First baby steps, CNC controller works! - RC Groups
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Jun 29, 2011, 11:44 PM
Wood Chucker
Lacquerhead's Avatar
Yippee!

First baby steps, CNC controller works!


To be perfectly honest I feel mostly lost in this company but I'm learning a lot. I admire all the work you guys do and hopefully one day I'll be able to participate at that level. In the interim I'm started down the road to CNC awesomeness. I bought a HobbyCNC controller last week, assembled it over the last two nights and figured out the wiring for some cheap mystery motors I got at a local electronics salvage shop.

4-axis hot wire first
XY laser cutter next (foamies and sheet balsa never seem very far)
3-axis mini-mill after those, probably add a 4th axis later.

I've got a lot of learnin' to do with respect to drawing and converting to g-code and I'm sure I'll waste a fair amount of material before I get it sorted but it should be fun!
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Jul 03, 2011, 10:38 AM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
Makin dust is what it's all about. If there's a usable part left at the end, that's a bonus.

Welcome to our obsession. The water's warm
Jul 03, 2011, 10:55 AM
Wood Chucker
Lacquerhead's Avatar
LOL. Thanks, I think.
Jul 04, 2011, 04:03 AM
Everything's A Compromise
Larrikin's Avatar
OMG... I'm so subscribed. I've wanted to venture down this path for ages. Document every and spare nothing It'll be great to follow you from the raw beginning.
David
Jul 04, 2011, 04:14 AM
Bill from Coffs Harbour
Hi there Wood Chuckker.... I am into this thread also.... I will follow your progress with interest...
I have the desire to build a CNC router and perhaps a foam cutter as well... I have already scrounged some very thick aluminium angle that may be good for a router chassis... so the dream begins...

Regards
Bill from Coffs Harbour
Jul 04, 2011, 06:48 AM
Registered User
I will be watching with intrest. My controller arrived on Friday and plan to start my CBC build in the next few weeks
Jul 05, 2011, 07:14 AM
Registered Loon
Blackrat's Avatar
i must say, getting the 4axis wire cnc to work properly in the beginning is a pita , but once you have done all your test cuts you start to learn what temp the wire needs to be at for cutting whatever mediums and then it become cool ... just get thru the whole setup and keep at it

i would like to buy some ultra thin cutting wire for the thin cores .. one day
Jul 05, 2011, 07:05 PM
Wood Chucker
Lacquerhead's Avatar
OK, for those of you watching here's where I'm at now. My table is a fairly traditional XYUV four axis design. I bought, assembled and tested a HobbyCNC Pro driver board. I'm not afraid of soldering things together and figuring out what I did wrong. Years ago I built a engine control computer for my 1984 Mazda RX-7 track/competition car and I had no problem with that so the HobbyCNC should be easy. It was. If you take your time and follow directions EXACTLY then you'll be OK. Paying very close attention to detail is a must as the instructions were written by an electrical engineer for an engineer. Thankfully I'm an engineer (software) and a tinkerer/fabricator. I read Competition Car Aerodynamics and Computer Graphics - Practices and Principles for fun. If you're not like me get an assembled board as the owner of HobbyCNC can be quite abrasive and short tempered. Shame, he has an otherwise solid product.

So my board is assembled, voltages and currents are set, time to get some steppers. Being the cheap bastard that I am I wanted to do a proof of concept with motors that didn't cost $60 ea. Off I went to a local electronics salvage store a/k/a the Geek Candy Store. $25 later I had four small five-wire unipolar stepper motors in my hands.

I had to figure out the wiring so off to Google I went and found contradictory information on the particular model I found. For anyone not so adventurous I suggest just buying new motors with a known configuration. Because of the inconsistent information and failed attempts at guessing which was right I decided just to disassemble one of the motors and look for myself. This is usually pretty easy for steppers since they tend to be screwed together rather than crimped like a standard DC brushed motor.

With the wiring finally sorted I tested the motors on the board using the Linux-based EMC2 Live CD. I'm a Linux geek already so if you're not I don't advise you follow me here. Use something you're comfortable with that lets you test the motors appropriately. Google helps and there are a handful of respectable free bits of software. For full time use I suggest something more robust than what is typically available as freeware, unless you're the adventurous (cheap) type.

Next up, build the base. Mine is a piece of 3/4" plywood cut a bit smaller than my rather small workbench. The largest piece I can cut will probably be in the order of 11"(X) x 18"(Y) x 4" (Z). The work area is about 2/3 of the sheet size which is about 2/3 of my desk size. I'm using ball-bearing drawer rails from the local home improvement store for my linear slides. I feel I can get away with this since hot-wire generally doesn't produce much dust/grit. If I were milling something I would probably suggest something like the Igus Dry-Lin linear bearings but I haven't sourced them yet. I have seen other people suggest them so I expect they are available in single quantities. Since they are self-lubricating they shouldn't attract as much dust and grit but I digress. I'm also too poor to buy any of the Acme screws I found so I'm using 1/4-20 all thread that I ran down with long coupling nuts to smooth out the threads. I'm using a blind nut in a piece of 1 1/2 x 3/4 oak as my lead screw nut. I can run those at high speed the entire length of the 1/4-20 rod chucked into my drill using nothing but gravity to hold the wood down. Sure there will be a fair amount of backlash but until I can afford a zero backlash screw and nut I will have to learn to make do with it.

So that leaves you where I am now. I have the X axis down and tested and I'm mounting the U axis now. Once those two are finished I'll have to mount the Y and V axes and get those wired. I'll probably just get a solid state relay at the local Geek Candy Store to turn my hot wire on and off then wire up the limit switches. I don't believe I have enough channels to set home switches.

Pictures to follow.
Jul 05, 2011, 07:08 PM
Wood Chucker
Lacquerhead's Avatar
Quote:
Originally Posted by Blackrat
i must say, getting the 4axis wire cnc to work properly in the beginning is a pita , but once you have done all your test cuts you start to learn what temp the wire needs to be at for cutting whatever mediums and then it become cool ... just get thru the whole setup and keep at it

i would like to buy some ultra thin cutting wire for the thin cores .. one day
I understand many people use guitar string. I used to play guitar so I have a number of guages from .015" down to .009". In stores I've seen as small as .008". Experimentation is the key here. I haven't used any of these yet so take what I'm saying with a grain of salt.
Jul 07, 2011, 12:43 AM
Wood Chucker
Lacquerhead's Avatar

ACME screw-lite, or, How to make threaded rod suck less


Acme screws are dang expensive. Really expensive. Even in the tiny little 1/4-x sizes they're $100 for 6 feet of screw + $20-$40 Acme nuts for each axis. Very quickly two axes would be more than the balance of my CNC investment. Solutions I've seen frequently for ultra-light duty are timing belts on linear slides and threaded rod with blind nuts. I opted for the later since there's a Lowe's Home Improvement almost within walking distance and a Home Depot across the street and down half a block. That's the good news.

The bad news is that threaded rod sucks as a lead screw. Particularly the inconsistent and frequently bent stuff often found in bulk barrels at said stores. I figured this out after I'd assembled my X and U axes. My $5 stepper motors kept stalling regardless of how well I lubricated them and aligned and realigned the axis. Finally I disassembled it and figured out quickly why. The stupid thing was binding horribly thanks to the awesomeness of the bulk threaded rod. I couldn't run even a normal nut up and down the thread without some serious effort. I read on some site that I can't find at the moment that you can hone the threads with a coupler and some sort of mild abrasive that escapes my mind. I got a coupler and ran it down the thread a few times with one end of the threaded rod firmly attached to the chuck of my drill and the coupler in a nice gigantic wrench. It definitely loosened up so I reassembled the axis and gave it another shot. Much, much better. And then it bound. And then it stalled. And then I cursed. A lot.

Fast forward to today. After waking at the crack of 7:30 and getting some much needed C8-H10-N4-O2 (caffeine) I wandered across the street to Lowe's. There I acquired a tap and die set and set about truing the thread on my threaded rods. While waiting for my laptop to boot, VPN to connect, etc. I cleaned up one axis and reassembled it. Thence over the course of the next several hours the next axis was cleaned up and reassembled it just before lunch. There were shavings all over the table so it must be perfect by now, right? Boot up ye olde CNC machine and start running tests. Absolutely, positively . . . . worse. Much, much more cursing.

It was at this time that I remembered seeing somewhere that a local store had some nice shiny threaded rod instead of this bronzish looking stuff I found at Lowe's. I figure it must have been Home Depot so off I went at lunch to search for it. Sure enough, right in front of all the other threaded rod were some shiny threaded rod whose tags said 'Zinc' on them. I assume these are some kind of mild steel that are zinc plated. I also got some push-in threaded furniture inserts made of what looks and feels like pig iron. I cleaned the threads up quickly with the tap. These furniture inserts would make several rotations under their own inertia if I gave them a good spin. These had to have been 10x better than the blind nuts but the longer barrel length with demand greater precision in alignment, or so I thought.

After wrapping up work for the day I cut some more bearing plates, measured and drilled them for the inserts and pressed them in with my handy, dandy desktop vise. A careful alignment at the far end of the threaded rod, threaded in an inch or so for good measure. I was surprised at how smooth and consistent this assembly was. I ran it for two solid hours in a loop, forward and back across the length of the lead screw. No issues. This is my final answer. I found that this new solution was able to traverse literally twice as fast as the previous configuration. Conclusion: a crap ton less drag equals a boat load more speed. It should also aid in accuracy and repeatability but I suppose time will tell.

Conclusion:
  • Most threaded rods suck, some suck less. Use a long coupler to field test thread quality.
  • Blind nuts suck as lead screw nuts.
  • Furniture inserts suck less.
  • Cut your threads yourself. Invest in a tap and die if you don't have one.
  • Measure four times, adjust infinitely.

Tim in TX
http://www.lacquerhead.com
Jul 07, 2011, 04:04 PM
Registered User
Quote:
Originally Posted by Lacquerhead
Acme screws are dang expensive. Really expensive. Even in the tiny little 1/4-x sizes they're $100 for 6 feet of screw + $20-$40 Acme nuts for each axis. Very quickly two axes would be more than the balance of my CNC investment. Solutions I've seen frequently for ultra-light duty are timing belts on linear slides and threaded rod with blind nuts. I opted for the later since there's a Lowe's Home Improvement almost within walking distance and a Home Depot across the street and down half a block. That's the good news.

The bad news is that threaded rod sucks as a lead screw. Particularly the inconsistent and frequently bent stuff often found in bulk barrels at said stores. I figured this out after I'd assembled my X and U axes. My $5 stepper motors kept stalling regardless of how well I lubricated them and aligned and realigned the axis. Finally I disassembled it and figured out quickly why. The stupid thing was binding horribly thanks to the awesomeness of the bulk threaded rod. I couldn't run even a normal nut up and down the thread without some serious effort. I read on some site that I can't find at the moment that you can hone the threads with a coupler and some sort of mild abrasive that escapes my mind. I got a coupler and ran it down the thread a few times with one end of the threaded rod firmly attached to the chuck of my drill and the coupler in a nice gigantic wrench. It definitely loosened up so I reassembled the axis and gave it another shot. Much, much better. And then it bound. And then it stalled. And then I cursed. A lot.

Fast forward to today. After waking at the crack of 7:30 and getting some much needed C8-H10-N4-O2 (caffeine) I wandered across the street to Lowe's. There I acquired a tap and die set and set about truing the thread on my threaded rods. While waiting for my laptop to boot, VPN to connect, etc. I cleaned up one axis and reassembled it. Thence over the course of the next several hours the next axis was cleaned up and reassembled it just before lunch. There were shavings all over the table so it must be perfect by now, right? Boot up ye olde CNC machine and start running tests. Absolutely, positively . . . . worse. Much, much more cursing.

It was at this time that I remembered seeing somewhere that a local store had some nice shiny threaded rod instead of this bronzish looking stuff I found at Lowe's. I figure it must have been Home Depot so off I went at lunch to search for it. Sure enough, right in front of all the other threaded rod were some shiny threaded rod whose tags said 'Zinc' on them. I assume these are some kind of mild steel that are zinc plated. I also got some push-in threaded furniture inserts made of what looks and feels like pig iron. I cleaned the threads up quickly with the tap. These furniture inserts would make several rotations under their own inertia if I gave them a good spin. These had to have been 10x better than the blind nuts but the longer barrel length with demand greater precision in alignment, or so I thought.

After wrapping up work for the day I cut some more bearing plates, measured and drilled them for the inserts and pressed them in with my handy, dandy desktop vise. A careful alignment at the far end of the threaded rod, threaded in an inch or so for good measure. I was surprised at how smooth and consistent this assembly was. I ran it for two solid hours in a loop, forward and back across the length of the lead screw. No issues. This is my final answer. I found that this new solution was able to traverse literally twice as fast as the previous configuration. Conclusion: a crap ton less drag equals a boat load more speed. It should also aid in accuracy and repeatability but I suppose time will tell.

Conclusion:
  • Most threaded rods suck, some suck less. Use a long coupler to field test thread quality.
  • Blind nuts suck as lead screw nuts.
  • Furniture inserts suck less.
  • Cut your threads yourself. Invest in a tap and die if you don't have one.
  • Measure four times, adjust infinitely.

Tim in TX
http://www.lacquerhead.com
nice writeup.

i find the zinc plated threaded rods at HD quite rough too. the ones from Lowes are better, could also try OSH. the other option is to get stainless steel rods, more expensive but seems to be better (i don't use them myself).

i think the long coupling nuts also help prevent or reduce backlash.
Jul 07, 2011, 05:34 PM
Everything's A Compromise
Larrikin's Avatar
Zinc (or stainless) threaded rods, funiture inserts or long couplers and tap/die set... got it. Thanks for taking the time to report.
David
Almost forgot, also need "some much needed C8-H10-N4-O2"
Last edited by Larrikin; Jul 07, 2011 at 05:36 PM. Reason: adding the PS
Jul 08, 2011, 12:50 AM
Wood Chucker
Lacquerhead's Avatar
Quote:
Originally Posted by noobee
nice writeup.

i find the zinc plated threaded rods at HD quite rough too. the ones from Lowes are better, could also try OSH. the other option is to get stainless steel rods, more expensive but seems to be better (i don't use them myself).

i think the long coupling nuts also help prevent or reduce backlash.
Thanks. Interesting that you had *EXACTLY* the opposite experience I did. I think the lesson here is to take those coupling nuts with you and run them down the straightest piece of all thread you can find. I took multiple pieces and held them against each other to check for warps just like I do with sheet balsa at the LHS. If your coupling nut starts to feel like its binding while you're running it down just take it off and put that piece aside to try the next one. Once I found pieces that didn't have any apparent problems I bought them and took them home to clean them up with the die. I ran the threaded rod through the furniture inserts without trouble but ran the tap through them anyhow. It bound a bit, cut fresh thread and then we were off to the races so to speak.

Make sure you get the inserts with the flange on the outside. Found these at Home Depot : Crown Bolt 1/4-20 x 20mm Zinc-Plated Steel Type E Insert Nuts (4-pack)

My reasoning behind the flange is simple. I used a vise to press them in to the 11/32" holes I drilled in my hard wood mounts. The insert will naturally stay parallel to the wood while being pressed in thanks to that flange. I pressed two in at a time to even out the pressure. Probably overkill but I had to do one for each side anyhow, right? Measure, mark, drill, press, cut. Done. For lack of a better term due to my ignorance I'll call this a bearing plate since it bears most of the force in translation.



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Description: 3/4" oak, Crown Bolt 1/4-20 x 20mm Zinc-Plated Steel Type E Insert Nuts  from Home Depot pressed in using a bench top vise.
Jul 08, 2011, 12:55 AM
Wood Chucker
Lacquerhead's Avatar
Quote:
Originally Posted by Larrikin
Zinc (or stainless) threaded rods, funiture inserts or long couplers and tap/die set... got it. Thanks for taking the time to report.
David
Almost forgot, also need "some much needed C8-H10-N4-O2"
I use the couplers only as a test mechanism. I couldn't figure out a good way to mount them to the pushing plates so I abandoned that. They were the longest threaded thing I had though so I figured they would most readily point out flaws in any piece of threaded rod I was inspecting. The furniture inserts are what I used for motion translation.

C8-H10-N4-O2 is a must. In fact, I think I'll have some now. Beer is good on a hot summer day (like it is here in the Great North) but you folks down under are in the throes of what you call winter. Unfortunately beer is also an Error Inducing Elemental Inebriant Oscillator or as we Yanks call it, E.I.E.I.O. Ok, that's a bit of a stretch but it was fun to write.
Jul 08, 2011, 03:55 AM
Registered Loon
Blackrat's Avatar
im using the stainless rods and the long hex bolts and it works great

as the stainless threaded bar is cut it is alot smoother than the plated threaded rods

pressing in two of those inserts..... you will need to see if the pitch aligns or the rod wont screw in , but im sure thats an easy fix

cmon, progress !!!


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