard and mouse have to be around the computer and a desktop computer itself needs a larger space than a laptop computer. He didn't want a messy workbench, you know? A Laptop computer doesn't require a larger workplace as its battery works as a UPS, so when it's needed to search something the laptop computer can easily be connected to the internet because it usually comes with a wireless adapter.

The key device to connect the laptop computer and the CNC router is a UC100 USB motion controller. He uses 32 bit Windows XP for controlling the CNC router now but he made sure that 64 bit Windows 7 can also be used without problems, thanks to the device.


CNC routers are very convenient machines, but still have awkward things that have to be solved like other woodworking machines, that's sawdust. Here is the dust boot Juno made of plywood.


To collect the sawdust efficiently, he elaborated the shape of this dust boot using the CNC router. The brush underneath the spindle motor was bought at AliExpress.

Depending on the type and length of milling bits, the height of the dust boot can be adjusted by undoing the star knob.


The dust boot helps to collect the dust well, on the other hand there is a problem changing the milling bit. Someone used magnets and made the bottom half of the dust boot able to be detached easily, or someone set the dust boot to not move with the milling head to give accessibility to the milling bits. Those experiments can be seen on a thread at the cnczone.com.

Juno made a door with a star knob in front of the dust boot as shown in the picture below. He says that if he has a chance to make a dust boot again, he will use magnets instead of a star knob to keep the door shut.


He had been using a vacuum cleaner type dust collector, but there were some issues:

- The suction power is weaker than an industrial model extractor.
- The room where the CNC router is set gets hot in a short time.
- The vacuum cleaner is not designed to be used continuously, for several hours.

Recently, he did some plumbing work to connect the CNC router and the big dust extractor.


He mainly used 100mm PVC pipes and partially used flexible hose. When the CNC router is not in use, he puts a cap on the L connector. When it is in use, the flexible hose is inserted into the L connector.


To make the pipe and the connector rigid on the wall, he made a special chunky bracket. (There are no noggins to put screws in behind the wall.)

The CNC router and the dust extractor are about 10m (32.8 feet) apart. It's not convenient to go to the dust extractor just for turning it on/off every time he uses the CNC router, so he bought a cheap remote switch.


Since he started using the remote switch for the dust extractor, the work environment has been improved dramatically. The cost-effectiveness of this remote switch is high, it's highly recommended.

That's all for today.
See you next time!

Yukari

Tuesday, March 14, 2017

The New Puzzle "Pseudo Ovolo"

Today's topic is about Juno's latest puzzle "Pseudo Ovolo" that he had started making on 30th January, 2017.

He bought timber that has been kiln dried from the local lumber dealer who he is familiar with. First of all, he made the timber a little thicker than the target measurement and rested it in the shed for a while. And then he re-worked the timber to the target measurement. Pseudo Ovolo is made with Karri (red-brown timber in the picture) and Silver Ash (white timber / citrus family tree).

This was the very first time using Karri for him, and he realised that Karri is difficult to handle and if he used up all the stock of Karri, this time may be the last time for using Karri.

 

After he processed the timber into sticks, he cut the elements from the sticks. At this stage, he has arrised some of the elements. For gluing each piece, he made a jig to support two elements of timber to be glued at right-angles. As you can imagine, there are so many jigs remaining in our workshop because he makes jigs every time he makes new puzzles.


As shown in the picture below, after he finished gluing the pieces made from Karri (red-brown), he cut the groove for reinforcement on each end of the piece. He prepared a replaceable sacrifice board (white board in the picture) in front of the piece to eliminate chip outs.


He had cut the white timber (Silver Ash, citrus family tree) a bit larger, and after gluing to the red-brown pieces, sanded them until it became the correct size.


Every red-brown piece was glued into an O-shape and then, it was cut to a C-shape. Herewith, the grains of the two ends of the C-shaped piece look linked and also the piece can be made accurately. The next step is arrising the edges of every piece.


Then, it was finally time for coating. A thin coat of lacquer spray makes timber more beautiful and protects timber from dirt.


After every piece was dried, he sorted the pieces by colours and grains, and then assembled pieces into a puzzle in which the timber colours and grains are matched.


Ta-da! Here is the puzzle "Pseudo Ovolo."


Juno named this puzzle "Pseudo Ovolo" because he was inspired when he saw Yavuz Demirhan's "Ovolo" and wanted to show his respect to Yavuz Demirhan.

Pseudo Ovolo is available on our website.
Juno and I hope that puzzle lovers would love Pseudo Ovolo.


Yukari