Member postings for mgnbuk

There must be a way to import an .obj or .3ds model file and convert it to G-Code

That is done with a CAM program. Cambam is one of the lower priced versions :

http://www.cambam.info/

You can download an evaluation copy & use it 40 times unrestricted, then it hobbles to a limit of 500 lines of code. Cambam is not a full 3D program, but it does say in the blurb that it imports 3ds files. I have a copy but, as with many areas of interest, have not yet found the time to explore it's capabilities. I have had limited experience with OneCNC Mill Advantage at work - a combined Cad - Cam package that will import from other Cad programs or allow you to draw from scratch, convert to a machining strategy & post-process to produce a part program to suit most control formats. IIRC, our single seat 2 1/2D 3 axis package cost around £1300 (+Vat)

Other progams are available, but many of the full-feature industrial packages are priced outside the realm of most DIYers.

Out of interest, what are you wanting to make ?

HTH

Nigel B.

(edited to correct spelling mistakes - this editor is dire !)

Edited By Nigel Barraclough on 16/08/2012 19:44:47

I Googled nccad8 & on this page :

http://www.max-computer.de/x5e/download_nccad8_help.html

is a downloadable html based manual ? I have had a quick look at this - it downloaded Ok and runs, but I have not checjked out how much depth it goes into. Might be worth a look ?

Regards,

Nigel B.

Would the 22c and v22 parts indicate intended 22v operation

More likely an indication of the motor frame size, I suspect. That is usually the case on larger industrial motors.

Sorry can't be of more assistance, as I have no experience of dc motors of that size.

Regards,

Nigel B.

I thought the She(a)rline bed was an anodised aluminium extrusion and therefor no suitable for scraping, grinding or any other "remedial" work?

Steel bed section on my Sheline long bed lathe - every thing else anodised aluminium.

I would not let abrasive pastes anywhere near a machine tool !

Nigel B.

I have no experience with Heidenhain but if its conversational I should be ok and I'm a fast learner.

Have either of you guys used Hurco control? And any dealers in the south east you would recommend?

Heidenhain pioneered the conversational approach - programming & operation is very straightforward. The adoption of the early models as standard equipment on Bridegport Interacts helped get them widely established here - the current "high end" controls are 5 axis & optimised for high speed machining (fast block processing times).

I have no experience of Hurco controls - though one of my old customers had one & was very complimentary about it. I used to work for a CNC machine tool rebuild & retrofit company & my experience is with the controls we used to fit - Heidenhain, a (very) few Bosch, GE Fanuc, Osai, Siemens and 1 Fagor installation. As Hurco use an "in house" control that does not appear to be made available for third party installation, I did not get the opportunity to play with one. Likewise, I have no experience of Semco machines, though a quick look at their website shows the current bedmills as being "Ajax" branded. Ajax CNC milling machines used to be Spanish (Lagun) when the company was based in Stockport. I am not sure where the current owners of Ajax source their machines, but the Laguns were well made & sturdy machines.

As I live "Up North", I have no experience of Southern based dealers. My current employer largely stays clear of dealers, buying mainly from auctions. I sort them out, install them & keep them running (easier said than done sometimes, as the company is purely a graphite machining operation). The previous employer was, in the later years, a dealer of sorts - he would buy machines & rebuild/rewire/retrofit for stock to sell against new machines when rebuild or retrofit orders were slack. He specialised in the larger end - the last few years were mainly 48" and larger vertical borers, though we also did a few Butler Elgamill travelling column milling machines & similar. The size of machine shown on the Semco site was not cost-effective to rebuild or retrofit from the mid-90s, as the price of a new Far Eastern machine was less than the cost of a rebuild or retrofit (the volume MTBs were paying less for a complete package of control, axis & spindle drives, axis & spindle motors and cables than we could buy the control alone for).

I have retrofitted a Heidenhain TNC320 onto a Cincinnati Sabre 2000 recently & have a Heidenhain Manual Plus turning control under my desk waiting to go onto a Gildemeister NEF1020 lathe. Both these machines are only worth the cost of retrofitting because of their capacity. Both were bought at auctions for relatively low prices & will stand at less than a normal dealer price after retrofitting. In both cases, the cost of the retrofit hardware (not taking my time into account) was 2-3 times your initially stated budget ! The Sabre really had to have the control changed,as the original Acramatic 850 proved difficult to get going & the trouble with an older "oddball" control is that you can quickly run up a very large bill with the few specialists capable of looking after them. Hence the decision soon after installing the machine to bite the bullet & replace the 850 rather than pay to get it sorted.

Good luck with getting much of a warranty - most older machines will not come with much beyond having it demonstrated as working when installed.

Why with an Anilam control ? As Anilam are no longer developing or manufacturing (bought out by Heidenhain IIRC) long term support may be an issue, particularly as Anilam were never what could be called mainstream controls over here.

For a conversational control on an industrial mill, I would go for a recent-ish Heidenhain control - the older TNC145, 150, 151, 155, 351& 355 controls are getting more awkward/expensive to fix though, so don't pay a premium for those models. For universal "appeal" - go Fanuc. For seriously expensive spares & "different for the sake of it" - go Siemens

What to check for ? Depends how much time you have & how much the vendor wants to let you do. I would try to pull all the slideway covers back to check for scoring on the ways & that the lube system is working. On older machines with plain bearing slides it is not unheard of for the slideway liner (if fitted) to come loose (if there is what looks like a thin piece of plastic coming out from under the slide - light green or beige usually - that would be the anti-friction liner. Expensive fix !).

Jog all axes at rapid traverse & listen for untoward noises - grumbles, rumbles or speed-dependant whines could suggest ballscrew or support bearing problems (or linear bearing problems if the machine does not have plain bearing slides). Expensive fix ! The axes should accelerate & deccelerate smoothly and not generate servo alarm messages on the control. Be aware that many machines operate at reduced traverse speeds in manual modes - get the vendor to demonstrate the full traverse rates in auto modes. Jog the axes in alternate directions (full forwards directly to full reverse) & listen for knocks that could indicate excessive backlash in the drive system. To properly check for backlash requires a dial gauge.

Try to get the vendor to machine a "NASA" test piece - a cylinder above a square diamond above a square. The square & square diamond should measure the same across the corners & across the flats - if not there could be geometric errors. Mount a dial gauge in the spindle, position over the centre of the cylinder & "tram" around the cylinder periphery. The cylinder should show round, not oval (geometry or servo setup error) without steps or marks at the 3,6,9 & 12'clock positions (backlash or loose gibs).

The spindle should run up smoothly to full speed (forwards & reverse) without untoward noises - though backlash in the gears can show up as a a rattle under light loading that reduces under machining load. Check the spindle taper for scoring & excessive wear (Blue up a good toolholder, insert in taper, release & check for even marking in the socket). Do a tramel check to the table - vertical machining centres usually wear the head (Z axis) so that the spindle is out in the Y axis direction. Expensive fix !

If it has an ATC, have it demonstrated & check all pockets for damaged retention clips.

Try to talk to an operator who has run the machine (or management where it was last operated) to find out if he has had any issues with it - more difficult if it is at a dealer or auction, but I have managed to track down original owners of some of our machines in the past & no one has told me to "go away" (or words to that effect ! ). Most have been very helpful.

Check that all the documentation & data back-ups are present - this can be almost impossible (MTB gone out of business) or serioulsy expensive (if they are still trading, or have an ex-agent still trading) to get hold of. Loose the parameters or PLC program due to a control failure or back-up battery failure with no data back-ups & no documentation - expensive fix !

If you are not sure what to look for - try to take along someone who does. A thorough check-out is not a two minuit job, though.

HTH

Nigel B.

Does the original motor/drive not work ?

One of your photos shows what appears to be a basic DC drive - if the motor & drive are working I would leave them be for the moment & use the machine "as is".

FWIW I would not look to replacing the current arrangement with a 3 phase motor / VFD combination. Unless you fitted an external fan to cool the motor, I suspect it would overheat at low speeds. Should the motor die (replacement drives are easy enough to source for small dc motors if the drive dies), I would be looking for a small dc or ac servomotor & drive, as these are designed to supply their rated torque down to a standstill & would be quite happy running at low speeds for extended periods.

Regards,

Nigel B.

Hope you didnt pay too much £120?

£90 IIRC

Most of the machines I saw at the Harwarden open days appeared to be damaged in transit, rather than having been stripped for parts. I guess that the price they pay for complete machines is so low that it is cheaper to canibalise some for parts rather than hold a dedicated spares stock.

Is any one interested in me running a post on what I do and How I get on ?

If it's not too much trouble to document what you find as you go along, I would be interested.

I think that is the model I bought from one of Chester's open days as the basis of a CNC conversion - the machine appeared complete apart from missing it's electronics box & the changewheels. It even came with both steadies, the 3 jaw chuck & a QC toolpost with 1 toolholder fitted. It looked as though it was a new machine had had the complete electronics box removed - possibly to be supplied as a spare part ? - but was the disposed of in the sale incomplete rather than having the electronics replaced.

As many parts will not be required for my use, I'm sure we could come to some arrangement if I am discarding parts that you find you require.

Regards,

Nigel B.

A small industrial dc drive should do the job. There are a couple on Ebay at the moment :

300746884698 is a Control Techniques Lynx 240V 8A unit

320939772839 is a Sprint 3600 XRi 4 A unit

Both are a bit on the big side current wise. As your motor doesn't have a tachogenerator for speed feedback, something that has armature voltage feedback would be best. The Sprint outputs 180v dc for 240v supply - you would just loose a bit of speed at the top end at the lower voltage (http://www.sprint-electric.com/products.php?cid=7&sid=17&pid=13 for more details on this drive).

http://www.acpd.co.uk/sei/s/1488/control%20techniques%20lynx%20dc%20drive%20manual.pdf gets a Lynx manual, though I have not checked that this manual is for the same version drive as the Ebay link.

I bought a used Fincor 2200 drive (http://www.ctiautomation.net/PDF/Fincor/Fincor-2200-Drives.pdf) from Ebay to use with a Chester mini lathe bought drive-less at a Chester openday as the basis for a CNC conversion. I have yet to that project underway, though - still collecting parts & enthusiasm !

Most small industrial dc drives have an isolated 0-10v speed command input, so can either be controlled manually from a pot or from a computer for CNc applications.

HTH

Nigel B.

I re-greased anyway.

Re-greased which bits, David ? Only ball & roller bearings are greased usually on a machine tool, evrything else is oiled. Greasing slides & screws leads to their premature demise.

Nigel B.

My main camera is an Olympus E410 digital SLR

Pages 49-51 in the E410 manual (the on-line version from the Olympus website) describe the whie balance function & how to set a custom white balance.

I use a Pentax K20D, which is set in a similar manner.

Digital slr or film, Ray ?

If digital, no filters are required as the white balance can be set to suit the lighting conditions. Take a piece of white paper as a reference & set a custom white balance by taking a picture of it (you would have to refer to your camera manual for the specifics) under the lighting conditions at the venue. If your digital pictures from last year just have a colour cast, this should be correctable with a photo editing software package (Photoshop, Photoplus etc).

For filters for a film camera, I suspect you would need to know specifically what type of lighting is used in the hall to get the correct value.

HTH

Nigel B.

Jason,

Not directly related to the engine, but a query about the link showing the 3D model as a .pdf

We received a component drawing from a prospective customer today in this form & would like to get dimensions from it - do you know if this is possible ? Right clicking on the page gets a menu that includes "3D preferences" - in here are settings for 2D and 3D measurement, but there doesn't appear to be a toolbar for measuring ?

Being able to check dimensions on the Cad model would maybe help with the point you initially raised ?

Regards,

Nigel B

Harold,

I can see where you are coming from, but starting up a home workshop is never going to be a cheap occupation regardless of how you try to do it & the cost of a precision level as described is not much more than 10% of a fairly basic entry level lathe. If I had put links to the kit used at the last employment, that would be a very different matter - IIRC the M&W block level was £250ish+Vat, and the Level Developments magnetic box level over £600+Vat, both prices being probably 10 years out of date. It would be impossible to justify such an investment for a home workshop. The changes to supply that have made small machine tools far more affordable have also been at work with the metrology side of things.

Again, perhaps it is my industrial background that makes me aware of the ongoing requirement for "extra" kit to make a machine useable - the rule of thumb I was told when I started out that "you will spend as much again on tooling & workholding equipment for a (CNC) milling machine as the machine cost" is probably not far off the mark if you buy new, reasonable quality items.

How often a precision level gets used is dependant upon your individual checking regime - if a machine is initially set level, it is a matter of moments work to check it has not moved (and they do move) before committing to a particularly accurate or demanding job.

All setting a lathe up by turning & measuring will tell you is that it can turn a 4" or so piece close to the chuck parallel. What is happening further down the bed ? A lot of small part turning may well be done within the 4" or so from the chuck, but what happens when you want to line bore a casting bolted to the cross-slide, working further down the bed ? Or set up a vertical slide - extra length for a milling chuck + vice on the veritcal slide + component = out of the "tested" area ? If you have introduced a twist in the bed to compensate for localised wear close to the chuck, how will you know ?

I wonder how many would-be home workshop practitioners start out with a tired lathe, install it using the "turn, measure & tweak" method, then get disillusioned when parts don't come out as expected & subsequently give it as a bad job ?

Having set my machines with a level, and regularly re-checked them, I can be fairly confident when something goes awry that it is most likely to be "operator error" rather than "machine error" that is to blame.

This appears to be (yet another) area where the exponents of two different camps (industrial methodology versus ME methodology) use different means to get to nominally the same end - and neither side will budge on their prefered method !

Nigel B.

Small three square (triangular) scraper ? Like this one on Ebay 251023998259. Handy for deburring all kinds of awkward places.

Nigel B.

David,

I have never worked in minutes of arc, all the levels I have used have been graduated in the form of a slope - typically either 0.05mm or 0.02mm per metre per division. As a divison is typically around 5 or 6mm wide, it is easy to read to less than quarter of a divison - 0.005mm in a metre (around two tenths of a thou in 40" in old money) or better. As the length of the bubble varies with temperature, the position of the bubble is read relative to both ends of the scale, the aim being to get it central. From memory, most machine specs. have called for level to be set to a maximum error of 0.04mm/metre - less than one division on a 0.05mm/metre level. As with most things engineering, there are tolerances given for levels, as it is rarely possible to achieve perfection. When I was involved in putting rebuilt CNC machine in at customer premises, we normally aimed for around haf the permitted error or better, but "within spec." is all we were required to supply & if the levels had to be sent to one side of the tolerance or the other to get all alignments with spec, then so be it.

As I said earlier. setting level is the first part of checking the overall alignment of a machine. What could reasonably be assumed, though, is that if the machine was initially levelled during manufacture & the alignments adjusted so that they were within specification while the machine was in a levelled state, when the machine was installed at the customer 's site re-levelling should also put the machine in to it's as-built alignment. Most of the time this is how it worked, though some "tweaking" of levels & alignments within the allowed tolerances may have been necessary.

The "cut & measure" bit was usually done on the first component that went on the machine - I can't recall having had a customer requesting test pieces being cut after having had the alignments demonstrated. The main bit of cutting I did was on rebuilt vertical borers, where the machine was used to face the top of it's own faceplate. This was pretty well the last operation, after I had been through the levels & alignments with the fitter who had done the machine. A slow operation - 0.1mm /rev, running in constant surface speed but most machines had a top speed on 300 rpm or so & tables of 1500mm diameter or larger & programmed tapered to produce a concave surface.

When I put my ex-school Myford in at home I used a 0.02mm/metre level. Checked across the bed at headstsock, mid bed & tailstock ends & along the bed on both shears it levelled to better than the width of the division line (maybe 1/10th of a division) at all points. This suggests to me that a). that Myfords did a good job of grinding the bed initially, b). that the casting must have been pretty much stress free when it was ground and c) that the school didn't use it much. I did a "dumbell" turning test after installation. but cannot recall the numbers - I guess it was with the limits I was expecting, as I have not made any headstock-related adjustments.

Regards,

Nigel B.

I would like to think this is simply a matter of terminology, i.e. you really mean "removing wind (twist)" rather than levelling. Otherwise I'm afraid you are just confusing anyone new to this.

You appear to be the only one getting confused ? The terminology is well established in industry, but some model engineers appear to want to use different terms, or seem to think that the industrial methods & terminology doen't apply (thinking particularly about the ME affliction for calling a lathe spindle a "mandrel" here).

A precision level does not have to be particularly expensive (Ebay 290723844611 - or for a little bit more, a box level 360464357901). Such a sensitive instrument for relatively little compared to the cost of machines.- & using one makes installation of and subsequent checking of a machine much easier.

But to each his own.

On the point of slant bed lathes - recently had one delivered at work (Gildemeister CTX500), along with all the original documentation. First requirement when the machine is sited ? According to the supplied manual - level it ! First entry in the alignments ? Confirmation of levels ! Only then on to the other geometric checks.

It has been the same with all the machines I have worked with over 30+ years - the confirmation of levels is the first entry in the alignment checks. On some of the bigger machines, like Webster & Bennett vertical borers, it can be "interesting" getting the levels correct and the squareness checks within spec. - often requiring much tweaking to get the levels to one side of limit to get the squareness within the other side. Particluarly as the "levels" also include the front & side of the column and the cross-rail, as well was on the table top (faceplate or chuck in lathe parlance - a vertical borer being effectively a lathe sat on the back of the headstock, with the bed pointing upwards from the floor). And putting "borer" in the machine description appears to be shorthand for " reduce all values from a "normal" machine by half " !

One thing I was suprised to see not commented on was that the OP said he purchased the machine from a dealer - was the dealer not contacted to rectify the problem ? The error described seems to be a long way from acceptable & should have been reasonable cause to seek redress.

Nigel B.

NEVER get a mill with a round pillar you will regret it.

Given the choice of a mill with a round column that I could afford, or no mill, the round column machine won - and no regrets. Particularly as the first round column mill I bought (an Emco FB2 clone) has a full length key to maintain head alignment (not all round column mills loose position when the head is moved !).

I also have an RF30 mill/drill - not yet fully installed, but a bigger machine that was, again, affordable. With 130mm of quill travel (and a bit of forward planning with regard to tooling) I don't anticipate to much trouble.

Either machine is light years ahead of using a vertical slide on the lathe - a very restricted, frustrating arrangement almost totally lacking rigidity.

Just as well that HH didn't take this advice - MEW would have been rather light on milling articles over the years had he done so !

£0.02

Nigel B.

My concern now is my new HBM 6 inch 4 jaw chuck

I purchased a HBM camlock 3 jaw chuck with 2 piece jaws as a replacement for the Harrison 330VS at work & it is good in all respects - fits the spindle well, the jaws are a good fit in the body & grip the workpiece parallel. The top jaws are a very snug fit the the base jaws. I did a runout check on a bit of ground bar when it arrived, though I can't recall the reading - but it was low enough not to be an issue.

We also use RDG's ER collets at work on CNC VMCs, as they are a lot cheaper than the industrial suppliers & the ones I have checked have been very good for runout. No complaints from the operators about them either.

At home I have a HBM rear QC toolpost on the Super 7 - again, nicely finished, the tenon fit the tee-slots snugly & it works well.

The same cannot be said of the supposedly Myford fit Soba ER collet chuck - which doesn't. I should have sent it back (bought at Harrogate last year), but didn't get around to it at the time. It is tight, though, so it will get sorted eventually. But a small Soba boring head with interchangeable shanks is nicely made, the 2MT shank fits the machine taper well & it works fine. Perhaps Soba have a QC problem, or maybe they buy in from different suppliers for different products & just brand them all Soba ? It does seem to be a bit of a lottery as to how useable their products are.

Nigel B.