Full Version: Just curious
From: precisionlaser [#34]
2 Apr 2005
To: Engravin' Dave (DATAKES) [#30] 2 Apr 2005
Hi, David.
I'm surely no expert, but I've exposed Rapidmask HT for 3 minutes (on my Letralite) and it seems almost perfect. The dark areas will snap in two when bent and when I'm blasting, those areas blast away almost immediately. I've had no blow outs yet, either. I wonder if part of the problem could be the freshness of the resist. Does your resist have a "born on" date? ;-)
I don't know how to convert from 3 mins on a Letralite to your exposure unit, but the documentation does state that Rapidmask is very tolerant to overexposure, so just expose away and see what happens. They say that when you can get the dark areas to break with a snap when you bend them, that this is when the exposure is correct.
Mark
From: Engravin' Dave (DATAKES) [#35]
2 Apr 2005
To: precisionlaser [#34] 2 Apr 2005
Mark,
That will be the plan during my next testing period. My most recent results have all the symptoms of inadequate exposure.
Are you using AccuArt 2 and an inkjet for creating your negatives? What inkjet and inks are you using?
ÂÂÂÂÂ
EDITED: 2 Apr 2005 by DATAKES
From: precisionlaser [#36]
2 Apr 2005
To: Engravin' Dave (DATAKES) [#35] 2 Apr 2005
Like you, I have a C86 and I'm using the partial black cartridge we received in the box. We are using AccuArt 2. The only thing that may be different besides the exposure time is that I had our graphic artist set up a special printer setup for the accuart to improve the opacity of the black on the film. It sounds like that wasn't your problem, though.
Seriously, how old is your RapidMask? I think I remember your mentioning this in an earlier post...maybe it's aged a little and that has affected the adhesive (?). Also, when I apply the RapidMask, I use the wet application method and that "may" improve the adhesion...don't know because I've never been able to apply it dry right the first time. I got a cheap misting bottle, filled it full of tap water and after removing the slip sheet, I spritz the mask and apply it to the glass, move it around and then squeegee all the water out pretty hard to get all the bubbles out. I do let it sit for a few minutes while I am prepping other pieces, and perhaps this lets the adhesive "set up" or something. One of the very nice things about using the water assisted mounting method is that it's very easy to work the bubbles out so you have a perfectly smooth surface on the glass...at least for flat surfaces.
As you can tell, I'm a real authority on this! HA.
From: Engravin' Dave (DATAKES) [#37]
2 Apr 2005
To: precisionlaser [#36] 2 Apr 2005
Mark,
I would guess that it is less than two months old. If it can't handle a shelf life of six months I'll be sticking with my old washout resist that appears to have a shelf life of years rather than months.
Have you had any problem with small amounts of pitting around your image? This may be caused by not achieving an opaque enough print.
Do you mind sharing what your graphic artist did to improve the opacity of the print?
From: UCONN Dave & Lynn too (DANDL48) [#38]
2 Apr 2005
To: Engravin' Dave (DATAKES) [#30] 2 Apr 2005
David,
For Rapidmask I blast at 22PSI with 180 grit Silica carbide, what are you using and what are the settings. Another thing you need to check is air bubbles under the areas to be blasted. if not poped it can cause blowouts.
Dave
From: precisionlaser [#39]
2 Apr 2005
To: Engravin' Dave (DATAKES) [#37] 2 Apr 2005
I don't mind sharing the printer settings at all...but I'll have to wait til Monday when I get back in the office. I'm sure that shelf life is not the problem if it's only two months old (it better not be!).
I blast with 30 PSI or just a tad higher with 180 grit. I hold the nozzle about 6 inches away and try to keep the nozzle perpendicular to the substrate...I'm sure none of this is new to you...I can't think of why you're having a problem.
As for edge pitting, no problems that I've noticed, but perhaps I need to look harder.
Mark
From: LaZerDude (C_BURKE) [#40]
2 Apr 2005
To: Engravin' Dave (DATAKES) [#33] 2 Apr 2005
From: LaZerDude (C_BURKE) [#41]
2 Apr 2005
To: Engravin' Dave (DATAKES) [#28] 2 Apr 2005
David,
I use an HP 1200 to print on the accuart2. The area surrounding the image needs to be darn near black with no light coming through.
The exposure unit I have is the Letralight (sp?) also and like UCONNDAVE said, exposrue time is 3 minutes. My rapid mask has sat in a box since the end of last October. Since I was moving I did not even bother to unpack the blaster, so shelf life is not the issue. I think maybe you just need a longer exposure time for the rapid mask.
I tried using the 2 mil and the 4 mil, neither had a blow out. I just could not get them to lay flat.
As for the adhesion, I did not use the misting methon, but that would work well for placing the image.
My wife Lisa who is much more patient than I, could not get the resist to lay flat either.
From: Engravin' Dave (DATAKES) [#42]
2 Apr 2005
To: LaZerDude (C_BURKE) [#40] 3 Apr 2005
Chuck,
The black border around my image was about a quarter inch on each side. After the exposure, I cut the darker part of the border to allow for an easier removal of the carrier sheet.
From: Engravin' Dave (DATAKES) [#43]
2 Apr 2005
To: UCONN Dave & Lynn too (DANDL48) [#38] 3 Apr 2005
Dave,
I didn't bother to change my settings because Photobrasive has recommended settings of 30-35 psi. I have my system set at 30 psi.
I also use 180 grit silicon carbide for my blasting media.
From: UCONN Dave & Lynn too (DANDL48) [#44]
3 Apr 2005
To: LaZerDude (C_BURKE) [#41] 3 Apr 2005
Chuck,
It wasn't me saying to use 3 min, we use 4 and it works fine. Very difficult to overexpose RapidMask.
Dave
From: UCONN Dave & Lynn too (DANDL48) [#45]
3 Apr 2005
To: Engravin' Dave (DATAKES) [#43] 3 Apr 2005
David,
How close do you hold the nozzle from the media? You might want to try 6" and back off on the pressure.
Dave
From: LaZerDude (C_BURKE) [#46]
3 Apr 2005
To: Engravin' Dave (DATAKES) [#43] 3 Apr 2005
David,
I tried blasting these with 33psi as recommended by Photobrasive. When I turned the pressure down to 27psi, I got a much nicer etch.....
From: Harvey only (HARVEY-ONLY) [#47]
3 Apr 2005
To: LaZerDude (C_BURKE) [#46] 3 Apr 2005
Probably nothing but the standard inaccuracy of the pressure gage. Minor wear in the nozzle or venturi mixing area can make large differences also.
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