Page 1 of 5


Posted: Thu Jun 20, 2013 6:00 pm
by WillAdams
Finally lining everything up to do this.

For those not familiar w/ it, a Repstrap is a small 3D printer built to print the parts for a larger 3D printer --- there's even a specific sub-category of them for milling machines: ... small_mill

In theory, it should be as simple as:

- source an extruder
- connect it to one's control board
- print

The problem seems to be that it's possible to have a control board which can drive a mill, but not a 3D printer. This seems to fall under a couple of categories:

- stepper board only has 3 connections which are used for XYZ
- 3D printer control programs seem to require higher-end control boards --- there isn't a 3D printer control program which will run on a typical low-end Arduino / 328P?
- control board has to be re-flashed to switch between 3D printer and milling modes

I ask 'cause I have an AtomCNC board and implemented a driveshaft for the Y-axis so as to have a stepper to spare for the extruder --- what is the Grbl-equivalent for a 3D printer?


Re: RepStrapOko

Posted: Thu Jun 20, 2013 6:50 pm
by WillAdams
Do I understand correctly that this:

is a version of Grbl which will run on a 328P and drive an extruder in addition to XYZ?

Re: RepStrapOko

Posted: Thu Jun 20, 2013 7:38 pm
by Will Winder
WillAdams wrote:Do I understand correctly that this:

is a version of Grbl which will run on a 328P and drive an extruder in addition to XYZ?
Unfortunately it looks this is a port of GRBL to run on the different hardware, it doesn't add new features besides that.

Re: RepStrapOko

Posted: Fri Jun 21, 2013 12:53 am
by WillAdams
Okay, it looks like Teacup is the only 3D printer control software which will run on an Arduino w/ a 328P, so that's good --- the thing I'm hazy on is why one has to re-flash the firmware between Teacup and Grbl to switch betwixt printing and milling --- why can't one mill w/ Teacup?

Re: RepStrapOko

Posted: Fri Jun 21, 2013 1:26 am
by bjbsquared
I'm not familiar with Teacup but some firmwares require the extruder temperature to be in a certain range before it starts printing. Perhaps it could be fooled with a switch and some resistors or overridden with a gcode command.

Re: RepStrapOko

Posted: Fri Jun 21, 2013 2:35 am
by WillAdams

So, an extruder is more than just on-off --- that explains that PID algorithm note I glossed over --- the control board should have an input for monitoring temperature.

Re: RepStrapOko

Posted: Sat Jun 22, 2013 2:59 pm
by kbot3d
the temp controls can be run independently. a ta4 with a solid state relay will do the same. the reason you want them on an all in one controller is fail safes. when the temp is too cold you want something to shut off the extruder which is just a 4th axis motor to prevent damage. think of a hot glue gun. when its cold, you cant push the glue sticks thru. under torque you risk damage to an overpriced hotend but more than anything it just strips out the filament and wastes alot of time. on the other hand should you have a runaway heat source it shuts everything down on the spot.

grbl, teacup, sprinter, marlin can all be used to mill or laser cut. they are all simply g code interpreters. the firmware settings for temp control can be overridden at any point.

Re: RepStrapOko

Posted: Sun Jun 23, 2013 2:29 pm
by WillAdams
That's good to know.

Somehow I missed this blog: which seems to examine the problem pretty thoroughly.

I'm currently bogged down on the software side, and am thinking that I'm probably going to work up some scripts, or maybe a plug-in to use w/in FreeHand to facilitate designing in 3D.

Re: RepStrapOko

Posted: Mon Jun 24, 2013 3:01 am
by kbot3d
this might save you a few headaches. try repetier host as control software or pronterface. both are python scripts

Re: RepStrapOko

Posted: Tue Feb 25, 2014 12:03 am
by WillAdams
Okay, a bit further along on this. I have:

- ShapeOko 2 chassis w/ motors
- AtomCNC control board w/ empty stepper driver socket for a 4th axis
- 24v power supply
- 24v fan (currently being used to cool the AtomCNC stepper drivers)
- the Kbot3D version of Greg's Wade Reloaded Extruder
- J Head Hot End Kit 0.35 mm Nozzle 1.75 mm Filament - Resistor, Thermistor, Teflon Tubing

soon to arrive are:
- CanaKit Stepper Motor with Cable ( believe this has a short enough housing to fit, if not, I see myself taking a Dremel to the extruder)
- SainSmart A4988 Stepper Motor Driver for Arduino Mega2560 Mega1280 RepRap Ramps

and I've finally found time to begin looking over the instructions, so I see now that I need narrow kapton tape to wire up the resistor and thermistor in the hot-end and to wrap the hot end in. I also haven't ordered any filament yet, and I'm debating on whether or no I'll need to get a heated bed or no.

I'll also have to re-flash the AtomCNC board w/ the Teacup firmware, and will have to move the SO2's Arduino and gShield over to the SO1 (mental note, make a note of the settings for both machines).

Anything else I should be aware of at this point?