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Thread: Adventures in Converting my Precision Mathews Milling Machine to CNC

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    *Registered User* CNCJoseph's Avatar
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    Default Adventures in Converting my Precision Mathews Milling Machine to CNC

    A couple of months back I purchased the Precision Mathews PM-25MV (see image links below). The goal was to convert it to CNC so I could do my own rapid prototyping. I looked around for conversion kits, but nobody had any in stock and it would be a while before anyone could make one. After a quick search on McMaster to estimate how much the aluminum stock would cost, I decided to save both time and money and make my own kit. How hard could it really be?

    I started by completely disassembling my PM-25MV and measuring everything with my vernier calipers (they were passed down to me from my dad and I've been too sentimental to buy digital calipers). After I put the machine back together I moved onto the next step, making a CAD model. Big mistake! Turns out not all my measurements matched up, including under the saddle (or was it my bad hand writing?). I had to completely disassemble the machine a second time to verify a few measurements.

    After I had designed my own kit using my CAD model, it was time to make chips. MANY hours later, all the parts were machined and everything was ready for the CNC conversion. I disassembled the machine for the third time and rebuilt it using my new parts. The X and Y axis conversion went smoothly. I only had the Z axis left to do... and one of my parts wouldn't fit! There was a mistake in my design! The only way to fix it was to completely disassemble the machine, rebuild the machine back to its manual configuration, and remake one of the parts for the Z axis conversion. At this point I could completely break down and rebuild a PM-25MV in my sleep, including tramming the head!

    After correcting my design flaw, I disassembled the machine for the 5th time, removed all the lead screws, and replaced them with my new ball screws and CNC conversion parts. This time everything worked perfectly.

    Here's the image link to the machined parts for the first conversion kit I made:

    Original Conversion Kit

    I was quite pleased with my conversion, especially considering all parts were made manually. However, I didn't like the way the stepper motors protruded out almost 8 inches. I also didn't like the way the couplers and bearings were exposed to chips and cutting fluids, especially if I were to upgrade to flood coolant in the future. I decided to go the extra mile and redesign my conversion kit in Fusion 360. This would allow for a much more compact design. At this point in the project I also finally caved in and bought digital calipers.

    After disassembling my machine for the 6th time and rebuilding it with the newer parts, I finally had the CNC conversion kit I wanted (and had been dreaming about). I had also put 200+ hours into the project and had spent more money than the cost of a ready-to-go, bolt-on conversion kit. What an adventure!

    So, if you're thinking about doing your own CNC conversion, I have some advice to share:
    1. Don't do it if you think you'll be saving time or money.
    2. When creating the CAD model, don't rebuild your machine until you've measured everything at least twice and drawn the entire model.
    3. Get digital calipers if you don't own them already. It's cool using the vernier calipers my dad used and handed down to me, but he got it in the days of valve radios, back when dinosaurs still roamed the earth. I'm starting to see why the world went digital.
    4. Don't be surprised if you start having dreams about rebuilding your machine and making conversion kits in your sleep.

    Here's image links to my current CNC conversion:

    PM-25MV with Conversion Kit
    X and Y Axis
    Machined Parts

    I'm also happy to answer any questions you might have about converting the PM-25MV to CNC. I also made a couple extra sets of parts while making my own kit if you would like a bolt-on ready kit.

    Now I need to decide what adventure I want next... spindle speed upgrade, flood coolant, or maybe power drawbar and ATC? Any suggestions?

    Happy machining!

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  2. #2
    Gold Member Jim Dawson's Avatar
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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Nice job!

    I'm still using vernier calipers that I got back when the dinosaurs roamed the earth. I have digitals also, but I like my verniers. I do have to use my magnifier to read them now.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Looks awesome!

    Spindle motor and coolant were huge steps for my G0704 when I did them.

    Power draw bar is a nice luxury to have. ATC, for the type of work I do might be cool and potentially would save me some time, but it would be pretty minimal. Especially after balancing the amount of time it would take to create the ATC in the first place. That's a lot of manual tool changes.



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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    It sure looks beautiful!

    I've just ordered my own PM-25MV, and I'm avidly searching the internet for any additional information about it.
    Have you any information on the amount of backlash you get in your axis? From my reading, ball screws aren't perfect.

    Right now, I'm totally strapped for cash, and there is no way I could go out and buy a CNC kit for my new mill.
    So I entertain myself with plans to 'make' all my own parts over the course of a few months.

    Just out of curiosity, can you make your CAD models available?



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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Search Franco CNC on YouTube. He has really good cad models of the PM25 linked in one of his videos.



    Sent from my SM-G892A using Tapatalk



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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Thanks fusion.

    Yes, I have seen Franco's videos. And have been playing with his free plans for the last few days.

    I think I see elements of Franco's designs (or at least some similarities) in CNCFusion's parts. But there are a few differences as well.

    It makes me wonder if CNCJoseph and Franco are the same individual, or if they have shared some aspects of their design with each other.
    In particular, the X and Y stepper mounts are visually similar to each other.

    Anyway, I await CNCJoseph's input into this matter.



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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Same here, Thanks Fusion.
    I'm going to be buying a clone machine the next size up from the pm25.
    Looks almost identical apart from more depth for extra Y travel.
    Will have a look at those plans



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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Nice Job!!! I'm in the research part of my conversion. I know I have settled on the pm-25mv though. Did you go with mach 3,4, or acorn? Just custion on the spec side of your build also. Thanks



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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Well.
    I've just put a deposit down at Amadeal on my machine (AMAT25LV-R8) to secure one, due in around 2-3 weeks. They go pretty quick so wanted to be sure. I've downloaded as many plans as poss and my lil' SiegX2 can make the bits.
    Ordered some couplings, oiling/greasing parts & about to start building a base/enclosure thing.
    Can't order screws yet until I know the exact sizes of the machine.

    Busy time coming. Can't wait

    I may have to look at the Z travel. I use a few direct collets as well as the chuck so may need to bring it closer to the table. Might have to figure out a new gas strut design. The one in the back may limit how low I can go.
    I'll machine the slot in preparation and leave it until it gets some funds back. Going to expand the Y hopefully another 15mm at least as well.

    So much for warranty



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    *Registered User* CNCJoseph's Avatar
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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Ziptie007, thanks for the kind words. I actually went with the Centroid Acorn. I haven't had any issues with it. I also got their pendant which was a nice upgrade. As for other specks, I used 640 oz-in stepper motor on the Z axis and 570 oz-in stepper motors and the X and Y axis. I know people have had success with the 570 oz-in on the Z axis, but I liked the idea of having a little more torque on the Z.

    LBay, actually Franco and I are not one and the same. Thanks for the compliment though I developed my conversion kit before Franco released his video.

    I'm happy to answer any other questions anyone has on my conversion kit. It's been running great for six months now.

    Happy Machining.



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    *Registered User* CNCJoseph's Avatar
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    Default Re: Adventures in Converting my Precision Mathews Milling Machine to CNC

    Quote Originally Posted by CL_MotoTech View Post
    Looks awesome!

    Spindle motor and coolant were huge steps for my G0704 when I did them.

    Power draw bar is a nice luxury to have. ATC, for the type of work I do might be cool and potentially would save me some time, but it would be pretty minimal. Especially after balancing the amount of time it would take to create the ATC in the first place. That's a lot of manual tool changes.
    CL_MotoTech,

    I have decided to take your advice and focus on the spindle motor next. Unfortunately I am having a hard time finding any information on upgrading the spindle motor on the PM-25MV. I started a new thread to this effect.

    How to Increase RPM on PM-25MV (or similar G0704)

    Since you have experience with the G0704 spindle motor upgrade, it would be very much appreciated if you (any anyone else with spindle motor upgrade experience) could chime in on that thread.

    Thanks



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    Quote Originally Posted by CNCJoseph View Post
    CL_MotoTech,

    I have decided to take your advice and focus on the spindle motor next. Unfortunately I am having a hard time finding any information on upgrading the spindle motor on the PM-25MV. I started a new thread to this effect.

    How to Increase RPM on PM-25MV (or similar G0704)

    Since you have experience with the G0704 spindle motor upgrade, it would be very much appreciated if you (any anyone else with spindle motor upgrade experience) could chime in on that thread.

    Thanks
    I went through several option trying to control the stock motor with acorn or upgrade the spindle motor. The Chinese one from automationtech is garbage. Leeson makes a metric 1.5hp d80 face motor that is small enough to make work. Especially if you extend the head with a spacer. You will need a VFD too. I ended going with a small 3 phase motor from Groschop. The most powerful one they make is 1.1 hp. They have a controller and signal isolator to match too. The motor and controllers were about $500. They were really helpful with the purchase and will customize the shaft if you want. The one I got could not have the encoder mounted because it needs a fan. I was able to machine the fan a bit so I could mount my own encoder. I am now able to turn on, turn off,acorn can see the spindle speed and control the spindle speed through acorn. Max spindle speed is 6240 at 1:1 ratio using the stock pulleys(modified for shaft size) and belt . It is amazing that the machine now runs cooler. I can run at 6000 rpms for hours and the warmest spot on the machine is about 150 deg F. I did upgrade the spindle bearings to SFK bearings but did not switch to AC bearings.

    I also upgraded to a TTS power drawbar. I used the G0704.com project as a guide to make it. This is an expensive upgrade that took several attempts. The pneumatic cylinder is expensive and I had to buy 2 because I got some bad advice. If you want to make your own it may save some $ but I doubt it. I now have a working power drawbar TTS spindle. It is really nice. Effortless tool changes. Just be aware that Tormach only recommends 1/2” bits and smaller with tts. Increasing the hp may be counterproductive along with the TTS depending on your intentions.

    I can help more if you are interested. The motor is nice. I do wish I had gone with the Leeson just because of the higher hp. It is substantially larger though and would require the head spacer and not money. I do believe that the stock motor is controllable through acorn but would require more advanced electrical knowledge than I have. The trick is turning it on an off. Spindle speed is pretty easy with a signal isolator. There is very little info on the stock controller electronics so I scraped it and upgraded.

    My next project is to increase the y-axis travel. I am right in the middle of the head spacer project right now. One flaw of the PM is that only about 5” of the 6.6” of y axis travel is usable because the spindle isn’t centered over the travel. (I made the mistake of using a double ball nut so my travel is about 6.6.) I need to flip the ballnut and get a longer ballscrew. I haven’t determined if this will do the trick or not.

    Last edited by TCanndee; 11-11-2018 at 02:00 PM.


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Adventures in Converting my Precision Mathews Milling Machine to CNC

Adventures in Converting my Precision Mathews Milling Machine to CNC