EBay CNC Machine Review (Very Bad)

[BillSN]

About a year ago I decided to jump into the CNC hobby with an entry level machine that I purchased on EBay. I wasn't expecting much when I bought it, just something I could cut my teeth on and quickly move on. I wanted to spend a total of about $1500 for the set up which is pretty cheap.

After a small amount of research I settled on a CNC router built and sold by Moosecreeksales on EBay. I paid a little over $1,000.00 for a custom sized CNC router. After buying the router spindle and mount from a local supplier my total outlay was about 1,500.00. I was pleased.

It took a very long time to get my machine from Moosecreeksales, about 3months. I was just happy I finally got it!

I finally received the machine and I went about buying the software I needed. I am an engineer so I already have a copy of AutoCAD 09 (work). I ended up buying Sheetcam and Mach3. Both are great!

In about a week or so I was cutting different shapes out of Acrylic, wood, wax, etc. I was doing lots of experimental cutting. I bought the machine originally to machine circuit boards. Quickly I found out that this would not be possible with this machine, nor would I be machining anything else for that matter. It was nothing more than a paper weight. It basically began to fail every time I used it. Here are the problems I have encountered:

The Z axis has way too much play in it. The axis deflects about .15" in all directions. (I actually started a thread about it here ) The culprit is very shoddy, slipshod assembly with poor tolerance bronze bushings used as linear bearings, and a standard thread drive screw with a rubber hose coupler. The guide rods are nowhere near vertical or parallel.

The gantry does not contact the "bearing guides" (with all of it’s roller-skate bearings.) When you move the gantry along its axis only 3 of the 8 RS bearings actually make contact with their respective guides. It’s nowhere near square.

The Y axis binds all of the time due to misalignment of the drive screw with reference to the gantry. The gantry to screw distance varies by as much as 0.1 inches along it's travel! Also not helping is the fact that there is only one bearing supporting the drive screw. The other end is held up by the motor coupling (.25" ID rubber hose). This loose support setup, I believe is a must for tolerances this bad. Keep in mind it uses Stepper motors so when it binds then lets go the whole part gets screwed up. (This happens every time it is used now).

The "drive nut" is made out of a cheap grade of Nylon. It’s not really a nut either, it just a very roughly shaped "block" with 0.50" acme threads cut into it. Very roughly shaped.

The tolerances on this machine are terrible; there is no way you could interchange parts from the opposite sides due to the slipshod nature of their assembly.

I would not recommend buying one of these Moosecreeksales machines.

The bottom line is you get what you pay for period. My unit just self destructed after a few weeks of use. I am in the process of rebuilding the machine with more bearing supports for the screws, new drive screws and nuts, new bearings, couplers, and motors, and a more square assembly. I couldn't possibly sell it to someone else otherwise.

I have since purchased a real professional CNC router (cost me $10K+) but it is fantastic! I really enjoy using it and the Machinist community is a really great group of people. I hope I have helped someone make a more informed decision when entering this great hobby/business. Experiences like mine can really deter new comers. I’m just hard headed and stubborn

Anyone else have any experience with these machines? I can't see that my particular machine is an anomaly, due to the very poor design and construction.

[axis]

for 1000 bucks i would expect no more that the experiance you had. most people just hear cnc and think it will run like the big boys. the machine is what you would call a starter machine the one you crash learnimg g code you wont be making arrow space parts on it. it was your start and you moved on to better things. it is amazing what another 9000 bucks gets you in a machine.

[xcayba]

I looked at that MooseCreek machine several times before and was even ready to buy one, but he was out of stock when I was ready. Glad to hear I wasn't missing anything.

I too had a very bad experience on Ebay buying my first machine from Hickory Ridge CNC. That was about $300 bucks down the tube for the frame. I dumped many hundreds of dollars more into other parts (couplings, steppers, controllers and so on). It too took a very long time to deliver at about 4 months. I soon learned that it was poorly constructed from good materials. Don't be fooled by all the aluminum extruded metal which looks good since poor workmanship can't be seen in the pictures until the unit arrives and you try to use it. I tried to cut a few things with it, but nothing was usable. After spending a few weeks puttering with the bearings and all, I decided it was time to get it gone and let someone else fix it up. The boss (aka wife) agreed to let me buy another one if I could sell the one I had. I found a buyer willing to take on the challenge to fix this one up and sold it for about half what I paid for it.

Back to Ebay, but this time though, I was reading through the feedback to select my machine instead of going with a guy with no feedback about machines he built. I went with a Zenbot for $550. From the day it arrived (shipping took about a week), I have loved every minute. Luckily, my investment in the Xylotex control box, MeshCAM and Mach3 software was transferred over from the previous encounter. I route with it at 100 IPM most of the time and have cut wood and lexan parts with it. The speed is lowered due to the limitations of my bits, not the machine. I could cut much faster, but that would overload the chip load on the bits. I have the rapids turned down to only 200 IPM until I get used to it. It is reported that it will run up to 800 IPM, but that just seems excessive given the size of the table travels at 6" x 8". The speed and accuracy are absolutely awesome. I couldn't be happier. It is pretty forgiving to my newbie mistakes too (like forgetting to zero the axis before hitting the go button ). The builder is pretty helpful as well. Anyway, there is lots of junk out there for sure but at least there is one good machine that I know of out there for a reasonable price. Hopefully others will report some degree of success with other vendors as well.

I've made some soap stamps with it lately. Here are a few pictures of the impressions the stamps made that my wife took. She is the soaper. I had to show her how spending all this money was going to benefit her too. Always good to keep the boss happy

http://www.flickr.com/photos/anhoki/2838169167/
http://www.flickr.com/photos/anhoki/2839002046/
http://www.flickr.com/photos/anhoki/2832289382/
http://www.flickr.com/photos/anhoki/2818186914/

[bassman2914]

This thread is really old but I still want to talk. For $1500(plus software) you should be able to get a really nice machine(if you know where to buy). I don't know if you looked into building a machine but that's what I'm referring to. You buy one and you're going to pay 5 times as much to get the same quality. To keep it short I'll just say, for $1000 I built a machine that it made out of solid aluminum(with mdf spoilboard) and weighs around 200lbs. It comes with precision ground preloaded linear rails(zero backlash, only deflection which is in the .00001" range under heavy aluminum cutting) 6 of them each 41" long with one linear block each(each is 8" long!!). I have 3 380oz/in steppers running on 36volts with 1/2"-10 precision acme rods with anti-backlash nuts. I was able to find all free software and spent so much time learning I probably know more than a lot of pros. It's theoretical single step accuracy is .0005" and it can run easily at 60in/min through 6061 aluminum at .05" doc with a .25" endmill with under .0003" deflection from any given axis. This is also with precision spindle(<.001" runnout) with a usable rpm of 5-30k. Maybe in 3 years prices have gone down but if you look in the right places, and you have some time, you can get a lot for very little money.

[piperpilot]

Bassman,

I'd be interested in seeing your $1000 design. Do you have anything you can share?

PiperPilot

[bassman2914]

There's only so much I can do since some things were on ebay but I'll tell you what I can.
Linear rails off ebay (the ones I used weren't designed for cnc so they weren't particularly straight but If you design the machine right you can allow shimming so it's as accurate as you can measure)
CNC Stepper Motor and Components This is where I got my motors and you get get some other useful things here also.
IMService The anti-backlash nuts on this site are so inexpensive.
The router was a bosch colt with precision collets, google it and you'll find more info easily.
Couplings | Mechanical Components for Assembly Automation - Misumi eCatalog This site has any coupling you could imagine to fit your needs and at a good price. You can get generic ones but disk couplings from here are truley zero backlash, but if you over load them they will flex.
Thrust Bearing:Ceramic,Miniature Ball Bearings This site has all the bearings you could need but I only got thrust bearings here. Radial bearings I got on ebay.
Power supply-ebay
stepper control board-cheap ebay thing, If you have the money for something good don't hesitate, but invest in the machine first
For metal go to speedymetals.com(best site) or onlinemetals.com, they have a lot of stuff and shipping isn't all that bad concidering the freight.
Acme screws are from McMaster Carr-if you can afford ball screws get them!! But the good ones are so much more expensive than acme and even the same accuracy ones are far more expensive and anti-backlash ball nuts are serious $$$. McMaster Carr is great for a lot of things, take some time and look around.
Tips-purpose build your machine!! don't try to make it super rigid, super fast and super accurate. Pick what you need and want and then keep that purpose in mind, it will save a lot of money. Don't be afraid to use steel and aluminum in the construction, always check the tradeoffs with cost, weight, rigidity and your ability to work with the material.
Useful links- (End Milling Horsepower Calculations For Kennametal End Milling Application) (Beam Deflection Calculator - Engineers Edge) (Engineering Section Properties Rectangle Engineering Calculator - Engineers Edge) (www.SuperPID.com - Super-PID Closed-loop Router Speed Controller) This is useful if you plan to cut metal
That was a mouthful, don't expect your machine to be cheap if you want it to be great but if you have the budget that BillSN used then you should be well off. As you can see from the pic is has support in every way imaginable so it's super rigid which allows quality high speed machining with minimal vibrations at fairly high accuracy(depending on how well i setup the rails)