@Jeff_Lamb Please check your grbl Settings via “$$” command and compare this with follow settings: https://drive.google.com/file/d/0B3A9wmWsyWK1MWhzMDJJU004Mm8/view?usp=sharing
Hi, There are a few settings that are different, but nothing that I would see as causing the problem. I’ve changed the settings to match (apart from $140 + $141 as they are the current for the drivers). and still no difference.
@Jeff_Lamb ahh, i know the softpot are deactivated in our firmware. U can’t set the current. Please try the original firmware from @Todd_Fleming
I’ve got the one with softpot support, and the settings you sent me got me thinking that it may be something to do with that so I set $140 higher and it is now working. I’ve had to set it so $140=6 which seems way too high so I suspect something is going wrong in the i2c on the sbase rather than a code issue on grbl side.
Next problem is the laser won’t fire. I’ve got it attached to the low side of 2.5 as i had previously on the smoothieware. HW fire button works, but test fire in LW or when doing job it doesn’t work.
+Peter van der Walt ah, ok … i don’t check @cprezzi github 
This sounds not bad. Please add “M4” in start gcode @ laserweb. After that it works for me … and please read this webpage: https://github.com/gnea/grbl/wiki/Grbl-v1.1-Laser-Mode this helps me a lot to see if my laser fired or not.
actually scrub that last comment! It now test fires but doesn’t fire when engraving!
Its Alive!!! Thanks very much guys 
I’m definitely not getting enough current to the steppers as i can barely move the x stepper at even 100mm/sec without it stalling. I think I’ll be ordering a C3D board and just be done with it.
@Jeff_Lamb moment, you have the mks sbase correct? What is happend if you use a higher feedrate. If the motor screwing, then your max feedrate is too much. Also please check the temperature of ur steppers after 5min running time. They are too hot (you cant touch it or higher as 70° degrees) then ur current is to high (6 means 6 Ampere(!) … but one ampere is perfect.
Check ur microstep jumper on the board (8 is perfect, 16 is ok), here i found this text “All of the above are 1/32 multistepping. In order to use 1/32 you also need to set the correct jumper on your Controller. It is located almost at the upper right corner with 16|32 next to it. The pins are named J3.”
@Frank_Herrmann I know that the current isn’t being set correctly on the sbase board as it worked well on the smoothie firmware in terms of speed. I know the 6 setting should mean 6 amps but it isn’t setting to that as I can stop the carriage with my little finger when it is moving. I’ve ordered the c3d so I’ll go that way first and then look at upgrading the 24v supply to one that can drive more than 1 amp.
@Jeff_Lamb Did you set $140 and $141? The SBase board has the i2c chip. So you need to use the right firmware.
I have tested my K40 with a SBase board and I had to set X stepper to 0.4A ($140=0.4) and Y stepper to 0.6A ($141=0.6). My X-motor is smaller than Y. Do not set values over 1.5-1.7 or your drivers get to hot and switch off!
I did have them both set and y was working but x didn’t although it make a noise as though it was trying to move (not slipping teeth though). I increased the level and eventually it moved. Anything above 2 didn’t seem to make any difference and the drivers and steppers didn’t even get warm.
You hit the digipot’s max value.
You should check your stepper cables. That sounds like probably one wire is brocken.
My new C3D has arrived and i’ve fitted it and it looks like one of the stepper motors is dead. I’ve checked resistance and each coil of the stepper seems ok but if I swap the motors around the fault follows the motor. I’ve ordered a replacement, but in the mean time can anyone tell me if grbl-lpc supports an A axis (for rotation)? Thanks.
@Jeff_Lamb I hope you didn’t forget to set the motor current correctly ($140…142).
There is also a second test to check if the motor is ok. Connect a voltmeter to the ends of one coil and turn the shaft. If you see see some voltage while turning the shaft, then this coil is ok. Repeat with the second coil.
@cprezzi I’ve just done that and seem to be getting voltage. I’ve already ordered a new stepper so I’ll try connecting it up when it arrives next week. I presume I can connect directly to the stepper pins at the top of the c3d board rather than having to connect to the K40 ribbon cable - that way I can eliminate the ribbon cable as well. Thanks.
@cprezzi I tried the “4 Axes version for boards w/o i2c stepper current chip” and am running into the Y axis homing issue. Does this version have the correct limit port fixed here https://github.com/gnea/grbl-LPC/releases ? Rotary A axis seems to work good, but I have to test more in the coming weeks. Thanks!
@Arion_McCartney This version has limit pin definitions for boards with 6 limit pins configured to x-, y+ and z+. Homing will not correctly work with a C3D Mini, because the mini only uses the min limit switch pins. I can compile a special version for the Mini, if you need it.
@cprezzi I would very much appreciate that. I just build a rotary and would like to use one firmware with X/Y/A axis. Thank you very much in advance.