Mach3 Sherline EdgeCAM Compatability

[rob@enigmatech.ca]

I bought EdgeCAM and a Sherline 4axis CNC Mill, am running Mach3 and have been having some problems with losing the home and origin positions during machining.  I am cutting an organic shape that has been laser scanned.  The Laser scan and resulting CAD model are fine.  It's the EdgeCAM to Mach3 to Sherline process that is causing some problems.  I am losing my home position by 0.015" in the x axis, 0.020" in the y axis and 0.010" in the z axis.  I set the home before machining using an edge finder, run the program, and when I check the home following machining I am out the values listed previously.  The problem occurs irregardless of speed, so I'm not going to too fast (22in/min as recommended by Sherline).  If I run the program a second time, then the error is cumulative and thus worsens. 

I've checked backlash and repeatability on each axis and I am within tolerance (0.001").  The issue arises when I run complex 3D profiles as most of these organic shapes are.

I am cutting in 3 axis mode and have manual code written for a 180 degree indexing operation to machine the bottom side.  I am using a Mach3 post for EdgeCAM that I found on this forum.  I am running Mach3 confgured for Sherline as downloaded from the Sherline website.  I am cutting modeling board which is light weight and using brand new cutters.

The whole reason I bought the Sherline was for precision.  My TechLine CNC router iis more precise right now.  The TechLine runs a different Mach xml, but G-code is generated by the same Mach3 post for EdgeCAM.

Can anyone please help or offer suggestions?  I am just about ready to return the Sherline and have many thousands invested.

[RICH]

Is the Sherline stepper or servo driven?
What contoller are you using?
Are there homing switches and what kind / from who?
Post your xml file.

I would imagine that if you started at the same point, positioned the machine properly / the same way, and re-ran the program the second time, you should end up repeating rather closely
to what you did on the first run. Not progressively get worse. It should be within some tolerance of your milling machine.

I installed a brand new  Sherline Lead screws / nut along with their backlash lock and preload system on a Sherline lathe.
There was nothing wrong with the lead of the screw but trying to maintain backlash at ( .001" no way....maybe .003") was almost impossible over a short period of running time.
Same goes for my Sherline Mill. Nice to play with ...so i hope folks don't think I am bashing Sherline.

I know nothing about EdgeCam, but, the machine will do what the code says.

RICH

 

[fixittt]

Slow it down,  hat speed are you running the sherline?  The sherlines I believe have 20TPI lead screws.  That is alot of RPMS on the stepper to get a descent feedrate.  Possible loosing torque and missing steps?

Turn off the view port in mach3

Im going to assume that your toolpath is quite large in filesize.

I cut 3d organic shapes all the time and have found that with small tools and high stepovers the viewport cannot keep up to well.

Most of my problems were noticed on flips ect.

Also check your motor tuning.  do you have any axis`s that are tuned higher then the rest?  I used to have a maxnc with a 4th axis.  My x y and  z were tuned to 800 mm a min.  the A axis was tuned to 2500 mm a min.  after every small a rotation the X would stall out big because the computer did not like the differences in processor load.

[rob@enigmatech.ca]

Is the Sherline stepper or servo driven?
What contoller are you using?
Are there homing switches and what kind / from who?
Post your xml file.

I would imagine that if you started at the same point, positioned the machine properly / the same way, and re-ran the program the second time, you should end up repeating rather closely
to what you did on the first run. Not progressively get worse. It should be within some tolerance of your milling machine.

I installed a brand new  Sherline Lead screws / nut along with their backlash lock and preload system on a Sherline lathe.
There was nothing wrong with the lead of the screw but trying to maintain backlash at ( .001" no way....maybe .003") was almost impossible over a short period of running time.
Same goes for my Sherline Mill. Nice to play with ...so i hope folks don't think I am bashing Sherline.

I know nothing about EdgeCam, but, the machine will do what the code says.

RICH


Hi Rich,
The Sherline is stepper driven.
I am using Mach3 to control the Sherline CNC.  I have the whole Sherline CNC package that comes with steppers, driver, wiring and the mill straight from Sherline themselves.
There are no homng or limit switches on the Sherline.  My part datum is 0,0,0 and my machine home is 3" straight up in the z axis.  I check the part datum using an edge finder before and after machining and get the errors noted.
I've attached the xml file.
If I run the program, re-zero the datum/home, and then re-run the program, then the error repeats itself.  If I don't re-zero between runs, then the error cumulatively gets worse (0.020" 1st run plus 0.020" 2nd run = 0.040" total for y axis).
The machine is almost brand new, so I'm getting about 0.001" now with minimal use.  I'm not trying to hold this though.
Thanks,
Rob

[RICH]

Your xml hangs up my computer every time I tried it. Can you repost it again?

If you don't re-zero you are starting out with some error around .020", so that error is going to accumulate by that error for each run.
If five runs it would be out by say .1". The question is how do you reduce that intial error. I have found the lead of the screws on the Sherline to be quite linear.
So some of that error can be due to the backlash created in the thrust bearing / washer and the nut ( i'll assume that the coupling is tight and not slipping any ).  
 I  think it is more than .001" , Sherline says .003 to .005",  but that's just my nickle, ( you would need a very tight Sherline to achive that ...gib, preload on bearings, and nut adjustment) and when that is done your using a lot of available motor torque. I think the stock ones are around 135in oz. You can be loosing steps and not hear it.

The thing you do have going for you is that it's repeatable. So cut the accel to 2 and velocity to 10IPM for a test and see what happens on a test run.  

RICH

[Hood]

Have you tried with Sherline Mode enabled?
Hood

[rob@enigmatech.ca]

Have you tried with Sherline Mode enabled?
Hood

Can you please fill me on on running with Sherline Mode enabled?  How do I do this?  What will it do?
Thanks,
Rob

[Hal]

EdgeCAM is just programming software. I do not think this is the issue. I would say you are missing steps. I had a the same problem with with a BobCAD program. I had to slow the motor tuning. Slowed the accel and deccel. I even increased the kernal speed.

Sherline mode increases the steps by using half windings in the stepping motors. It is a check box in the set up menu.

[Hood]

My apologies, just had a look at your xml and sherline is already enabled.

Hood