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:

https://www.cnczone.com/forums/attac...d=424162&stc=1

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

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:

https://www.youtube.com/watch?v=XYMfvXzbOM8

Cliff

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.

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

Quote:

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Originally Posted by federicocnc

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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Not 0.001 - 0.003" I said 0.01 - 0.03mm - I thought you were metric in Italy. Cliff

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.

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.

Quote:

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Originally Posted by rdsi

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.

...

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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.

Quote:

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Originally Posted by federicocnc

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.

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.

Quote:

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Originally Posted by keen

Not 0.001 - 0.003" I said 0.01 - 0.03mm - I thought you were metric in Italy. Cliff

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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 ..

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.

So you have gone ahead? Well it is a good price. When you have it all going please post your thoughts here. Cliff

Quote:

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Originally Posted by jwatte

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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I don't expect such great precision 10 micron, but 0.8 mm is not good. I would settle for 0.02 / 0.03mm like my now self-built CNC.
(Anyway, one I know has a used Cortini m300a, accuracy: 0.01mm, you don't need to spend 100K to get a good machine) only you have to find the opportunity.
He for example spent 12K, and now has a professional work center.

Quote:

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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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Yes, and it gives a bit that I have to do maintenance at my CNC and now I have set the Backlash on Mach3, but I try to use it to the minimum necessary.

Quote:

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So you have gone ahead? Well it is a good price. When you have it all going please post your thoughts here.

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No, in the end, the machine, with all the accessories sold separately, I got to 4.5K (euro), honestly I was already striving to take it now because it's an opportunity, but I don't even have a lab ready, I had to do two I thought again of expensive transportation of the machinery and many other problems.
I'm sorry, because it's really a nice machine.

Moreover, while I was shooting like a desperate person on the internet, I found a Chinese manual machine with a spindle of 1.1Kw, a large work surface, just like I need it. 20.5 x 58 CM.
So I opted to build it from 0, Hiwin precision screws, 34 Clearpath size servomotors, etc...

It will be very fast on rapid movements and certainly very precise .. It does not have the same tonnage as the Tormach, but in any case I only work aluminum and plastic materials, in fact, I don't need a 530 Kg machine.

Maybe I open a new Topic as soon as the machine arrives, so I show you step by step what I can do!

Quote:

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I don't expect such great precision 10 micron, but 0.8 mm is not good

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I think you missed a zero there :-)

Note that "theoretical microstepper resolution times ballscrew pitch" is not what you'll actually get out of the machine.
The machine has flex; the entire power train has backlash and flex, and especially microstepping is known for not having as much holding power "in between" full steps so high cutting forces will deflect the workpiece, even if you use fat carbide cutters. And then there's spindle and collet runout.

I would be highly surprised if you actually get 1 thou (0.025 mm) actual delivered precision on arbitrary work cuts with something that costs $4.5k. (Unless it's for watchmaking or something, perhaps?) (Also note:typically, I'd count the "worst/typical result" not the "best possible result I've measured." because if you iterate enough, you can typically walk in a toolpath that gets spot on all your critical dimensions, taking your mill specifics into account...)

If were are able to buy a Tormach 1100 in good condition for $4500 euro you would be getting a smoking deal.... especially considering the cost to ship there. IMO, nothing you are going to build from a chinese manual mill would compare to the Tormach. You would be better of tweaking the 1100 to make it right.

Quote:

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Originally Posted by David Bord

If were are able to buy a Tormach 1100 in good condition for $4500 euro you would be getting a smoking deal.... especially considering the cost to ship there. IMO, nothing you are going to build from a chinese manual mill would compare to the Tormach. You would be better of tweaking the 1100 to make it right.

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+1
Unless your day job is designing and building full dress machine tools. IMHO Retrofit tools just don't measure up to a full working system out of the box. These machines are complete and for the most part ready to go to work day in and day out for years. Replacement parts are easy to get for most part and keeping the machine in good working order is imho straight forward. Then when you consider accessories like electronic probes, tool setters, 4th axis, PP control, large user group...……….. the system starts to shine like a little diamond. Takes time, experience and planning to retrofit anything to make a full working system. I have seen it done around here from time to time. D. Cossitt is an older one that comes to mind.

not every machine gets inspected
these Chinese certificates are worthless
please stay away from Alibaba
you find better products in Taiwan

Quote:

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Originally Posted by rdsi

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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[QUOTE=federicocnc;2310090]I don't expect such great precision 10 micron, but 0.8 mm is not good. I would settle for 0.02 / 0.03mm like my now self-built CNC.
(Anyway, one I know has a used Cortini m300a, accuracy: 0.01mm, you don't need to spend 100K to get a good machine) only you have to find the opportunity.
He for example spent 12K, and now has a professional work center.


12K what USD or? for the Cortini M300A?

Br
Finn