Problem buying PCNC 1100, am I asking too much?


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Thread: buying PCNC 1100, am I asking too much?

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    Unhappy buying PCNC 1100, am I asking too much?

    Hi everyone.

    They are a happy owner of a Sieg X2 transformed by me into a CNC, I have created something wonderful, but now I need something more.
    I went to a user who sells a Tormach PCNC 1100 in Italy, I think the only person in all of Italy to have one ...
    Yesterday I went to see her and I brought the comparator behind to do some tests.

    I positioned the comparator and verified the backlash between the various axes, here are the results:
    Z axis: 0.001 inc (0.03 mm)
    X axis: 0.003 inc (0.09 mm)
    Y axis: 0.003 inc (0.09 mm)


    The machine is in good condition, very little used, the Z axis has left me stunned, it was really good, but in my opinion the X and Y plane is very bad, moreover if I lean on the floor or try to push it in the various on the X axis there is a further backlash, small, but there is.

    I read in the manual that a similar backlash is normal, but maybe I couldn't translate the text well.
    here is the part of the manual:

    buying PCNC 1100, am I asking too much?-backlash-jpg

    Do you think the machine is okay?

    I would like to understand if by recording the gib and the angular bearings I can reduce it, for me this is absurd.
    In my self-made machine I have a backlash of 0.001 in all the axes ...
    it doesn't seem normal to me that there is such a game in a machine of this size, even if it is economic.

    I ask you experts for advice.

    Thanks in advance


    Federico
    Italy

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    Attached Thumbnails Attached Thumbnails buying PCNC 1100, am I asking too much?-backlash-jpg  


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    Default Re: buying PCNC 1100, am I asking too much?

    Hi - Most 1100's can be adjusted so that the X Y total backlash or lost motion is down to 0.01 - 0.03 mm.

    But there are quite a few things to check and adjust, including:



    Cliff



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    Default Re: buying PCNC 1100, am I asking too much?

    Hi, thanks for the answer,
    After the adjustment can I stay in a range between 0.001 and 0.003?
    does not seem very comforting, I would still have a machine not very precise,
    it is cheap, but I would like something more ...
    I think I will not buy it ...
    The Z axis is fantastic at 0.001, but I also want X and Y at 0,001.



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    Default Re: buying PCNC 1100, am I asking too much?

    Most machines of this type have small Z backlash because gravity pulls the weight of the head against the screw


    Sent from my iPhone using Tapatalk Pro



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    Default Re: buying PCNC 1100, am I asking too much?

    Quote Originally Posted by federicocnc View Post
    Hi, thanks for the answer,
    After the adjustment can I stay in a range between 0.001 and 0.003?
    does not seem very comforting, I would still have a machine not very precise,
    it is cheap, but I would like something more ...
    I think I will not buy it ...
    The Z axis is fantastic at 0.001, but I also want X and Y at 0,001.
    Not 0.001 - 0.003" I said 0.01 - 0.03mm - I thought you were metric in Italy. Cliff



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    Default Re: buying PCNC 1100, am I asking too much?

    Besides the backlash on Z you also have table flatness. For a small area the flatness can be pretty good but overall my table varies across X about 0.003" & Y about 0.002". This is a little more that the G2 inspection report says it should be and a lot more than the QC department measured on my report.

    Since my manual mill" (10" X 50") is flatter than I can measured (less than 0.0002") I've been thinking about pulling my table off and fly-cutting it.

    Most of the time I can live with the Tormach slop, or account for it, but in the back of my mind I'm always wishing for tighter machine but then I have to remind myself about the price point.

    You can download the Certificate of Inspection from Tormach to get an idea of what to expect. I would look closely at the max allowed values because that's likely where most machine are - they don't tend to be better IMHO.



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    Default Re: buying PCNC 1100, am I asking too much?

    I would suggest checking if it can be adjusted out mechanically first, but backlash can be compensated out in PathPilot/LinuxCNC by adding a line to the AXIS section of the INI file with BACKLASH = X.XXX.



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    Default Re: buying PCNC 1100, am I asking too much?

    Quote Originally Posted by rdsi View Post
    Besides the backlash on Z you also have table flatness. For a small area the flatness can be pretty good but overall my table varies across X about 0.003" & Y about 0.002". This is a little more that the G2 inspection report says it should be and a lot more than the QC department measured on my report.

    ...
    Interesting. I thought mine was bad when the table dished a little in the front (Y-) center by 0.0004" (0.01mm). I guess I should feel lucky now.



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    Default Re: buying PCNC 1100, am I asking too much?

    Quote Originally Posted by federicocnc View Post
    Hi, thanks for the answer,
    After the adjustment can I stay in a range between 0.001 and 0.003?
    does not seem very comforting, I would still have a machine not very precise,
    it is cheap, but I would like something more ...
    I think I will not buy it ...
    The Z axis is fantastic at 0.001, but I also want X and Y at 0,001.
    I think it depends on how good you can tune the machine and condition of the machine you get. I managed to get my 770 compensated with about 5 microns backlash (0.005mm/0.0002"). But with caveat, I do not get the same precision on the full table travel, and the thermal growth of the spindle cause Z to change up to 0.05mm. And you probably have to be very careful with the entire machine to keep it this way.



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    Default Re: buying PCNC 1100, am I asking too much?

    The gibs are probably to tight or angular contact bearings too loose(or a combo of each)... The machine needs to be trammed in as well. If the base is twisted, it will cause backlash as well.

    If the machine has low hours, its probably fine. Both 1100s Ive owned which were roughly 10 years apart had less than .001" backlash once adjusted.



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    Default Re: buying PCNC 1100, am I asking too much?

    Quote Originally Posted by keen View Post
    Not 0.001 - 0.003" I said 0.01 - 0.03mm - I thought you were metric in Italy. Cliff
    Sorry, you're right, I was thinking in Inch because I was talking to you and I didn't notice that you were speaking in metric instead. Well, then it's a good result.
    However in the end I decided not to buy it, I opted for the conversion of a Chinese machine, I found one with X: 580mm Y: 205mm, it looks like a decent machine to convert, here is the link:
    https://www.alibaba.com/product-deta...75d5416d4phQUL

    I know it's not as robust as Tormach, but for aluminum and light work, as I do I would say that it will be fine, I will use quality screws and above all I want to mount Nema 42 engines, because I want it to be really damn fast ..
    I've seen videos where they reach 5000 feeds, the tormach reaches around 2700, and it's not bad, but I want to do better ..



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    Default Re: buying PCNC 1100, am I asking too much?

    If you are very worried about anything measured in one-ten-thousandth of an inch (or 10 microns or less) then you will be disappointed by any mill under 100k. And even some mllls over 100k.
    At the point of measuring tenths, having heavy people walking by the mill on the floor at the wrong time may conceivably affect the cut. (If your floor is split slab, or too thin, at least.)
    Holding 3 thousandths of an inch on a Tormach is totally achievable and a decent result, though -- this is about 0.075 millimeters.



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buying PCNC 1100, am I asking too much?