I have a C-beam XL that I have been using for various projects, some of which have me milling HDPE. I've noticed that the z-height seems to be inconsistent when performing tool changes, i.e. after a cutting operation, the tool is now ~0.02" higher than the initial zero. Also, when jogging with the .01" increment, the Openbuilds Control software doesn't always register the movement change. Is it possible that my z-gantry is too tight, which may explain both of these things?
Not totally sure if I'm reading your first point right, but are you re-setting Z zero after a tool change? Secondly, the gantry being tight should not affect what the controller says - it sends the command but has no feedback from the stepper so will just assume that it moved. Does the controller software indicate the movement?. If not, Peter should be able to help with that.
if a 0.01" jog does not register it means that this is a smaller step than your hardware can take. and that depends on the pitch of your leadscrews and the steps per rev and microstep settings of your motors. let me illustrate with an example: My Z uses a standard OB leadscrew which is 4 start 8mm pitch, ie one turn moves by 8mm. my motor is a 200 step per rev motor. my driver is set to 4x microsteps. this means that it takes 200 * 4 = 800 steps to move the leadscrew one turn. since 1 turn is 8mm, this gives 800steps/8mm = 100 steps per mm (the $102 value in GRBL settings) 1mm/100steps = 0.01mm per step. when I jog at 0.01mm per jog the leadscrew moves 1 step everytime I press the button,, and a 0.1mm jog moves the leadscrew 10 steps. but if I jog at 0.005mm per jog, it will only move the motor after every 2nd button press because it cannot physically move with such a small step (and the display may or may not be able to display this 'movement'). similarly my X and Y are belt driven and do 0.025mm per step, so trying to jog at 0.01mm is pointless, it moves only every 3rd or 4th button press depending on the controllers internal floating point rounding math. so the questions are, what motor, what leadscrew, what driver microsteps and what GRBL settings?
I just did my first v-carve with the end mill doing a clean out first, and the v bit doesn't follow as close to the material as the end mill, thus not leaving a clean finish, what is going wrong.
What CAM application, what parameters did you have set up, endmill correctly configured? Include the project files if you can, helps to check
Thanks for the reply. The change in z-height seems to occur during the cutting operation. Here's my workflow - I'll set z-zero on a piece of material cut from the same stock that I am using for my project, as I've been setting the WCS to originate at the top of the stock, lower left corner. I'll run the job up until it's time for a tool change, then send the router back to the piece of stock used for setting z-zero. When the tool is over the same stock, at the same coordinates, the cutting tool is now a bit higher than it was before the cut, even with the machine at what is set to z-zero. So the cutting tool should rest on the stock, in the exact same place, but there is now a space between the stock and the cutting tool. Regarding the controller readout, I'll click the 0.01" button to move the z-gantry down, the machine will respond, but the software may or may not indicate a change in z-value. This appears to be new behavior. I did run the update the software just before the job, but I don't know if that has anything to do with it.
Thank you for the reply. I used the materials from the C-bean XL bundle to build the machine. The motors are nema 23's with the inscription of 1.8 degrees/step, and the leadscrews should all be the standard Openbuilds pitch from what I recall. The drivers are the Wantai DQ542MA drivers, with the switches set to two up, two down, two up, two down. I'll have to look up what that refers to, as it's been awhile since I set it up. The GRBL settings are 199.1 mm per step.
I think I see what is happening. The inch display has only 2 decimal digits when it should have 3 (or 4). if you do g20 g0 x10.955 you see 10.96 on the screen if you jog X+ by 0.1" it moves to 10.965 and displays 10.96 (again), the next jog goes to 10.975 and displays 10.97 your inches per step comes out to 0.00019774, so just about 2 tenths of a thou. so the display would be useful at 4 decimal places in inch mode @Peter as for Z losing steps, I think you need more current. Your setting is off,off,on which is 1.69A I think you need on.on.off for 2.05A RMS. this will give Z the extra power to overcome cutting forces. of course one also has to make sure that feedrate is slow enough for the material, tool is sharp, ramp in not straight plunge. if you still have trouble after increasing Z current then there are 2 things to do - disconnect the motor and turn the leadscrew by hand, end to end, to make sure there is no sticky spot - reduce microstepping to 4x (800 in Wantai instructions). sets steps/mm to 199.1 / 2. this will increase stepper power without increasing heat.
That's great, my sincere thanks for the thoughtful analysis. It makes sense and I will change the switches on the drivers to apply greater power. Regarding the level of precision in Openbuilds control, I was a bit surprised to see that it only goes to the hundredths place. I have considered switching to a different control program, but I really like the UI and the ease of changing settings with the Openbuilds control. Hopefully there will be an update to address this in the near future. =)
