Here's a mini 3in1 that has servos mounted to the three axes.
It is an evalutaion model for a company (Shoptask)to possibly market it.
The mill assembly ,although it looks nice, is full of problems. Each one of those aluminum collars that are used as guides for vertical movement are drilled differently so reassembly was a puzzle to get them right side up and in the correct location to align with the holes in the mill cross arm (or whatever it is called).
Mostly what I did to this was just true everything up and get the motors from ebay, make the mounts and cover, and build a reinforcement frame that supports the base and mill....and of course...paint it. The vertical mill glide rods are bolted into an aluminum "stamped" angle plate that is secured to the lathe bed and back frame. I'll be posting more pics...am working now but have this online in the background.
At that forum I have pointed out some of its shortcomings...one, the mill assembly is using simple collars for the glides tightened only enough to remove slop. They are secured with oversized holes for alignment and I am sure when stressed with side loads would shift and, as has happened to me, bind the vertical movement while losing (if slightly,but enough) position.
...So, the glide system on this is going to be worked on.
The lathe? It works great and because the servos have a lot of OOOmph, I can tighten up the ways snugly for good tolerances.
The pictures show it upon delivery by UPS..(that was the first test) it failed but with clever packing this can be avoided
other pics are apparent...I added the angle/tube frame to add rigidity to the whole thing as the heavy sheet metal flexed somewhat affecting accuracy.
Note the deliverey picture....the enclosure with the sliding plexiglass doors was realy an obstruction....difficult to get access to the controls and cleanout would have been very laborious. I'm working on "swing away" type door system that opens up for complete machine access.....OR. a housing that just lifts off.
Mill spindle...not very good.. it is basically a three jaw chuck, and although the controls allow reverse, the chuck immediately spins off. It's mount was also iffy (note two holes for attachment? I've since put four mounting screws at the four corners.
There is much to be done to this machine to make it a good sturdy 3 in 1.
For now only light cuts with the mill.
Oh! the mill spindle motor is also under powered and has too low RPM. It doesn't respond to the speed control when load is applied... but the lathe motor holds it's speed under load rather well...
This model uses a 240VAC input.....will be changed to 120VAC if the machine's problems can be eliminated.
I was thinking that these mounted in place of the mill's vertical glides with the pillow blocks secured to the mill head/bracket on each end would be a step in the positive direction. http://cgi.ebay.com/ws/eBayISAPI.dll...848855337&rd=1
Maybe a similar set with larger diameter shafts....
anybody see on ebay a 180VDC motor with 2-3 thousand rpm? could be more. At present the diameter of the motor can't exceed 3".
I would also like to extend the mill head out more and move the whole works-lathe and all-out away from the back an inch or two. This would allow a larger diameter spindle motor or at least more room for adjustment.
As it is now, the frame is pretty solid (relative to the machine's size) and just the mill's vertical linear bearings(collars ) are the really weak link.
Here's the back enclosure which adds a lot of strength to the little bugger..along with those gussets on the sides.
...included ...another shot of the angle/tube iron "cradle" I added with adjustable feet.
The whole idea here with this machine is to keep it compact and the weight down so it can be shipped within UPS's constraints.
I think with that extra angle and tube iron I went over the limits. But it could be shipped separately....as the extra fourjaw and tools were.
some closeups of the servo mounts.
also note in the background the black plastic cover installed behind the carriage to protect the gears.....this should be standard on ALL mini lathes shipped from any supplier.
That aluminum "crank" on the Y-axis came with the unit....its more in the way but can't be removed as the pulley was press-fit tightly onto it.
Mounts were made with pieces of aluminum found in my scrap box. My Shoptask Bridgemill big 3in1 did a nice job with the small slots and other parts.
That cover over the X -axis was made from a discarded Sears garage door opener housing.
From my experience with a converted 7X12, you really need to have the X axis drive belt enclosed, as swarf will cause problems here over time (mine isn't yet, and it is a pain).
Does this use the apron split nuts for the Z axis drive? Isn't backlash a bit problem? I replaced both leadscrews with acme (ISO) when I converted mine, but will get some ballscrews next time I come to the states and do the job properly.
You're right... it should have proper drive screws.
Yes, the split/half nut is driving the carriage....I increased the little ball and spring that engages it and while making the ball a little bigger, moved the detent in the shaft so it applies more pressure to the acme screw...
This seems to work well....for now.
For a lathe a bit of backlash in Z is not a big deal (Dave K of TurboCNC still uses the same set up with the halfnuts). Backlash in X is a pain. But for milling you will need to address the backlash in all three axis.
I take it from your posts that this conversion wasn't done by you, but that you are considering taking it to market?
My impression is that it has too many parts to every be made to a competitive price. For an amateur, it is easier to make lots of simple parts into a complex whole. for production, it is normally cheapest to make a minimum of parts, even if the items are more complex. A good example is to compare the number of parts in you Mill slide with the single cast iron dove tail on this grizzly, http://www.grizzly.com/catalog/2004/418.cfm?
What does it cost per item for a chinese foundry to cast a few hundred slide columns, and then run then each, one pass on a horizontal mill and one pass on a three spindle vertical mill to clean up the dovetails.
Grizzly is selling that bigger machine with collets, chucks, QCTP, mill attachment for $1200.
No not me! I don't have any knowledge of marketing. I've just been asked to evaluate it. I wasn't supposed to make any major changes, but I thought it wasn't close to production and did some minor changes to make it more acceptable though still inadequate.
See the fifth post about the Delphi forum site for this machine.
I've edited many of my posts, so it might be a good idea to review some of them. They may make more sense in the second viewing.
I'm not sure how far the potential seller will take this machine before (if) putting into production.
The good part is that I get to keep the machine...so I intend to continue to improve it until it meets my standards (within reason)
You see a lot of guys trying to make money off the bottom of the market. I would guess this is a recipe for frustration. You either make a cheap product and sell it to cheap buyers who then complain endlessly about all the miriad of faults, or you fix all of Siegs design defects and add a well engineered conversion, but end up with a product which is too expensive to have any real chance in the market.
Here the chinese have an advantage, if the product is crap, the customer doesn't bother trying to get them to address it.
I would think there is a much better business model to invest the same amount of effort to make a machine which is a good product and slots in much further up the feeding chain.
When I look at the amount of work I have put into my CNC conversion, I just can imagine any chance of making a decent commercial product out of one for a list price less than about $3500, with any hope of making a reasonable profit. The Mill attachment would be on top of that.
One thing that was talked of was to sell this machine (with many of its shortcomings) to educational areas and let the students take it apart and build it back up while at the same time "fix" the numerous areas in need. At the same time they would be learning about manual and CNC operations and how they relate to the components of the machine. A real educational tool!
I hear ya! I was just joking.... And to get the machine "up to snuff" would make it so expensive that the educational system considering it wouldn't have the budget. I mentioned to Shoptask that they could hurt their reputation if they tried to sell it in a "less than" way. JT(shoptask owner) returned with "good point."
This machine, aside from all the other flaws, would be alright if those mill glides were replaced with some good open pillow blocks and vertical supported large diameter rods.
The operation was supposed to include manual but without an engagment control at the end of the feed gear train, the gears would "howl" when CNC operation took place. So I removed the last gear and finally took them all off.
Unsupported bars as linear guides are always going to be a dodgy choice for a machine that cuts steel.
You often see guys do conversions which keep the manual option. I'm glad I didn't bother. You can make the installation much more compact if it is CNC only, can better enclose the machine and avoid the danger of spinning handles.
I briefly considered selling plans for my conversion, but quickly decided:
1/ the info is freely avilable over the internet (where do you think I learnt).
2/ I like to give back to the community I have learnt so much from.
3/ If I did it again I would do some things differently.
4/ Many of the things I did because I only have this one machine, not even a drill press
5/ The income gained devided by the number of hours providing support leads to a wage of about 10c/hour. I'd rather keep my hobby and the -50c/hour it currently earns me
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CNC'd mini 3 in 1 lathe/mill
) are the really weak link.
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