Feedback Please!

[bumperscoot]

Hi All!

I am nearing the home stretch in a "Fact Finding" mission to determine which CNC mill machine I will purchase. I plan to use my mill for light production and prototyping while I test the waters and potential business plan for my small startup company.

I have narrowed my search to a few machines, the front runners being IH and Tormach. I did visit IH and was suitably impressed with the newer and beefier version of their mill, and it has been my target machine to date. I do plan to visit a local company tomorrow that operates a Tormach in a production environment, I am anxious to see its application and observe it under power.

I would like to ask the members of this community if they could describe their operating experiences (both good and bad) with their IH mill. How is its accuracy/repeatability under power? When machining a long part (i.e., ~17" in length), what kind of end/end runout are people seeing?

Tormach was very forthcoming with their customer contacts and user base allowing me to ask real world questions to real operators while drawing from their kudos and gripes. I have asked the same to IH, and have not received any data as of yet.

I would appreciate feedback from current IH users (preferably those in commercial service), specifically from those using the newer mill (as that is what my purchase decision is based upon). I look forward to reading your replies!

Best Regards and Thank you in advance,

Steve

[ppsi]

Steve-
You haven't talked about the type of parts you want to make with your mill. I think the answer to your question will come from looking at the demands your business plan will put on your cnc machine and a good understanding of the difference between servo and stepper control. The fact that you have a business plan indicates you do your homework. Your next assignment is to review your product and determine your needs with respect to throughput and tolerance. Good Luck.

[bumperscoot]

ppsi,

Good point..

I'm not anticipating mill runs 24x7 (although I could only hope!), I am planning at most 20-30 hrs/week.

The majority of the work I plan to produce are parts for automated opto-mechanical parts for large-aperture telescopes. The remainder of the machine work time will be spent refining a few low-tech, low-accuracy parts for truss-pole mountings and cPCI chassis front panels.

Much of my opto-mechanical and electro-mechanical assemblies are interference fit parts and require an accuracy or tolerance not to exceed + 1.5thou over 4" max (my most critical part). this needs to be fairly repeatable.

The low-tech stuff can have a fair amount of "slop" without issue.
One of my assemblies is a long bar-shaped part ~17" long. While the absolute dimension is not critical, the parallelism of the top/bottom faces should stay within +/- 2 thou over the length.

I guess at this stage in my homework I am looking for the anecdotal experiences of the user (as this is the real-world experience under real-world conditions data I am looking to hear) and how consistent from user to user it is.

Steve

[SMW Precision]

Originally Posted by bumperscoot Hi All! I am nearing the home stretch in a "Fact Finding" mission to determine which CNC mill machine I will purchase. I plan to use my mill for light production and prototyping while I test the waters and potential business plan for my small startup company. I have narrowed my search to a few machines, the front runners being IH and Tormach. I did visit IH and was suitably impressed with the newer and beefier version of their mill, and it has been my target machine to date. I do plan to visit a local company tomorrow that operates a Tormach in a production environment, I am anxious to see its application and observe it under power. Steve

Let us know your conclusions as you complete your research. I will be posting a longer message on IH components and build in the next week or so. I own the IH CNC kit and was allowed full information on what components are used in the CNC kit and frankly I am amazed at the quality and value.
Let's look at ballscrews; from posted Tormach information they use a medium accuracy ballscrew, I did not find the diameter or manufacturer listed. While IH supplies an American made Premium grade Rockford 3/4" ballscrews with a static load rating of 1950 lbs. Ballscrew selection has a major effect on both accuracy and operation life.
Compare closed-loop servo versus an open loop stepper power system. The IH mill is unlike anything else available in size, rigidity or price. All CNC components are high grade and all US built. Machining for mechanicals is completely done on an IH mill.

[philbur]

As a happy Tormach user I feel obliged to put the record straight:

Tormach has 3/4" ground ballscrews with a precision P4. IH are rolled ballscrews (so probably T grade) with no stated precision grade. P grade is normally used on precision motion systems and T grade on general purpose transport systems. P grade have a maximum allowable cumulative error T grade do not and (from memory) are normally not better than precision 7. P4 on machines of this quality would never be considered as medium accuracy. If this were the case then the rolled ballscrews would be the equivalent of using a tape measure for positioning.

The Tormach has a maximum backlash of 0.001" in the x and y and 0.0015" in Z. This is the total system backlash, allowing for the mount bearings and stretch/compression of the system due to stiction etc. Mine measured at equal to and better than the maximum allowable. The best option for the IH has a stated 0.002" in the ball screw alone.

Tormach issue a comprehensive test certificate with every machine, a sample certificate can be down-loaded from their website. It would be useful if IH produced a similar certificate to allow potential buyers to make a direct quantitative comparison.

Regards
Phil

Originally Posted by SMW Precision Let's look at ballscrews; from posted Tormach information they use a medium accuracy ballscrew, I did not find the diameter or manufacturer listed. While IH supplies an American made Premium grade Rockford 3/4" ballscrews with a static load rating of 1950 lbs. Ballscrew selection has a major effect on both accuracy and operation life.

[SMW Precision]

I have been researching ball screws a bit more before commenting back. Rockford ball screws are rolled version. IH Mills and kits come with Rockford’s Premium grade ball screws with a potential linear deviation between 0-0.003" in 12 inches. All of mine were under an .001" in 12" deviation.
Maximum potential backlash from Manufacturer specification is .001. Linear error is far more complicated than just a 12" lead error measurement would lead you to believe. All ball screw CNC setups can benefit greatly from table mapping and parameters setting. Deviation may be either plus or minus in any rotation. On a 5 TPI; 12 inches is 60 rotations.
Rockford Ball screws are commonly used in many CNC retrofits as well as by CNC equipment manufactures. The other factor in ball screw is Dynamic and Static load ratings which are key to determining ball screw life span. IH ballscrews with a 1950 lbs Static load rating will run for tens millions of inches of travel before degrading.

[bumperscoot]

I too have done a bit of homework on this issue, and have found this point mostly irrelevant for this implementation. The major benefit of a P grade vs. a T grade ballscrew is the control of accumulated error along the screw. Since this measurement is typically performed over a 1 meter section, the errors involved for either application are minimal if not non existent..

The following articles were of interest.

http://www.machinedesign.com/ASP/str...tedArticle.asp

http://www.machinedesign.com/ASP/str...tedArticle.asp

[LUCKY13]

Bumperscooter, what is it that is much better on the new IH machine. I will soon be making the same choice as you are is why I ask. It seems that the price of the full CNC heavy machine is getting up there a bit. So I wander what would be the reason for buying one. Wiht the price getting around the 12,000 range, I wander about the software that goes with it. I am afaid this area is something I dont know much about (software). So I worry about what is capable with a system like this compaired to something like Centroid/Ajax,Traxs or other retro fit systems. ALthough I will be starting out the basic things I want to be able to expand when the time comes. The whole thing is a bit overwellming to a new comer and it worries me about getting stuck with something that want fit the bill. Of course the machine itself will have a lot to do with things, but it goes beyound that in the end.


Jess

[SMW Precision]

Originally Posted by LUCKY13 What is it that is much better on the new IH machine. I will soon be making the same choice as you are is why I ask. It seems that the price of the full CNC heavy machine is getting up there a bit. So I wander what would be the reason for buying one. Wiht the price getting around the 12,000 range, I wander about the software that goes with it. I am afaid this area is something I dont know much about (software). So I worry about what is capable with a system like this compaired to something like Centroid/Ajax,Traxs or other retro fit systems. ALthough I will be starting out the basic things I want to be able to expand when the time comes. The whole thing is a bit overwellming to a new comer and it worries me about getting stuck with something that want fit the bill. Of course the machine itself will have a lot to do with things, but it goes beyound that in the end. Jess

Look at the Standard IH mill and not the heavy duty version. Unless you have some specialized needs. I know it gets confusing and the more you compare the more confusing it gets.
Current IH machines come wirh Mach 3 and Dolphin Cad/Cam level 2 Milling which is 21/2D Cad and Cam conversion. Mach 3 is Windows based, friendly and flexible. Provides the conversational features and much more. Advantage or this program is it is being constantly upgraded with almost all upgrades being free. Both of these programs have free downloads to play with and lots of user comments on CNC Zone and many other places. I believe IH is the only one currently supplying a CAD/CAM package with Mill purchase.

[philbur]

My main conclusion is that secondary suppliers of ballscrews and suppliers of CNC machines should state the grade and precision designation so that the potential buyer can properly compare and assess. The phrase "super precison" has no meaning and indicates only an intention to hide and/or confuse.

Regards
Phil

PS: The difference between P grade and T or C grade starts to become relevant for travel distances over 300 mm not 900 mm.

Regards
Phil

Originally Posted by bumperscoot I too have done a bit of homework on this issue, and have found this point mostly irrelevant for this implementation. The major benefit of a P grade vs. a T grade ballscrew is the control of accumulated error along the screw. Since this measurement is typically performed over a 1 meter section, the errors involved for either application are minimal if not non existent.. The following articles were of interest. http://www.machinedesign.com/ASP/str...tedArticle.asp http://www.machinedesign.com/ASP/str...tedArticle.asp

[SMW Precision]

This thread has peaked my interest in the Tormach mill. Perhaps some one with more engineering and ballscrew experience would take a look at the Tormach setup. It is shown in owner’s manual section 9.55. I don't understand the setup at all from details given.
Preload specifications are for a 0.0004 to 0.0008 backlash and X-axis setup does not seem to be a conventional double nut ballscrew. Appears from pictures and diagram to a have a very small ball load. They describe it as a free floating ballscrew system.
Also unconventional on the Tormach mill are Plastic machine Ways. According to their information they are using 0.031" PFTE attached on Way as a bearing surface. I've tried several web searches and can not find any relevant information on this usage. I use PFTE for various things; though it would worry me with this type of machine application.

[philbur]

The PTFE coating is similar to Turcite B Slydway, which is commonly used on "upmarket" machine tools slideways. It has some very significant advantages over metal to metal contact. It is not unconventional just uncommon in the hobby arena. I would not be worried about the concept. The real issue would be how well has it been implemented.

I can't find any reference in the user’s manual to "a free floating ballscrew system"

If you have not already found it you may find this document interesting:

http://www.tormach.com/document_libr...0Design_v1.pdf

Some would claim it is highly slanted, but it is quite logical and at least give food for thought for us “know nothing” amateurs.

Regards
Phil

Originally Posted by SMW Precision They describe it as a free floating ballscrew system. Also unconventional on the Tormach mill are Plastic machine Ways. According to their information they are using 0.031" PFTE attached on Way as a bearing surface. I've tried several web searches and can not find any relevant information on this usage. I use PFTE for various things; though it would worry me with this type of machine application.