Fine DRO Adjustment & Measuring Overall Turns Ratio

All things related to the Centroid Acorn CNC Controller

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762x51
Posts: 118
Joined: Wed Aug 02, 2017 8:40 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: B0D5CC56DD75-0605170063 , 985DAD4295CF-0928170127 , 38D2694E4703-1222170401
Location: Near Guilford College, Greensboro, NC
Contact:

Fine DRO Adjustment & Measuring Overall Turns Ratio

Post by 762x51 » Sat Jan 06, 2018 4:10 pm

Here is what I have been able to find showing how to calibrate your Acorns axis's and getting the DRO to read accurately.
Thanks to Marty for this very informative video:

https://www.youtube.com/watch?time_cont ... XE4-5xstWQ

You can find the printed instructions in the Allin1dc Installation manual on page 63 found here:

http://www.centroidcnc.com/centroid_diy ... oller.html

There is also Tech Bulletin TB036 with the same info here:

http://www.centroidcnc.com/dealersuppor ... ads/36.pdf
Last edited by 762x51 on Sat Jan 06, 2018 5:34 pm, edited 2 times in total.

762x51
Posts: 118
Joined: Wed Aug 02, 2017 8:40 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: B0D5CC56DD75-0605170063 , 985DAD4295CF-0928170127 , 38D2694E4703-1222170401
Location: Near Guilford College, Greensboro, NC
Contact:

Re: Fine DRO Adjustment & Measuring Overall Turns Ratio

Post by 762x51 » Sat Jan 06, 2018 4:19 pm

It looks as if the Turns Ratio that you enter into the Wizard is just a starting point and the procedure shown in Marty's video is the real deal.

cnckeith
Posts: 605
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
System Serial Number: none
Contact:

Re: Fine DRO Adjustment & Measuring Overall Turns Ratio

Post by cnckeith » Sat Jan 06, 2018 5:01 pm

Please use the Wizard to enter the exact Overall turns ratio for each axis.

Remember the Overall Turns ratio is a mechanical truth.
It is simply the fixed mechanical specification of an axis drive system
If the machine has a decent screw all you need to know is the pitch of the screw and the ratio (if any) that the axis motor is connected to that screw.

Setting the Overall Turns Ratio Common Newbie Pitfalls....
- DO NOT go and adjust the steps per rev to tweak the DRO! steps per rev has NOTHING to do with the Overall Turns Ratio.
- Poor axis movement measurement techniques. Often newbies dig themselves a hole by trying to fine tune the overall turns ratio of an axis with poor axis movement measurement techniques.
- combination of the two listed above.
- trying to remove the last .0001" of error out of the ratio

Overall Turns Ratio Examples

1.) with an axis motor direct connected to a 5 turns per inch screw. enter "5" in the wizard for the the overall turns ratio
2.) with an axis motor belted to a 5 turns per inch screw with 24 teeth pulley on the motor and 48 tool pulley on the screw. enter "10" in the wizard for the the overall turns ratio.
3.) with an axis motor direct connected to a 5mm pitch screw. in metric mode enter ".2 mm" in the wizard for the the overall turns ratio, if in inch mode enter 5.08
3.) with an axis motor belted to a 5 mm pitch screw with 24 teeth pulley on the motor and 48 tool pulley on the screw. in metric mode enter ".1 mm" in the wizard for the the overall turns ratio, if in inch mode enter 10.16

Simply knowing the pitch of the screw and the connection between the axis motor and the screw produces good results.
and for alot of machines this is all you need to do. But some screws will not have an exact as advertised pitch of 5 turns per inch or 5mm etc..
That where the very fine measurement technique comes into play. Now let me stress if you setup a 10 inch long gauge/standard or an Electronic scale it must be perfectly parallel with that axis before you use it to make the measurements between commanded movement and actual movement. So use good machinist practices to line things up before running off and tweaking the overall turns ratio number!:-)

762x51
Posts: 118
Joined: Wed Aug 02, 2017 8:40 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: B0D5CC56DD75-0605170063 , 985DAD4295CF-0928170127 , 38D2694E4703-1222170401
Location: Near Guilford College, Greensboro, NC
Contact:

Re: Fine DRO Adjustment & Measuring Overall Turns Ratio

Post by 762x51 » Sat Jan 06, 2018 5:35 pm

Keith, Thanks for pointing out that the great tool "Wizard" can be used and folks don't have to go deep into CNC12 and maybe make a mistake.

cnckeith
Posts: 605
Joined: Wed Mar 03, 2010 4:23 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
MPU11 & GPIO4D -w/ 3rd Party Drives: Yes
DC3IOB: Yes
CNC11: Yes
CPU10 or CPU7: Yes
System Serial Number: none
Contact:

Re: Fine DRO Adjustment & Measuring Overall Turns Ratio

Post by cnckeith » Sat Jan 06, 2018 7:01 pm

Please reserve using the CNC12 configuration menus for advanced features and settings in CNC12 not supported by the Wizard.
All basic cnc control configuration settings for Acorn should be completed by using the Wizard.
The Wizard sets the CNC12 parameters and creates the matching CNC12 Acorn PLC program automatically for the choices you made and the data you entered in the Wizard.
All new users should be using the Wizard to configure and get the machine up and running for a no brainier, no reading of the manual approach to setting up the CNC control.
After you have successfully configured the machine and are cutting good parts and made a report.zip back up file.
Feel free to go into the CNC12 parameters and monkey about.:-)

762x51
Posts: 118
Joined: Wed Aug 02, 2017 8:40 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC11: No
CPU10 or CPU7: No
System Serial Number: B0D5CC56DD75-0605170063 , 985DAD4295CF-0928170127 , 38D2694E4703-1222170401
Location: Near Guilford College, Greensboro, NC
Contact:

Re: Fine DRO Adjustment & Measuring Overall Turns Ratio

Post by 762x51 » Sat Jan 06, 2018 10:55 pm

Using Keith's suggestions and Marty's video for reference I was able to get my Techno-Isel router, that has 4mm ball screws, calibrated to within 0.001" on the X&Y Axis and 0.0015" on the Z axis.

I did find that it's better to set the Wizard to Imperial if you're calibrating the DRO in inches. Setting the wizard up in metric and saving the file in metric then changing the DRO from metric to inch doesn't appear to be the best way to do things when you're calibrating.

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