Hi all; thanks again for the help with the electronics and mechanics choice for my X2 CNC conversion process. I've ordered all but the limit switches and the e-stop and I'll be snagging those soon. Now I have a few general questions...
1) Should I trammel the mill fully before I install the CNC kit? It seems like I should wait, but trammeling is a black art to me and I'm not sure what will knock things out of alignment. I've got the great tutorials people have put online so I think I'll be ok doing it, just not sure when is the best time. I even kicked together a surface ground 8" diameter disk in my machining class that supposedly makes trammeling easier.
2) Where are people getting these tiny shims used in trammeling? I assume it's something obvious as no one ever mentions it but I wanted to ask. Are they just thin sheet metal or something like it?
3) What size do the t-slot nuts need to be for the Harbor Freight X2? I have a clamping kit but I got the wrong t-slot nuts for it and they don't fit. I figured I'd just buy the nuts from LMS directly.
4) I need to cut out a series of 2d shapes from 1/4" and 1/8" mild steel. Lots of them actually - I got really popular with some friends when I told them I was finally going CNC. I will be picking steel with a good machinability index. What end mill or bit do you guys typically use on an X2 to cut parts out? It's a stupid question but one I'm very curious about. Since I'm still on the stock gears, I don't have a ton of RPM to work with so I can't use something tiny. I don't have really fine detail on these parts so I'm pretty open to sizes, it's just I've never seen anyone talk about what size end mills are used for cutting parts out. Generally I just use whatever end-mill has a small enough radius for the finest detail but with CNC I thought it might be different.
5) I've seen people reference onlinemetalsupply.com and speedymetals.com are these the prefered online sources for materials? They are both very inexpensive compared to my local supplier.
6) Last question (for now ) - I've seen quite a few different ways to reinforce the z-axis to take the flex out and remove the rotation ability. Is there a preferred one? For every suggested approach, I've seen several detractors. The one that looked simplest and effective to me was a c-channel bolted vertically from top to bottom against the back of the mill. Seems it would provide both side to side and front to back stability but there was a lot of discussion about it not being ideal though testing showed it worked well enough. The original was in aluminum, but I'd likely use steel as I have some channel lying around already. Just wanted to know peoples thoughts on this.
Thanks again for all the great help!
1.Since you will have to strip the mill to carry out the conversion at least in part your question is best split into phases. Firstly check that the Z axis travel is lined up with the column. That is the tool will plunge parallel with the column. I suggest you check this prior to pulling the mill to bits. The adjustment is checked with a DTI mounted on the column and reading on a piece of ground stock (drill stock or silver steel) held in your normal milling collet. I suggest you check this at the extremes of Z axis travel and rotate the rod for each reading and average the results for comparison with the results from the other extremity of Z axis. The adjustment is messy and requires the two parts of the head to be parted and correction shims to be added. This has been well described by Hoss amongst others. If the indicated readings are within 0.001 inch or better leave well alone!
The column also needs to be perpendicular to the table. This adjustment on the X2 mill needs to be checked from time to time as the 90 degree adjustment to the X direction relies on the column bottom joint and is readily adjustable. In the Y direction of travel the adjustment is by shimming the column mounting under the rear or front pair of bolts that hold the column foot to the base. The adjustments in this paragraph can be left to after the CNC conversion.
2.Shim stock is obtainable from many engineering supply houses but those specialising in model engine making often sell packs of shim stock comprising of small sheets of the material. There are other alternatives to buying shim stock. Alli drinks cans are a good source of thin stock as are foil cooking trays. Paper of the hard glossy kind has been used as has stiff plastic foil. My own preference is to cannibalise a cheap set of feeler gauges.
3.Tee slot size should be in the manual that came with the mill the common X2 size is a 12mm slot and a 10 mm thread. Just make sure the bolt does not go right through and pop the cast table. Many commercial 'T' nuts have a thread that binds as the bolt is passed into the nut. These are easy to make and cost a lot particularly if you need a lot. Can you make your own and reuse any other clamping bits you have?
4.No need to change other than to keep axis feed rate in proportion to spindle RPM just as in manual. CNC pundits tend to go as fast as possible to make more cash per hour of machine time.
5.I am the other side of the pond and use online suppliers as they deliver quickly a wide range of stock cut to the size I want. I only have a small band saw and value my fingers being a real coward!
6.May I suggest you check the movement you get measured with a DTI on the table reading the column movement. The X2 generic design has improved a lot over the years and latter machines are a lot more ridgid assuming that the packing grease has been removed from between the mating surfaces of the column base and the tilting pivot and all the bolts are tight. It is a good idea to coat the mating surfaces with a thin rust preventative oil so that they will part cleanly in the future if required. This remark also applies to shimming the head in 1 above
Hope this helps and if others know better perhaps they will jump in. After all there are many ways of skinning this particular cat!