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  1. #1
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    May 2013
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    PM-30MV-L CNC conversion

    Hey everyone,

    This might be a few days early to start this, but I figured I would get it going and post some initial thoughts/questions and see if anyone has anything to suggest or add.

    I ordered the machine on Friday, and should be getting it middle of the week this week. I will snap plenty of pics and document this entire build.

    Some background first. My name is Erik and my entry into machining and CNC has been robotics.

    I started out with a 3D printer to be able to make parts for robots and other things, built a RepRap MendelMax, and was instantly hooked on cartesian robotics.

    3D printing is really cool, and I still do a lot of it, but sometimes you just need more strength than plastic can provide.

    So I pretty quickly knew I needed to do a CNC conversion. I started with a LMS 3960 SX2L and bought a CNCFusion kit, and a pretty straight forward G540 and 3 Nema 23 steppers.

    Overall it has been a good machine, but I need more workspace and more precision. After a lot of fiddling, the absolute best I can do for backlash is 0.0025" X, 0.002" Y and 0.004" Z.

    I know if I wanted to, I could get it down further than that by replacing the balls in the ball nuts, and scraping the ways, but I want more rigidity and more space, hence the PM-30MV-L.

    99% of my cuts are aluminum.

    I want 0.0005" backlash or better on at least my X and Y, and would love it on my Z.



    OK, so now for my thoughts/plans so far:

    I have read a lot of conversion threads and bought Hoss's G0704 DVD.

    Other than the Mill, I have not bought anything yet. Figured I would post my thoughts first to see if anyone has any feedback.


    First off, in order to achieve the low backlash, I am thinking about using a double nut system on at least the X and Y axis with a spring separating the two. I plan on using Roton per Hoss's DVD, and I also plan on replacing the balls with oversized ones as Hoss does. I am wondering if the oversized balls AND the spring separated double nut system is overkill and will provide more friction than good, as it seems like one or the other may be sufficient. Would love to get anyones thoughts on this.

    I plan on using Hoss's plans for the AC bearings and the mounting systems for each axis. I may need to use some different sizes depending on my mill's measurements when I get it.

    I am also planning on using steppers instead of servos. From what I have read the accuracy is the same either way, and it seems like the tuning of the servos may be a pain in the neck. If anyone has reasons I should definitely use servos, I am open.

    I am thinking that 570oz steppers should be good for the X and Y, and 906 or possibly 1200 Nema 34 for the Z should be good. Gecko has worked well for me, so I am inclined to go with Gecko just based on familiarity, but again I am open to change and suggestions.

    The next thing I am up in the air about is to build a stand/bench or use the stock one. I have never ventured into coolant before, and have always used air to blow chips away which has been fine to date for aluminum. I know eventually I will have to go to coolant, so I want to make sure that whatever I use for a stand will be OK.

    Either with or without coolant, I really want to build an enclosure as I have for my SX2L, just to keep chips under control. My shop is in my garage and my wife is not fond of me tracking chips through the house.

    If I use the stock stand, I am not sure how I would be able to build an enclosure, I suppose I could lay down a 5 foot piece of plywood and laminate it, and build some supports from the stand to hold it, but that seems clunkier to me than just building a stand.

    If I do build a stand my plan was to build a wooden stand which should help reduce vibration as well, and use a laminated surface as a bench top. Having never used coolant, I do want to make sure when I do go to a coolant system, that my stand can handle it. I am a bit unsure on how that works and how far down the coolant can wander. So if anyone has any thoughts on this I would love to hear them as well.

    I plan on eventually switching to belt drive, but that will be a bit down the road. I plan on buying Hoss's belt drive DVD again as a guide since I will have a different machine.

    Looking forward to getting the machine in and tearing it apart.

  2. #2
    One thing while I have a minute, I would get C7 screws and nuts from linearmotion on ebay instead of rotons, much better quality and lead error.
    You have plenty of room to use double nuts still and there would be no reason to use oversize balls.
    Hoss
    http://www.hossmachine.info - Gosh, you've... really got some nice toys here. - Roy Batty -- http://www.g0704.com - http://www.bf20.com - http://www.g0602.com

  3. #3
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    Great, thanks for the feedback Hoss.

    I would have expected the opposite, so I appreciate the advice.

    Once I get my machine apart I will measure the lead screws and revise the drawings you did for the g0704 and place an order.

    Thanks.

  4. #4
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    QMT shipped out the Mill Monday morning and I received it yesterday. Very fast shipping and great communications.

    Crate was enormous, two pallets. Unfortunately the top of the two pallets was pretty badly crushed which made it a real PITA to get the mill off since I could not get the screws out from underneath the crate that holds the mill in place, and my cherry picker was not wide enough to get around the big pallets.

    After about 2 hours I had everything uncrated and up on the stand.

    First impressions are the fit and finish looks overall pretty good. I chipped up the base a bit getting it on my stand.

    I did some very basic cleaning as I did not have much more time and had to get to work this morning. I took a ton of pictures.

    Couple of interesting observations that I was not aware of or expecting. First the column attaches to the base different than the G0704. It attaches to the top of the base rather than the back of the base. This will make it very difficult to expand the Y travel as far as I can tell as I cannot envision how I will add a spacer.

    I also noticed there is a hole and connector for what looks like a coolant drain and hose, that is pretty cool.

    I thought to myself several times I am very glad I did not go to any of the RF45 clones, as this thing is beast enough working by myself. I am very concerned with how I am going to get the head off this thing, as it appears to be very heavy, my guess is it weighs over 150 lbs.

    I tried to get it started up to make sure it worked. Plugged it in, made sure the chuck guard was in place, hit the e stop and pressed the green button. Nothing happened. I noticed on the QMT web site they say to make sure the gear box is closed and the guard is down, the manual says the fuse breaker may be switched. I could not find the fuse breaker, so I will give QMT a call to figure this out and hopefully get it turned on tonight.

    I took some close ups of the ways on the Y and Z. They feel pretty smooth to the touch, but there are some pretty clear V marks on there which look worse than they feel by finger touch. My hope is that those are intentional to hold the oil/grease, and not an unfinished job, I don't recall seeing that on other mills that I have looked at.

    I have read a lot of people scrapping or lapping their ways, so I would be curious to hear if anyone thinks this needs to be done on these ways.

    Also would be curious to hear if this is considered OK for Ways or if this is flat out unfinished.


    One other thing I noticed is that in what looks like an oil indicator glass, I don't see any oil. Nowhere in the instructions does it mention oiling the gearbox or the head in anyway, so I am wondering if this is something I need to worry about.


    Next steps are to get it turned on and make sure it works, and then I will start to tear it down so I can take measurements for the ball screws and the mounts I will need to make.

    Here are a bunch of pics:










































  5. #5
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    Those V's are where it was scraped. It is to help hold lubricant in that case. It doesnt look like enough coverage to improve overall flatness and alignment. Looks good.

  6. #6
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    Quote Originally Posted by Fastest1 View Post
    Those V's are where it was scraped. It is to help hold lubricant in that case. It doesnt look like enough coverage to improve overall flatness and alignment. Looks good.
    Fastest1, thanks, that was my hope. Thanks for clearing that up for me.

  7. #7
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    I have a Weiss 30 and it is a great mill. It looks like the motor controller has been upgraded on yours because you have heatsink fins on the back of the control box and I don't.

    You will like the mill and it is heavier that it looks. I haven't pulled the head but it is nothing like a RF45 head which I can lift by myself on a good day. If you remove the spindle first it should not be too heavy.

    The 570 steppers will be fine for the X and Y, if you want a little more power for the Z get the 4mm pitch screw for the z and you will be fine with the 570 OZ stepper.

    The Y travel is fairly good on the 30 but the slide could go a bit more forward but it already over travels a fair amount. you could cut 3/4" or so with not much fuss.

  8. #8
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    Thanks for the advice, I appreciate it.

    Have you done a conversion on yours or are you using as a manual mill?

    Quote Originally Posted by arizonavideo View Post
    I have a Weiss 30 and it is a great mill. It looks like the motor controller has been upgraded on yours because you have heatsink fins on the back of the control box and I don't.

    You will like the mill and it is heavier that it looks. I haven't pulled the head but it is nothing like a RF45 head which I can lift by myself on a good day. If you remove the spindle first it should not be too heavy.

    The 570 steppers will be fine for the X and Y, if you want a little more power for the Z get the 4mm pitch screw for the z and you will be fine with the 570 OZ stepper.

    The Y travel is fairly good on the 30 but the slide could go a bit more forward but it already over travels a fair amount. you could cut 3/4" or so with not much fuss.

  9. #9
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    Quote Originally Posted by Fastest1 View Post
    Those V's are where it was scraped. It is to help hold lubricant in that case. It doesnt look like enough coverage to improve overall flatness and alignment. Looks good.
    Hi All
    Actually those little Vs are called flaking marks and none of these chinese machines are scraped. Those are for cosmetics only, and are a bad idea, they will hold oil and swarf(fine metal chips) which will cause faster wear. Bad idea but looks like quality work. The ways on these are poorly ground and then covered up by machine flaking them to look like a high end scraped way. Those should be only on the areas where they are not exposed to chips, like the under side of the saddle. You will be lucky if they are flat and level to within +-.002/12" of way. My G0704 was almost .005 out from end to end. Ground ways are a bad deal. The grinding will cause heat which bows or warps the way so no way will they be flat and level. Plus none of the castings are stress relieved so they just keep moving over time with age.
    Just FWIW
    CH

  10. #10
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    Quote Originally Posted by COMachineist View Post
    Hi All
    Actually those little Vs are called flaking marks and none of these chinese machines are scraped. Those are for cosmetics only, and are a bad idea, they will hold oil and swarf(fine metal chips) which will cause faster wear. Bad idea but looks like quality work. The ways on these are poorly ground and then covered up by machine flaking them to look like a high end scraped way. Those should be only on the areas where they are not exposed to chips, like the under side of the saddle. You will be lucky if they are flat and level to within +-.002/12" of way. My G0704 was almost .005 out from end to end. Ground ways are a bad deal. The grinding will cause heat which bows or warps the way so no way will they be flat and level. Plus none of the castings are stress relieved so they just keep moving over time with age.
    Just FWIW
    CH
    CH, after reading your comments I did some research and looked closely at my ways.

    Your right they are definitely not scraped.

    I did some research on scrapping, and it looks to me like it is a very time consuming, tedious exercise that requires learned skills.

  11. #11
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    That is the conclusion I had come to also regarding scraping. Though I didn't know the nuances of it, ie flaking.
    A lazy man does it twice.

  12. #12
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    The Chinese machines are the lowest quality and cheapest. The Taiwan machines which is The Republic of China are light years ahead of the Mainland China. Some of the ROC machines are hand scraped and held to very tight standards. Richard King who I got help from teaching myself. Teaches classes over there and they are very good at scrapping. I'm a self taught doing my own scraping only plus what learned on here and other online sources one of the guys here scraped his G0704 or a BF20 in himself. I followed his build thread a lot and with Richards help was able to get my G0704 much better here is my saddle that was +.0035 from end to end. I was able to get it so flat that my .0005 DTI would not move from end to end and from side to side. The ways are hand flaked to hold oil where needed as you can. Before I could not get it trammed right now it. If you looking for .0005+- with you machine you should learn scraping.
    Good luck
    CH

  13. #13
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    Quote Originally Posted by COMachineist View Post
    The Chinese machines are the lowest quality and cheapest. The Taiwan machines which is The Republic of China are light years ahead of the Mainland China. Some of the ROC machines are hand scraped and held to very tight standards. Richard King who I got help from teaching myself. Teaches classes over there and they are very good at scrapping. I'm a self taught doing my own scraping only plus what learned on here and other online sources one of the guys here scraped his G0704 or a BF20 in himself. I followed his build thread a lot and with Richards help was able to get my G0704 much better here is my saddle that was +.0035 from end to end. I was able to get it so flat that my .0005 DTI would not move from end to end and from side to side. The ways are hand flaked to hold oil where needed as you can. Before I could not get it trammed right now it. If you looking for .0005+- with you machine you should learn scraping.
    Good luck
    CH
    I have been reading a lot about this, and watching youtube videos.

    I am pretty sure I could do this.

    The ways are clearly ground, and I am not sure if they are hardened or not. If they are hardened, to me it comes down to how good of a job they did at grounding these.

    One challenge I have is I don't have a big enough milling machine to put any of the ways on to and use a DTI to test. I do have a magnetic base, but I would imagine you would need a huge perfectly flat surface to be able to test the surface out and see.

    If you or anyone else has any way of testing this, I would definitely like to do this to assess where I stand and if I actually want to take this on.

    Thanks again!

  14. #14
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    adjust your gibs, make sure you don't have any binding at the ends of travel, put an indicator in the spindle, zero on the table at the corner and run the table to all corners making notes along the way to any changes. if it's way off you may need to scrape, if it's only a little or there is some binding a light bit of lapping may be all that's needed. none of you hobby guys need to worry about getting .001 accuracy you just think you do.

  15. #15
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    Quote Originally Posted by bjones View Post
    adjust your gibs, make sure you don't have any binding at the ends of travel, put an indicator in the spindle, zero on the table at the corner and run the table to all corners making notes along the way to any changes. if it's way off you may need to scrape, if it's only a little or there is some binding a light bit of lapping may be all that's needed. none of you hobby guys need to worry about getting .001 accuracy you just think you do.
    Wha you say here makes a lot of sense.

    I think I will do just this and see what the results look like. I would rather not have to lap or scrape if it's not necessary, but will if I have to.

    Thanks for the advice.

  16. #16
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    Starting to think about a stand for this mill. I'm not crazy about the base and it feels flimsy for the size of this mill.

    I'd love to weld one using steel, but I don't have a welder nor steel cutting tools and I really don't know how to weld.

    I am thinking of either using wood, which I would think would be good for vibration reduction, or possibly metal framing channel from Home Depot.

    Either way I plan on doing a chip tray and likely an enclosure.

    My concern with wood is if I add a coolant system, would it get down to the stand eventually, or can it be fully contained? Also, I suppose wood could possibly warp or bow with moisture in my garage over time.

    If anyone has any thoughts or recommendations I would love to hear them.

  17. #17
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    Quote Originally Posted by AVRnj View Post
    I have been reading a lot about this, and watching youtube videos.

    I am pretty sure I could do this.

    The ways are clearly ground, and I am not sure if they are hardened or not. If they are hardened, to me it comes down to how good of a job they did at grounding these.

    One challenge I have is I don't have a big enough milling machine to put any of the ways on to and use a DTI to test. I do have a magnetic base, but I would imagine you would need a huge perfectly flat surface to be able to test the surface out and see.

    If you or anyone else has any way of testing this, I would definitely like to do this to assess where I stand and if I actually want to take this on.

    Thanks again!
    The best way to check all your bearing surfaces is on a Granite surface plate. That is the only way to know what areas need to be scraped and set flat and level with your reference surface. You would want to do this when you have the machine apart for the conversion. That is when I did mine. I used gauge blocks to rest the part on while indicating the bearing surfaces. You may want to order some replacement Gibs after scraping everything you may need to replace the factory ones. I did on my X axis it was so bad you also need to buy or borrow a dove tail straight edge to mark all surfaces that need to be scraped. You will most likely want a granite surface plate any way for checking parts and so on. I bought a Grade B which is just fine 24"x24" on sale and built my own stand. There is a great set of scraping articles in the "The Home Shop Machinist" Vol30 number 3 is the first and 9 more running in each issue there after. You can order back copy's at the web site. The articles are called "Scraping for the home shop, part 1-10. This is the only way I know to get these machines square true. With this level of machine it seems foolish to do this to an under 2500.00 USD machine to some, but I have no plans to go bigger. I'm retired so time is not a factor. I made 99% of my scraping tools and I have found many things like my drill press, my lathe, tool rests, tail stocks, rotary tables, x-y vise, cheap sine vises and plates, all needed scraping to get them flat now I have a shop full of nice accurate tools and accessories. When every thing is tight and accurate setup time is reduced and your confidence in you equipment and your parts is much better. Don't get me wrong here to each his own, and this is not a task to take on lightly it is back braking, slow tedious work. when you need to take off thousands to get flat and each scraping only takes off 2-5 tenths you can see how this can get real old fast. I would not do this by starting a mill you can ruin a table or saddle in a hart beat. I learned by scraping a 2X12" cast iron bar for about 3 months. When I did my first tool scraping the bar was only 1 3/8"x12" but it was so flat it would jo-block on my granite surface plate. this is something that you learn in a 3 day class but takes years to master. Sorry for hi-jacking your thread, but you will not be able to hold the tolerance you stated in you goals, with out doing it.
    Good luck
    CH

  18. #18
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    CH, not a hijack at all, your advice and experience is much appreciated. I am trying to achieve a very high level of precision, and I am willing to go to extremes to get there if needed.

    One question I have is regarding the 24" x 24" granite surface plate, if my x axis table is 34" long and my z column is probably longer, can I still use a piece that small?

    Do you just do a part of the surface at a time?

    I do agree that it is a good thing to have in the shop anyway, and I will have this machine torn apart so I might as well have a look.

    Thanks again!

  19. #19
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    Quote Originally Posted by bjones View Post
    adjust your gibs, make sure you don't have any binding at the ends of travel, put an indicator in the spindle, zero on the table at the corner and run the table to all corners making notes along the way to any changes. if it's way off you may need to scrape, if it's only a little or there is some binding a light bit of lapping may be all that's needed. none of you hobby guys need to worry about getting .001 accuracy you just think you do.
    True most don't need more than .001 but when you CNC these machines and you electronics is capable of repeating to even less. A saddle or table that is .0035 out of flatness and parallel there is no way your going to improve that by tightening the gib's. All that does is bind the machine up in some areas, and it lose is in others. Lapping want do it either all that does take off material in all areas and you are still not flat and parallel. I see guys here build elaborate little wonderful machines with flood coolant, enclosures 3,4, and 5 multi axis machines and scrimp on the tolerances of the slides, ways and dovetails. Now if you don't need a 20-40 k CNC that's ok too. But if you look at Hoss's machine, man I bet he has 15K in that beast and almost that in hours. So, I say why not, to each is own. It is funny how so many in the world feel they need to tell others what they need and don't need. If a Hobbyist wants a .0005 or .001 machine I say good for you, That is what freedom is about , right.
    Take care and Happy Holidays
    CH

  20. #20
    Quote Originally Posted by COMachineist View Post
    But if you look at Hoss's machine, man I bet he has 15K in that beast and almost that in hours.
    CH
    Not even close, if you look at what I buy and give links to it's generally the lower cost items, no kurts, not everything is starett, what good tooling I have is from my days on the job, new things for the 0704 were more economical. My time on this stuff is seriously no more than 10 hours a week on average so about 2000 hrs since I got the 0704 and don't forget to subtract time spent on 3d printing and videos. I do spend time planning and designing so when I go to make something I'm not wasting time making scrap, I hate to have to make a part twice but it happens to all of us.
    Hoss
    http://www.hossmachine.info - Gosh, you've... really got some nice toys here. - Roy Batty -- http://www.g0704.com - http://www.bf20.com - http://www.g0602.com

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