Mike, I've been grinding away on the design, I'll post some pics in a day or so when I'm ready for criticism. -Carl
Mike, I've been grinding away on the design, I'll post some pics in a day or so when I'm ready for criticism. -Carl
Anoel,
I agree with most of your requirements but I do think a few may not work. 1st we are, at the moment, planning on skate bearings or another ebay bearing, maybe bigger. The speed you mention 80-150 ipm, I am no expert on steppers but I really don't know if these numbers can be reached with any torque left in the motor to do the cutting. Servos would have no problem with the numbers but the cost would put us into the high end design. Now to the size. As the old saying goes "It's easy to take some off but it's hard to put it back on." This definately applies to CNC as well. If we design this machine to be a 3'x4' work area it is simple to downsize to any size you want, with no loss in rigidity. Now concerning rigidity I fully agree no MDF here. We can go steel, aluminum, 80/20 or whatever the group decides. At the moment I am liking Carls rail design. It should be a vast improvment over other, more expensive, designs I have seen on so called mid range machines.
So I hope no one is offended but no MDF in this thread please. Lets also try to come up with some new and inovative ideas that can cut cost and improve quality!
Thanks Jimmy
Use 2-4 turns per inch screws (multiple start acme) and you should have no problem. Taus uses Nema23 steppers on his K2 and gets ~120 ipm. See post #84. http://www.cnczone.com/forums/showth...7&page=3&pp=40Originally Posted by Jimmy Southern
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
3'x4' is managable... as well. I just want to make a point that "midrange" doesn't mean a "bigger" hardware store machine.
Speed... I get reliable rapids of 60ipm on my current MDF machine with unsupported drill rod rails and a 1/2"-10 2 start lead screw... Acetal anti-backlash nuts and 120oz steppers... I'm sure that with 200oz steppers I could squeeze that up to 80ipm or more wth no trouble. My axis are not frictionless by any means either, they are much tighter than they should be but it works and I'm not screwing with it. I did a test axis that moved very freely and with the same steppers and lead screws I could get around 100ipm. So I don't think that the speed numers I posted are out of line at all. 80ipm for steppers and 150ipm for Servos... (I should have mentioned that though)
I guess that my vision of "high" end machine is like that of a Techno-Isel or other manufactured machine with highspeed spindles and run 600ipm rapids and automatic tool changers.
Nathan
Hey Guys,
I could not remember seeing a stepper design exceed 80 ipm, so thanks for the clear up. I just want to avoid having too high of expectations and people loosing interest. I am really looking forward to seeing the design come together!
Keep the Ideas coming!
Jimmy
I've heard of 300+ ipm rapids with 150oz motors and rack and pinion drive.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
another long rant but,
i tend to agree with most points
speed of the machine though well ok 150 ipm well thats going to be determined by the steppers / servos used and the lead screws used
think this is best left to builders choice , its posable to upgraded to bigger steppers and different lead screws but as the builder may not have funds i think the best option is to provide a standard stepper mounting ,
theres nothing stopping it having a stepper mounting drilled to accept a couple of sizes of steppers , and well the lead screw , well again that should be builders chioce, the mountings for it tend to be the same for 2mm per turn as for 10mm per turn (for metric ones )
and yes no MDF , if the main use is going to be woodworking then the bed from ply or mdf maybe (it should be made easy to replace )
i also like the idea of carl's rails , but i can see a problem that may be troublesome
that tends to put me off
if the rails are made from aluminium they are going to wear fast , also aluminium in that configuration is going to deform quickly where most working pressure is applied causing kinks in the rails
making them from steel well the running surface is going to be prone to rust that will make the surface uneven after a year or so
and unfortunatly stainless steel is not readily avalable in angle section
i don't fancy having to strip down the machine and sand down the rails every 12 months or keep having to replace them because they wear, should do the job right and with the right materials so this machine should last a long time
maybe using flat 1/2" by 1 1/2" section stainless steel or whatever size is best suited bolted to the frame for the x&y axis and another method for the z , bar or square section may be better in the long term for wear and environmental reasons
grease is only going to get squashed out of the way by the bearings , and add to the friction
skate bearings well ok there readily available and cheep ( but dose not mean there any good )
we could look for a bearing that is as widely available and used in a comman everyday item like a bike or car (of the right size that is ) if skate bearings don't look like there going to do the job
Dave
Using aluminum for the rails would be unacceptable, for the exact reasons that you say. In fact that thought never occured to me, I have been planning on using angle iron. As for the rust, It might be a problem, but it should be negligible, perhaps by keeping the tracks oiled? I'll post some pics tonight. -CarlOriginally Posted by achiestdragon
ok turns out that it may not be a problem about the rust
looks like http://www.arenastock.co.uk/ do stainless steel in angle section
think there international so there may be a US site for them also
interestingly they only list it with metric mesurements though
Dave
McMaster-Carr has galvanized angle. Much cheaper than SS.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
supose but galv tends to chip and feel shure that if running bearings on it will cause it to flake off in the long run ( looking at old galv it seems to do this ) a heavy presure rolling on it would cause it to flake after some use , maybe 2 to 3 years , less if under constant use , i dont know if theres any info or figures for that avalable though
and ok so SS is expencive but should be low mantanance and should not need to be replaced normaly in the machines life (unless you waire it out)
Dave
Nah, just regular old angle iron should be adequate...The bearing running across the way will keep the rust down, just paint the angle and it'll be OK. Stainless would be nice if it were hardended, but at that cost point might as well hit up ebay for some used thk style rails.
I still like the way that ShopBot and EZ-Router are using V-groove bearings on the angle iron.
Nathan
The tables of most of my woodworking machines are unfinished steel. I wax them every now and then. I don't see much rust.
I get a conservative 120ipm on my machine with 1/2" 8 2 start and 200oz steppers. I have run it at 150ipm, but it is so light that the whole machine shakes. I have it just sitting on a table with large casters. Probably not a good idea.
Steve
Steve, What drives are you using? HobbyCNC? What voltage?
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Izzlestar
I saw your post regarding your angle iron carriage.
Wow what a nice design... will be interested in your progress.
My design was going to be a copy of the Shopbot design ( using dual-vee bearings ). I dont see why your design may not be even better.
Thank you for sharing your design and especially the pics ( worth a thousand words)
regards
Domenic
(Sydney, Australia)
Jerry,
I am using a PWM HobbyCnc controller and their 200 oz steppers set to 8 microsteps. I am supplying 3 amps per coil from my 39 volt DC supply. Is this what you are asking? I do not like the way it performs on my Z with a heavy router. I can stall the motor by grabbing the shaft collars with my fingers when it is lifting (not when lowering). I can not stall the other motors with my fingers. I plan to switch to a higher tpi for the Z. (?)
Izzlestar, I like it.
Steve
Yeah, that's it. Thanks. Are you using the 1/2-8 2 start on the Z?
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Yup, 1/2-8 2 start all around.
I've got 1/2-10 for my Z, and a 250oz stepper. I'm hoping that's enough. I've read about a lot of people on the Mach2/3 group losing steps on the Z axis. Apparently people think the Z needs the least torque, but in reality it needs the most.
Gerry
UCCNC 2017 Screenset
http://www.thecncwoodworker.com/2017.html
Mach3 2010 Screenset
http://www.thecncwoodworker.com/2010.html
JointCAM - CNC Dovetails & Box Joints
http://www.g-forcecnc.com/jointcam.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
How about running a cable counter weight and pulley setup on the Z to lighen the load.Originally Posted by ger21