Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: christopherwoods on October 22, 2006, 05:46:52 AM
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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.
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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.
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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.
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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.
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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. :-)
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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.
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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.
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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.
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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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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.
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Hi,
I have a K2 cnc router too, it's a K2-2514 and I have been having problems with the stepper motors loosing there place, it seems like the get stuck and then get freed and start cutting again but out of place. I played with the acceleration and velocity and almost had them down to nothing. With a tip from K2 I started using WD-40 on the leadscrews and it helped a lot but I was still limited, it still screwed up once and a while. I changed from Mach2 to Mach3 and that made a big difference as well, but I'm still not too sure about finding the sweet spot. What I've been told is to crank it up till it screws up then back it off until it stops screwing up, but I can't afford to do that it always does it at times when I don't want it to. Does anyone have any better way to find the limit for the machine?
I was thinking about building a router like the K2 models, 4x8 with 6in Z travel any tips?
Thanks,
Greg
P.S. try www.harveytool.com for small endmills for example .001 dia x .003 long or TiAIN coated 4 flute 1/32 ball for$22.20.
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Greg, Hello. I had a lot of problems with my machine at first as well. First question for you is, you said that you had better results using Mach3 over Mach2. Have you had any problems using Mach3? Meaning, is it your CNC that is messing up or the computer/ software side of things?
- make sure that your electricity is adequate. I had big problems due to the fact that I was using a long under rated extension cord for power. Changing to a heavy duty and short cord made a huge difference for me.
- In Mach3 under motor tuning, what do you have for: Step Pulse & Dir Pulse? By default, mine was originally set at 0. And I was loosing steps which would get really bad over a period of 15 minutes or so of running a program to the point where the machine would be way off when I set it back to zero. I inquired about it on this forum and was told to try setting these to 5 for each one. Since then I have been running smoothly. There was another guy who was having the same problem who eventually had to get some kind of an output signal booster because his computer port pins were not giving out a strong enough signal.
Hope this info helps you out.
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Also run a driver test and see if you have a nice flat line :)
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I think its the machine side because if I run the machine at slow feeds in doesn't screwup but if I turn my feeds up it at random will screw up. I can run one program at high feeds and no mistakes then the next program will screw up at some time, sometimes it will not happen at all that day but on the next day it happens all day, it seems totally random.
I have everything running to one power bar, then into the wall, I have my computer, monitor,speakers, stepper box, router, light and fans running off the one power bar. Do you think thats the problem? The only time I had a problem is when it lost it's location and then it slammed into the top of my aluminum work piece and it blew the breaker.
Step pulse is set to 6 and the Dir pulse is set to 0.
The Driver test this is what the screen said,
Pulse per Sec. in 25Khz Mode=23853
CPU Speed=1999
Apic timing constant=4192
and the line had some fuzz in it and it would go flat then come back and so on....the fuzz never went more than the line above or below.
Did your K2 Stepper box get very hot?
Thanks for the input!
Greg
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Greg, well I dunno. I am not expert in these areas. I was just relaying my experiences. With my situation, the problems would occur more consistently so I was able to do things to make the problem happen, change something and then I'd know pretty quickly if it worked or not.
How about when you shut your mechaine down, are you able to turn the axis easily by hand? Does the problem always happen to 1 axis or does the whole thing freeze up?
I think that my stepper box gets a bit warm but not hot.
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By the way, anyone know if there is a particular file that I can back up to save all of my Mach3 settings? I'm thinking of re-installing my OS to get a bunch of junk off the computer. And would like to back it up just incase....
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Thanks for the reply, I just want let you know all the details just so I don't miss telling somthing that might be the problem. I think is screws up at random, I attached a few pics to show you want I mean.
I can move the machine when the power is off with out a problem.
I had to add fans to my stepper box because it was getting too hot to touch especially after long period of time, even if it wasn't running.
What do you think of the Dir pulse being set to 0?
I wonder what Barker thinks of the Driver Test results?
Thanks,
Greg
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Hi Chris,
I think if you back up your xml files. screen sets, and keygrabber profile you will have everything you need. Let someone else confirm though.
Also, I saw my machine acting weird one day that is was in a long run. The drives were hot. I cooled the drives off and it smoothed right out. I'm not sure this was the problem. Since then I have kept air going across the drives and have not seen that again. :) I'm building a cabinet this week with fans. The first box is very small, it was one I had laying around.
Brett
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Hi all, just getting started in the wood engraving / routing end of CNC. Ger21 I was interested in your comments on feed rates etc.
What router motor do you recommend? I want to be able to take a log (12 dia x 30" length ) cut a large flat on it, then engrave lettering on it. My machine is a converted Atlas knee mill. I want to use a router instead of the 3hp motor.
Thanks for any suggestions!!!
olf20
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Here is what I have found using my machine. First, here is the machine:
http://homepage.mac.com/bigvelvetdog/workshop-cnc.html
It is an older K2 and has the Hatachi 3Hp varible speed router. I almost always run the router at full speed. My most common setup is cutting alder or mahohany, sometimes with a hardwwod top like maple with a .5" 2-flute straight bit. I typically do rough cuts a 75 IPM. Precision cuts at 50 IPM or less. If I am just skimming the surface I may run at 100 IPM. And If I am using tiny inlay bits I run at about 15 IPM.
In a nutshell, this is what works for me on my machine.
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Set your direction prechange to about 10 and the step pule to 10 on the motor tuning page... That should help (I hope)