Chris G0704 Build

ChrisAttebery

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Back in October of 2012 I started a G0704 build thread on CNC Zone. The Benchtop Mills forum over there is practically dead so I thought I'd start a thread here.

Chris G0704 Build on CNCZone.com

To catch up the machine has the following:
CNC Fusion Premium Ball Screw kit.
3 x KL-5056D Digital Bipolar Stepper Motor Driver-32 bit DSP Based
3 x NEMA23 570oz/in 5A 3/8” Dual Shaft Stepper Motor (KL23H2100-50-4B)
1 x 48VDC/12.5A Switching CNC Power Supply
Ethernet Smooth Stepper
CNC4PC C35 - QUICK SETUP BREAKOUT BOARD
CNC4PC C6 - Variable Speed Control Board
Manual Oiler
Vista CNC iMach P1A-S pendant
Mach Standard Mill running on Mach3.
Touch plate for MSM automatic tool offset measurement
2" head and column spacers.
ABEC 5 AC spindle bearing upgrade
Home brew fogless mist cooling system
1100W 4500rpm motor. IMHO the bare minimum for a decent CNC conversion.
KBIC-225 DC motor controller

2 speed belt drive. Based on Hoss' design. I wound up turning a pair of Multi V pulleys using a J6 belt. 3:2 high ratio and 1:2 low ratio. With the 1100W motor I wound up with 6750 rpm in high and 2250 rpm in low. The spindle pulley is a light press fit into a 6007 bearing. I turned a bushing to fit that bearing into the head casting. This setup is MUCH quieter than the L belts that I started out with.

IMG_5658.jpg

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ChrisAttebery

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I made a full enclosure using TNUTZ 1010 rails and brackets. I used 1/4" Lexan for the front panels and sliding door. I just used Coroplast for the back walls. The machine sits on a steel stand that I welded up using 3/16 wall 2x3 and 2x2 tubing.

IMG-5618.JPG
 

ChrisAttebery

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That's basically where the machine was up until last week. On Thursday I was milling a block of steel that was going to run for a few hours. I was running a 1/4" 4 flute carbide end mill at 6000 rpm, .250 DOC x .020" WOC. The machine should have only been using about 1/3 HP but apparently I had abused it for too long and it melted down. It shorted out internally and smoked the KBIC in the process. Of course this happened when I had 6 orders sitting on the bench waiting to be machined over the weekend.

On Friday I ordered a MTRP-002-3BD36 2hp, 3600rpm 3 phase motor and a WEG Electric CFW300 series vector drive from Automation Direct.

I bored my motor pulley to .626 on my lathe. I didn't have any small HSS so I just used a piece of sharpened HRS in a tool block to cut the key slot.

IMG_7751.jpg
 
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ChrisAttebery

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I’m in a tight spot since I don’t have a motor for the mill so I can’t machine a new mount. I decided to model the top of the machine in Fusion 360 and see what I could come up with. I realized that if I turn the motor 45 degrees that the bolts will clear the outside of the head. I made a couple plates from 3/16” steel on my drill press to mount to the head and turned a couple spacers out of 1” CRS on the lathe. This will move the motor 1” farther back than the 1100W motor but it will still clear the column but about 1/4”.

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ChrisAttebery

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I received my shipment from Automation Direct yesterday. They shipped everything FedEx Overnight. That was a nice bonus.

I was able to get the VFD wired up to the controller and motor. Programmed the VFD and was able to start the motor from Mach3. I programmed the VFD to give the motor a 4500rpm top speed so that it matches the 1100w motor it's replacing. That way I can reuse all of my G code.

I got the pulley fitted. The key slot was a PITA and needed to be filed about a dozen times.

Here’s a side by side picture with the new motor and the 1100w motor. It’s roughly twice the size.

IMG-7773.jpg

Here's the new motor sitting on the head. The belts should be here this afternoon. I need to grab a couple 3/8-16 x 3" SHCS screws from the hardware store.

IMG-7774.jpg
 

Reddinr

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Well done. Always good to see machine build/conversion/rebuild projects I can selfishly learn from! I bet you will just feel better not having to baby the motor anymore. I've been thinking about converting my RF-45 type cnc mill to belt drive so I can get higher RPM and quieter operation. I just have not gotten up the nerve to tear down a perfectly fairly good machine yet. For now, for high RPMs I rig a porter-cable router to the head and that has worked OK for some things.

I have a, now dusty, ethernet smoothstepper that I figured I would implement at the same time. I need to figure out what kind of bearings to use for the spindle. I want to keep or improve the spindle run-out I have now but get it as fast as practical.
 

ChrisAttebery

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The belts came in so I got the machine put back together. I ran a batch of parts for about an hour. The motor was at 105F, about 20 degrees above ambient. On these parts I use a 3 flute 3/8 end mill at 6750 rpm, .650” DOC and .030” WOC. The finish looks better. It think the old motor was struggling to keep up.


 

ChrisAttebery

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Yesterday I took it easy on the first part but after that I went right back to the speeds and feeds I used with the 1100w motor.

Some observations:
1. The motor is quiet below 3500 rpm. As in with hearing protection it’s hard to hear it. Above 3500 rpm the fan is the dominant sound. It isn’t bad though. It’s kind of a low woosh sound.

2. I set the accel and deccel to 1 second each. I immediately noticed how much quicker the spindle ramps up and down compared the the DC motor setup. No more waiting for the spindle to stop before I change tools.

3. I had some parts that I started with the old motor and the finish seems to be better now. I think the old motor may have been struggling for a while.

4. After an hour of running non stop the motor was only about 25 degrees warmer than ambient. The old motor would have been 70-80 degrees over ambient.

5. Even though I have more power I don’t think I can push the machine any harder. I tried increasing the feed rate on one of my roughing cuts and I could hear the machine start to chatter and vibration levels increase. I think 1.5 cubic inches per minute in aluminum is about the limit for these machines. They just aren’t stiff enough to handle more than that. One exception is drilling. I had limited myself to 1/4” and below with the old motor and high speed belt drive. I should be able to push 3/8”-1/2” drills in the high speed setting now since the motor has constant torque down to 1350 rpm at the spindle.
 

GunsOfNavarone

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I gotta ask as I am ready to do something now...
What does it cost to do this kind of conversion? The little I have checked into makes me want to buy a Tormach or..... instead of converting what I have. I assume the ballscrews have completely eliminated the backlash? There is the learning curve as well. I'm jealous! Great work! I really think something like this is more than I want to bite off. The VFD conversion wan't bad on my lathe, but this is FAR more entailed.
 

ChrisAttebery

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Someone on the other forum mentioned that he regularly pushes his machine 2x harder than I've been pushing mine (3.4 cu in/min vs 1.5cu in/min). I took a look at my mill this morning. The screws all seem to be tight but I could feel some slop in the table if I grabbed the ends and pushed them in opposite directions.

The Y axis seemed to be the culprit. I was able to tighten it down quite a bit. It was enough that I decided to pull the gibb and take a look at it. There's a wear mark where the very top of the dovetail on the base is touching the gibb. It doesn't look like they are machined on the same angles. After playing with it for a while I got it about as tight as I can without stalling the axis. I think the only cure for this would be to buy a new gibb and grind or scrape it to fit the casting.

The X axis seems OK. I pulled the gibb and there are a few spots over the entire face that are contacting. It's not a lot and it's not very even, but it's better than the Y. I tightened it down until the screw bottomed out in the casting. That axis seems to be OK though.

I checked Grizzly's web site and the gibbs are available for $8.50 each. I think I'll order a pair and see if I can get a better fit on the machine.

Anyway I'm going to try pushing the MRR a bit harder over the weekend and see how the machine reacts.
 

GunsOfNavarone

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I am curious how the new gib shim works out..keep us posted.
 

ChrisAttebery

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I ran a test cut using a Best Carbide 3/8" 3F Carbide at 6750rpm, 81IPM (.004" IPT) .75" DOC and .030" WOC (1.5" MRR) and worked my way up to .060" WOC (3.65" MRR) in .005" increments. The machine seemed quite happy at 3.65" MRR. I stand corrected. Apparently my weak spindle motor and sloppy gibbs were giving me the impression that the machine was tearing itself apart.
 

ChrisAttebery

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I gotta ask as I am ready to do something now...
What does it cost to do this kind of conversion? The little I have checked into makes me want to buy a Tormach or..... instead of converting what I have. I assume the ballscrews have completely eliminated the backlash? There is the learning curve as well. I'm jealous! Great work! I really think something like this is more than I want to bite off. The VFD conversion wan't bad on my lathe, but this is FAR more entailed.
I don't remember what I paid to be honest. The mounts and ball screws were around $1k. Automation Technologies has a conversion kit now. I bought my drives, PS, steppers, etc from them too. The motor and VFD I just bought were $400.

If I had to guess it'd be around $2k-$2.5k to get one up and running. Oh yeah add in a PC, and software (mach4, Acorn, linuxNC). Add another $400 for the bigger motor. The belt drive you can do for about $100. Maybe $3k to get up and running with a decent machine base. Then you need a bunch of tool holders. I use R8 set screw holders and I have about 20 at the moment. Then plan on ruining a few hundred dollars worth crashing them, burning them up, etc.

You need to ask yourself do you want a machine to make money with or just a machine to play with and upgrade as you go? I have countless hours into my machine. I originally bought mine to make money with. I do enjoy upgrading it from time to time it but most of the time I just want it to work. Even a Tormach isn't going to give you industrial class reliability though. If I had the room I'd buy an old Fadal or VF1 and just make parts.
 

ChrisAttebery

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A quick update: Since installing the 2hp motor I've been able to double the MRR on every one of my programs that I've run in aluminum to roughly 3" pre minute. I've done this mostly by increasing the WOC. I feel really comfortable with the machine running 81IPM (.004 IPT) with a 3 flute carbide end mill. The other day I was tweaking a program and had the feed override set to 150%. The mill powered right along at 120IPM and 4.5" MRR but the finish suffered a bit.
 

ChrisAttebery

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I got the flat parts of the new motor mount machined out of 1/2" 6061 last night. The inner pieces mount to the head and the outer pieces mount to the motor.

IMG-7865.jpg

I went to make the round threaded spacers I need and realized that my 3/8-16 tap can't cut deep enough. :rolleyes:
 

ChrisAttebery

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I was thinking a pulley tap would work, but that nut tap looks like what I need. I'll have to see what the local tool shop has in stock.
 

Buffalo21

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I was thinking a pulley tap would work, but that nut tap looks like what I need. I'll have to see what the local tool shop has in stock.

I pulley tap has a long reach, but the overall shank diameter is larger than the tap part


top - a 3/8”-16 pulley tap
Bottom - a 3/8”-16 nut tap


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Buffalo21

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Chris,

I find this build and some of the others, very interesting, I see CNC equipment on a daily basis, but have no concept of what it take to make a part. I work with computers, in my business, on a constant basis, We have a locked core of safety procedures and protocols, we can alter some of the operating parameters, the fuels being used and set the combustion fuel/air curves, but the locked core can not be altered. When I first started in this business, I need a VOM, a couple screwdrivers, a few wrenches and sockets and a number of pipe wrenches, now I still have all of them equipment, plus welders, plasma cutters, pipe threaders and now 3 laptops and an iPad.

I basically grew up in my grandfather’s machine shop, where everything was 100% manual, the equipment in my shop ranges in age from 1930s to current, but all of it is still manual. I understand the premise of CNC, but wonder if its a one off, its it quicker/easier to do it manually or spend the time to program it, then wait for the program to run, then if errors, rework. If your doing 150 parts, its another story, so is CNC, based on the scale of the job?? Is it the sense of accomplishment?? Mind over electron??

It looks to me that people buy an inexpensive (relative term) bench mill, then spend 3-4 times what they bought the mill for to convert it to CNC. Maybe my view is somewhat askew to the actual premise or goal of the CNC operator. Spoken by a man who has at least 15 welders (still looking for the perfect one).

All of my questioning aside, the workmanship, design and execution is amazing. The idea of “throwing” a bunch of numbers into a machine, that then carves a part is, truly amazing. Maybe if I understood it better.
 

BGHansen

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To me CNC is a game changer even for one-offs. Naturally depends on the one-off. Make a bracket from a piece of angle and drill 6 holes, do it manually. I made a clamp to fit my G0709 lathe's tail stock ram for a DRO. Manually machined it on a mill with a rotary table. It came out nice and works great. But I'd have done the job in a third the time with my Tormach.

CNC doesn't have the "charm" of old-school craftsmanship, no question. Our tool makers at the GM Lansing Grand River Assembly Plant tool room all completed an apprentice program of 8000 hours of various disciplines. They're all over 55, so little to no CNC in that training. Our local community college is spitting out "CNC Machinists" by the dozen with a less than 1 year program. They take one class in manual machining using a lathe and mill.

Strip out an M6 thread and need to fix it? Go to a young "CNC Machinist" and they'll tell you you're screwed (pun intended). Go to one of the old-timers, they'll probably tell you to drill and tap it for a 1/4"-20.

I admit to still being fascinated by watching the stepper motors do exactly what I told them. A couple of weeks ago I cut some helical gears on the Tormach using the 4th axis tipped at a 45. Coordinated moves in the X, Z and A axis that could never be done manually. The CNC just opens up the possibilities to what you can imagine and turn it into a part in minutes.

Bruce
 

Buffalo21

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Bruce,

Thanks for the reply.

Are you programming from start every time?? Or are you modifying an existing program?? Are there “canned” programs, that allow to insert certain segments?? And you program from segment to segment?? How intuitive is the CNC software??, can you import a drawing and have the machine “read” the drawing and duplicate it?? Or is it line after line of G code, you have to input??

Sorry for all the questions, I find the subject incredibly interesting, personally its not something I’d probably ever do, but every I see it, I have more questions.
 

ChrisAttebery

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I model everything in Fusion 360 first, then make the CAM files, and then run them on the machine. There's no way I could do it most of it on a manual mill. I probably put 3-4 hours into the design, and 1-2 hours on the CAM, but then those plates took about 5 minutes each on the mill.

On the CAM side there are routines built into Fusion that will do pockets, follow a contour, etc.
 

ChrisAttebery

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On the tap, I only needed another 1/2" of thread. I looked for a tap but nobody has one locally. I decided to chuck the tap in the lathe and grind the shank down with a cut off wheel in my Dremel tool. Afterward I realized that the tap is just HSS and I have some good inserts for hard metals. I cleaned up the ground area by taking light cuts at 190 rpm.
 

Buffalo21

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On the tap, I only needed another 1/2" of thread. I looked for a tap but nobody has one locally. I decided to chuck the tap in the lathe and grind the shank down with a cut off wheel in my Dremel tool. Afterward I realized that the tap is just HSS and I have some good inserts for hard metals. I cleaned up the ground area by taking light cuts at 190 rpm.
Glad you got it
 

ChrisAttebery

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Here's a picture of the entire assembly. I downloaded a step file for the motor from Automation Direct. Everything else I drew from measurements.


AC Motor Mount.jpg
 

BGHansen

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Bruce,

Thanks for the reply.

Are you programming from start every time?? Or are you modifying an existing program?? Are there “canned” programs, that allow to insert certain segments?? And you program from segment to segment?? How intuitive is the CNC software??, can you import a drawing and have the machine “read” the drawing and duplicate it?? Or is it line after line of G code, you have to input??

Sorry for all the questions, I find the subject incredibly interesting, personally its not something I’d probably ever do, but every I see it, I have more questions.
I'll shoot you a PM so I don't mess with Chris' thread
 

ChrisAttebery

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Good news, good news, bad news...

The first good news is that I machined a bunch of parts yesterday morning and the mill is much more satisfying to run now that I've cranked up the metal removal rates.

The other good news is that the new spindle and gibbs showed up a couple weeks ago. I finally got around to installing the new spindle yesterday. It seems to have a bit better runout. I measured it at .0015" TIR roughly 1.25" from the end of the spindle with a 1/4" carbide shank in an R-8 end mill holder.

The bad news is that the ABEC 5 bearings that I installed in May are shot. The lower has a click and the upper feels like it's full of sand. :^( I ordered two sets of the cheap AC bearings from VXB that I had originally used. They should be here by the middle of the week.
 
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