Extending X capability of KX1?

[Jim GuthrieParticipant @jimguthrie82658]

I’ve been using my KX1 for a good few months now and am getting on very well with it. It might be having the easiest life of any KX1 since its main work so far has been to mill styrene sheet with carbide mills in the range 0.4mm to 2mm with low feed rates and no cut depth over 0.25mm. The results have been excellent.

But I’m running into a problem of requiring more X travel. The ~250mm X travel of the KX1 limits what I can do and I would really like about 500mm travel. I’ve had a look around at possible options but larger milling machines with this length of X travel are really veritable sledge hammers to crack my particular nut. I am looking for a desktop solution.

I have had some thoughts on nicking the x portion of an X/Y work table of suitable length/travel and mounting it on the KX1 table and machining long projects in two parts, moving the work table a requisite amount between parts. But I thought the weight of the table might be a bit too heavy for the KX1. Another option is to use a simpler option of a piece of plate 500mm long fitted to the table and move it lengthwise between parts with some sort of register (although I don’t know how I might machine this plate since my other mill is a Centec 2A which has about the same X travel as the KX1. )

I’m looking for any suggestions which won’t cost me an arm and a leg. A newer, bigger machine is almost out of the question since I spent all me money on the KX1.

Here’s a picture of some of the work – cutting panelled sides for model railway coaches – at the moment in S scale (1:64)

 

You can see why I could need a lot of length doing model coaches where the subjects can be ten times as long as they are high.

ACAD LT and Rhino are used to do the CAD. Cut2D and Cut3D do the CAM work with a bit of hand hacking to merge Cut2D and Cut3D files for the lower coach side, where the quarterlight window frames are full 3D machining and the rest of the side is panel and pocket cutting from Cut2D. To give you some idea of size, the quarterlight window openings in the lower picture are about 6mm wide.

 

Jim.

[Jim GuthrieParticipant @jimguthrie82658]

[Keith LongParticipant @keithlong89920]

Hi Jim

The material you’re cutting is light and the forces you’re exerting on it are very low – so you don’t need a heavy table or support plate, just a rigid one. Why not try a piece of mdf with (if necessary) some bracing underneath or on the top around the edges to male the support plate. You should be able to put a decent straight edge along it with woodworking techniques or use a length of ali extrusion from on of the diy sheds and run that against a fence of sorts on your mill table. Cheap and pretty quick to do and you’ll see it the idea flies or whether it gives you other problems.

Keith

[David Clark 13Participant @davidclark13]

Hi There

I think all you need is a few holes at the top of the coach that can locate on the machine table.

Then just move the plasticard along, put it onto the pegs and away you go.

You might have to make a simple drill jig but that would be a one off operation.

Can we (me) have more information on the cutters, speeds and feeds.

Plasticard is not easy to machine as it is so soft but you seem to be doing ok.

regards David

 

 

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Keith Long on 12/07/2011 15:35:35:

Hi Jim

The material you’re cutting is light and the forces you’re exerting on it are very low – so you don’t need a heavy table or support plate, just a rigid one. Why not try a piece of mdf with (if necessary) some bracing underneath or on the top around the edges to male the support plate. You should be able to put a decent straight edge along it with woodworking techniques or use a length of ali extrusion from on of the diy sheds and run that against a fence of sorts on your mill table. Cheap and pretty quick to do and you’ll see it the idea flies or whether it gives you other problems.

Keith

Keith..

 

I’ve been using something similar to MDF up till now – a bit of Contiboard – to give a base to stick things to for milling, and also to raise the part to get it within the bottom Z range of the mill. Even a 2MT ER25 collet holder doesn’t project enough to allow small mills to be used close to the table. See the picture in my answer to David. I find that I am having to work to under 0.025mm/1 thou accuracy in the Z axis with the work and I have had to spend quite a bit of time clocking and adjusting the Contiboard to try and achieve that, with variable degrees of success. I am trying to think of a more suitable solution which might also let me work to longer X lengths.

 

Jim.

 

 

[Anonymous]

Probably the best solution is, as has been mentioned, a larger sub-table that can be moved in the X axis and located on pegs or similar, so that each position is repeatable. However, if you are concerned with consistent Z heights, don’t diddle about with mdf, use aluminium tooling plate. This is a rolled and tempered aluminium plate that is Blanchard, or similar, ground, so the it is flat and parallel to much better tolerances than normal rolled sheet or plate.

 

As an aside, I don’t know about machining plasticard, but I do machine a lot of plastics, especially uPVC. I find that relatively slow speeds and high chip loads are best. The one thing you don’t want to do is melt the plastic. Not only does it get messy, it smells bad too!

 

Regards,

 

Andrew

[Jim GuthrieParticipant @jimguthrie82658]

Posted by David Clark 1 on 12/07/2011 15:41:37:

Hi There

I think all you need is a few holes at the top of the coach that can locate on the machine table.

Then just move the plasticard along, put it onto the pegs and away you go.

You might have to make a simple drill jig but that would be a one off operation.

Can we (me) have more information on the cutters, speeds and feeds.

Plasticard is not easy to machine as it is so soft but you seem to be doing ok.

regards David

 

 

David,

 

I need to hold down the Plastikard sheet very firmly. At first I used double sided tape on a piece of Contiboard, but the adhesive on the tape proved to be a bit too strong and the styrene sheet got distorted with the forces of pulling it off. I then came across a product called Seklema Multimat. It’s a double sided sheet which has an adhesive form of surface on each side and it works superbly, holding the styrene sheet very firmly, yet letting it be removed quite easily with very little stress. Here’s a pic of the setup on the mill.

 

I might be able to set up a peg system but it might get a bit complicated with the Multimat and also cutting parts out. I’ll give it more thought.

 

As I’ve said to Keith, I was looking at a more solid support than the Contiboard. It does the job quite well but I want to work to less than 1 thou/0.025mm accuracy in the Z axis and the Contiboard can take a lot of setting up to get anywhere close to this. My main consideration is when cutting though. The Multimat is self healing to a certain extent and can accept a small amount of cutter action if the cutter gets too low. But it is pricey material and I want to avoid excursions into it as far as possible, hence trying to cut as close as possible to the surface of the Multimat when breaking through.

 

On the settings for milling the styrene sheet, I’m still finding out. Everything is empirical so far. I have to confess that one of the criteria is not breaking the small cutters..

 

At present I an using two flute carbide cutters from 0.4mm up to 2mm diameter. I’m working the 2mm cutter at 2000rpm and 240mm/min feed. I am running a 0.5mm cutter at 5000rpm and 60mm/min feed. 1.5mm and 1mm cutters have feeds and speeds proportionally between these feeds and speeds.

 

The depths of cuts are quite conservative – from 0.25mm for the 2mm down to about 0.1mm for the 0.5mm cutter. I think I can push these harder. I certainly found out that I could put the 1mm cutter through 0.75mm of styrene, double sided tape, the plastic Contiboard covering, and a millimetre of chipboard with no breakage when I once forgot to set the tool zero in the early days.

 

At these feeds and speeds I get an excellent finish, especially on the panels with absolutely no sign of any machining marking. The finish is a smooth matt finish. Funnily enough, the only cutter that gives me slight tool marks is a 5mm one which I use for large area surfacing, but I am tending to push it harder than the smaller ones.

 

I had always thought that machining styrene was not possible. But I picked up on an American group some time ago that carbide bits could be used successfully. Presumably the carbide mills are sharper and run cooler so there is no melting of the styrene.

 

Here’s a pic of the most recent set of sides I completed for a fellow S scale modeller – a Drummond NBR four wheel Brake Third – 30 thou/0.75mm sheet and using 2mm, 1.5mm, 1mm, 0.7mm and 0.5mm cutters.

 

 

I do like the KX1.

Jim.

Edited By Jim Guthrie on 12/07/2011 23:11:44

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Andrew Johnston on 12/07/2011 22:48:06:

Probably the best solution is, as has been mentioned, a larger sub-table that can be moved in the X axis and located on pegs or similar, so that each position is repeatable. However, if you are concerned with consistent Z heights, don’t diddle about with mdf, use aluminium tooling plate. This is a rolled and tempered aluminium plate that is Blanchard, or similar, ground, so the it is flat and parallel to much better tolerances than normal rolled sheet or plate.

 

As an aside, I don’t know about machining plasticard, but I do machine a lot of plastics, especially uPVC. I find that relatively slow speeds and high chip loads are best. The one thing you don’t want to do is melt the plastic. Not only does it get messy, it smells bad too!

 

Andrew,

 

You’ve just given me an answer to something I have been searching for today – aluminium tooling plate. I had picked up a mention of it a short while ago and I could not remember exactly what it was called. I’ll do a bit more thinking about doing a peg setup using this material.

On machining Plastikard, I think that my settings are so conservative that there is little danger of me heating up the material.

Jim.

Edited By Jim Guthrie on 12/07/2011 23:41:48

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Andrew Johnston on 12/07/2011 22:48:06:

Probably the best solution is, as has been mentioned, a larger sub-table that can be moved in the X axis and located on pegs or similar, so that each position is repeatable. However, if you are concerned with consistent Z heights, don’t diddle about with mdf, use aluminium tooling plate. This is a rolled and tempered aluminium plate that is Blanchard, or similar, ground, so the it is flat and parallel to much better tolerances than normal rolled sheet or plate.

 

Andrew,

 

I’ve just had a dig around on Google and this popped up in the searches

 

http://cgi.ebay.co.uk/Tooling-Fixturing-Plate-Sherline-Mill-19-Long-USA-Made-/320562575430?_trksid=p5197.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D4%26po%3DLVI%26ps%3D63%26clkid%3D1309688001107492512

The size is about right for me and it would just requre me setting up mounts for the KX1 table to hold it and provide some form of locating. Probably a bit more expensive than getting a piece of material from a supplier which might need firther machining, but it could avoid the need for machining a piece that is too large for the mills I own.

 

Jim.

[Anonymous]

Hi Jim,

 

If it works for you then that’s good enough! You certainly seem to get an excellent finish and apparently no burrs; very good.

 

Your depths of cut are definitely conservative. I’ve never run really small cutters, but as an example I run a 2mm cutter full width engagement and 0.4mm depth of cut in 316 stainless steel. So, in plastic, bigger depths should be no problem.

 

Regards,

 

Andrew

[Steve WithnellParticipant @stevewithnell34426]

Getting of the track of Jim’s initial question, what’s the capacity of a KX1 with Arc’s 4 inch rotary table?

 

Could I machine this:

 

(IGNORE THE ANNOTATIONS)

 

It’s cut from a 6 inch blank, and making this manulally takes a stack of repetitive cuts, ideal for CNC I would have thought.

 

Apologies for the hijack, just thought I’d take advantage of the KX1 experience…

 

Steve

 

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Steve Withnell on 16/07/2011 12:39:19:

Getting of the track of Jim’s initial question, what’s the capacity of a KX1 with Arc’s 4 inch rotary table?

 

Could I machine this:

 

(IGNORE THE ANNOTATIONS)

 

It’s cut from a 6 inch blank, and making this manulally takes a stack of repetitive cuts, ideal for CNC I would have thought.

 

Steve,

 

I’ve just measured the KX1 table and it is 400 mm long. I also have the 4″ motorised rotary table and it is just under 80mm deep, from face of table to bottom. So that leaves about 320mm to accommodate part and tailstock. I don’t have a tailstock so don’t know its dimensions.

 

The axis of the rotary table is ~65mm above table height on one orientation, and a little more the other way. The maximum Z position on my machine gives ~260mm between spindle nose and table, and ~210mm between the nose of my ER25 holder and the table.

 

Apologies for the approximate measurements – the machine is set up for another job and I am having to eyeball the distances using a steel rule as close as I can get it.

 

So it looks as if it might be possible to hold the piece, certainly if one end was held in a collet in the rotary table. Others might have more experience of using the KX1 to do metal cutting like this – my experience is so far limited to styrene.

 

I would be interested to know what CAM software you would use to do this job – that doesn’t cost an arm and a leg.

 

Jim.

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Andrew Johnston on 16/07/2011 11:33:57:

Hi Jim,

 

If it works for you then that’s good enough! You certainly seem to get an excellent finish and apparently no burrs; very good.

 

Your depths of cut are definitely conservative. I’ve never run really small cutters, but as an example I run a 2mm cutter full width engagement and 0.4mm depth of cut in 316 stainless steel. So, in plastic, bigger depths should be no problem.

 

Andrew,

 

Yesterday, I wandered along the M4 to near Swindon and picked up a 500mm offcut of 10mm cast aluminium tooling plate from Metalfast. Both long sides are “off the saw” so I’m going to look around local machining companies to see if I can get the edges trued and some holes drilled for locating pegs. The KX1 and my Centec 2A aren’t long enough for the job and I’m reluctant to try and do the job in two setups, so spending a bit of cash getting someone else to do it might be worth while.

 

On the matter of depths of cut, most of the pockets and panels I’m cutting only require depths of 5 or 6 thou. Even cutting out is in 30 thou sheet, although I find I have to do that in several passes if there is fine detail close to the cutout, because of the flexibility and fragility of the styrene. I started off worrying about my cutters and now I worry about the material.

 

I’m going to keep increasing feeds as I gain more experience. Certainly some of the work I’ve been looking at doing would take about 10 hours to machine at present feeds, and I would like to get that time down somewhat. I’ve also been using stepovers of 15 – 20% and I might try upping that to 25 – 30% and see if there is any reduction in finish quality.

 

Jim.

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Andrew Johnston on 16/07/2011 11:33:57:

Hi Jim,

 

If it works for you then that’s good enough! You certainly seem to get an excellent finish and apparently no burrs; very good.

 

Your depths of cut are definitely conservative. I’ve never run really small cutters, but as an example I run a 2mm cutter full width engagement and 0.4mm depth of cut in 316 stainless steel. So, in plastic, bigger depths should be no problem.

 

Andrew,

 

Yesterday, I wandered along the M4 to near Swindon and picked up a 500mm offcut of 10mm cast aluminium tooling plate from Metalfast. Both long sides are “off the saw” so I’m going to look around local machining companies to see if I can get the edges trued and some holes drilled for locating pegs. The KX1 and my Centec 2A aren’t long enough for the job and I’m reluctant to try and do the job in two setups, so spending a bit of cash getting someone else to do it might be worth while.

 

On the matter of depths of cut, most of the pockets and panels I’m cutting only require depths of 5 or 6 thou. Even cutting out is in 30 thou sheet, although I find I have to do that in several passes if there is fine detail close to the cutout, because of the flexibility and fragility of the styrene. I started off worrying about my cutters and now I worry about the material.

 

I’m going to keep increasing feeds as I gain more experience. Certainly some of the work I’ve been looking at doing would take about 10 hours to machine at present feeds, and I would like to get that time down somewhat. I’ve also been using stepovers of 15 – 20% and I might try upping that to 25 – 30% and see if there is any reduction in finish quality.

 

Jim.

[Steve WithnellParticipant @stevewithnell34426]

Thanks Jim, sounds like the KX1 would have no problem. Haven’t looked at using more than Mach3 so far.

 

Steve

[Anonymous]

Hi Jim,

 

Funny you should mention Metalfast, I use them for all my aluminium requirements. Total shambles in the sales office but very pleasant, but then that seems to be the case with every professional metal stockist I’ve used! Although I don’t live near Swindon they do have an outlet in Huntingdon, so I can collect, as delivery charges are a bit steep. They used to do some cutting at Huntingdon, so I could rummage through the scrap bin, but sadly they’re just a distribution centre there now, so no scrap.

 

I find Metalfast to be useful for metal for jigs and the like, as you can ring up and enquire about offcuts. For instance I wanted a plate to act as jig for assembling my traction engine wheels. I specified at least 600mm square, anything from 8 to 20mm thick and I don’t care if it has a gouge or several in it. That can be useful, as the finish sometimes gets damaged on partial sheets and so they’re prepared to sell them well below normal price.

 

Ok, I understand why your depths of cut are shallow. It’s interesting to note your step over values. They seem very small to me? If I’m facing a flat area or pocketing out I’ll use a step over of between 70 and 90%, to make full use of the cutter. This is true for both plastics and metals. To a first approximation I’m not sure that the step over will have much effect on the finish. I think that feedrate is probably the most important factor?

 

Regards,

 

Andrew

[Jim GuthrieParticipant @jimguthrie82658]

Andrew,

 

The people at Swindon were good. We agreed on one of their offcuts over the phone but they said they would double check that it was there and phone me back – which they did. The only slight hang up was the operation of their card machine which seemed to be tied in to their VAT reporting on their accounts and required some apparently involved setup entry to work for my payment. But it was all very pleasant and a nice day for a drive.

 

I’ve been doing further experiments with feeds and stepovers and increasing values and the results so far have been good. The only problem I am having is with one particular 1mm cutter which is leaving a lot of rag ends still attached to the cut. I suspect it has been blunted or chipped but I need some sort of microscope to check it out. My eyes and my binocular viewer are not good enough to see if the cutting end is OK. It is my last 1mm cutter so I’ll order up another couple to try some alternates.

 

Jim.

[Clive HartlandParticipant @clivehartland94829]

Have you considered a vaccuum table to hold down the styrene you are machining?

You could make a table exactly the size you require and again using pegs relocate for the next step of macining.

A good vaccuum machine would give all you all the suction you require.

The table will have to have a lot of small holes drilled in it where your workpiece sits.

I do believe these sort of vaccuum tables are available commercially.

 

Clive

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Clive Hartland on 19/07/2011 09:06:50:

Have you considered a vaccuum table to hold down the styrene you are machining?

You could make a table exactly the size you require and again using pegs relocate for the next step of macining.

A good vaccuum machine would give all you all the suction you require.

The table will have to have a lot of small holes drilled in it where your workpiece sits.

I do believe these sort of vaccuum tables are available commercially.

 

Clive

 

Clive,

 

As I mentioned at the start of the thread, I am using a product called Seklema Multimat to hold the styrene sheet on the table. The product is designed specifically for engravers and is double sided with both sides “sticky”. I think it works on the same principal as the tax disk holders on a car windscreen – a very smooth, slightly tacky and resilient surface which holds flat sheet very firmly. I’ve had no movement at all when using it. I started off using double sided tape, but the adhesive was too strong and parts tended to get distorted when trying to prise them off the tape. The Multimat releases the parts quite easily – just pick up one corner with your finger nail and the rest peels of with little effort.

 

http://www.graviermaterial.de/showpage.php?SiteID=107&lang=2

 

It is a bit expensive – a square foot cost me about £65 (inc VAT) but that should last me for some time. My first piece on the machine is still in use on the first side used, even with one or two slightly deep excursions with the cutters on a few occasions.

 

Jim.

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Andrew Johnston on 18/07/2011 23:57:25:Ok, I understand why your depths of cut are shallow. It’s interesting to note your step over values. They seem very small to me? If I’m facing a flat area or pocketing out I’ll use a step over of between 70 and 90%, to make full use of the cutter. This is true for both plastics and metals. To a first approximation I’m not sure that the step over will have much effect on the finish. I think that feedrate is probably the most important factor?

 

Andrew,

 

Just did some more experimenting yesterday with feeds abd stepovers cutting 1mm styrene sheet. The maximum stepover I could apply was 50% – that’s all that Cut2D will let me apply. I worked a 5mm cutter up to 480mm/min with 50% step over and started getting tool marking – not too much but still enough to require finishing with sanding. I am assuming that the reason for this is that the styrene is flexible and the Multimat holding it down to the table can also be compressed so that the work might be deflecting under the tool when the pressure of cutting increases. I’ve started backing off to get the good surface finish.

 

Also, I can’t work out why I still get untidy cuts with the 1mm cutter. I tried a new one yesterday at various speeds and I still get the rags of swarf left attached to the work if it is only cutting on part of its width round a part. It cleans up quite easily, but it’s annoying. I don’t get vthis problem with any other cutter.

Jim.

[Clive HartlandParticipant @clivehartland94829]

My work was once on Plotting tables where the ‘Cut and Peel’ materiel was held in place by vaccuum . The table was aluminium and had numerous small holes drilled uniformly all over at about 10 to 15mm spacing. The table was at least 1Mtr square and there was never any shift of the ‘Cut an Peel’ materiel. It had a porous matting placed on the surface.

I have used the vaccuum method on an engraving machine on thin perspex which is difficult to cut and engrave and incidently is not flat but has undulations on its surface!

The items were line engraved and legend placed on it and then cut out as a shape.

It worked very well.

I did note that you were using an adhesive underlay but only offered the vaccuum method as a viable alternative.

The machining marks indicate that the cutter lip is picking up and and carrying a bit of plastic which is stuck on the cutter face. This is much like the build up on a lathe tool.

It might help if you use a single lip cutter as it runs cooler.

A continuous air jet can keep things cool.

 

Clive

[Jim GuthrieParticipant @jimguthrie82658]

Posted by Clive Hartland on 20/07/2011 09:57:36:

I did note that you were using an adhesive underlay but only offered the vaccuum method as a viable alternative.

The machining marks indicate that the cutter lip is picking up and and carrying a bit of plastic which is stuck on the cutter face. This is much like the build up on a lathe tool.

It might help if you use a single lip cutter as it runs cooler.

A continuous air jet can keep things cool.

Clive,

 

Sorry – I misread your message about the vacuum holding.

 

However, I don’t want to get too involved in doing this job. I intended to use the KX1 for other purposes and only ventured into the styrene cutting as a “wonder if I can do this” project. I agree that vacuum holding would be better but that would involve me in a lot more work than I really want to do. The extension plate is already pushing me into areas that I didn’t originally intemd to get into. I’ve got a fourth axis rotary table here which was bought for my original intentions which hasn’t been used in anger as yet, and I would like to start work with it.

 

Jim.

[Anonymous]

Just did some more experimenting yesterday with feeds abd stepovers cutting 1mm styrene sheet. The maximum stepover I could apply was 50% – that’s all that Cut2D will let me apply. I worked a 5mm cutter up to 480mm/min with 50% step over and started getting tool marking – not too much but still enough to require finishing with sanding. I am assuming that the reason for this is that the styrene is flexible and the Multimat holding it down to the table can also be compressed so that the work might be deflecting under the tool when the pressure of cutting increases. I’ve started backing off to get the good surface finish.

Hi Jim,

 

Hmmmm, 50% maximum step over is a bit of a limitation. It won’t make any difference in plastic, but in metal it is a good idea to avoid step overs around 50%, as it hammers the cutter teeth and shortens tool life. Either less or more than 50% is fine.

 

If you’re increasing the stepover, and keeping the feed rate constant, I suspect the difference in finish may be due to the effective chip thickness varying. When cutting at low radial engagement (small stepovers) the effective chip thickness is much less than that implied by the feedrate, which will give a better finish.

 

Regards,

 

Andrew

[Jim GuthrieParticipant @jimguthrie82658]

I’ve just found out that the Seklema Multimat I have does not have a very good tolerance on thickness – just in case anyone else is contemplating using it on a milling machine. I had changed my methods of referencing tool height this week. previously I had set the tool level from the top surface of the styrene but that had given some problems due to the variation in thickness of the styrene sheet. So I started refernceing from the base of the material and I would use thicker sheet and surface it down to the required thickness before milling out the details.

 

But I had been getting poor results with depths of cut apparently all over the place. I’ve been double checking Mach and the KX1 to see if something in them was causing the problem. I hadn’t even considered the Multimat until last night, when I put a steel rule flat on the surface and ran a clock gauge in the spindle along it and found a 15 thou variation in about six inches. When cutting I had been setting tool height at the edge of the Multimat with a piece of metal of known thickness, then moving into the material and mat to do the cutting.

 

I had assumed that the Multimat would have had quite close tolerance if it was to be used for engraving. The unused bit I have has a variation betwee 2.25 – 2.80mm when measured round the edges with a caliper. I’ve sent a message to the makers via their web site to see whet the tolerance should be.

 

Meanwhile, back to low tack double sided tape. There are so many cut through holes on my work that I don’t think a vacuum table might work.

Jim.

[Author]

Posts