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What is a good feed rate?
« on: October 22, 2006, 05:46:52 AM »
Hello everyone.  I need some expert advice on feed rates.  I have a K2 CNC and I build guitars with it.  I have been re-vamping my files to reduce the time spent on the CNC.  I have been able to shave 45 minutes off the total time just by tweaking my feed rates and order that things are done.  Used to take 2 hours and now at 1:15.  Most of the time I am cutting alder wood with a .1/2" bit at 50 IPM and .25" depth of cut.  This works very well on the alder wood but on the occasion that I cut something like Bubinga, it does bog down the router.  So here are my questions...  How fast of an IPM can I run my motors at without burning them out (Nema Steppers) even with no load.  I have the max velocity set at 100 and am afraid to go any higher then that.  Can I jog at 200, 300, 400 safely?  -  Anyone else cutting a similar wood to alder or other types,  what feed rate do you cut at?  -  I've just been afraid to push the machine too hard for fear of damaging it.  And because I am relatively new to this,  I don't know what is appropriate as far as what are the maximum capabilities.

Offline zealous

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Re: What is a good feed rate?
« Reply #1 on: October 22, 2006, 10:51:07 AM »
Hey Chris,
Big fan of yours  ;D

Are you using the K2 39x25 (G?)?
Did you get the Steppers from K2, whats the spec's on those steppers?

I have the K2 39X25 with the upgraded Z axis, servo motors and a Porter Cable Router.
I use Onsrude carbide bit's.
I'm achieving 200 IPM in Hard Maple at about 0.002 accuracy with a 1/2 carbite bit at 0.25 depth.

The most important parts to getting fast and accurate cuts with the K2 cnc is having the upgraded Z axis,servo motors and good carbide bits. I would give K2 a call and get the servos, I believe there 300.00 for all three.

Tune your motors
If you stick to what you have and your motors are tuned correctly, jog the machine to see what kind of travel speed your getting without butchering the motors or the frame, this will be the max that your machine can handle.

After this it'll be up to your router.
Your bit should be clearing out the material giving very little resistance to the travel of the machine.
I spend around $75 a bit and they don't last long till there dull.

I would love to talk guitars and design softwear if you have the time give me an email. zealouseappex@comcast.net
I also have some screen designs that work good with the K2 machines and other stuff.
« Last Edit: October 22, 2006, 11:02:02 AM by zealous »

Offline ger21

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Re: What is a good feed rate?
« Reply #2 on: October 22, 2006, 01:01:25 PM »
If your spending $75 a bit, check out www.vortextool.com You'll get a 30% discount when you buy 3 or 4 bits, maybe even 2 on the more expensive bits. The chipbreakers will let you cut faster, or deeper, or both. Cleaning them after each use with a good bit cleaner will make them last longer.
Gerry

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Offline DAlgie

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Re: What is a good feed rate?
« Reply #3 on: October 22, 2006, 03:40:30 PM »
I buy .500" solid carbide ballnose mills, 2" LOC, 4" OAL, and use them as router bits. I see that Vortextool had this bit for $87, I get them from Wholesaletool.com for about $37. These will cut over 240 gallons of MDF wood chips and still be reasonably sharp.
Re: What is a good feed rate?
« Reply #4 on: October 22, 2006, 04:44:46 PM »
Thanks for the replys!  To be honest.  I have been buying the house brand router bit from Rockler.  I can definitely tell the difference from a brand new bit as opposed to one that I have already cut 20 guitar bodies with.  But I am looking forward to checking out some better bits.  I suspect that once I give these a try I'll never use anything else.  That is usually the way.  -  Zealous,  I'll email you.  I bought my K2 used from another guitar builder.  What he told me was that this machine was one of the first K2 prototypes.  So it doesn't really have a model number.  My steppers are Nema 23.  I don't know any other specs on these.  Also the router is set up for a Hitachi.  I am just not sure that I want to do a lot of upgrades to this machine.  It runs pretty well as is, and I think that ultimately I wan't to have 2 CNC's for my work and will save that upgrade money for the next machine. :-)

Offline zealous

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Re: What is a good feed rate?
« Reply #5 on: October 24, 2006, 09:04:26 AM »
I had a feeling I was paying allot for router bit's  >:(. Onsrud's home base is about a half an hour away and I've heard there the best.

I'll have to try out those suggested bit and see what they can do.

Thanks for the links. I'm interested in the "chipbreakers", I usesome small 1/16 for cutting inlays and they work well.
Wonder if a 1/2 chipbreakers would give a super clean cut. I currently use downward spiral bits form my finishing cuts but they seem to dull out the quickest.

Offline ger21

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Re: What is a good feed rate?
« Reply #6 on: October 24, 2006, 09:45:05 AM »
I use the Vortex chipbreakers exclusively when cutting hardwoods, and they do cut very cleanly, although you may get an occasianl small ridge that can easily be sanded off. If you're making multiple passes, you probably won't notice. Downcut spirals dull very quickly, so I rarely use them. If you're making a finishing pass around the perimeter, try a compression spiral.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
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Re: What is a good feed rate?
« Reply #7 on: October 24, 2006, 01:17:53 PM »
I'll pass on another link for router bits.  -  http://drillcity.stores.yahoo.net/  -  drill bit city seems to specialize in small sizes.  I get my 1/32" there for my inlay work and these sizes are hard to find. 

By the way,  I kicked my "velocity" up to the max which was 150 in Mach 3.  The machine seems to run fine at that speed for jogs.  Although 50 IPM seems like a good cut rate and I probably won't go any higher.  But its nice to be able to jog the router out of the way quicker...  But I am surprized that 150 is the max.  Don't know if I am missing something, and I don't think that I need anymore speed then that, but I assumed that faster speeds would be possible.

Offline Chaoticone

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Re: What is a good feed rate?
« Reply #8 on: October 24, 2006, 02:09:53 PM »
I don't know if this will help, but I hope it does.

The standard is to run the feed rate up slowly until you break the bit. Back off 10% and that is optimal. Now keep in mind, this is in production runs where you are planning on using a lot of the same cutters for a long time. Of course I would not do this on a single piece, or if I just had the one cutter. If you are planning on using the same size, style, etc. for a while it may be worth scrapping one cutter to know.They will last a long time using this rule though.

Brett
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Offline ger21

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Re: What is a good feed rate?
« Reply #9 on: October 24, 2006, 07:45:59 PM »
The standard is to run the feed rate up slowly until you break the bit. Back off 10% and that is optimal.

With a 1/2" bit, I'll bet you can stall the Porter-Cable before the bit breaks, when cutting wood. I've been cutting wood for about 9 years on a large router, cutting over 1" deep per pass @ 400ipm with 1/2" tools, and have never broken a bit. (without hitting metal :D ) Most newer large commercial routers can easily cut over 1000 ipm.

In the woodworking industry, the rule I've always heard is increase speed until cut quality suffers. In other words, cut as fast as possible while maintaining acceptable cut quality.
« Last Edit: October 24, 2006, 08:07:39 PM by ger21 »
Gerry

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JointCAM Dovetail and Box Joint software
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