Category Archives: Experiments

Overview of Standard and Alternative CNC linear guides – part I

Precision and strength of CNC machines is highly dependent upon the linear guides on which elements move. There are many many different ways CNC axis can move around. Part I is about general overview of existing linear guides and some alternatives. Part II will be about experimentation with T aluminum profile for use with small CNC machines.

Highly precise machines usually use linear motion guides like the one from HiWin. Such linear motion solutions are due to their complexity rather expensive. MGN12 model usually used in making high end Delta 3D printers can cost up from $40 for 40cm and up depending on length.

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But there are alternatives. The most known alternative is MakerSlide which started as Kickstarter project. In europe amberspyglass offers 1m lenght makerslides for £12.00.

It is good for medium sized machines but when going for small to tiny machines the where size and weight is an issue they are not that practical.

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Makerslide offers good rigidity for the price. It was aluminum profile of choice when building Shapeoko  CNC machines.

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Slightly beefed up version on makerslide is c-beam and V-slot from Openbuild. Also OpenRail is a good add on to standard aluminum profiles to make them into high end linear rails.

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Also standard aluminum profiles 1010 or 2020 are popular in making 3D printers, especially Kossel mini.

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Somewhere in between of HiWin and Makerslide are guide rods. They can be purchased from tiny to massive diameters and are used all over the place.  They are not that expensive by them self but require additional items to make them fully useful.

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Such guides offer a wide array of carriages that can ride on the rail.

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Now, all of these are more or less standard ways of making CNC machines move with precision. While making smaller or huge CNC machines such linear guides are sometimes impractical and other times prohibitively expensive. Thus I needed an alternative solutions for linear guides. While experimenting it was found that almost anything with little imagination can be used as rails for CNC machines.  Especially pipes, square, T and V aluminum profiles.

Note: I dont have images of all experiments so Im using internet images.

Some of examples are:

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V profile, good for large scale 3D printers as they have no Z axis force put on them.  Easy to acquire and fast to guild.

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Simple setup for use with medium CNC machines. Has no limiters so prone to wobbling.

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Rather robust setup for use with square or round pipes.

One of good examples of alternative guide lines is Mostly 3D printed CNC. Files and videos can be found of thingiverse.

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What I learned from over a year or two of using ESP8266 01 module.

First off, ESP does not tolerate 5v, under any circumstances. Not to power it up nor as communication voltage. Usually when you read that a piece of tech does not tolerate 5v, usually it does. It tolerates it but for short time, not ESP. Just try and show it 5v and it will blow up. And the worst thing is that there will be no white smoke to indicate that something went very wrong. It will continue to sit there, not working, while you rearrange the code for the tenth time trying to figure out what’s wrong. To make things even worse, the red led will be on just to taunt you into believing it’s still alive.

There are 12+ different variants of basic ESP reference board. With the simplest and most prolific being the ESP-01.

A good and stable power supply is a must as ESP does not like fluctuations. The ones that happen when it turns on its WiFi are enough for it to reboot. ESP-01 onboard power supply filter is virtually nonexistent with only a small 100 nF capacitor. There should have been at least another 10 uF, which is not there. I would suggest adding another 10-100nF decoupling capacitor together with a larger >300uF capacitor between Vcc and Gnd to the board.

Who ever designed ESP-01 board was one massive troll. All of those component should have been there in the first place. I can almost see him, the engineer that designed the ESP boards, snickering as he plots his troll move on the unsuspecting Makers around the world .

Most of those traps are now fixed with more complete prototyping boards like NodeMCU and others.

USB, Arduino and other power sources will not be sufficient for normal operations of ESP with WiFi turned on. Most such sources only provide around 100ma while ESP needs more than 150ma to work properly. One symptom of not enough current is that you can upload a firmware but it will constantly cause watchdog timer (wdt) reset if you try to connect to a network. Or, in other words it will constantly reboot. A good rule of thumb is to provide at least 300ma or even better, a minimum of 500ma able power supply. ESP consumption can peak at around 300ma.

ESP ADC is used internally by the chip to measure internal voltage and to adjust WiFi power output. This causes a lot of problems if you wish to sample a large sample using ADC. If watchdog timer can not access ADC ti will raise a fault.

There is no warning faults, all faults are critical and cause reset of watchdog or a straight out reboot. If anything goes wrong, even if it’s not important it makes it important.

The good practice is to allow the watchdog to do its thing every now and again or simply call delay() or yield() every 50ms or 500ms on the outside. This will let watchdog do its thing and keep WiFi alive. This is true for all actions not just when reading ADC. It’s more sensitive when ADC is used but any task that takes more than 500ms to finish without watchdog having its chance to rowe around will cause it to crash and burn, or just reboot.

As with all new things ESP had its childhood problems (and trolls). As the platform matures and bugs are ironed out, both hardware and software it’s becoming a powerful replacement for Atmel based arduino.

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