Thinking About A Home Cnc

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phazertwo

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Hello everyone, I have been lurking here for a few weeks, and this seems like a great forum for this.

I have been contemplating getting a home size CNC mill for years, and have finally saved up enough money that it can be a reality. I am a mechanical engineer and am pretty well versed in programming our Fadal VMC-15 at work (3axis only). Modeling and CAM are not a big deal to me, and I'm well versed in electronics as well so I think I'm ready to take "the plunge" into a home CNC.

Reasons I want a mill (so you get the idea of what I'm looking for):
-I am a rock crawler, I have a '92 Toyota with more time and money into it than I care to admit, but I'd like to be able to make/modify my own parts for it. It's currently in the middle of en engine swap.

-I have a 1959 International T-340 that is configured as a track loader. Parts are not easy to come buy, and the parts I find are from China and usually pretty low quality.

-I'm a general tinker'er. I tend to make all sorts of gizmos and wiz-bangs.

I have looked at Tormach, its nice but IMO it's to much $$$. It would probably eat up all my budget and I would have nothing left for tooling.

Currently I am looking at a Matthews Precision PM-45M CNC. However the 8" Y has me really holding back. There is a lot of support for this mill on this forum, and everyone seems to be pretty happy with it. I can probably swing the 4th axis budget wise, which can make up some of the Y travel. Again I might be short $$$ for tooling if I get the 4th axis.

Also considering a PM-940. (26" X, 12" Y). This would allow for larger parts for the truck and crawler, but doesn't come in CNC... I can convert it to CNC for sure, I know I'm capable of it. BUT it seems like it would take quite a bit of time, and I'm not sure I would get it done before I just ended up wishing I had a factory CNC machine.

Thoughts and comments? Anyone seen a good review on the PM-45M CNC?

Thanks for the help,
Brenden
 
phazertwo said:
Hello everyone, I have been lurking here for a few weeks, and this seems like a great forum for this.

I have been contemplating getting a home size CNC mill for years, and have finally saved up enough money that it can be a reality. I am a mechanical engineer and am pretty well versed in programming our Fadal VMC-15 at work (3axis only). Modeling and CAM are not a big deal to me, and I'm well versed in electronics as well so I think I'm ready to take "the plunge" into a home CNC.

Reasons I want a mill (so you get the idea of what I'm looking for):
-I am a rock crawler, I have a '92 Toyota with more time and money into it than I care to admit, but I'd like to be able to make/modify my own parts for it. It's currently in the middle of en engine swap.

-I have a 1959 International T-340 that is configured as a track loader. Parts are not easy to come buy, and the parts I find are from China and usually pretty low quality.

-I'm a general tinker'er. I tend to make all sorts of gizmos and wiz-bangs.

I have looked at Tormach, its nice but IMO it's to much $$$. It would probably eat up all my budget and I would have nothing left for tooling.

Currently I am looking at a Matthews Precision PM-45M CNC. However the 8" Y has me really holding back. There is a lot of support for this mill on this forum, and everyone seems to be pretty happy with it. I can probably swing the 4th axis budget wise, which can make up some of the Y travel. Again I might be short $$$ for tooling if I get the 4th axis.

Also considering a PM-940. (26" X, 12" Y). This would allow for larger parts for the truck and crawler, but doesn't come in CNC... I can convert it to CNC for sure, I know I'm capable of it. BUT it seems like it would take quite a bit of time, and I'm not sure I would get it done before I just ended up wishing I had a factory CNC machine.

Thoughts and comments? Anyone seen a good review on the PM-45M CNC?

Thanks for the help,
Brenden
Click to expand...

Hi Brenden and welcome to the forum. From what I've read Tormach makes a good machine. Have you tried searching for a used one? Occasionally they come up for sale on eBay. There are a few PM-45 CNC owners on this site. From what I've read they like their machines. Do a search. I'm sure you will find some good reviews.

Going the turn-key route can get expensive especially if you want 12", or more, of Y travel. You might want to take another look at converting a manual machine if you have a tight budget. I have a PM-932 I converted a couple of years ago. It does everything I want it to do. There's a simple modification you can make to these machines that get's you a couple more inches of travel. Here's the link to jbolt's PM-932 build thread, http://www.hobby-machinist.com/threads/pm932-cnc-build.21442/, and my build thread, http://www.hobby-machinist.com/threads/taking-the-cnc-plunge.24858/. Jumps4 converted a Wholesale Tool ZX-45 a few years ago. A wealth of information that is a good read.

Keep posting your questions and concerns. There's a wealth of knowledge on this site and lot's of members willing to help you out.

Tom S.
 
Thanks for the response!

I have been searching for CNC machines in my area for over a year (Denver) and just haven't been having much luck with the size of machine I want. Funny because there is a nice full size production machine for sale less than an hour away ready to rock for $4900 (with phase converter)... but there's no way to get a 6k lb machine in my garage.... Just not going to happen.

I am very intrigued about converting a manual machine. However, I seem to already have too many projects, and would like to use the machine to make those projects easier/better. Doesn't mean its out of the question, but I think something along the lines of adding a 4th axis to a machine that already has 3 would be a better decision.

I contacted Matt at PM, and you can actually get a PM-940 with CNC. After looking at the pricing a variable speed machine w/ 3 axis would just fit my budget, and allow a few hundred dollars for tooling. Figuring out a 4th axis later could be a fun little project.

PZ
 
PZ, Welcome to the forum.
I have the PM-45-CNC and I am very happy with it. The only regret I have is that I saved some $ initially and did not get the 4th axis thinking that I could add it later. Of course, I can add it later but it is going to be (slightly) more work that I would expect. While there is room in the electronic cabinet for the 4th motor controler as you would expect, for some reason the existing 3 controllers are spaced such that I will have to re-mount them in order to make room for the 4th. I guess in the big picture this is not a big deal but a little frustrating that I have to do that. Also all of the parts in the cabinet are mounted to a large plate that is in turn mounted to the cabinet. This means that you will have to remove the plate in order order to get to the nuts or screws on the back side. I am not sure that the wiring harness will easily allow this.

Anyway that story was just to say that if I had it to do over again, I should have tried harder to find a way to get the 4th axis initially.

Looking forward to seeing more of you journey!
 
Have you looked for an older used machine? I see them on CL, they are old and would need the electronics/controller updated in most case but have the ball screws and stepper motors already. There is one right now that doesn't run CNC so is being sold as a manual machine at a manual price.
 
Boswell said:
PZ, Welcome to the forum.
I have the PM-45-CNC and I am very happy with it. The only regret I have is that I saved some $ initially and did not get the 4th axis thinking that I could add it later. Of course, I can add it later but it is going to be (slightly) more work that I would expect. While there is room in the electronic cabinet for the 4th motor controler as you would expect, for some reason the existing 3 controllers are spaced such that I will have to re-mount them in order to make room for the 4th. I guess in the big picture this is not a big deal but a little frustrating that I have to do that. Also all of the parts in the cabinet are mounted to a large plate that is in turn mounted to the cabinet. This means that you will have to remove the plate in order order to get to the nuts or screws on the back side. I am not sure that the wiring harness will easily allow this.

Anyway that story was just to say that if I had it to do over again, I should have tried harder to find a way to get the 4th axis initially.

Looking forward to seeing more of you journey!
Click to expand...

Very good information to have, thanks. Sounds like a pretty standard in cabinet panel, are you sure they have nuts on the back side and are not tapped? Seems like I usually encounter these as tapped holes in the field, which makes replacing components MUCH easier. A few additional questions for you if you don't mind:
  • Did you get the variable speed, or the 6sp gear box?
  • Do you have any problems losing steps? I see that this machine comes with 600oz-in motors for x and y and 1200oz-in for the z, seems a little weak compared to the motors some guys are using for the conversions (1600x, 1600y, 4250z)
As far as finding a used machine, I'm not really willing to buy one unless I can see it run, which means I'm limited to the Denver area (or ~100 mile radius). The risk is just too high IMO. In the mean time I will keep watching CL on a daily basis until I pull the trigger on something.

Thanks for all the help!
PZ
 
PH,
Several years ago I was in your position, looking for a CNC large enough to work with and cheap enough I could afford it. I ended up getting a used Syil X4+ CNC. It has travels of about 7" in Z, 11" in X and 6" in Y axis. I'm still lacking the 4th axis.

For what it is (a bench top mill) it has served me well and gave me a good learning platform for CNC milling. The small size is the drawback. (Size, rigidity and power seem to go hand in hand.) While I've been able to do most things I need to do I would really like a larger mill. But for my purposes I think I would keep the small CNC rather than trading for a larger manual mill.

However, for machining parts for rock crawlers and such I recommend that you give serious thought to size. I make motorcycle accessories and badging. Those parts are small. Not every part fits in a vise. Keep in mind that you are going to lose (at best) an inch or so clamping a part to the table, another 1/2" or so if you need to profile using an end mill strong enough to go over 1/2" deep. You lose a few inches if you have to use a drill chuck and a drill bit. If you subtract an inch or so from the limits of my mill you end up with a maximum stock size of around 4"x 10" x 5" high. Sometimes you can't make a whole lot with stock that is only 4" wide. Of course there are tricks to getting bigger pieces machined, but you can't just slap a 6 x 5 x 10 inch piece of stock on the table and start milling.

You can make most things with manual mill, but you cannot make a big part with a small mill of either type.
 
This is why I'm focusing on the larger machine. With a 12" Y I should be able to make everything I can think of (right now). I did toy with the idea of buying a small CNC Sherline for sale here on CL, it comes with a boat load of tooling. http://denver.craigslist.org/tls/5901119481.html

And now that I can post links, here is the large machine for $4900. http://denver.craigslist.org/tls/5936229217.html
This machine has been for sale for at least 6 months. I could probably walk away with it for $4500... But it would take up half of my garage, and how would I even get it in there!

Considering I'm looking at spending ~$8k on a PM-940 CNC, I could have a full production machine for quite a bit less. That $3000 could buy a lot of tooling!

PZ
 
phazertwo said:
Very good information to have, thanks. Sounds like a pretty standard in cabinet panel, are you sure they have nuts on the back side and are not tapped? Seems like I usually encounter these as tapped holes in the field, which makes replacing components MUCH easier. A few additional questions for you if you don't mind:
  • Did you get the variable speed, or the 6sp gear box?
  • Do you have any problems losing steps? I see that this machine comes with 600oz-in motors for x and y and 1200oz-in for the z, seems a little weak compared to the motors some guys are using for the conversions (1600x, 1600y, 4250z)
As far as finding a used machine, I'm not really willing to buy one unless I can see it run, which means I'm limited to the Denver area (or ~100 mile radius). The risk is just too high IMO. In the mean time I will keep watching CL on a daily basis until I pull the trigger on something.

Thanks for all the help!
PZ
Click to expand...


You might be right that the holes are taped and can be fully accessed from the front. I don't think I ever looked to carefully. I would still need to re-mount the drivers to space them properly for four.

I did get the variable speed but find that with a Maximum speed of only 3000 rpm I almost always run it it at 2500 or 2750 RPM and adjust the cut depth as needed. Some exceptions to this are when I use larger diameter tools like a slitting saw.

I have never noticed any missed steps. I have the acceleration low and also have my RAPID movement set to a maximum of 50IPM which I think is fairly conservative. Time is NOT money when used for hobby work so I can afford to keep the movements a little on the conservative side and reduce the risk of missed steps.
 
Thanks a bunch for answering my Questions Boswell, I think you've convinced me I should get the PM-940 3 axis...
 
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