Elrod Z-axis kit: One guy's experience

[FlySox]

Background: For those of us converting knee mills to CNC, arguably the trickiest piece is the Z-axis. Historically, the premier solution to this problem was the Elrod Z-axis kit designed, patented, and sold by Elrod Machine out of Flagstaff, AZ. Sometime around April of 2018, Elrod Machine was acquired by Servo Products Company, a much larger firm headquartered in Eastlake, OH. What follows is my recent experience, having chosen to enhance my X/Y Sharp conversion with the Elrod Z kit.

My high-level summary for those of you considering this path: Your $2.5K investment will get you a well designed, quality product sold by a company that doesn’t seem to care about it at all, nor the success of those who buy it.

I ordered the kit in mid-January and after several follow-up phone calls and emails, I finally received it in the first week of April (79 days later). Ostensibly, this was due to ball screws being back-ordered, but that info was not relayed to me until 7 weeks had passed, and only because I was very proactive in contacting them. They did not make any effort to reach out to me to let me know there would be an unusual delay in the fulfillment of this order.

When the kit did arrive, it was well packaged and nearly complete (it lacks an important alignment tool, see below). However, the instructions included are woefully, ridiculously, shockingly poor. You will receive no link to a series of videos nor even to a PDF with color pictures. Nope: a photocopy with black and white pictures, many of which are fuzzy and/or too zoomed out to be helpful--and NONE of which are annotated with callouts, arrows or circles--are the best the company could come up with. The whole thing reads like Exhibit A in an argument that there have been no innovations since the 1990s that could be leveraged to make installation easier for customers.

I could go on and on in great detail about the shortcomings of the documentation, but it's quite likely this is a product the company is quietly killing off, so I don’t know who or how it would help. Here’s a top line summary, though, so you know what you're getting yourself into:

- The fasteners and other accessories are neatly sectioned off in a long, heat-sealed strip, with each section numbered. However, these numbers are *never* referenced in the instructions! The numbering also does not correspond to their order of installation, so it's unclear why they bothered at all.

- Part numbers shown in the parts list are *not* referenced in the instructions

- The top thrust bearing assembly comes pre-installed *upside down*! You won't notice this until you have already gone through a painful alignment process and subsequent assembly that makes taking this off and flipping it really inconvenient.

- There is an alignment tool that is crucial to the installation (the instructions assume you have one; no work-arounds are given) that is NOT included. They do include a plan for how to make one, which assumes you own or have access to a lathe (I do not). For $2.5K, I think they ought to be able to include this tool.

- Instructions are at times woefully high-level. For example, here's their complete recommendation on wiring the two limit switches: "Slide the limit switch cable [not included] through relief and fasten to the microswitches". Not a single wire routing, heat shrinking or zip tying recommendation, not even a picture.

- The instructions are not internally consistent. For example, you are asked to remove the quill handle early on and are later asked to use it to raise the quill on the ballscrew - there was actually nothing in the assembly that required you to remove the quill handle before this step. They also have you tighten the ballnut holding assembly erroneously at least once.

- There is an entire step that seems out of place / redundant (step 36).

- Pictures show and refer to hex head bolts when socket head cap screws are provided

- Figure 9 will make you laugh: it almost entirely cuts off the thing it's supposed to be of

- The exploded view parts diagram does not contemplate the way in which parts will be installed (e.g. if you followed it, you’d install the pulleys *below* the top ballscrew bearing assembly)

- Regardless of whether your order includes the very expensive linear scale (mine didn’t) the exploded view includes it and its supporting parts

- Fasteners are not included in the exploded view and at least one part number is incorrect (213 should be 216)

All told, the kit took a lot longer to install with a lot more frustration, trial and error, and re-reading of instructions than it should have. The most charitable reading of this situation is that Servo Products Company has not fully ingested this product post acquisition of Elrod Machine and that things might improve in the future. However, the acquisition was made nearly a year before they fulfilled my order, which suggests to me they simply aren't committed to the success of this product --they wouldn't ship it with the current documentation if they were.

My research suggests that Dwayne Elrod himself was quite helpful to his customers post sale and this is possibly how the product succeeded in the past despite its poor documentation (it seems untouched since his day, complete with references to Elrod Machine, Inc). With his retirement, however, current buyers do not have this option. Given my pre-sales experience, where it was clear they really don't know much about this product, I didn't even think to reach out to Servo Products for help during installation (and again, while quite often uncertain and frustrated, I was never completely stuck).

I hope this didn't come off as a disparaging rant; that was not my intention. I simply want to give those of you who are thinking of buying this kit the information you need to make a fully informed decision. You will (eventually) receive a quality product. You will also likely be frustrated during install. Hopefully, the above can help to reduce your frustration. I will happily help where I can; I'd hate to think my pain couldn't be put to good use in preventing the same for others.

[tblough]

Your experience with Servo Products closely mirrors mine. I contacted Servo Products numerous times over the period of three months just after the sale inquiring on the purchase of the Elrod yoke for my ballscrew conversion. Multiple emails (to servo products) went unanswered, direct calls to their sales department were met with blank stares over the phone as they had no idea what I was talking about. Finally located a telephone number for the President of Servo products (He also owns a machine shop in the same area - that's how I located him) and a few days later got a ridiculous quote for the yoke. It's unfortunate about the Elrod products because otherwise, the Servo Product's power feeds, and their sensitive drill presses are top of the line.

Luckily, when it came time for the Z-Axis kit, I had one at work that I could reverse engineer so I made my own. As FlySox says, it's a very well done piece of kit, even more impressive with the scale option ("Smart-Z"), with woefully inadequate documentation. Having installed three of them, if you have any questions, give me a shout and I'll see if I can help.

[Reedfirst]

I think I still have the alignment tool I made for my Elrod kit.

Let me know if you want to borrow it. Just cover shipping both ways.

-Adam

[FlySox]

Thanks for the offer! I should have thought to ask the forum earlier. As it turned out, I 3D printed one. At 90% infill (i.e. nearly solid plastic), it's sufficiently rigid to do the alignment job it's intended to do:

[Reedfirst]

No problem!

Pretty cool solution you cam up with. And I agree, for the cost a simple turned piece of aluminum should have been included.

[Muzzer]

There are quite a few Z axis solutions other than Elrod that use a large yoke extending out from the quill to clear the head casting (Southwestern Industries and others) but they result in a bulky installation and large stresses around the yoke attachment where it is attached to the quill.

I took a slightly different approach to my Z axis. There is (just!) room to get a 16mm ball screw in the position normally occupied by the feed trip adjustor ("micrometer depth stop"), which can be driven from either end by means of a toothed belt etc. This approach keeps the yoke overhang to a minimum and reduces the extent of the installation. It also doesn't require any significant strength in the additional parts or any butchery of the main head casting. The Elrod housing is pretty substantial, as it has to withstand a variety of loads from the quill, ballscrew, belt drive etc.

In my case, I was also able to replace the glass DRO scale where I had originally fitted it, in front of the installation. You might argue it's now redundant but it indicates actual position rather than commanded position and was already cut to the right length. The final part of the installation will be a guard to protect the ballscrew, belt drive etc from swarf and dust.

I'm not suggesting this is the definitive solution by any means but it may provide ideas for those thinking of developing their own solution.

There's a guy down under who did something similar but drove it from the "top" end of the ballscrew:
https://www.youtube.com/watch?v=RsUnoXgFtaE
And a thread on cnczone: https://www.cnczone.com/forums/knee-ver ... 8-cnc.html

[martyscncgarage]

One of you should CAD up a drawing and make it available to others...as you have noted, its difficult to find much information on converting the Z axis of the head of a knee mill....or post copius pictures OR an enterprising fellow would kit one up for sale....thanks for sharing the knowledge.

[martyscncgarage]

I'm looking for the Elrod Z axis kit install instructions. I have to remove one off an old Bridgeport head and reinstalling on a new head. Any gotchas, and particularly interested in the alignment tool dimensions.
Thanks in advance
Marty

[cncsnw]

Marty,

Here is what I have from ca. 2004.

[martyscncgarage]

Marty,

Here is what I have from ca. 2004.

Thank you very much Marc. At least I'll have the heads up with what I'm getting into.

Marty