jonhall Posted April 8, 2015 Share Posted April 8, 2015 I finally had a go with the laser cutter at my local makerlab yesterday, we had some good results (photos to appear once I'm home) but I've a couple of questions 1) the parts I have all smell of smoke - any suggestion about what I should use to wipe the parts down with to reduce the odour (2mm MDF) ? 2) there is quite a lot of backlash in the machine (I should have taken notice of make/model but I did not) it is a belt driven type - are there any tips/tricks to reducing the backlash/improving the index of brickwork? Thanks, jon Link to post Share on other sites More sharing options...
Gt.Shefford Posted April 8, 2015 Share Posted April 8, 2015 Welcome to the laser owner/user club. As the laser is burning the material away there will be a smoky smell to the parts. Give it a few days and It will become less obvious. To get rid of any burn residue from plastic a quick wipe over with meths does the trick - might work on the MDF to get rid of the smoky smell. The backlash in the lasers XY axis is primarily down to the adjustment of the belts, however if there is a registration issue it is more likley down to the pulse count on the stepper motors (not hard to adjust but takes about an hour of trial and error) This forum might be worth looking at - its run by HPC lasers http://www.laserscript.co.uk/phpBB3/ Jonathan Link to post Share on other sites More sharing options...
Rabs Posted April 8, 2015 Share Posted April 8, 2015 Hi Jon 1) It's probably unavoidable but you can minimise the amount of burning by getting the focus, cut power and cut speed spot on for the material. I do lots of birch plywood and it smells really nice! Are you using a laser-friendly type of MDF? Some laser-specific MDFs use different binders which are supposed to be more friendly to the laser optics and to your lungs. They might also smell less. 2) Lots of things to check here but they all involve digging into the guts of the machine. If the makerlab's management are ok with you doing this then I'd be happy to list out the usual suspects for backlash in a belt system. How did you diagnose the backlash? Is it in one or both axes? Link to post Share on other sites More sharing options...
jonhall Posted April 8, 2015 Author Share Posted April 8, 2015 Photos in the layout thread. http://www.rmweb.co.uk/community/index.php?/topic/11520-hamworthy-dorset-coast-c1988/?p=1773575 We are using laser MDF from 4D modelshop - its not clear if we are using the right settings but we have done a fair bit of trialling so far. The machine is on loan from an individual - it was his suggestion that there was backlash and I think he might be amenable to making adjustments if we knew what we were doing. Thanks, Jon Link to post Share on other sites More sharing options...
Gt.Shefford Posted April 9, 2015 Share Posted April 9, 2015 Hi Jon Looking at the photos I'm less inclined to think its a backlash or pulse count. The burn through at the start of an engrave line is easy to fix (depending on the laser control software) On the cutting profile box there should be an option for corner power (or what ever word the Chinese have chosen) it should set to the same figure as the main cut power - for engravingsomething between 10-15 on a 40 Watt machine. Did you have to download and run the brick engrave programme first then download and run the cut seperatly as it might be that the origin point for the two drawings is slightly different. Tell you what if you PM me the wall section I'll run it on my machine and upload the result. Jonathan Link to post Share on other sites More sharing options...
jonhall Posted April 9, 2015 Author Share Posted April 9, 2015 Looking at the photos I'm less inclined to think its a backlash or pulse count. The burn through at the start of an engrave line is easy to fix (depending on the laser control software) On the cutting profile box there should be an option for corner power (or what ever word the Chinese have chosen) it should set to the same figure as the main cut power - for engravingsomething between 10-15 on a 40 Watt machine. OK I'll look for a control like that next week when I go there - the more I think about it the more I think that a slower less powerful cut is what I need I think we came out at power 14 speed 200 for an etch on this machine, power 18 gave pinholes, power 12.5 was a bit faint. Did you have to download and run the brick engrave programme first then download and run the cut seperatly as it might be that the origin point for the two drawings is slightly different. No its all one file, all the etch (including both the normal bricks and the arches over windows) were in one layer engraved first, and the cutouts were done by turning the other layer on and re-cutting - whilst we were experimenting with the end we were doing both etch and cut with just one instruction, but once all the other parts were added the etch/cut order seemed to get a bit random, and I thought it would be best to get all the etch done first rather than have some parts cut before others were etched. I'm also worried about holding the sheet down - it was only done by gravity we could have added a bit of weight to one edge of the sheet but that didn't seem like a good idea putting the weight only on the non-cut part. Tell you what if you PM me the wall section I'll run it on my machine and upload the result. Thanks Jonathan that's very kind - I will sort out the file and pop it over this evening. Thanks, Jon Link to post Share on other sites More sharing options...
Gt.Shefford Posted April 9, 2015 Share Posted April 9, 2015 Can you send it as a .dxf (I'm running AutoCAD 2013 so a 2010 or R12 .dxf is best) could you also add a square 20mm x 20mm somewhere on the drawing so I can check if any scaling has occurred. Engraving/half cutting at speed 200 sounds awfully fast - not knowing the make of the laser, but with that information I might retract my earlier suggestion that it wasn't a backlash issue which has caused some machine shift. To hold down I have a range of brass blocks which I place around the sheet where needed. Jonathan Link to post Share on other sites More sharing options...
Rabs Posted April 9, 2015 Share Posted April 9, 2015 Those problems don't look like backlash to me. If it was backlash I would expect to see alignment errors every time the direction of travel of the laser head reverses. On a pattern like bricks this would be all the time and your bricks would all be irregular sizes. Instead you seem to have alignment problems between different groups of features. The only things that I can think of that would cause this are either that the commands being sent to the laser are wrong (have you re-checked the artwork?) or the panel moving during cutting. Could vibration be making the panel walk? Have you tried sticking it down with masking tape? Are you cutting these as line vectors or as a raster image? Good luck! Link to post Share on other sites More sharing options...
jonhall Posted April 9, 2015 Author Share Posted April 9, 2015 The file is drawn in AutoCAD2000 and converted to a DXF to go to the machine software (again I didn't take a note of what - I will next week) the 'etch' is all on one layer and the cut on another and I think I've been pretty good at ensuring only one line in each location. Speed could definately be a problem - I suspect we are going too fast, suggestions about a normal speed would be welcolm, presumably we need to turn the power down as the beam will linger longer and burn more? Movement of the sheet on the bed is certainly possible I will try both weighting and taping down. Thanks, Jon Link to post Share on other sites More sharing options...
Gt.Shefford Posted April 10, 2015 Share Posted April 10, 2015 So this is what my laser produced. I upped the power of the engrave by 3% so I could get a good picture. If its a 40W machine I would try speed 45 power 10 for engraving (10% is right down at the bottom end of the power range and you might find that some tubes won't 'fire' but just work up in 1% increments) Next time your the machine try seeing if it is possible to push the cutting head when the machine is switched on. In theory when the machine is running the stepper motors should make it all but imposssible to move the head, but if you can move it then the problem might be be with the cross shaft. Jonathan Link to post Share on other sites More sharing options...
jonhall Posted April 10, 2015 Author Share Posted April 10, 2015 Thanks Jonathan. J Link to post Share on other sites More sharing options...
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