Power Vs Accuracy

cohokidd

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I am looking at and researching a new CNC router. As a journeyman mold maker I know the components of what I use at work, a Mikino VMC. Which like most big mills runs on servo drives and ball screws. When I started researching CNC routers I became aware of the other choices available. First the stepper motors that can replace the servo's and 2nd the rack transmission systems that are used instead of the ballscrews. I am looking for any knowledge and advice about these 2 subjects. So far I think I would rather go with the stepper motors. They seem to be very close in accuracy and require less maintenance. So the cost of upgrading to servos doesn't seem worth it. Am I missing anything major on this topic? I am certain I want to go with ballscrew and square guide rails on the Z axis and was fairly certain I would go with that same setup on the XandY axis. Then I read in a few places that when going with a large router spindle (larger then 2.2KW) that a rack and gear system is required/strongly suggested on the XandY travel. How true is this? How much loss of accuracy is there by not using the ballscrew? Is the extra power worth the loss of accuracy? Thank you to anyone who can give me any advice on these topics. Please don't hesitate to add in any other information you feel is critical when choosing a CNC router.
 
Hello cohokidd,

I am sorry I have no experience to add, but I wanted to say I appreciate the topic/question and have "watched" the thread so I don't miss anything.
Welcome to the group!

-brino
 
Hello cohokidd,

I am sorry I have no experience to add, but I wanted to say I appreciate the topic/question and have "watched" the thread so I don't miss anything.
Welcome to the group!

-brino
Thanks for the interest. I have pretty much picked the router I want to go with, at least the frame and manufacturer. There are just a few customizable components, like these I need to choose before placing the order.
 
Welcome Aboard!

I have worked with just about every configuration of router out there. So far, I haven't seen a lot of difference in accuracy between the rack & pinion vs. ball screws. There are also some that have a timing belt drive, but I have no experience with those.

For the tabletop type routers the most common is ball screws and stepper motors. I have never seen one that didn't have a ball screw on the Z axis. On some of the wider routers, I have seen ball screws on both sides of the gantry. My 4 x 8 is all ball screw.

If this is for home hobby use then open loop steppers are a good choice. Accuracy is not as good as with closed loop servos because it is possible to lose steps and then the controller has no idea where the tool bit is at. For hobby work this is not normally a problem. It is possible to close the loop on steppers, and operate them like servos. This is what I'm doing on my machines, but it is relatively expensive to do so.

If your router is going to be used for commercial work or you need high accuracy and higher speeds, then I would recommend going with hybrid steppers or servos for increased accuracy and higher performance. I just did an upgrade on a 5 x 10 Multicam router for a customer and installed Teknic Clearpath SD servos. I found those the be a nice little unit. Direct bolt in for a NEMA 34 motor, and they take a step & direction input just like a stepper, and have the drive built in. I think they also have a NEMA 23 motor size. They close the loop internally.

Looking forward to seeing you new toy...er, tool:) We love pictures.
 
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When we were researching the build for the high school I spoke with many manufacturers of commercial routers. What I found is that on the rack & pinion systems they would claim 0.001" positioning accuracy but when pressed about operational accuracy it was 0.005" to 0.007".

R&P is better for rapids than ball screws. For the high school accuracy out weighed speed so we went with ball screws plus we primarily only cut aluminum sheet up to 3/8".

We use servos at the school. I have steppers on my mill and small router at home. If sized properly the chance of missing steps is very low.

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I know nothing about the company nor have I seen their products. In the pictures it looks nice, professional. You can't beat owner testimony, so that is a plus. You might ask the US customer if they have worked with aluminum on that machine. As you know, there is no substitute for mass when it comes to machining.

The Panasonic servos should work fine, top of the line equipment.

A few questions come to mind. What control software are you planning on using, and is it being supplied with the machine? Is this supposed to be turn-key out of the box? Do you know anything about what CAM post processor is needed?
 
I know nothing about the company nor have I seen their products. In the pictures it looks nice, professional. You can't beat owner testimony, so that is a plus. You might ask the US customer if they have worked with aluminum on that machine. As you know, there is no substitute for mass when it comes to machining.

The Panasonic servos should work fine, top of the line equipment.

A few questions come to mind. What control software are you planning on using, and is it being supplied with the machine? Is this supposed to be turn-key out of the box? Do you know anything about what CAM post processor is needed?

It is the heaviest gantry I could find on any router of similar size. Both Mach 3 and DSP are offered. Not sure which to choose lots of reading available out there on that subject!!! Sounds like personal preference to me. They both work. The post processor has crossed my mind but a guy at work that wrote ours for Gibbs Cam said he'd write one for me.


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Here's a direct link to the ELE-6090 product with specifications, samples and close-ups:
http://elephant-cnc.com/product/en/Product-20160928-014930.html

It looks pretty capable from here.

-brino

Thank you. I have talk to multiple sales people and even used my wife's email to switch things up. I pretty much always got the same info from them. So either they are fairly honest or they have theirs story very straight between all sales people


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