Chris Hall
Cast Iron
- Joined
- Feb 28, 2013
- Location
- Greenfield, MA
This post concerns a Zimmermann pattern making mill, which, being German, I thought might be best posted here rather than another section.
I've had the mill for more than a year now and everyday find new uses for it. It's been great, but not without some issues, especially lately. These issues are unsurprising given that the mill was made in 1971 and is 46 years old.
Known problems:
-quill is sticky and takes too much force to plunge up and down with. It's so sticky that the automatic feed will disengage itself.
-quill has a degree of rotational slop as well, normally not an issue unless one bolts the right-angle milling head into place. It will not keep it aligned.
-quill lock is also sticky, and if clamped tight then seems to jam itself closed, making for a disassembly if you want to loosen it.
-when raising in Z direction, there is a groaning noise at a certain portion of the travel.
-occasionally the powered Z-travel will get stuck 'on' when raising up, requiring a mad dash to the wall to pull the circuit disconnect. A Minor electrical issue somewhere. I've taken the switch itself all apart but the problem does not lie inside the switch. The problem happens only occasionally and cannot be predicted.
-the manual brake inside the pulley block atop the drive spindle had worn out, so changing tool holders is now a hassle.
-the table has powered rotation, however this suddenly stopped working a couple of weeks back, right in the middle of a project naturally. I am suspecting that either a gear inside has worn out, or perhaps become unmoored from it's position. There's no way to tell without removing the entire saddle from the knee. The drive motor, which also handles x-travel, works fine, and x-travel drive works fine.
Not huge problems but merely annoying:
-the machine accepts ISO 40 taper tooling, however instead of using a draw bar, it uses a large collet nut to fix the tool holder, which presents some limitation as to the range of tool holders which can be fitted. I would prefer to have a powered drawbar retrofitted.
-the machine has a secondary spindle at the other end of the ram, which can turn up to 14,000 rpm. I can't make much use of it however, due to the unique tool holding system, made by Zimmermann, comprising a MT3 taper with a male threaded spigot on the upper end. I have a few tools for it, but not enough to make it worthwhile swinging it into place from time to time. It is basically a large paperweight at this point. I'd rather change it over to ISO 30 tool holding if possible.
-when I fill the saddle and knee up with way oil, it leaks. It's an old machine, it leaks.
Zimmermann is very much in business, making CNC machining centers for the mold and pattern industries, however they offer zero factory support or parts for my machine. That kinda sucks, frankly, but I understand why that is.
Of course, everything can be rebuilt, but always at a cost, which is what scares me. I do not have a second mill and a precision lathe, etc., etc., for fabricating parts myself, or making other repairs so I would have to pay a machine rebuilder to tackle any of that work. I can well imagine that fixing the main spindle alone could suck up $4000~5000. I am under the impression that a rebuild of the saddle and knee, including a whatever scraping is required could be a $20,000 bill. I'm just guessing though. I feel I could tackle the scraping myself, though I have no experience in that area and lack many of the reference tools. I'd welcome the challenge, but know that I would be stepping into a sink or swim sort of situation. And there's also the question of the amount of non-paying shop time that can be devoted to this, as my shop is a business and not a hobby.
Compared to purchasing a new machine, rebuilding is still a cost-effective option. but I wouldn't be in the market for a new machine regardless. And I'm wary of the can of worms effect if I start taking anything apart, finding more and more things needing attention. For less than the price of the rebuild, I could find myself another machine, perhaps a newer version of the same machine, and of course, there are going to be unknowns with that. Maybe it will prove to need rebuilding too. Unless you know the sort of service and maintenance life the mill has undergone, it can be hard to predict condition from photos, and flying to Germany to inspect is, well, another cost (probably worthwhile though, especially if there were several options to look at, which at present there are not). Better to stick with the devil I know, or not?
So, what to do? I'm $10,000 into the mill at this juncture. I can't afford a full rebuild by a professional company that does the work for a living. I'm still getting use out of the machine, but how long until something critical fails and the machine becomes unusable? Problems are mounting and will need addressing before long - well, the sooner the better of course. I'm sure many of you have been in a similar boat at some point in time. What would you do?
I've had the mill for more than a year now and everyday find new uses for it. It's been great, but not without some issues, especially lately. These issues are unsurprising given that the mill was made in 1971 and is 46 years old.
Known problems:
-quill is sticky and takes too much force to plunge up and down with. It's so sticky that the automatic feed will disengage itself.
-quill has a degree of rotational slop as well, normally not an issue unless one bolts the right-angle milling head into place. It will not keep it aligned.
-quill lock is also sticky, and if clamped tight then seems to jam itself closed, making for a disassembly if you want to loosen it.
-when raising in Z direction, there is a groaning noise at a certain portion of the travel.
-occasionally the powered Z-travel will get stuck 'on' when raising up, requiring a mad dash to the wall to pull the circuit disconnect. A Minor electrical issue somewhere. I've taken the switch itself all apart but the problem does not lie inside the switch. The problem happens only occasionally and cannot be predicted.
-the manual brake inside the pulley block atop the drive spindle had worn out, so changing tool holders is now a hassle.
-the table has powered rotation, however this suddenly stopped working a couple of weeks back, right in the middle of a project naturally. I am suspecting that either a gear inside has worn out, or perhaps become unmoored from it's position. There's no way to tell without removing the entire saddle from the knee. The drive motor, which also handles x-travel, works fine, and x-travel drive works fine.
Not huge problems but merely annoying:
-the machine accepts ISO 40 taper tooling, however instead of using a draw bar, it uses a large collet nut to fix the tool holder, which presents some limitation as to the range of tool holders which can be fitted. I would prefer to have a powered drawbar retrofitted.
-the machine has a secondary spindle at the other end of the ram, which can turn up to 14,000 rpm. I can't make much use of it however, due to the unique tool holding system, made by Zimmermann, comprising a MT3 taper with a male threaded spigot on the upper end. I have a few tools for it, but not enough to make it worthwhile swinging it into place from time to time. It is basically a large paperweight at this point. I'd rather change it over to ISO 30 tool holding if possible.
-when I fill the saddle and knee up with way oil, it leaks. It's an old machine, it leaks.
Zimmermann is very much in business, making CNC machining centers for the mold and pattern industries, however they offer zero factory support or parts for my machine. That kinda sucks, frankly, but I understand why that is.
Of course, everything can be rebuilt, but always at a cost, which is what scares me. I do not have a second mill and a precision lathe, etc., etc., for fabricating parts myself, or making other repairs so I would have to pay a machine rebuilder to tackle any of that work. I can well imagine that fixing the main spindle alone could suck up $4000~5000. I am under the impression that a rebuild of the saddle and knee, including a whatever scraping is required could be a $20,000 bill. I'm just guessing though. I feel I could tackle the scraping myself, though I have no experience in that area and lack many of the reference tools. I'd welcome the challenge, but know that I would be stepping into a sink or swim sort of situation. And there's also the question of the amount of non-paying shop time that can be devoted to this, as my shop is a business and not a hobby.
Compared to purchasing a new machine, rebuilding is still a cost-effective option. but I wouldn't be in the market for a new machine regardless. And I'm wary of the can of worms effect if I start taking anything apart, finding more and more things needing attention. For less than the price of the rebuild, I could find myself another machine, perhaps a newer version of the same machine, and of course, there are going to be unknowns with that. Maybe it will prove to need rebuilding too. Unless you know the sort of service and maintenance life the mill has undergone, it can be hard to predict condition from photos, and flying to Germany to inspect is, well, another cost (probably worthwhile though, especially if there were several options to look at, which at present there are not). Better to stick with the devil I know, or not?
So, what to do? I'm $10,000 into the mill at this juncture. I can't afford a full rebuild by a professional company that does the work for a living. I'm still getting use out of the machine, but how long until something critical fails and the machine becomes unusable? Problems are mounting and will need addressing before long - well, the sooner the better of course. I'm sure many of you have been in a similar boat at some point in time. What would you do?
You can go around proprietary seals/bearing but at some cost to time - don't ask how I know that. In the end, there is nothing wrong taking it apart, inspecting it and fixing only what really broken. It's not like it's going to run three shifts. Z is an issue and needs fixing, quill rotation as well. Otherwise, I'd open the spindles, wash the bearings and put a decent wheel bearing grease inside. If those pack up, you have a big problem with maybe, no solution.
