Intro. & UCP simulations to semi-quantify benefits of higher laser power

[Samuel Espy]

I have been lurking this forum for months while developing my business plan and preparing to launch my business later this summer. Many thanks for all the informative posts. It is high time I delurkify myself. I have not yet made my laser purchase, but extensive research has narrowed it to a VLS3.5 or Trotec Speedy 100 (if I can get good enough show pricing). As part of my machine-selection research, I investigated the benefits of increased laser power for both raster and vector engravings on a variety of materials. I know the simple answer is "buy as much power as you can afford", but I am interested in a understanding, in a semi-qualitative way, the benefits of increased power. After all, increased power is not cheap and I must spend my modest resources to maximum benefit of the business. As I don't have my laser yet, I am certainly not an expert. However, it is my hope that the information in this post along with comments by veteran laser engravers might benefit other newbies in their laser power selection.

My approach for quantifying the benefits of higher laser power leveraged the job time estimator in Universal Laser's Universal Control Panel (UCP) with different simulations varying the base laser power for various materials. The job estimator proved quite accurate during earlier demonstrations by my rep. Even without a PC being connected to a laser, UCP offers significant functionality. My ULS rep. provided a link for its download. I used one file for all raster simulations which contained a 5.76"x5.76" photo, and a file containing a grid of alternating 1" squares and circles across the 12"x24" engraving area for all vector simulations. A VLS3.5 with a 2" lens and suggested P/S settings from UCP's materials database were used for all simulations.

Table 1 Raster job estimates from UCP using 5.76"x5.76" photo; 500 PPI; image density=5 (500 LPI); 2"lens

Material	Base Laser Power [W]	P[%]	S[%]	UCP time [h:mm:ss]		Increase in machine power compared to 30W		Engraving time speedup compared to 30W for same material		Increase in S compared to 30W for same material
Alder	30	100	70	0:15:16		0%		0%		0%
Alder	40	100	80	0:15:00		33%		2%		14%
Alder	50	100	95	0:14:49		67%		3%		36%
Anodized Al	30	43	100	0:14:41		0%		0%		0%
Anodized Al	50	25	100	0:14:41		67%		0%		0%
Soda Lime Glass	30	100	53	0:16:43		0%		0%		0%
Soda Lime Glass	40	100	68	0:15:16		33%		9%		28%
Soda Lime Glass	50	100	84	0:14:56		67%		11%		58%
Hard Marble	30	100	70	0:15:16		0%		0%		0%
Cast Acrylic deep engrave	30	100	49	0:17:26		0%		0%		0%
Cast Acrylic deep engrave	60	100	86	0:14:53		100%		15%		76%

Observations regarding power/materials raster study:
Increasing machine power from 30-60W offers minimal improvement in engraving times for these materials (not that surprising). What does surprise me is the magnitude of engraving-time improvement (very small) compared to the appreciable increase in S for higher powers. For raster I would expect far less increase in engrave time than S increases, but not as small as the UCP estimates indicate. Obviously it takes time to switch directions at the end of each scan line, but I would have expected a somewhat better increase in engrave times for a 5.76" square image.

Table 2 Vector cutting time estimates from UCP using grid of alternating 1" squares and 1" D circles with 0.25" gap between each shape (across 12"x24" bed); 2" lens; 0.25" material thickness; standard vector performance

Material	Base Laser Power [W]	P[%]	S[%]	PPI	UCP time [h:mm:ss]		Calc. time: (t of 30W)*(power machine)/30W [s]		UCP time/ calc time		thickest cut possible ["]
Maple	30	100	2.3	300	0:44:38		0:44:38		1.00		0.30
Maple	40	100	3.1	300	0:34:53		0:33:29		1.04		0.39
Maple	60	100	4.3	300	0:25:28		0:22:19		1.14		0.51
Balsa	30	100	10.0	300	0:11:36		0:11:36		1.00		0.40
Balsa	40	100	12.0	300	0:10:13		0:08:42		1.17		0.52
Balsa	60	100	15.0	300	0:09:13		0:05:48		1.59		0.67
MDF	30	100	2.4	250	0:43:06		0:43:06		1.00		0.40
MDF	40	100	3.2	250	0:33:49		0:32:20		1.05		0.44
MDF	60	100	4.8	250	0:22:56		0:21:33		1.06		0.53
Cast Acrylic	30	100	1.3	1000	1:16:23		1:16:23		1.00		0.46
Cast Acrylic	40	100	2.0	1000	0:50:02		0:57:17		0.87		0.46
Cast Acrylic	60	100	3.1	1000	0:34:53		0:38:12		0.91		0.57

Observations regarding power/materials vector cutting study:
For wood materials and two lasers of max power W1 and W2 requiring cut times of t1 and t2 respectively for the same job, t2 will require slightly more time than t1*W1/W2. This assumes that both cut jobs are made using max power.

As indicated by Balsa example above at 60W, this relationship does not hold for some cases. I am not sure what is causing the Balsa outlier. Three things I notice which are different for the outlier: 1) the thickness of material is considerably less than max thickness that can be cut for that laser power, 2) the speed is slightly higher than the others, and 3) these are likely related to Balsa's low density and properties. This relationship is not valid for Acrylic. Surprisingly, (UCP time)/(Calc time) [i.e. t2*W2/(t1*W1)] is less than 1. Possibly due to the details of how Acrylic melts, conducts heat, etc.

[Michael Hunter]

Interesting .... but -

The vector simulation tells you nothing about the *quality* of the cuts in the various materials.

60W will not only cut wood or MDF considerably more quickly than 30W, but will normally make much cleaner cuts in 0.25" material with very little char or resin residue on the cut edges to clean up afterwards.

[Samuel Espy]

Agreed, and I understand/understood that cut-quality would not be addressed by the simulation. I certainly don't intend to indicate that the higher powers are not usually superior for most vector cutting work. I just wanted some indication of how closely the cut speed increase was proportional to the power increase since the upgrade costs are not trivial. Again, no earth-shattering revelations from the study. The conclusions have been stated many times as rules of thumb, but I feel better seeing some actual numbers to expound on them, even if they are a simulation.

[Mike Null]

Sam

Glad to have you join our group. Your analysis is interesting and might be useful if it were real but I don't think I would be comfortable making a purchase decision based on it. I, like many others, have found that manufacturers' settings are not more than a guide. Quality of cutting and engraving can't be measured by this method.

One thing is certain, there are some materials which can be run at full speed on a 30 watt machine so a higher powered machine might be unnecessary if those materials represented the bulk of your work. I know some very successful engravers in the awards business who have managed with 30 watt equipment for years.

[Rodne Gold]

A better strategy is to buy 2 x 30W lasers rather than the same platform with 60w , you *will* double your thruput and you will have redundancy.

[Samuel Espy]

Thanks for the responses. Obviously the consensus is that UCP (and other machine) estimates are too inaccurate to be useful for my intended purpose. If my plans hold, a large portion of my work will involve raster engraving and cutting veneer. However, I do have several products in mind that will require cutting Acrylic and some bulk wood. It would be foolish to ignore the extensive experience of those that commented so I will go back to extracting information from this forum regarding thicknesses people have success cutting at different base powers.

[Rodne Gold]

Actually thickness is more determined by your lens than power..lasers do NOT curt thick stuff well at all.. neither wood nor acrylic..ultimately 1/4" to a max of 8mm is as far as it goes for superb or useable/saleable cuts , thicker stuff is better cut by other means , like a CnC router.
Veneers require VERY little power for engraving or cutting , and if you up power for mainly these applications , you will soon run into a 100% speed ceiling.
Even for cutting thin stuff , you might find you cannot run at the speed your 60w or high power tube requires to be more productive in that the quality of vector cuts will suffer if you turn up the wick on speed.
You must also realise that tubes are inherently somewhat flaky , you might get 10 years use or maybe 3 years or maybe 6 months... a high power tube is VERY expensive to replace (and you have to budget for it)