View Full Version : Trotec Rotary Proportions Issues - Cone vs. Rim Drive Roller Mechanisms

Jeff Heinrichs
05-21-2017, 4:38 PM
I am finally getting back to troubleshooting a problem I've been having engraving with my Trotec rotary accessory. I've read through the forums and while there have been others who have had issues with proportions I don't think it fits what's going on in my case.

While using the Trotec cone drive the proportions on my engravings are exactly as expected. Switching over to the rim drive all the proportions immediately get elongated in the Y-axis (laser side)/Horizontal as looking at the engraved surface (everything rotated 90 during rotary engraving).

The logo I'm engraving is this one:



You can see in the image the top engraving looks proportionally accurate 1.5"H x 1.5"W and this was done on the cone rotary drive. The image on the bottom is horizontally elongated 1.5"H x 2.125"W. All settings remained unchanged between the runs.

In an effort to at least manipulate the the elongated engraving I tried changing Job Control settings. I change the diameter from 2.75" to 10" and it actually didn't change the engraved proportions at all. The end result engraving was still 1.5"H x 2.125"W. I tried changing the rotation speed to 50%, but that didn't have any impact.

My thoughts are this has something to do with the drive gears. The cone drive belt (bottom pic) has one large gear while the roller (rim) drive employs two smaller gears (top pic) that replace the large gear used for the cone drive. This will obviously change the gear ratio if not compensated for, but the Trotec rotary accessory actually has micro switches that are engaged depending on which drive type you are using, cone or roller so the system should be able to compensate for the differences in gear ratio.


Has anyone else experienced something similar to this with their Trotec rotary accessory?

Natasha McWilliams
05-22-2017, 12:57 AM
I had the exact opposite issue just after I received my rotary, we were getting "squished" images.

It turned out that the cup portion was loose on ours (we tightened it without having to open it up at all) so the glasses were sliding in the attachment and not rotating at the speed they should have been.

Maybe check yours and see if it loose as well? I've heard from another Trotec user local to me they had the same issue.

Kev Williams
05-22-2017, 2:42 AM
your measurements, specifically the 2.125" dim around the arc, is that measured 'as the crow flies' or as actual surface area? (wrap some tape around, mark the ends of the logo, lay the tape flat on a table and measure the space between the marks)...

Assuming actual surface area, your length is roughly 142% of height, height roughly 71% of length. If the rotary is consistent at that ratio, then a bandaid fix (my specialty :D) would be to adjust the image before sending it to the laser. If the height along the straightaway is accurate, then group the engraving and squash the width to 71%. This will work until you locate the actual problem...

Scott Shepherd
05-22-2017, 9:06 AM
What's odd here, help me trouble shoot Kev, is that the elongated one doesn't seem to be missing anything. You'd think if something was at the wrong ratio enough to make it that elongated that you'd see strips that didn't engrave because it was rotating too far. If it takes .005" of "Y Axis" movement to have an overlap, and it's rotating .010" between strokes, you'd see a lot of unengraved lines, but I don't see them.

However, on the Universal, you can change the ratio for it in the software and it will still engrave without missing a line. We don't have a rotary for the Trotec, so I'm thinking out loud on this one.

Jeff Heinrichs
05-22-2017, 9:21 AM
Scott that does make some sense. If it was mechanical in nature you would think there would be missing data. If it was software related you would think the job preview would reflect the elongated output.

I do know Job Control can tell whether the rotary accessory is setup for cone or roller drive, because it actually rotates the engraved object in the opposite direction depending on configuration. If setup for cone drive the top of the art is facing towards the left in the Job Control preview and if setup up for roller drive the art faces right. This I believe is due to the micro-switch that is engaged when you install the roller drive onto the carriage. That micro-switch is not engaged when the cone assembly is used.

Jeff Body
05-22-2017, 2:28 PM
I'd be willing to bet the difference in the gear ratios will be the exact difference in the image length.

There has to be a setting somewhere that lets you change the pulse width or circle pulse. This is the signal that's sent to the driver.
I can't see the program just "knowing" these settings because no 2 stepper motors are alike. You always have to fine tune the settings.

Kev Williams
05-22-2017, 6:46 PM
The driven gear wheels on each rotator are different diameters because they work different-

a cone/chuck rotator's turning distance is based purely on the circumference of the part and how many degrees of rotation are needed to cover a given distance... to engrave a 1/2" wide logo around a 1" diameter cylinder requires 180 of rotation, but only 18 of rotation to engrave 1/2" wide around a 10" diameter cylinder. So the size of the gear is only relevant to how the stepper is programmed to move the cylinder in DEGREES. The software for the most part figures this out and adjusts degrees of movement accordingly.

But a hot-dog turner's wheels move ANY diameter object the exact same distance per IT'S 360 rotation: if the hot dog wheels are 2" in diameter, each rotation of the wheel will move the surface of the cylinder 6.283" regardless of its diameter. The gear ratio between the stepper and the wheels is determined beforehand by the designers, engineers, etc.

In the elongated version above, at the 71% figure I came up with, IF the cup is actually 2.5" in diameter, then the engraving would be correct for a 1.77" diameter cup, very close to 1.75" diameter-- so now I'm curious as to how you're entering the dimensions for each rotary?

Troubleshooting help :) -- IF the machine thought it was engraving a 1.77" diameter cylinder instead of 2.5", AND the engraved DPI (lines per inch) setting was 500, running at 142% of that only lowers it to 355 DPI well within the bounds of 'decent looking' engraving...

I don't have a doggie-style turner, so I have to tell my print driver the diameter- it then tells me the actual "plate height", aka the circumference, which is then what I enter as a plate height in Corel (although I just usually use a calculator first ;) )-- my machine successfully mated two ends of a diamond grid pattern I did on a goose call, first try. Had I missed by even .001", it wouldn't have worked...

But I hot dog turner doesn't NEED to know the diameter of anything, only a working area that fits. But depending on the software, maybe it does correlate height to width, as in, if the cup is 9" tall and 7.854" wide (circumference) ACTUAL, but you enter 9" x say 5.5" wide, it MAY adjust the engraving's height/width ratio accordingly...

this kind of stuff is a little like http://www.engraver1.com/gifs/pullinghair.gifhttp://www.engraver1.com/gifs/nilly.gifhttp://www.engraver1.com/gifs/banghead.gif (:D)

so I'm thinking it may be a measurement-input thing... Maybe... ;)

Scott Shepherd
05-22-2017, 7:09 PM
What does Trotec Tech Support say?

Jeff Heinrichs
05-22-2017, 8:24 PM
Thanks Kev. It may have something to do with what you are saying, but it feels like it's reacting in an opposite fashion. If the cone drive depends on my inputs for measurements whereas the roller/rim drive doesn't care, then it would seem if I entered the diameter improperly it would impact the result of the top bottle engraving, but the cone engraving is spot on.

I do like how you are thinking here and I think you may be on to something. What you say does totally make sense in the sense that in my troubleshooting I entered a random 10" diameter for the bottle and it didn't have any impact on the output of the roller/hot dog turner drive. Exactly as you state, the hot dog turner doesn't care.

The Trotec software only asks for the diameter of the object (e.g. 2.75" in this case). It calculates the circumference and I did verify that Job Control did the calculations properly. There aren't any other settings under the "Rotary Accessory" settings other than how you want the job to finish (rotate to start, etc.,)

Steve - Trotec Support said: "What would be a good number to reach you at Sir?" I told them that I have a day job and am unable to troubleshoot it at the laser until the evenings and would appreciate some things I can check in the mean time... no reply from Trotec after that.

Doug Fisher
05-22-2017, 9:39 PM
Tell them you would like to set up a specific date and time over your lunch hour for you to call them and that you need a name and extension number for the person you are supposed to contact.

Jeff Heinrichs
05-22-2017, 10:04 PM
Thanks Doug. I'm trying to do what I can on my end and work through this with the great support team that is Sawmill Creek. I actually have very good contacts within Trotec all the way up through management. Earlier this month I had an warranty issue that Trotec really took to heart (once I escalated the issue) and I had daily/nightly calls with Trotec management. I have a great deal of respect for the Trotec team and believe in their product design and the value they provide. I won't go into the warranty issue on this thread, but I really want to give the support team the opportunity to work through this issue without me escalating this.

I am really looking at this as a setting issue on my end and I'll pursue it like that for now. If it ends up looking like there may be an issue with the system then I will escalate this.

Jeff Heinrichs
05-22-2017, 11:57 PM
I think I figured out my problem and it was all on my end. :mad: The threads on the top of the aluminum bottle were not engaging with the rubber o-rings on the drive wheels. That wasn't the only issue because this was also occurring with pint glasses. I am still not sure why the image was actually looking longer and w/no breaks in the engraving.

Thanks to Kev I started watching the rotation over the hot dog wheels (rim drive). I calculated that for a 1.5" engraving the 2.559" wheels should make 19% a rotation and for a 2.32" engraving 28% of a complete rotation. I was able the tell that the wheels were rotating just shy of 1/4 of a complete rotation or just shy of 25% which meant that it couldn't actually be a 28% rotation.

That told me there had to be something else occurring that was causing the engraving to repeatedly be a 2.32" engraving. I took the bottle off and put on a large new roll of 6" engravers masking tape. The problem went away. At that point (egg on my face) knowing this was ALL rookie inexperience. I put the aluminum bottle backwards on the wheels with the small neck resting on the passive wheels and the 2.75" base resting on the drive wheels. I loaded the bottle with some AA batteries for weight and presto the image looked perfect. Previous attempts to put batteries in with the small neck still resting on the drive wheels, resulted in the same elongated engraving.

I wouldn't have figured this out as quickly if it wasn't for all your inputs, so a definite thanks goes out to you all. I'll crawl under my rock now and hope that this post helps someone down the road who's experiencing the same issue... :o

Scott Shepherd
05-23-2017, 8:49 AM
Good job in troubleshooting Jeff! Glad you solved it. I'm sure you weren't the first to have that happen and won't be the last, so hopefully this post will help someone in the future.

Kev Williams
05-23-2017, 3:56 PM
Great find on the problem for sure! This thread may be worthy of being 'stuck' :)

Jacob John
05-23-2017, 8:27 PM
I had the exact opposite issue just after I received my rotary, we were getting "squished" images.

It turned out that the cup portion was loose on ours (we tightened it without having to open it up at all) so the glasses were sliding in the attachment and not rotating at the speed they should have been.

Maybe check yours and see if it loose as well? I've heard from another Trotec user local to me they had the same issue.

When we were having this issue, this is exactly what was wrong.