Category Archives: Modification

Modification related posts.

Laser cutter continued … (PT2.)

This is probably going to end up being as long as my first rant on the laser cutter, if you’re considering buying one or having problems with overheating MOSFETs, tuning your motors or just a long rant about getting to a comfortable functional state, you’ll probably want to read that first.

So not much has changed since I last updated the previous article, the laser cutter is working well, I’ve cut a few more adventurous objects this week and done plenty of engraving. also cut two mounting plates for the relay board and the control board both of which I’ll add to the downloads page when I get chance. I’ve been running a mix of hatching jobs figuring out what works well and how to produce tones using the relay board. Cutting needs refining, currently running between 175-200mm/s cut rate and 35 to 40 passes (4mm ply), Engraving is also working well running at 1000mm/s with a single pass works very well with wood, still yet to test any plastics, but pleased to say I’ve got some primitive extraction sorted. (120mm extraction hose and 12v fan mounted inside.)  Whilst this works surprisingly well currently, when I make an enclosure, I’m pretty sure the fan will be 100% effective (which is a very good thing :0D ).

The new control board has arrived, it features a much bigger transistor (F540NS), the board is much more capable than the last, with a lot of IO, support for x / y / z limit switches, x / y / z motor support each axis has independent drivers. The arduino nano is opto isolated from the twelve volt supply and the circuit board is black, which yes looks nice, but makes it remarkably more difficult to follow the traces, maybe that’s just me? There’s also an i2c header and support for reset / abort and hold switches. Everything else is rather self explanatory four connections for the motors, two terminal blocks one for the twelve volt supply the other for a fan / laser, complete with matching JST sockets.

There are four connections on the board I’m currently unable to identify S_EN (which I think is spindle enable.) DIR (Spindle direction?) and C_EN (not sure) and E_S (emergency stop?)  These aren’t that important at the moment, but they’d be nice to know.

Procrastinating a little, I’ve grown quite fond of the current set up.

Plus what little documentation I’ve located (and translated images + text) it would appear (i hope) that the board supports lasers up to 10w, but recommends installing benbox (argh nope), this may however indicate the PCB is 100% GRBL compatible (meaning all the settings and configuration I have will work 1st time or … I’m back to square one.). I’m not going to flash the included board just in case  I need to revert to for some reason. Meh.

Less procrastination more action, as long as I don’t damage the laser or motors I can always revert to my current set up. Time for a hot beverage and then some cable swappage.

BTW. I’m sitting here writing this whilst the storm is raging outside.

This tea however is fantastic.

Progress!!! GRBL working! Motors working! More tea needed before I test the laser. Taking this opportunity to flash the device and update all the default GRBL settings to my preferred defaults. NB: The settings are contained in c:\users\uname\Documents\Arduino\libraries\grbl\defaults.h

My current settings are as follows …

#ifdef DEFAULTS_GENERIC
#define DEFAULT_X_STEPS_PER_MM 80
#define DEFAULT_Y_STEPS_PER_MM 80
#define DEFAULT_Z_STEPS_PER_MM 80
#define DEFAULT_X_MAX_RATE 6000.0 // mm/min
#define DEFAULT_Y_MAX_RATE 6000.0 // mm/min
#define DEFAULT_Z_MAX_RATE 6000.0 // mm/min
#define DEFAULT_X_ACCELERATION 75.0 // 10*60*60 mm/min^2 = 10 mm/sec^2
#define DEFAULT_Y_ACCELERATION 75.0 // 10*60*60 mm/min^2 = 10 mm/sec^2
#define DEFAULT_Z_ACCELERATION 75.0 // 10*60*60 mm/min^2 = 10 mm/sec^2
#define DEFAULT_X_MAX_TRAVEL 600.0 // mm NOTE: Must be a positive value.
#define DEFAULT_Y_MAX_TRAVEL 500.0 // mm NOTE: Must be a positive value.
#define DEFAULT_Z_MAX_TRAVEL 100.0 // mm NOTE: Must be a positive value.
#define DEFAULT_SPINDLE_RPM_MAX 1000.0 // rpm
#define DEFAULT_SPINDLE_RPM_MIN 0.0 // rpm
#define DEFAULT_STEP_PULSE_MICROSECONDS 10
#define DEFAULT_STEPPING_INVERT_MASK 0
#define DEFAULT_DIRECTION_INVERT_MASK 0
#define DEFAULT_STEPPER_IDLE_LOCK_TIME 25 // msec (0-254, 255 keeps steppers enabled)
#define DEFAULT_STATUS_REPORT_MASK 1 // MPos enabled
#define DEFAULT_JUNCTION_DEVIATION 0.2 // mm
#define DEFAULT_ARC_TOLERANCE 0.02 // mm
#define DEFAULT_REPORT_INCHES 0 // false
#define DEFAULT_INVERT_ST_ENABLE 0 // false
#define DEFAULT_INVERT_LIMIT_PINS 0 // false
#define DEFAULT_SOFT_LIMIT_ENABLE 0 // false
#define DEFAULT_HARD_LIMIT_ENABLE 0 // false
#define DEFAULT_INVERT_PROBE_PIN 0 // false
#define DEFAULT_LASER_MODE 1 // enable
#define DEFAULT_HOMING_ENABLE 0 // false
#define DEFAULT_HOMING_DIR_MASK 0 // move positive dir
#define DEFAULT_HOMING_FEED_RATE 25.0 // mm/min
#define DEFAULT_HOMING_SEEK_RATE 1000.0 // mm/min
#define DEFAULT_HOMING_DEBOUNCE_DELAY 250 // msec (0-65k)
#define DEFAULT_HOMING_PULLOFF 1.0 // mm
#endif

Well currently I’m ecstatic the 540N / new control board is doing a great job, the laser currently works using MOSFET when performing line drawings with the gate fully open. I’m just looking for a bitmap to start some rastering tests. Running some more line drawings and hatching then on to some raster work, all systems nominal, everything is running beautifully so far. (fingers crossed.)

Sleep was needed will pick this back up in an hour or so need to sort a few orders out and tidy my space.

Rastering results so far, it works, but, to get the laser down to an acceptable power, without the MOSFET getting ridiculously hot, I’m having to defocus the laser, which in turn causes fidelity issues with the final burn. So … more testing will report back soon.

Observations, I think this time around the MOSFET under rastering is getting too hot because of the 8khz PWM rate, I’m not really able to generate a good range of colours when rastering unless the image is just black and white not grey scale. The 8khz PWM rate (I think) is having an effect on the amount of operations per second the arduino is processing. So going to reflash the existing firmware but try the default PWM setting and a few more raster operations.

To change the PWM rate you need to edit cpumap.h
Earlier in this guide I tried to change the PWM rate to 8khz, which didn’t have the desired effect so I’m just changing it back to GRBLs default which is 0.98khz

That section of my file currently looks like this …
// Prescaled, 8-bit Fast PWM mode.
#define SPINDLE_TCCRA_INIT_MASK ((1<<WGM20) | (1<<WGM21)) // Configures fast PWM mode.
// #define SPINDLE_TCCRB_INIT_MASK (1<<CS20) // Disable prescaler -> 62.5kHz
// #define SPINDLE_TCCRB_INIT_MASK (1<<CS21) // 1/8 prescaler -> 7.8kHz (Used in v0.9)
// #define SPINDLE_TCCRB_INIT_MASK ((1<<CS21) | (1<<CS20)) // 1/32 prescaler -> 1.96kHz
#define SPINDLE_TCCRB_INIT_MASK (1<<CS22) // 1/64 prescaler -> 0.98kHz (J-tech laser)

So altering the PWM rate has had an effect on the speed off the rastering operation but similarly still having issues with temperature and unable to get a good range of colours without the MOSFET getting too hot.

Altered the GRBL x/y/z acceleration value to 75 on the control board with no noticeable negative effects on the motor drivers.

Will update this blog article as I go as I know a lot of people are having similar problems.

18/01/2018 – Adding pictures.

Uncovering the biggest scam in modern history … printer cartridges.

I’d never really paid much attention to printing or print materials till early this year, never had a need to print much out. Since starting out with the plotter I get some requests, a lot of which I have to turn down for labels and printed contour cut stickers, which is really annoying. The entry level for UV / solvent based printers is still rather high, a basic printer will set you back anything from £3k to around £5k depending if you just require a solvent printer or one with a contour cutting head. The latest and greatest roland cutter/printer could set you back as much as £24-28k. Maybe I’m understating what these machines are capable of ie. the above machine will print photo quality 6ft+ wide and has an incorporated cutting head for printing and cutting stickers options include take up rollers on the front of the machine etc. absolutely amazing machines but way out of my price range.

Saving my pennies till I can afford a decent solvent printer cutter combo. (Yes im aware there are some workarounds, but the longevity of inkjet printing and water proofing / UV protecting the stickers is rather and involved process something I could mitigate all together with a better printer, unfortunately the solvent inks are far to aggressive to attempt modifying an existing inkjet.)

I had a few old inkjet printers knocking about so thought I’d attempt restoring them to working order whilst having a play around with inks and refilling the old cartridges. Simple, obviously I just put more ink in the cartridges and place them back in the printer and continue to print putting some old hardware to good use.

Well that’s how I thought it worked. NOPE.

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The &%$%ing laser cutter …

Yup, I bought a cheap Chinese laser cutter, not a CO2 one but a diode based banggood/A3 clone (5.5 watts 50x60cm bed). It seemed like such a good idea at the time. I couldn’t sleep knowing I’d finally got my hands on something I could use to create physical objects from work on the computer. I could use the laser cutter to build a simple CNC machine and expand my range of products. We’ll that’s what I thought.

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Hakology Day 82: Digistump … rickroll all the things.

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Well merry crimbo, I hope you had a great day whatever you spent it doing. So i’ve been really busy the last few weeks but I’m starting to have a little more free time now … and thought I’d take this chance to start writing up a little code and project for the digistump.


What is a digistump?

A digistump is a small USB development board that emulates a HID (Human interface device (Usually a keyboard or mouse but there are other variants)). The digistump allows the user to flash up to 6k of code to the device which when plugged in to a computer after programming will execute the code on the device as if it were a keyboard and/or mouse.

Why would I use one?

Its very handy for automating small tasks such as downloading a file and running an install or just editing settings on the pc that remain consistent across operating systems. eg. You could use the digistump to run a command in the command window or run a specific application with certain options automatically. All you need to do is plug the device in after programming and it will start executing the pre-programmed keypresses.

What operating systems does it support?
The digistump is cross-platform this doesnt mean one script works for all operating systems. This means the device is capable of running and executing code on Win/Linux/Mac but due to difference across the various operating systems scripts would need to be customised for each. The digistump has no way of reading data or accepting any feedback from the PC it just blindly presses keys. Your scripts will rely heavily on intelligent timing. Some commands will execute and finish on modern PCs faster than they would on older hardware, this has to be taken in to consideration when writing code.

Where can I get one?
The digistump is available from Digistump.com you can also find them available on ebay and similar sites. I bought mine from ebay for £1.50 each which is a tiny amount when compared to similar devices.

Installation?
The install procedure is pretty straight forward, download arduino IDE, install drivers and add digistump examples and templates. Which is all detailed on this page here … Getting started with the digistump
The setup is relatively straight forward.

So why am I reading all of this?

Well b/c the digistump is a relatively new product there’s not a lot of reference material on the internet so I started developing a small framework to make it easy to deploy and develop code very quickly. I’ve been busy working on my first little project for the device and right of passage to rick roll any windows 7 users. Although this project is a harmless bit of fun it’s helping me to develop a lot of standardised functions for running applications, opening web pages creating and saving files.

Rickroll notes …
I spent the first few nights tearing my hair out with this device. Here are some of the issues I encountered and how I mitigated them or formed some workarounds.

The first major issue I had was the backslash. The digistump by default outputs US scancodes, as I live in the UK this was an issue. So after much googling and head scratching I figured out that the scancode for the backslash on a UK keyboard was 0x64 yet the digistump was sending 0x31 the US scancode for the backslash.

Whilst I couldn’t figure out where the digistump library resided on the PC I wrote a small function to swap out the 0x31 for 0x64 which seems to have remedied my backslash issues. This is not the correct way to do things.

Eventually I found the library location last night (c:\Users\Username\arduino15\… ). I’m still yet to look through the code and figure out a conversion table for 101(UK en-gb 32) keyboards. Given a little more time I’ll get this fixed and not have to use any functions for string processing.

Another related problem was the saving of files using the %USERPROFILE% environment variable. Full filenames containing this variable were not being parsed properly ie. the environment variable was being read as %USERPROFILE% and not the actual users name. To mitigate this I broke the file string down in to sections and type each part of the save file string in separately. ie. C:\ [ENTER] Users\ [ENTER] %USERPROFILE%\ [ENTER] etc which allowed me to use the %USERPROFILE% variable when saving files.

I’m not going to upload all the code yet as its still messy and I have some functions that need more calling parameters adding so if I released the code now it’ll probably change before the final release and I want everything nice and polished before I release everything.

A great big shout to advancednewbie who’s been working on a special script for the digistump (More on that very soon.) his research and project helped me greatly in trying to figure out the key mappings for most default buttons and some of the UK differences. Given some more time im sure we’ll have this working seamlessly between countries and keyboard layouts.

Even though these issues don’t directly relate to the rickroll project I thought I’d include them just in case anyone else is having similar issues.

Download digispark digistump stumpyroll source code
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