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Using an old HP pen plotter to cut vinyl

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Post Fri Jul 31, 2009 12:52 am

Using an old HP pen plotter to cut vinyl

Hi,

I've just bought a Mimaki blade holder and some blades for my old HP DraftMaster I pen plotter which I'm hoping to use as a vinyl cutter.

Does anyone here have any experience of doing this?

Also, is there anywhere I can get hold of cheap offcuts of vinyl that I could use to experiment with? I suspect it's going to take quite a bit of trial and error to get it working satisfactorily.
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Post Fri Jul 31, 2009 10:55 am

Sorry Doug. Can't help you with that. :(

I know that you can use vinyl plotters with a pen, but I'm not sure that it will work the other way round.
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Post Fri Jul 31, 2009 10:58 am

It doesn't work mate. Tried this years ago. The drawing capabilities are different from cutting capabilities.
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Post Fri Jul 31, 2009 2:51 pm

Karl Williams wrote:It doesn't work mate. Tried this years ago.


That's a shame. I'd still like to give it a try now that I've got the blade holder, if I can find some offcuts to experiment with.

Can you remember exactly what the problem was?

According to the manual, the maximum pen force with this plotter is only 66 grammes, I guess that might be a bit of a problem but I've been hoping I can either add some weights to it, or possibly even alter the electronics to get a bit more pressure.
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Post Fri Jul 31, 2009 3:01 pm

bin there as they say

the mechanics are not strong enough and req about 80-130 grm force
also the cutter mode of offset is missing so it will make a mess of corners.

sorry but save up for a purpose built one

chris
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Post Fri Jul 31, 2009 4:04 pm

Chris Wool wrote:also the cutter mode of offset is missing so it will make a mess of corners.


Yes, I understand that; I was intending to compensate for that in the HPGL sequence sent to the plotter - overshoot each line a bit. Isn't that what dedicated cutters do internally?

sorry but save up for a purpose built one


At the moment I'm just doing this for fun, can't justify the expense of a real cutter.
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Post Fri Jul 31, 2009 5:35 pm

Yes, I understand that; I was intending to compensate for that in the HPGL sequence sent to the plotter - overshoot each line a bit. Isn't that what dedicated cutters do internally?


possibly understand what you are saying if drawing a box but the arks are all straight lights at normally 25 thou steps some software increase that as the ark gets larger giving the impression of a smooth ark .

some cheap blade holders on ebay enjoy your play around but it will not work satisfactorily on smaller shapes or letters.

enjoy

chris
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Post Fri Jul 31, 2009 8:18 pm

Chris....have you been on the pop this evening.
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Post Fri Jul 31, 2009 9:42 pm

mike it could well sound like that. but sadly no.

be interesting to see the posters reply

chris
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Post Sat Aug 01, 2009 12:38 am

Chris Wool wrote:the arks are all straight lights at normally 25 thou steps


¿Qué? :-?
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Post Sat Aug 01, 2009 12:43 am

With a cutter you tell it the blade angle. You can't do this on a plotter. It's just one command and the the force. All your lines don't join up. They end up looking like wobbly feet. And circles never join up. Anyway stop being a tight wad, buy a proper machine man.
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Post Sat Aug 01, 2009 7:27 am

Doug Woodrow wrote:¿Qué? :-?

What Chris is saying is that a curve is not plotted by one steady smooth flow, but rather made up of lots of very short straight lines.

That shouldn't matter on larger stuff because the blade doesn't lift between those segments but, like Chris says, it will struggle to cope with smaller radii.

As for your overcut theory, it might work on external corners, but what happens on internal ones?
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Post Sat Aug 01, 2009 10:14 am

thanks john

but i will say arcs and straight lines not lights :oops:

if our poster would like to output the hpgl to a file then read in notepad or simular. a 25mm square and a 25mm circle to see the difference.

back in the days of dos in was not uncommon to have to alter hpgl files.

still say you are waisting your time but understand we have to play with our ideas.

chris
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Post Sat Aug 01, 2009 10:59 am

Thanks John and Chris and Karl, I understand now, I obviously didn't make myself clear enough.

As I understand it, there is no major physical difference between my pen plotter and a dedicated cutter, apart from the force (and possibly the media handling, as Phil pointed out).

The difference is that the cutter has built-in firmware that will automatically compensate for the blade angle/offset. So for example when your graphics software tells it to cut a circle, it will actually move the knife a bit more than 360 degrees to allow for the blade offset. (I must admit I don't understand how cutters deal with the initial random orientation of the blade - doesn't that produce jaggies?)

What I intend to do is write my own software to emulate what that firmware does. So I won't be cutting directly from a graphics application: I'll pre-process the output first to compensate for the blade. Obviously this won't be trivial, but I think it must be possible - it is after all what the firmware designers have already done. I was hoping there might be some experts here who had already tried this.

I've been studying the HPGL language reference and there are several promising commands to play with - Velocity Select, Acceleration Select, Chord Tolerance, Curved Line Generator in particular.

But as I said, my other problem is finding some suitable cheap vinyl to experiment with. What do you professionals do with your offcuts?
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Post Sat Aug 01, 2009 11:17 am

The major physical differences are that the machines are much more robust than a pen plotter, chassis and carriage gear is uprated all the motors are uprated etc etc. Maybe nothing to obvious that you can see but they are there. As Chris has already said though if you want to experiment then go ahead and have fun.

As for vinyl off cuts, a lot of us pass them in to Schools and play groups. You should be able to buy vinyl quite cheaply from an auction site or failing that just pop into our local signmakers and ask them if they have any off cuts or a couple of metres you can buy.
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Post Sat Aug 01, 2009 11:58 am

Martin wrote:The major physical differences are that the machines are much more robust than a pen plotter

I can well believe that for some of the smaller pen plotters, but is that true for the HP DraftMaster? It seems to be built like a tank.

if you want to experiment then go ahead and have fun.

I'm sure I will :D. I'm only doing this for the fun of creating my own stickers to put on my car etc., it's not a business.

As for vinyl off cuts, a lot of us pass them in to Schools and play groups. You should be able to buy vinyl quite cheaply from an auction site or failing that just pop into our local signmakers and ask them if they have any off cuts or a couple of metres you can buy.

Thanks, good idea, I'll have to find one near here. As the low force of the DraftMaster is likely to be a serious problem, what is the easiest vinyl to cut that I should ask for?
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Post Sat Aug 01, 2009 12:09 pm

Doug you are on the right track about firmware and as you have found after the initialization string its basically pen up X-Y pen down X-Y and so on.
your next problem is a lot of the older plotters were stepper motors and if they found it hard going would skip a few x-ys and try to carry on out of position.
modern plotters use servo motors and encoder counters with overload protection.
all this has been tried before in the 80s when a basic cutting plotter was £3000 ish.
as i said bin there.

if you ask your local cutter plotter owner to put a pen into there machine and plot some shapes you will see exactly what the firmware does to the output, especially what it does to acute corners.
this brings back memories. and as i look back fun but a waist of time.
my first cutter was a A3 sized graphtec pen cutter plotter and it cost £2400 and then a houston dmp66 with tangential knife all run from DOS windows did not exist then.
there is no comparison to today's high speed - power machines
even today's £1000 machines are so superior.

enjoy

chris
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Post Sat Aug 01, 2009 2:11 pm

You were a cheapskate Chris, my first cutter, an Aristo AG50 Signline, cost me £5,750 plus VAT. Although it was sprocketed and tangential, so maybe a bit costlier than the average. In somebody else's hands it is still turning out cut vinyl today.

Doug,

My cutters allow for the initial random orientation of the blade by putting pressure down very gently to start with. That gives the blade time to spin to the correct direction before the real cutting starts. Whether all machines do it the same way I wouldn't know.

As for vinyl, you have a problem. Something that will cut at pressures as low as you can manage will need to be a thin cast material. That's more expensive than the normal everyday calendered stuff. You will also need more regular blade replacements than a proper machine because they will need to be kept sharp.

Have fun.
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Post Sat Aug 01, 2009 2:38 pm

If you're only doing hobby stuff, why not try a Craft Robo 199.99 +vat
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Post Sat Aug 01, 2009 2:40 pm

flash git:

also around that time was a machine from the states that had a hot blade to do the cutting well more like plough through the vinyl

i think my mate still has the A3 in his loft, it was anything in them days not to buy the spandex 4B. bring on the 4B fans :wink:
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Post Sat Aug 01, 2009 2:42 pm

gordon were not doing sensible in this thread. :wink:
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Post Sat Aug 01, 2009 2:46 pm

Chris Wool wrote:it was anything in them days not to buy the spandex 4B.:


:yes1:

I didn't like the Spandex business model, and determined not to buy equipment from them at almost any price.

It's a pity really because if I hadn't still got that impression of them in the back of my mind, I might buy more material from them today.
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Post Sat Aug 01, 2009 2:54 pm

John Childs wrote:My cutters allow for the initial random orientation of the blade by putting pressure down very gently to start with. That gives the blade time to spin to the correct direction before the real cutting starts. Whether all machines do it the same way I wouldn't know.

As for vinyl, you have a problem. Something that will cut at pressures as low as you can manage will need to be a thin cast material.


Ah, thanks John, that sounds like a good strategy. And I'll see if I can obtain some thin cast vinyl locally.
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Post Sat Aug 01, 2009 2:59 pm

Chris Wool wrote:if you ask your local cutter plotter owner to put a pen into there machine and plot some shapes you will see exactly what the firmware does to the output, especially what it does to acute corners.


Thanks Chris, if I can find someone to do that that would be very informative.
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Post Sat Aug 01, 2009 3:14 pm

I didn't like the Spandex business model,


what the stitch you up then bind and gag you model. just my view



i really do like one of there flat bed UV machines but as you say old feelings are hard to dispel.

gordon when we digitize a shape it should always be done in a clockwise direction and the start of a new loop should follow on, so as the knife is always in the correct direction to cut again.

chris
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Post Sat Aug 01, 2009 3:25 pm

I've got a 4B. £8.50 off ebay and it still works like new! :wink:
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Post Sat Aug 01, 2009 4:37 pm

Chris Wool wrote:what the stitch you up then bind and gag you model.

No, not that one. They never got me far enough into their jaws to work that.

I mean the one where they tried to sell me a cutter that would only work with vinyl that they supplied. :o That didn't appear anywhere in their sales patter.

Over twenty years ago now, so maybe their practices have improved, but I'm cursed with a long memory. :D
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Post Sat Aug 01, 2009 5:43 pm

Funny you should mention that John. About 10 years ago we had to call spandex out to do a repair on our edge. They asked what vinyl we were using so I told them Mactac. I was met with "It isn't showing on our system on your account any orders for mactac." I replied "Yes I know, we buy our stock from Amari." They totally refused to repair the machine even though the vinyl was the same as they sell. They changed there mind when we said "OK, when would you like to collect the machine and refund us any finance we'd paid!" Another supplier that thinks they're that big they've got you by the gooolies. :evil:
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Post Sun Dec 06, 2009 6:02 pm

Try Mac-Tac peel and stick shelf liner from the grocery store. Any old autocad program will drive it. May have to smash the top off so it doesn't fetch up when it goes in to pick up a pen. You have to attach the drag knife somehow. Make up a holder from some dead pens, drop some nuts over that for weight and have some fun. There is some sites on the net doing this and a demo on you-tube. But the other guys have this really great point: for the price of the pens to fit my old CalComp plotter , I bought a used Roland PNC 1000 that's made for the purpose and looks indestructible. They are in the back of shops worldwide gathering dust, and you can write Hp commands to it all you want.

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