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To build or not to build (CNC mill)
February 26, 2012
12:12 PM
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Rob
Upstate New York
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David, If someone can easily afford $7000-$8500+ then I wouldn’t hesitate to advise them to buy a Tormach mill.  And if they didn’t have the money but were going to use it in a business then I’d advise them them to somehow find the money.  I've seen them in operation up close and I think they're great machines and the company is a good one to do business with. 

And if they wanted to just play with CNC then I’d advise them to get a CNC router because you can do more with them.

One more thing. I attended a talk given by Roland Friestad, who started the CNC Workshop that’s been held annually in Michigan since 2005. Roland owned a successful business that built CNC machines until he retired.  At the same time he was writing for magazines and teaching others how to build their own CNC machines.  He said he was often told he was hurting his business by sharing his knowledge. But Roland disagreed, saying that those who want to buy a CNC machine will pretty much only considering buying one and those who want to build one will usually only go that route, and there’s not that much overlap between the two groups.

From what I’ve seen that appears to be a pretty true statement. 

February 25, 2012
9:14 PM
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David Sobel
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Hi Rob;

I guess i am looking at this from the standpoint of I would have to buy the mill and then convert it. A X3/X4 will cost about $1500 to $2500, add the cost of conversion at about $1500 to $2000 and you almost have the cost of a factory machine. A factory conversion will also have things like bonded slidways and ground ball screws as opposed to rolled. This is assuming that you do your homework and do not buy a bottom of the barrel machine.

I have been researching various company's that are selling CNC aimed at the small shop, home shop. It seems that there is not much out there that does not have problems with the machines or the after sale support.

I know that a lot of folks get off on messing with/rebuilding their tooling, but I really do not want to spend more time working on the tooling that making the parts for the toys I am making. Been there/done that with the lathe I have. It is a great little lathe now, but I put a ton of time in it to solve the problems that should not have come form the factory.

February 15, 2012
11:33 AM
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Rob
Upstate New York
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I’m not sure I understand what you’re advising people to do.  A $300 4-axis Gecko G540 will perform better than an $80 4-axis Chinese controller.  But I’m not sure the extra speed you’ll get is worth the extra cost, especially on a mill that typically cuts a lot slower than a router and doesn’t have to move over as large an area.  In industry extra time costs you money but for a hobbyist it’s just a little more time to drink a cup of coffee. There are plenty of people who have built machines with cheap controllers that perform well. 

Reliability, additional current and other protections, and a strong warranty are much better reasons to spend more.  I recently bought a G540 and it was a tough decision because I could have bought 3 or 4 Chinese controllers for same price.  I ended up getting it mainly because it was part of a nice package that included stepper motors, a power supply and a really nice enclosure for everything. 

Also, a CNC machine’s performance depends on a lot more than just the controller.  Its rigidity and the quality of its leadscrews and linear guides are much more important and unlike a controller are usually much harder to upgrade.  So those are the things I’d spend my money on if my budget was limited. 

I saw Tormach’s machines at last year’s CNC Workshop in Ann Arbor.  I’d love to own one but I think their least expensive model costs $6000 and that doesn’t include shipping or a lot of the stuff you’ll need to use it.  An X2 mini-mill with a nice CNC conversion will cost a total of about $1500-2000. And a converted X3 probably won’t be that much more (the additional cost of the bigger mill, bigger stepper motors and longer leadscrews).

One last thing, IMHO having a CNC mill is usually better than not having a CNC mill 🙂

February 13, 2012
12:06 PM
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David Sobel
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I just read Rob's post on his CNC mini mill. I have been thinking of converting my x2 mill to CNC. In doing some research I ran across the Tormack web page and their white paper on the research and testing that went into their III upgrade. Anyone even thinking of building your own CNC should read this. I was very surprised that they published the test results of the different drivers and steppers that they did. This is the type of testing that could not possibly be done by a individual without spending a ton of money or years of time. They also compared two phase and tree phase steppers.

It soon became apparent that the accuracy of your mill will greatly be dependent on the quality of the drivers and the steppers you use, and that the specifications of the components rarely matches the performance under use. Also the best driver and the best stepper may not give the best performance in actual use. To purchase these components from an authorized dealer is a bunch of money, but everyone says you can save a bunch by buying on ebay. Do these components really meet specification or are they slight rejects that still work. Without having very sophisticated and expensive test equipment You will never really know. A overly simple example is the common carbon resistor. Many people messing about with electronics do not realize all resistors are not created equal. They can be bought in an array of tolerances and specifications, +/- 20%, 10%, 5%, 1% and with other specs as to operating temperature, vibration, etc. 

With all said and done, if I had to buy the mill (I would like to have one that is X3 or X4 size) and then convert it I probably would not save much money. If I could find a REALLY good deal on one that was already converted I would be very tempted to get it.     

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