Build: CNC Surfometer

[LyonCNC]

Hello everyone,

I want to convert a nonfunctional CMM machine into a CNC Surfometer. The Idea is that a separate Surfometer will be attached to the z-axis and positioned to take readings by the CNC system once this project is completed. I have never retrofit a CNC machine before nor worked on them. I was hoping that I could get some idea of the hardware that I would need to accomplish this build and perhaps some guidance moving forward. Here is a link to a photo album of the machine in question:https://flic.kr/s/aHBqjBgnm9.

Previously this build was attempted with a stepper motor retrofitted on the X-axis servo and custom machined so that it would act as a conduit to avoid having to design new brackets etc. This resulted in a consistent drift of .001 that occurred over every move.

We would like to avoid using stepper motors this time around and switch over to closed loop servo motors with encoders to bring the accuracy and repeatability to within .0005 of an inch.

Any advice is greatly appreciated,

Thank you

[cnckeith]

ha! never seen this before.

[cnckeith]

toss those DC's and steppers, and put some AC servos on it and convert to timing belt (instead of the multi Vee)

[LyonCNC]

Okay, I will get started on that. I was thinking about going with something like a DMM DST620 Servo motor with their DYN4 drivers, what do you think?
I looked into timing belts after you mentioned that, but there are so many with different types of teeth. Do you have a recommendation on which direction to go? Do I need to know the gearing ratios or something related to calibrate anything in the future?

I am imagining ordering components for one axis to make sure that I can achieve the results that I want there. Do I need another power supply supplemental to the one provided with the board?

[cnckeith]

Okay, I will get started on that. I was thinking about going with something like a DMM DST620 Servo motor with their DYN4 drivers, what do you think?
I looked into timing belts after you mentioned that, but there are so many with different types of teeth. Do you have a recommendation on which direction to go? Do I need to know the gearing ratios or something related to calibrate anything in the future?

I am imagining ordering components for one axis to make sure that I can achieve the results that I want there. Do I need another power supply supplemental to the one provided with the board?

i like the leadshine AC servo packages better.
contact Chris at leadshine. 400 watt pulse direction units are what you are after for use with Acorn.
http://www.leadshineusa.com/ProductSubT ... rvo-drives


use the "HTD" or "GT2" belt and matching pulleys. this is the modern timing belt technology. don't use X, L, or XL

[LyonCNC]

Thank you for that advice. I reached out to Chris, he recommended an EL7-RS400P for the servo drive. Are there any resources that you can point me towards that could help me figure out which components I will need for the electrical side of things and how to wire something like this with the assumption that I don't know much?

[cnckeith]

full closed loop Ethercat controller with the ethercat version of the EL7's are on this page.
https://shopcentroidcnc.com/hickory-cnc-controller/

hybrid closed loop cnc controller kit (acorn) is on this page.
https://shopcentroidcnc.com/acorn-cnc-controller/
Acorn schematics and install manual are also on this page