Author Topic: Portable milling/grinding machine for machine way reconditioning  (Read 15241 times)

Offline PekkaNF

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Hello,

I have pretty old mill and it's ways need reconditioning. I have come to conclusion that outsourcing the work is not possible. Way too expensive and involved to work companies that really don't want to cater hobbyist. Ways need to be milled/ground to acceptable accuracy, now they have serious wear and that produces almost 0,4 mm dip in the 500 milled distance....I would be happy with 0,02 - 0,04 mm planar inaccuracy on 500 mm distance. Nothing impossible.

Ofcourse I could scrap it and start looking for a little less used, but here mills that are way better are really big industrial ones. Small hobby size (like bridgeport or such) are not often available and they are really expensive when they are.

So before scrapping my scrappy mill I might as well try fixing it and if I break it, I least learn something. Amount of metal removal necessary excludes manual scraping. I need to use power tools.

I have seen magnetic drills and mills bit like this on sites I used to go to:
http://www.hydratight.com/sites/default/files/products/images/geniSYS_II_milling_machine_product1.jpg

I never seen an linear portable mill, but apparently there are some:
http://www.hydratight.com/sites/default/files/products/images/geniSYS_II_milling_machine_product1.jpg

http://cdn.powermag.com/wp-content/uploads/2012/11/520004de14df6-Linear_Mill_-_Gantry_Mill.jpeg

Now the interesting design question: How to build "frame" which is a) bolted to milling machine frame to mill/grind milling machine upright flat ways straight, b) to mount that will hold table and it has dovetail ways, c) possibly knee.

Knee I might be able to farm out for milling least, maybe even grinding, but table is way too big.

I have been checking as much as I can without dismantling the milling machine (I need that on this condition to make some parts) and interestingly looks like there are part of the ways that still has original scraping left, I could use them as a reference to record shape of the ways and keep book how much screws and mounts have to moved to fit all parts together.

I considered plasma cut steel parts and welding....fast and easy, but I don't have immediate ways of heat treating them. I know that those structures have no long term stability, but for one-off work how much they live in a day/two time span? Or do they spring which ever way and live all the time during the stress of milling/grinding (not the rig/frame) but part?

I'm not considering concrete in any form. Makes a real mess on reuse of the metals and it shrinks first 400 years, first very much.

Most I'm considering hot rolled steel, minimal machining and all bolted joints.

I may be able to persuade one machine designer to give go/no-go advice on dimensions and such. Plan is to use some parts I have all ready and build bare minimum of structure/tools I will not have much use after.

Pekka

Offline awemawson

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #1 on: April 29, 2016, 03:33:22 AM »
What is the mill Pekka? A knee mill of some variety by your description, but a photo and rough dimensions would help us cogitate your problem a little better.
Andrew Mawson
East Sussex

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #2 on: April 29, 2016, 04:07:56 AM »
Damn. I should take pictures...it is small knee mill, about 1,5 metric tons in weight. Originally horizontal mill, but it has a universal vertical head - no drilling pinion. Maybe 3kW motor, gearbox 8-speeds from 25 to 700 rpm or so...and clutch.

Table is about 1000*250 mm and all parts are heavy :lol: Table and it's mating part are the only dovetail guide, others are flat guides, some 100 mm wide. Table/knee and horizontal flat guide have most wear.

For a German engineering lubrication is funny and and it has seen use, first school, then truck "shed" where they probably forgot to lubricate it.

Coolant tank was shot when I got and cardan shaft for feeds too, but gear and coupling works well. I will not win prizes but will shift some metal even when it is worn out. Someone had spooked the sound of the flat belts (squeeelll- clonk-clonk-clonk) and I got the cheap...delivered. I bought a new endless belt and it behaved well.

I have been looking a small mill/drill of about 300-1000 kg range, but good ones are completely out of my reach and cheap ones are crappier than mine.

Pekka

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #3 on: April 29, 2016, 12:28:04 PM »
Compulsory pictures.

Biggest and most annoying wear is on X-axle, table/knee axis. Y-axis looks weird, but has little impact. Z-axis has a dip in most used place on back of it, where the knee is hanging.

Pekka


Offline RotarySMP

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #4 on: April 29, 2016, 01:59:50 PM »
Do you have a surface plate and straight edges long enough to quantify the wear? It is extremely unlikely that you can fabricate a temporary mill or grinder able to improve this machine. You are better off downloading the PDF of Connelly's Machine tool reconditioning posted here yesterday, hacking a cheap sabre saw into a DIY Biax, getting access to a surface plate , scraping it back in.
Mark
« Last Edit: April 30, 2016, 03:31:31 AM by RotarySMP »

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #5 on: April 30, 2016, 01:53:50 AM »
I my biggest surface plate is about 600*400 mm and another 400*400 mm. Then I have three camelbacks 400, 600, and 1000 mm. I have pretty good 600 mm straight edge and 1000 mm straight edge is in order.

Table is easiest and hardest....it has few original surfaces, machined that can't have any wear, because they are no bearing surfaces, but they are on the same plane than bearing surfaces. On the other hand, it has a longitudal dovetail, that is going to need some attention and it is not trivial to measure.

Knee is hardest part....it has Z-axis bearing planes luckily on on plane (or should have) but Y-axis bearing surfaces have offset by design and it is going to complicate measurement. Good news is that it just about fits on my big surface plate - I can verify it and then check it against the knee ways.

I can borrow longer straight edges of varrying (known accuracy).

I will not try to attemp of scraping to shift the most of metal, there is simply too much of it.

I have been reading of Connelly's Machine tool reconditioning, rather nice reading if you can't sleep...It is very matter of the fact of course and I much liked it. However, I haven't mannaged to google anybody first timer that has tackeled this size project solely on scarping and has a proof of succeeding.

I need whole more controlled method of removing metal than angle grinder or such and faster than scraping.

Pekka

Offline awemawson

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #6 on: April 30, 2016, 03:00:17 AM »
Get a Biax and use it with a carbide scraper insert, you'll be surprised how quickly you can remove cast iron. (Steel is a different matter)
Andrew Mawson
East Sussex

Offline RotarySMP

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #7 on: April 30, 2016, 04:19:30 AM »
Sounds like you are well tooled up to do the job. Any welded frame supporting a grinder is going to take off metal fast,with The Risk of rapidly destroying the remaining accuracy of the mill. How many surfaces are really that worn that you need to take off tenths of mm? For those you are going to have problems with leadscrew alignment, and should consider milling out and moglicing them.

Offline chipenter

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #8 on: April 30, 2016, 04:24:08 AM »
I used a flat file ground the teeth off the edges and cleaned the file with a brass brush , still took a fortnight to remove ten thou from my lathe bed , and my hands were so black the kitchen sink went rusty .
Jeff

Offline RotarySMP

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #9 on: April 30, 2016, 05:16:39 AM »
There are a few guys on the Net who have hacked cheap saber saw's to reduce the stroke and mounted carbide scraping blades a cheap Biax. The feedback from those who have done it is that it works quite well, with a significant reduction of effort verse hand scraping.

http://www.cncecke.de/forum/showthread.php?59092-Schab-O-Mat&highlight=S%E4bels%E4ge+biax

http://www.practicalmachinist.com/vb/general/power-scraping-anyone-tried-convert-makita-hk0500-metal-161099/index2.html

https://www.youtube.com/watch?time_continue=4&v=uTu2iwdiCt4

"My own Aldi variable speed recipro saw adaptation which I call "Aldix" is not quite as good, too light and too much play in the blade guide, but I've used it a lot over the past 4 years and its still going well...."



Offline Jonny

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #10 on: April 30, 2016, 03:33:22 PM »
Scrap machine already so scraping nothing to lose.

Wish had a tenner for everyone that said ive only took a couple of thou off, to correct needed 40+ thou.

Offline tom osselton

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #11 on: April 30, 2016, 03:55:06 PM »
Interesting article what is the stroke on a Biax is it variable?

Offline hanermo

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #12 on: April 30, 2016, 05:53:09 PM »
This is perfectly possible, and not too hard.
Many people have done this, videos on youtube.

From 0.4 m error, you can quite easily get to 0.02 mm or near this (or less).

I have done similar, by using linear bearings, the proper profiled thk type.
Then just mounted  bench grinder onto the sled.
Worked fine.
Was maybe 0.02-0.03 max error or less.

These days, I sand ways flat.
It works perfectly well, if your process is suitable.

Ie, for me.
I use a big wide grinder. Cannot dip or groove.
Around 5" wide, iirc. Festool 1400W. Best on market. Expensive. (Sit down before You look at price).
I do lots of these.
I mark the areas to be ground "more" with felt tip. Felt tip == 0.01-0.02 mm.
Grind till its mostly gone.
All my material is wide and flat, tool steel.
Hand pressure can easily control to better than 0.01 mm error on flat steel surfaces, with some experiences.

Very important Point.
Edges get rounded with grinders. I only use centers, far from edges, so in my case its fine.
E.g. I need a 35 mm wide flat.
My surface is then 50 mm wide, and I sand flat over the total surface.
The edges are not flat, but the center part is, to better than 0.01 mm.

The Grand Old Man on precision rebuilding Richarch King has used similar and does not disallow these when used suitably.

I measure with precision ground straight edge (Vertex, 1m) and look for around 0.01 mm or less incremental error re: mount points.
You can easily feel/test/measure it by hand with linear guides.
Once they run smoothly, you know they are in range.



Offline PK

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #13 on: April 30, 2016, 06:10:00 PM »
This is perfectly possible, and not too hard.
Many people have done this, videos on youtube.

From 0.4 m error, you can quite easily get to 0.02 mm or near this (or less).

I have done similar, by using linear bearings, the proper profiled thk type.
Then just mounted  bench grinder onto the sled.
Worked fine.
Was maybe 0.02-0.03 max error or less.
Quote
I was thinking along the same lines.  We've built and bought a couple of machines using the Hiwin brand linear bearings. They are better than any of my measuring gear and relatively inexpensive.
PK

Offline Komatias

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #14 on: May 01, 2016, 06:56:32 AM »
Hi guys,
Last year i was looking to regrind my KRV and apply turcite. Having scraped a machine before and done all the messing with blue etc. I was not keen on repeating this myself. Before starting to do any thing, get quotes from professional machine tool grinders. You may be pleasantly surprised. I got 4 quotes from UK companies ranging from ridiculous to wow that is fantastic!

Typically machines require little work on the knee as it is not as worn as the X Y. So many places will tell you to ship them the knees table and saddle. Not sure what prices are for pallet shipping in your countries but here it is not bad.

It will save you so much time it is worth every dime spent and if they aplly turcite, you will have a fantastic machine!

Regards

George

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #15 on: May 01, 2016, 11:31:31 AM »
Thank you all!

Having this ground professionally is no go. I have asked prices and most said that they were not interested or I would be better of buying a new taiwanese one than paying a bit more for them to have a go on in.

One retired gearbox designer (industrial size, mines, wind turbines and such) visited me today an we plotted some ideas. It's not going to be too hard, but it might be too much work. Got three books on maching and measurement 1970-era, I'm not taking on knitting - yet.

I started measuring parts. It's nice to know which size parts are how much space I'm going to need.

Next step would be to figure out how to tackle each part and how to do it. Then I would have pretty good idea how big rig I need for it.

Some advice was really usefull, any pictures or links to projects members have done to regrind ways would be nice.

I did consider using a bench grinder as a grinder head. No way ideal, but it could work. I'm not too keen on routers or any die grinder....way too small stone and too much dressing.

Pekka

Offline Jonny

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #16 on: May 01, 2016, 12:37:39 PM »
What you have to bare in mind is no amount of beefiness unless a proper way oversized machine will be accurate. Typically these machines are solid objects weighing by the tonne and around 16 foot long.
C Linear bearings your limited by the frame beefiness and runout plus dia of bar used, terrible flex even for woodwork, soon as It starts theres no stopping it just gets worse and worse trying to correct even with a small dia cutter.

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #17 on: May 01, 2016, 01:10:07 PM »
Not sure if I follow you Johnny.

I agree that normal milling machines and even more grinding machines are a hefty affair. But that is greatly because the working envelope is big and they are designed for production = ability to shif crapload of metal in no time.

I have seen whole lot of amateur routers that are designed for huge work envelope and 600w chinese router....

I'm aiming here lower. Only one movement is large (X-axis), one axis has feed of 20-50 mm, cutting depth adjustment in order of 1-3 mm. 1,1 Kw motor and that's pretty much it. Rails have to be pretty close to cutting point here or there will be problems.

Pekka

Offline hanermo

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #18 on: May 01, 2016, 01:42:48 PM »
I used a glass dining table as my reference surface, for 2 m long surface.
The v1 linear bearings ran on it.
Worked ok.

Then, a wood tabletop, with 20 mm thk linear bearings bolted to it.
Worked very well.
The grinder was the typical 30 desk grinder.
Flatness had about 0.02-0.03 mm or less error, for 600 mm travel, +/-.

A grinder has tiny loads, if you are hand feeding it.
Typically, it might be 0.2-1 kg at most, of tool pressure.

*Because* everything is floppy, it actually works pretty well.
You dont get tool bounce, etc. It just bends off.

And a 350W motor has little mrr.
Grinding about 600 mm with 2-3 disc widths took maybe 1-2 hours, back in 2006 or so.

I had zero linkages.
Just a steel sled, rigid mounted grinder, linear bearings.
Push by hand.
Works fine.

The low-power grinder is (or seems to be) quite safe by hand.
It just bogs down.

As Pekka said, an industrial grinder thats used for grinding machine ways, is 20-30 tons.
But that because is has a 30 kW spindle and does one pass.. done.





Offline Pete.

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Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #20 on: May 02, 2016, 03:43:32 AM »
Pete....Looking for a hobby, not profession.....Hmm. if i retire on country and fill one barn with old slow oversize tools.....

Hanermo. Thank you for your pointers. I'm working on same size of envelope.

Luckily I have one real designer to help me with forces, deflections and such, because even I have a cursory knowledge on these things I'm too thick to be able to calculate them correctly. He can not only calculate, but he has these on his head and I make question like. I want to make a hydraulic broach of 4 tons of maximum force and I need a beam of 70 mm wide, 20 mm bolts on both ends - 250 mm apart and hydraulic cylinder rod of 25 mm must go trough it. How much I need thickness for it. he calculated/questimated few key figures and came out result that was very close to calculated one and exactly the prefered dimension I went to buy on junk yard. I could not solve those on few minutes no matter what I had at my hand!

Nevertheless, there is always some surprices.

Pekka

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #21 on: May 04, 2016, 05:28:01 AM »
I think I will lash up something Hanermo said, I'm going to try it first on scrap or something whole less critical to try it out and measure what sort of stuff it will be capable of doing.

I did measure a little of floor quality MDF and bit over 22 mm thick is not even near rigid enough to mount anything. But I can saw few strips and when deep beam is mainly on compression it looks rather doable, based on hasty measurements and numbers I am finding on MDF mechanical properties. My concern is now on how stable it will be....mainly on moisture. Looks like there are some P-grades and some are more resistant on moisture than others.

I basically could buy some, make small body that will fit on surface plate and easily check if it stays straight any time.

Pekka

Pekka

Offline PK

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #22 on: May 04, 2016, 06:21:58 PM »
Re reading, I realise I may not have conveyed the correct message in my previous post.
When I sugguested Hiwin linear bearings, it wasn't to construct a grinding jig. I was thinking about attacking the ways with an angle grinder, slapping a couple of cups of metal filled epoxy on them and bedding the linear bearings in as replacements for the dovetails...
You gotta think big, that's the key...
:-)

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #23 on: May 05, 2016, 03:20:23 AM »
Hi PK, you are right on thinking "big". That would do, specially if I could glue the whole thing upside down over a very big surface plate.

My reluctance stems due to fact that I work for a comppany that uses linear rails and bearings all the time to build machines and there is a learnig curve. Anyway, if you build something like 9-20 m long and 6-12 metres wide machine that has multiple ways every and each direction. On welded and machined frame. I know that the frame is not straight, but linear machine ways are machined pretty straight before installing the linear ways there. Because the rails are not straight either and no long linear ways is made out of one continous piece, but segments, there is a methology.

Unfortunately we have no more manufacturing on our location, therefore there are no extra pieces floating around.

On short distace linear way is pretty straight, but usually a large r, that they are easy to fit on stiff straight surface. Nothing magic there everything usefull is on linear bearing assembly and mounting instructions.

It is really not that big problem if they can be mounted on relatively flat structure, if gringing flat ways on same axis...who cares about 0,1 mm arc on sideways on 1,5 m distance - when it is on same plane than flat ways. Dovetail problem could be reduced to same problem when the dovetail flat is jigged ont same plane with ways.

Only problem here is that I don't have 1,2 - 1,5 m long linear ways at my disposal. Could buy them, but it would make pretty expensive rig for a one off. And I have no plans for a CNC hobby now.

I have a plan of buying some metres of key stock, that has been rolled into standard spesification and glue it on a frame. Have to device a method, I don't have a big eneough flat plane to rig it straight on one go, I have to think somehing.

I know the spesification, it's not great, but least is not bigger tha on bad grinding spindle. Have to keep eye on big picture here, no point of chasing the last 0,01 mm/m if something else produces bigger error. Local 0,01 mm I can scrape, but 1m long and 50 mm wide area of 0,5 mm are I can't.

Pekka

Offline PekkaNF

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Re: Portable milling/grinding machine for machine way reconditioning
« Reply #24 on: May 10, 2016, 04:06:09 AM »
Bit testing shows, that key stock over really deep section of the MDF might just do.

Has anybody done anything small succesfully out of epoxy concrete (granite/mineral)?

Found some links and lot of enthusiam, but very little end results and practically no long term follow up. This might be canditate for it :lol:

Something like this, but whole lot crappier for "cross slide":
https://youtu.be/-0Cn0WRXPKs

If I understand correctly, it's about aluminium density, compression strength is enough, tensile strength sucks and absorbs vibration about 3 times better than cast iron. Values to very good hobby grade mix.

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392008000400003

"According to Ashby & Jones13, granite has a density of 2.6 Mg/m3, a Young Modulus of 60 to 80 GPa, a tensile strength of 23 MPa and a compressive strength of 65 to 150 MPa."

Aluminum alloy (7075-T6) density of 2.7 Mg/m3, a Young Modulus of 70 GPa, a tensile strength of 510540 MPa.

Pekka