New to forum - have a DM2400

Greetings to all!
My name is John Herrmann. I live in Phoenix, AZ, and am a member of Valley Metal, the machinists' club founded by Marty Escarcega (also a member of this forum!) About a year ago I bought my DM2400 from Marty. My intention was to get familiar with CNC, and this looked like an excellent entry level machine. Marty had done a wonderful job of converting it to Centroid. If you look at any of Marty's DM2400 videos, you're looking at the machine I bought.

I retired some years ago from a lengthy career as a machine designer/builder at Hewlett-Packard. During the time, we were using a CAD program that has since morphed into CREO Elements Direct. Unfortunately, I can't afford their extravagant price. So all I have is the very limited free version. And it will not allow me to save anything in any industry recognizable format. FOOEY! So I've been searching for a good CAD/CAM package. Tried a couple (Alibre, CamBam, Fusion, etc.), as well as doing a bunch of hand G-coding. It's a bit of a slog, but I figure it's a good learning experience ... and my hourly rate is pretty low :) Almost all my CNC machining to date has been on various plastics (Corian, acrylic, Lexan, expanded PVC, etc.), though I've started doing a couple aluminum parts.

My initial "project" was a soap dish, made from scrap Corian. It's basically a 4"x5" workpiece, pocket milled to ?" depth, then north-south and east-west "streets" ?" apart, cut with a ?" ball mill to a total depth of 5/16" The little square "islands" that are left raise the soap above the streets and allow it to dry. I'd previously made these on a manual mill, and it's definitely not something that "needs" CNC. My goal, though, is to make at least one soap dish to fit my oval bathroom sink. It'll have curved east-west streets and radiating north-south streets. Definitely not something to try on a manual! And a PS - a special shout-out to Brian Lamb (Youtube monicker dmogbrian), who was using the mill before I bought it from Marty, and who wrote a sample G-code program for one of my soap dishes as a "demo" to encourage me to buy the mill.

Most recently, I've been a bit concerned with a hardware issue on my 2400. Whenever I'm doing anything like a slot cut (ie, cutting with both sides of an end mill), the spindle has been making the most distressing screaming/groaning noise. RPM, depth of cut, cutter diameter, and material seemed to have little or no effect. Couple nights ago I pulled out the spindle housing and did a careful check. Turned out the spindle had ~.003 or .004 of axial play. Not good. So I've taken the spindle apart and examined the guts. The spindle uses a pair of precision angular contact ball bearings at the bottom end, and a third one at the top. As best I can tell, some previous owner (NOT Marty!) had installed the bearings upside-down, so that none of them were riding on the angular contact surfaces! Holding a pair of the bearings between my fingers, I can get either zero play or lots of play, depending on whether I'm holding the "tops" or the "bottoms" together.

The bearings may well be OK, but I went in search of replacements. One local (un-named) bearing supplier quoted $388 for just one of the bearings! Then I tried Motion Industries (Phoenix), talked to Hillary Miller. She found the same bearings (FAG, Germany) for $166, but there was a 6 month factory lead time. Then she "went the extra mile" for me and found an online source (in England) that had them in stock for about $146. Needles to say, I went to the English website and ordered the bearings. Motion Industries didn't get any of my dollars this time, but they'll definitely be first in line next time I need a decent bearing or suchlike!

I've made detailed CAD models of all the spindle innards and plan to post these here, as well as lots of photos, part numbers, etc. as I reassemble the spindle.

That's it for now. Stay well!

Hi John,

I'm having similar problems with the spindle axial play. I'm planning on replacing the bearings, but would like to have the bearings on hand before taking the spindle apart. The part numbers I have for the bearings are 6002-Z, 7001 CD/P4A, and 71903 CD/P4A. Do you know if those are correct?

First off, sorry for not having published the info I've learned - this seems to be a relatively "slow" forum, and there didn't seem to be much interest. Yours is the first reply to my thread.

Anyway, the pulley bearings on my mill were indeed 6002Z (or ZZ). My spindle had 3 internal bearings - a pair of FAG B10739C at the lower end and a FAG B7001C at the upper end. Slightly different numbers than you mentioned, but probably the same bearings, just from a different manufacturer. Took me a bit of searching, but I was able to find them ... at about $150 each!!!! I bit the bullet, bought and installed them. The spindle no longer has any axial play.

I've posted a couple of CAD screenshots here - one of the spindle. It shows the outer housing as semi-transparent, so you can see where the innards are, and how they're oriented (note the "V" markings on the angular contact bearings). I use a special purple color to indicate threaded surfaces.

The other is a tool I made for spindle disassembly/reassembly. One end is a spanner for the lower spindle nut (marked LH to remind you which way to turn). The other end is a puller for the cap on the upper end. It uses M3 screws to grab the cap and 10-32 screws for jacking.

Let me know what other info you need.
- John

PS - Just for fun, check the orientation ("V" markings) of the bearings in your spindle. If yours don't match what's shown in my screen shot, that might possibly be the source of your axial play. If so, and the play goes away with the "correct" orientation, you've saved yourself some big bux!

As I'd mentioned in my previous reply, it's been a while since I first posted. So here (at long last) are some screenshots I've taken of the CAD model I "built" representing the head of my DM2400. Various parts have various colors, just for clarity. Some. like the head casting, have colors similar to the actual parts. About the only colors that have any significance are purple (threaded surfaces) and red (critical surfaces like tapers, and also feces of sectioned parts). Any questions, feel free to ask.

I guess I can only add 8 files to a post. Hare are the first 8. Others will be attached to subsequent posts.

Here are the next 8 screenshots.

...and here are the final two. Note that some of the earlier screenshots ones were taken when I was in a very early stage of modeling the head casting.

OK, one more ...

You CAD work is beautiful, hman! I wish I were that good with 3D, but I'm not!

If you ever feel like modeling a DM4400, let me know.... I'd love to have that. i wouldn't mind figuring out the cartridge better.

Quote:

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Originally Posted by MrMetric

You CAD work is beautiful, hman! I wish I were that good with 3D, but I'm not!
If you ever feel like modeling a DM4400, let me know.... I'd love to have that. i wouldn't mind figuring out the cartridge better.

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Thanks for the kind words. If I had a 4400 sitting here next to me, I could probably work up a decent CAD rendering. But it does take a bunch of careful hands-on measurement, then trying to design the part, then having to go back and finding the missing dimensions or details ... as well as figuring out how the various pieces mesh/link together. It's fun in a way, but a LOT of work!

Latest update ....
I've "discovered" what might possibly be the answer to my CAD dilemma ... FreeCAD. It's an open source CAD program that will run on PCs, Macs or UNIX boxes., And unlike Fusion, all the build files reside on your own computer ... and no surprises (like a price increase) later on! What's more ... it includes a native CAM processor (known as the "Path Workbench", that has Mach 3, Centriod, GRBL and other post-processors. I haven't installed it yet, but plan to pretty soon. I'll post again once I've tried it.

Hi John, I was a member valleymetal, not active anymore, just too busy. I'm in the Prescott area. I have a DM4500 still at a riggers warehouse to be delivered. I was going to suggest FreeCAD or Fusions but looks like your beat me too it.