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CNC a Harbor Freight 33686

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Bamban

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#1
Taking the hobby shop to different direction I am thinking about getting a HF 33686 from a friend and convert it to cnc, maybe with a 3 Axis. This would give me a good reason to turn down any more AR barrel work. Doing barrels turned into work, the very thing I did not want this hobby to morph into. I need something new to learn.

I found a BP S1 converted to CNC, after careful thinking, I really just need a little mill to make some small stuff.

Questions:

Is this Mill Drill good enough platform?
Could it take a 3 axis conversion?
Which servo drive kit would y'all recommend? Why?

Thank you.


Nez
 

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#2
The biggest thing I see is the Round Column. If cnc'd, I would think you could only use the quill feed for the Z axis. To raise and lower the Head, the clamp on the column would need to be released and that would allow the head to rotate around the column.

I have a Syil X3, which is a cnc version of the Grizzly G0619. I'm happy with it for my needs.
 

Bamban

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#4
Ray,

Thank you.

First time I checked the thread just now after you mentioned it, that is quite a conversion you did there. So, is the RF30 is basically the same as the HF unit?

Don't know how your conversion compares with Flashcut CNC Kitchen, but I sent out a RFQ for R-3V-200-3401, I think this is their higher amperage servo drive system. Might be an overkill for that little mill drill.

Lots to learn and planning.


nez
 

rdean

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#5
There are so many different ways to approach the subject and each has its problems and benefits. Which ever way you go the electronics are just the beginning.
In the end having fun and learning was a main consideration for me.

Ray
 

Bamban

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There are so many different ways to approach the subject and each has its problems and benefits. Which ever way you go the electronics are just the beginning.
In the end having fun and learning was a main consideration for me.

Ray
Ray,

The same thing for me, the joy of learning is what drives me. I have a pretty much accessorized Bridgeport S1 that I do the milling work now, a small cnc unit could be a lot of fun.

Last night I read through a few conversions and watched sinilar videos, I came to the conclusion a packaged kit would be the practical route for me. The only question is which one. Trying to sort through all the propaganda sheets is learning on its own for someone diving into this CNC world totally ignorant.

nez
 
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bpimm

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#7
The round column can be a limiting factor, if all the parts you are going to make are short so they fall within the quill travel it's not a problem. I have found issues when switching from collets to a drill chuck and long bit as the tool length difference takes a lot of the quill travel. once you set up you can't move the head without having to re zero everything. I have actually cut off drills to keep inside the envelope as well as using an endmill in the drill chuck (ducking for cover)...

I bought mine used and already set up with a lot of hours on it so they can do a lot of work.

Ugly but mostly functional.


There are a lot of things I'd do differently if I were to build one myself, I bought this one before I knew much if anything about machining and haven't done much about some of the questionable design characteristics it came with, like the light switch power switch. I think I would put it in a larger enclosure to contain the coolant spray rather than attach the containment to the table for one.
 

spumco

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#8
I'd recommend against it. The effort of converting a manual mill to CNC isn't trivial, and starting with a round column mill means you're going to end up with a white elephant when you're done. Get the mill if it's a good deal, and maybe even mount some stepper motors on the X&Y axis with belts just to play around and use them as power feeds. Here's the deal with converting a mill to CNC and achieving reasonable accuracy and ease of use:
1. Computer
2. Breakout board
3. Motion control board, optional but highly recommended
4. Spindle control, might be part of the BOB, might not. Quite a bit depends on the motor and existing control. Do you really want to fiddle with those step pulleys every time you drill a hole and then switch to an end mill? Tool changes could take 5-15 minutes (or longer if you have to raise/lower the head). Yuck.
5. Electrical/electronics misc: E-stop, limit or home switches, wiring, enclosure, stepper/servo drives and power supplies.

All of the above are going to happen regardless if you start with a little Sherline, that RF30 clone you're looking at, or a G0704 or RF45. This doesn't touch the mechanical parts:

6. Axis motor mounts & drive (pulleys or direct drive)
7. Quill drive (really now. How rigid is the quill when it's extended because you don't want to move the head?)
8. Ball screws, nuts, mounts. (not trivial. Requires some machining and fitting, and possibly modifications to the table and saddle)

All that work and you still have a round column mill-drill. The parts costs will be similar to a like-sized square column mill, and the installation & troubleshooting effort will be the same or worse. Even if you keep the acme screws and just do a 2-axis CNC with manual Z (quill or head), items 1-6 above still have to happen.

My advice, having gone through this over the past year and doing countless hours of research before I plopped down a dime, is to buy something that will be:

A) useful when complete, and not abnormally irritating. I want a pleasurable hobby, not a psychotic heroine-addict mistress of a machine tool.
B) possibly worth something to someone else if I decide to abandon the hobby or upgrade to a grown-up VMC.

If you're spending the $ and effort to convert, why not start with a mill that has much greater potential when finished? It's like deciding to go racing and planning the project around a minivan.

Buy the mill, but plan to use it to to help convert a G0704 or something similar. And then sell it or keep it as a spare drill press in the corner like most of the Bridgeports I see in job shops.

And while you're fiddling with the manual mill and shopping for a square column mill to convert, do yourself a huge favor and start learning CAD & CAM now, rather than when you have a CNC mill lurking in your shop that you can't really figure out how to drive.

Even better - convert your lathe to CNC and watch it squirt out AR15 barrels while you count the money. Then splurge on a turn-key CNC mill that your lathe paid for and start machining custom USPSA open-class 2011 slides to fools with more money than sense at $500 a pop.

-S
 

pberry26

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#9
Part of the hobby involves up-scaling the machine... how many of us have built multiple super cars, and took a loss when we sold them? But, the learning and time consuming work was a real pleasure! i have lots of time, experience, and parts, and figure the cost to make my ENCO RF-30 into a CNC machine, will be under $500.00, spent over 6 months... There are tons of hobbies that cost much more!
 

mksj

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#10
I think you might be better off starting with a small mill that is more common and there is information on CNC conversion. Also parts are available and others have worked out the bugs, or issues. You need to think of the size/rigidity, mass, sliding surfaces, lubrication/wear, etc. Also probably wnat a belt drive with a higher top end speed (probably in the 5-7K range, so you could change the pulley ratio on a belt drive but a gear head would need to be converted), so that also needs to be factored in. The Sieg X3 is very common, grizzly smaller mills and or maybe something like the PM-30MV which already comes with a belt drive. Some smaller mills may be more adaptable to CNC conversion and require less mods/cost/time.
 

pberry26

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#11
Craigslist find, from a tool and die maker. A 1984 Enco RF-30 ( for $600.00) with the Rong Fu Z axis gear drive. The HFT 12 speed unit is a virtual identical copy, sans the Z axis drive.

This has a single phase motor wired for 120 VAC, that gets quite warm after 5 minutes. No reverse. So, upgrades will come along slowly... First is that the missing Z axis drive belt is available on ebay, so ordered ($12.00?) and installed it. Cleaning up and lube was second. Then, thought of rewiring from the 120 VAC 32 Amp to 230 VAC 16 amp, with a drum switch to provide reverse... But, have acquired a 3HP, 2.2KW Marathan VFD 230 VAC 3 phase four pole 1725 rpm motor, ($50, on Craigs List, in the mounting frame, with the variable belt pulley! That pulley sells for over $55, new!), and, with the variable width belt pulley, will use the 23/32nd inch width belt, and, a VFD box, such as this:
http://www.vfds.in/3-hp-vfd-single-phase-to-three-phase-vfd-260617.html

Your experiences and input will help me greatly! A question is have you done this? Would it be better to get a more powerful VFD electronic drive machine, such as one for a 4 HP 3KW motor?

Oh, he included that huge US made machinist vise, two sets of clamps/dogs, in their storage frames, two fly cutters, small and the big one, with 8 bits up to 6 inch, complete set of three chucks on R8/M2 shafts. Most are US and/or German/Belgian made, for an extra $200.00.

Yes, there are great bargains to be found! I have been an electronics engineer, Air Force trained, 1965 to 1985, taught AC power for installers, in GEEIA, and have been a commercial welder on the FMC plant lines. I am an FCC licensed Radio Amateur, rebuilt computers and set up private class rooms for latch key kids, in several schools, since 1997, running only the Linux and the BSD operating systems.

So, next was to order the speed indicators, which are LED readouts, with magnetic sensors, that sell for about $4.00 on ebay. I have 9 volt 100 ma
DC power transformers to power them. Then, will be installing Digital Read Outs on all axis, for best accuracy, though initial set up of the vise and column, will be with the 1" dial indicators on magnetic bases. Last but not least is to eventually install stepper motors and CNC read outs.

Thanks for this opportunity to learn new things!
 

Paul Thompson

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#12
It may be too late but I've converted 3 of my own mills and 80 other people's. It costs far less than anyone else and it is everything you need to go. pthomps2@gmail.com
 

coherent

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#13
I've built a number of CNC machines and converted a couple of mills. If I already owned a round column mill I might try it, otherwise nope. Not that is can't be done, it's just a lot more trouble to get the z functional. Converting a mill to CNC isn't that hard and I would say anyone can do so if you have the right tools and are willing to invest the time. Buying a kit is the fastest and easiest, but fabricating it yourself is a great project in my opinion. While the manual mill is operational, many of the parts can be fabricated using it. Depending on your mill and the parts used you may have to do some mill work on the table (pockets or material removal to allow room for ballnuts, screws etc) which would require a different mill or hand grinding. Personally I'd do a bit of research on the web for cnc conversions folks have done on mills in your size/spec range and then decide which mill and conversion approach to take. I've seen lots of conversions on the HF mini mills as well as little machine shops version and of course a myriad of Grizzly, PM's and other imported models. Once you decide, you should be able to find and buy a used one as your conversion guinea pig. With some of the commonly converted models there are parts like pre-cut screws with the ends machined or motor mounts etc that allow you to mix and match what works best and fits your budget. Same goes with you electronics. You can piece together your own, or buy complete or partial kits. 570 oz nema 23 steppers are fine for smaller mills, but nema 34 and larger steppers or a servo motors are always an option. If you have another mill and a lathe, machining and fabricating everything yourself won't be hard. This place has about the best prices on components and kits unless you'd rather find individual parts on ebay or elsewhere on the web. https://www.automationtechnologiesinc.com/
If you have any specific questions feel free to pm me.
 
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