Category: CNC Projects

CNC Tips and Tricks – Cutting Extruded Polystyrene Sheets

So in this episode we are going to look at machining sheets of extruded polystyrene sheets we bought a  couple years back.  This was very cheap verses that of acrylic, however machining is a bit harder as the plastic wants to melt rather than cut.  So what we did was:

1. Use a 1/8″ 2 flute end mill (amzn.to/1LMWEJy)

2. Kicked the speed up to 100 Inches per minute

3. Slowed the spindle down to only 1/3 speed using a speed controller(amzn.to/1GUViXB)

 

A. Polystyrene

 is a synthetic aromatic polymer made from the monomer styrene. Polystyrene can be solid or foamed. General purpose polystyrene is clear, hard, and rather brittle. It is an inexpensive resin per unit weight. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year. Polystyrene can be naturally transparent, but can be colored with colorants.

As a thermoplastic polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100 °C, its glass transition temperature. It becomes rigid again when cooled. This temperature behavior is exploited for extrusion, and also for molding and vacuum forming, since it can be cast into molds with fine detail.

B. Polystyrene features

  •  Excellent light transmittance.
  •  High mechanical strength.
  •  Weather proof
  •  Non-toxic and chemical resistant.
  •  Easily be processed

C. Polystyrene applications

  •  Advertisement: blow molding board, CNC engraving materials, Laser engraving materials, sign board,  light box,  window, logo and mark, etc.
  •  Furniture: office furniture, cabinet, window, etc.
  •  Finishing Material: decorative sheets, storage racks, room segments, etc.

Autodesk 123D Make Laser Cutting Rocket Model on CNC

 

In this episode we will show you how take the Rocket model from Autodesk 123D Make and move it into Vectric Cut2D, convert it to gcode and cut it out on the laser.  Again remember safety first when ever using a laser!

If your interested in getting into laser cutting, check out some of the pre-built models like this one which can get you going quickly and easily:

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Vectric Cut2D Post Processor for Laser Cutter

 

In this episode, we will look how to a create a post processor file for Vectric Cut 2D to drive the laser cutter on our Probotix Fireball v90.  This should also work for all GRBL based machines like the Shapeoko or the XCrave too.  Below is the code for the millimeter based post processor file:

 

500MW DIY laser Engraver engraving machine Picture CNC Printer 17cm X 22cm

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Dwell Issue with GRBL Using a Laser

Appears there is a delay in GRBL (v0.9) with the issue of the M03 spindle direction command GRBL will delay its movement to allow time for the spindle to spin down, reverse and spin back up.  So instead of using M03/M04 for rapids, we have switched to using PWM (Pulse Width Modulation) using S0 to set to the lowest level (basically off) and S1000 for full power.

Arduino Uno 3 Ultimate Starter Kit Includes 12 Circuit Learning Guide

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Spindle and Laser Control for CNC Router using Gcode

In this episode we will look at using a dual relay board (amzn.to/1MeJCmN) connected to the GRBL controller to on and off either a spindle or small laser attached to the mill (we will be adding a 2 watt laser in another episode).  This is is current using pin 13 which is set control spindle direction as in stand PWM mode pin 12 for spindle enable does not respond to gcode commands and requires a change in the configuration.f and a recompile with upload.  I got the below table from (www.shapeoko.com/forum/viewtopic.php?f=3&t=5803) and it is a good reference if you want to make changes.

 

Disabling VARIABLE_SPINDLE will revert Grbl to the old pin layout, where spindle enable is on D12 and direction on D13. With it enabled, spindle enable/PWM is on D11 and direction on D13.

EDIT: Here’s a chart to make it a bit clearer.

VARIABLE_SPINDLE enabled:
D11 = Spindle enable/PWM speed
D12 = Z-limit
D13 = Spindle direction

VARIABLE_SPINDLE disabled:
D11 = Z-limit
D12 = Spindle enable (on/off only)
D13 = Spindle direction

VARIABLE_SPINDLE and USE_SPINDLE_DIR_AS_ENABLE_PIN both enabled:
D11 = Spindle PWM speed only
D12 = Z-limit
D13 = Spindle enable (on/off only)

SunFounder 2 Channel 5V Relay Shield Module for Arduino UNO 2560 1280 ARM PIC AVR STM32 Raspberry Pi

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Timelapse of the Probotix Fireball v90 running Chillipepper and GRBL on Arduino

 

So here is the time lapse video of the Probitix Fireball v90 CNC router running Chilipeppr via Arduino and GRBL software. Also in the video we have the string settings which we are using for garble so if you want to try the same this should provide reference point.

Arduino Proto Screw Shield

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Update to the Probotix Fireball v90 CNC conversion to GRBL

 

So we’ve now got the Probiotix Fireball V 90 running with all the major GRBL front ends including Chilipeppr, GCode sender and Easel. We have noticed a couple strange things, one of them being GRBL wants to flip the X and Y axis. This is in both the nature (i.e. X becomes Y and Y becomes X) and direction, to correct this we’ve had to use change the GRBL string $3=3 (inverting both x & y) to mask the directions of each access. With regards to the X and Y axis flip, we have tried inverting the wiring to reverse them, however this only results in what appears to be a mirror image when cutting sort of like from the bottom up rather than the top-down. So to correct for this we’ve just allowed the flip in axises and simply changed the homing location and perspective of the material which seems to work just fine. Watching the video you can see we’ve cut out several rather complex shapes without issue. However one of the interesting things you will notice in the video, there still is one part abandoning the material and this was caused by “user error”, as I forgotten and unplug the laptop causing the battery run out while sending G code, Oops. However other then several minor challenges overall the conversion process has gone rather easily, And in fact has been quite a bit of fun as my goal with all this was to create a simpler workflow and both Easel and Chilipeppr filled this goal. However I must say with regards to just GCode sender the jury’s a bit out as  I’m concerned as how effective that is, (because it is quirky compared to others) but hey it’s still early in the game. So look for some more updates soon Will be doing the final install of the Arduino on top of the Probotix driver box an the final wiring to complete this project so once that’s done I will do the video on that as well along with a video on the configuration file for GRBL itself.

Arduino Proto Screw Shield

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Wiring the Arduino & GRBL for the Probotix Fireball v90

 

In this episode we going to the shop and wire in our Arduino with GRBL into the Probotix Fireball V 90 CNC router. Again this is a rather simple build in we will solder the pins from the DB-25 parallel port connector into the header pins of the Arduino and once this is completed we will be able to control the Probotix Fireball P90 CNC router via the free Gcode sender or an application such as ChilliPeper or Easel.

How to wire Arduino w/GRBL for Parallel Port Control

 

So in this episode we are going to look at wiring the  Arduino running  GRBL to a parallel port CNC machine control yet before you get too concerned this is actually a pretty simple project as what we’re going to cover are the pinouts from the Arduino and matching them up with the opinions of the standard parallel port again most of this is simple soldering to a DB 25 connector which we will plug into the parallel port.

Key Links:

Probotix Pinouts: www.probotix.com/wiki/index.php/PBX-2

Arduino w/GRBL Pinouts:github.com/grbl/grbl/wiki/Connecting-Grbl