chmr

10 tpi (threads per inch, I would be worried if the screw had teeth 😉 means it will travel 1/10″ or 2.54mm per revolution. $4tr=2.54

Hi,
using the limit switch input for emergency stop is not really a good idea, because these inputs rely on the software. If the software goes haywire, the emergency stop would be useless.

Personally, I would love to see the emergency handling that I know from bigger controls used for multi-kW motors on autocranes or industrial robots: When an emergency situation occurs (emergency switch, access door opened, limit switch etc), the software gets a signal to shut down all movement as soon as possible in a controlled manner (emergency deceleration). Around 100-250 milliseconds later, all power is removed from the motors and the mechanical brakes are activated. This second signal is purely implemented in hardware (time-delayed relay and power circuit breakers). So if the software is not responding, it still shuts down the system (delayed by a split second), but in the normal use case, it shuts down the system fast and gentle (slamming the mechanical brakes in full speed would destroy them after just a few tries).

I would love to see that in tinyg V9, but it requires additional hardware (inputs for emergency stop and re-enable, AND-gate for all motor + spindle enable signals) and software.
And it could possibly raise liability issues (I guess that’s the reason why there is no emergency stop handling in current tinyg, thus the responsibility is shifted to the user).

Hi,
fb is your firmware build,
st is the status code as found in the source tinyg.h as STAT_PREP_LINE_MOVE_TIME_IS_NAN (comment: Never supposed to happen).

Check your $$ parameters, possibly one of them is set to NaN. If so, reset to default and reenter all customized parameters.

Carl, for schematics I would only recommend Eagle. The freeware version is already very capable, lots of tutorials online, many freeware designs are made with Eagle, every PCB house accepts Eagle files, many people use it. I drew the schematic above in LTSpice for quick simulation, but it has an abysmal user interface.

Yeah, there are several versions of it around. I read somewhere that when jumpered for the pot, it uses a simple 555 circuit to produce a home-made PWM signal and drives a FET with that.
Q1 in my schematic inverts the input signal, so it seemed safer to me to add a second stage to invert it back.
It would definitely be much easier if we knew the actual circuitry of the board. I was already tempted to order one just out of curiosity (but it takes 3-4 weeks from china to me). Found another bigger photo of one version: http://i.bosity.com/office_cache/274/14008974/4840000011395984469_14008974_6_image.jpg”

• This reply was modified 10 years, 2 months ago by chmr.

Alhaddar, the video link in your first post does not work. Please fix it.
Did you configure tinyg for use of pwm? See https://github.com/synthetos/TinyG/wiki/TinyG-Configuration-for-Firmware-Version-0.97#pwm-group-pulse-width-modulation

The ebay page also states “PWM input : level 3.5-12V VPP” in the fine print — tinyg can generate around 3V, so you might need a level shifter for it to work.

As long as the bootloader is still functional (blinking spindle-dir led), you should try a firmware-update via USB. That also tests the hardware of the serial port.

Hi, I try to chime in with some info to clear things up:

Threaded rod: TR8*8/4-start means: TR=standardized trapezoidal screw; the first 8 is the outer diameter of the rod; the second 8 is the lead, 8mm per revolution; 4 start means there are really 4 threads on the rod, each with 2mm offset (pitch) to the previous. 4-start helps with max load and smoothness, and is important to match rod and nut, but it does not influence the calculation of lead. Your $3tr should really be 8.

Step angle: According to the parts list, both the Nema17 and Nema23 motors are 200 steps per revolution (1.8 deg step angle). Set your $3sa=1.8 . Because your $3tr was also wrong, it evened out to the same distance (when tinyg tried to move the Z axis 8 mm, it calculated that it needs 0.5 motor revolutions = 200 steps with the old settings; with the new settings, it uses 1 motor revolution = 200 steps). But this does not explain the squirrelyness.

X/Y travel: 60mm per revolution is correct according to the parts list (20 tooth pulley * 3mm belt pitch).

I ran your gcode circle files, both of them run “fine”. I noticed some things in the files:
1. You placed 4 tabs on the inner circle, but not on the outer circle. For the tabs, the machine has to decelerate x and y, lift Z up a bit, cut the tab, drop z down, accelerate x and y again.
2. The gcode assumes that Z=0 is at the top of the material (very common). That means that positive Z coordinates are in the air, negative ones are cutting in the material. If you set up the 0 coordinate at the top of the work bed (not the material), it would explain why the machine tries to cut into the workbed.

Velocity: The feeds in your files and parameters seem to be quite fast (in fact, I think 5000 mm/min feedrate would be too fast for all except *very* soft materials). I cannot see the 50mm/min and slow speed to move the gantry. Did you do this test with a different file or different settings?

Limit/homing switches are a good thing, but I don’t think they would change anything about your problem.

Edit: Nearly forgot, another common issue with Z going to deep is when the Z axis actually goes too short when commanded to go up (caused by sticking/binding Z nut, over temperature of driver or motor, too fast max speed $zvm, slipping pulley/coupling, slack belt). I don’t think this is your problem, but you can try to send the Z axis up and down manually with “G0 Z35” and “G0 Z0”. If it does not stop at the same point every time, investigate further in this direction.

Btw, thank you for reminding me to download sketchUcam 1.2 🙂

• This reply was modified 10 years, 2 months ago by chmr.

I can see your frustration, and I try to answer your questions in sequence:

Json: Forget it for now, it is very useful for people developing programs that talk to tinyg, but nor for the average user. That said, it’s documented at https://github.com/synthetos/TinyG/wiki/JSON-Operation and https://github.com/synthetos/TinyG/wiki/JSON-Details , linked from the tinyg start page.

Firmware update: Carl already linked the page, but you probably don’t need it anyway. The easiest way to update the firmware is with tgfx.
Note: Firmware updates reset the configuration to default.

tgfx: Make sure you have the newest version, older versions don’t work properly with the recent firmware versions. You can get it from https://github.com/synthetos/tgFX#binary-downloads if you don’t have version 3625 already.

Cambam: I second Carls’ suggestion to postpone it until you have tinyg itself configured and running. I think most people run the generic gcode backend with tinyg (not using Cambam myself).

Flow control: Yes, tgfx sets $ex=2. Rightfully so, because RTS/CTS is the easiest and most effective type of flow control to use. Just set Coolterm options to also use CTS, save settings, and be done with it.

Axis configuration: I found https://github.com/synthetos/TinyG/wiki/TinyG-Configuration-for-Firmware-Version-0.97 to be very useful for basic configuration. My suggestion is to work with 1 axis at a time, start with X (the easiest), and when that works move on to the next. The settings above are already a good starting point, I noted the following settings need verification:
$1tr=40 (is 36.54 above, but 40 should be correct if you have the Nema23 upgrade from Inventables: pulley with 20 teeth, belt pich 2mm)
$xvm=4000 (start with a low value for max velocity, then tune it later when the rest is working)
$xfr=4000 (same)
$xjm=200 (max jerk: start low, tune it later)
Test it like Carl suggested.

When you’re happy with X, continue with Y (motors 2 and 3) and finally Z (reduce $4vm and $4fr; $4tr above seems to be correct for stock machine, but not if you have an acme screw upgrade; might also want to experiment with different $4mi values).

I really hope that gets your Shapeoko going, feel free to post more detailed questions if you still have problems.
And a slight warning for the Shapeoko wiki: Some of the pages describe the procedures for GRBL without telling so, and the procedure for tiny might be different. This bit me when I started with CNC. If in doubt, ask here or in the tinyg section of the Shapeoko forum.